ESO SL-9/Jupiter Information Package

        (JULY 16 - 22, 1994)
        Background information for the media
        Produced by the ESO Information Service 
        Date of Issue: July 5, 1994
        Click here to jump to 2. A Brief Summary of the Event
        Click here to jump to 3. The Possible Effects
        Click here to jump to 4. Basic Information and Tables
        Click here to jump to 5. ESO & Observations at La Silla
        Click here to jump to 6. ESO's Services to the Media
        1. Introduction
        1.1 General
        This Information Package contains background information which will be
        useful in connection with the media coverage of the collision between
        Comet Shoemaker-Levy 9 and the planet Jupiter on July 16 - 22, 1994.
        It provides a general overview of the main issues around this unique
        astronomical event, the like of which has never before been predicted,
        nor observed.
        The complete package consists of:
         - A comprehensive text, describing the event, the planned observations
           (especially at ESO) and the possible implications;
         - A series of photos, illustrating the preparations; and
         - A video tape with (unedited) illustrative sequences, suitable for
           broadcast use. Available in various formats.
        Copies of the ESO SL-9/Jupiter Information Package or parts thereof
        may be requested from:
        ESO Information Service
        European Southern Observatory
        Karl-Schwarzschild-Strasse 2
        D-85748 Garching bei Muenchen
        Tel.: +49-89-32006-276
        Fax.: +49-89-3202362
        1.2 Acronyms
        A number of common acronyms are used in this brochure:
        B&C   Boller & Chivens spectrograph (at ESO 1.5-metre telescope)
        CAT   1.4-metre Coude Auxiliary Telescope
        CES   Coude Echelle Spectrograph (at CAT and 3.6-metre telescope)
        CEST      Central European Summer Time (= UT + 2 hours)
        EMMI      ESO Multi-Mode Instrument (at the New Technology Telescope)
        ESA       European Space Agency
        ESO   European Southern Observatory
        Far-IR    Far-infrared wavelength region (about 5 - 20 microns)
        IRAC2B    Infrared Astronomical Camera 2B (at MPG/ESO 2.2-metre telescope)
        IRSPEC    Infrared Spectrograph (at the New Technology Telescope)
        JPL   Jet Propulsion Laboratory (Pasadena, California, USA)
        MPIA      Max-Planck-Institut fuer Astronomie (Heidelberg, Germany)
        MPIAe     Max-Planck-Institut fuer Aeronomie (Katlenburg-Lindau, Germany)
        MPG   Max-Planck-Gesellschaft (Germany)
        Near-IR   Near-infrared wavelength region (about 0.8 - 5 microns)
        NTT   ESO 3.5-metre New Technology Telescope
        SEST      15-metre Swedish-ESO Submillimetre Telescope
        ST/ECF    Space Telescope/European Coordinating Facility (at ESO-Garching)
        TIMMI     Thermal Infrared Multi-Mode Instrument (at the 3.6-metre telescope)
        UBVRI     Standard five-colour photometric system in astronomy (from
               about 380 nm to 900 nm wavelength)
        UT    Universal Time (earlier Greenwich Mean Time)
        VLT   ESO 16-metre equivalent Very Large Telescope (under construction
               at Cerro Paranal, Chile)
        2. A Brief Summary of the Event
        Beginning in the evening of July 16, 1994 (CEST = Central European
        Summer Time), fragments of Comet Shoemaker-Levy 9 will collide with
        Jupiter, the largest planet in the Solar System. The comet was
        discovered in March 1993, and its nucleus which may be likened with a
        "dirty snowball" of ice and dust, broke into more than 20 pieces
        during a close passage near Jupiter in July 1992. All of these
        fragments, which measure from a few hundred metres to a few kilometres
        in diameter, will hit Jupiter during a period of about 5 1/2 days,
        lasting until the morning of July 22. Astronomers all over the world
        now prepare to observe the associated phenomena with ground- and
        space-based astronomical instruments.
        Images of the comet have been obtained during the past few days with
        telescopes at the ESO La Silla observatory (Chile) and elsewhere.
        They confirm that there have only been minor changes and that at least
        20 cometary fragments are still present. These observations have also
        led to more precise predictions of the times of the impacts.
        The collisions will all take place on the far side of Jupiter and can
        therefore not be directly observed from the Earth. However, due to the
        rapid rotation of the planet, the impact sites will come into view
        within 10 - 15 minutes and it is likely that certain effects in the
        Jupiter atmosphere will then become noticeable.
        Each collision will result in the complete destruction of the comet
        fragment in the dense atmosphere of Jupiter. Depending of the mass of
        the individual fragments, the energy released may approach the
        equivalent of several 100,000 Megatons. Various effects have been
        predicted, ranging from an initial light flash when the comet
        fragments disintegrate, a subsequent rising column of superheated
        gases which may form a visible "mushroom" structure, as well as new
        eddies and whirls in the atmosphere, vibrations of the entire planet,
        and disturbances in the strong magnetic field, in turn leading to
        variations in Jupiter's intense radio emission.
        Observations have been planned at many professional observatories all
        over the world; due to Jupiter's position in the southern sky, the
        best observing conditions will be in the southern hemisphere (South
        America, Australia, South Africa). An international collaboration has
        been set up, linking the observers by computer networks which will
        ensure that information about all new developments can be rapidly
        passed on.
        At the ESO La Silla observatory in Chile, ten telescopes with a total
        of twelve observing programmes will be active during the critical
        Due to the lack of knowledge of the exact sizes and internal structure
        of the individual comet fragments, it has proven extremely difficult
        to make predictions about the magnitudes of the expected effects. For
        this reason, it is in principle not possible to state in advance what
        will actually be observed. It is believed, however, that the
        observations will provide new knowledge about the following important
         - Internal structure and composition of cometary nuclei ("dirty snowballs");
         - Composition and structure of the deeper layers of Jupiter's atmosphere;
         - Jupiter's inner structure; and 
         - The overall effects of such collisions.
        The last point is of direct interest to mankind, since comets have
        collided with the Earth in the past and are bound to do so in the
        future, albeit only very rarely.
      3. The Possible Effects
        Below is a condensed overview of the event and the possible effects,
        how it is intended to observe them, as well as information about the
        main uncertainties.
        3.1 What will happen ?
        There is absolutely no doubt that the collisions will indeed take
        place.  It is equally certain that they will happen on the rear side
        of Jupiter, just behind the visible limb and at about 45 degrees
        southern latitude.
        Accurate positional measurements of the comet fragments during the
        past year have made it possible to determine their orbits with very
        high precision, and we know at present the location of most fragments
        to within a few hundred kilometres. Jupiter's diameter is so large,
        just over 140,000 kilometres (that is, 11.2 times larger than that of
        the Earth), that any conceivable last-minute corrections to the orbits
        will only result in minor changes of the impact locations and times.
        The first fragment will hit Jupiter on July 16, 1994, at around 19:30
        UT (21:30 CEST; 15:30 Chilean time) and the last 5 1/2 days later, on
        July 22, 1994, around 08:00 UT (10:00 CEST; 04:00 Chilean time). These
        timings are still subject to improvement, but the events will probably
        not occur more than 30 minutes earlier or later.
        The comet fragments will hit Jupiter at a very high velocity, about 60
        km/sec. The correspondingly large motion energy (the "kinetic energy")
        will all be deposited in the Jovian atmosphere. For a 1 km fragment,
        it is equal to about 10^28 erg, or 250,000 Megatons (approximately 12
        million times the energy released by the Hiroshima bomb).
        When one of the cometary fragments enters the upper layers of the
        Jovian atmosphere, it will be heated by the friction with the
        surrounding molecules, exactly as a meteoroid in the Earth's
        atmosphere. The speed will decrease very rapidly and depending on the
        size of the fragment, it may evaporate completely within a few
        seconds, while it is still above the dense cloud layers that form the
        visible "surface" of Jupiter, or it may plunge right through these
        clouds (and therefore out of sight) into increasingly denser, lower
        layers. Whatever the altitude, it ultimately comes to a complete stop
        and disintegrates in a giant explosion.
        All of the kinetic energy is released during this process. One part
        will heat the surrounding atmosphere to very high temperatures; this
        will result in a flash of light that lasts a few seconds. Within the
        next minutes, a plume of hot gas (a "mushroom cloud") will begin to
        rise over the impact site. It may reach an altitude of several hundred
        kilometres above the cloud layers and will soon spread out in all
        horizontal directions. It will quickly mix with the upper layers of
        the atmosphere and it is possible that new whirls and eddies are
        Another part of the released energy will be transformed into shock
        waves that will propagate around the planet in the lower layers of the
        atmosphere and also into the interior of Jupiter, much as seismic
        waves from an earthquake do inside the Earth. When these waves again
        reach the upper layers of the atmosphere, they may be seen as slight
        increases of the local temperature along expanding circles with the
        impact sites at their centres (like waves on a water surface). The
        shock waves may also start oscillations of the entire planet, like
        those of a ringing bell.
        It is also expected that there will be some kind of interaction
        between the cometary dust and Jupiter's strong magnetic field. For
        instance, the fast-moving dust grains may become electrically
        charged. This will possibly have a significant influence on Jupiter's
        radio emission and therefore be directly observable with Earth-based
        radio telescopes, as well as from several spacecraft.
        Some of the dust may be deposited in the upper layers of the
        atmosphere and could possibly induce some colour changes of some of
        the cloud patterns.
        There may also be changes in the plasma torus that girdles Jupiter
        near the orbit of the volcanic moon Io, and some cometary dust
        particles may collect in Jupiter's faint ring.
        3.2 Which are the main uncertainties ?
        Both Jupiter and the cometary fragments have been extensively observed
        during the past months.  However, while we now possess more accurate
        information about the comet's motion and the times of impact, there is
        still great uncertainty about the magnitude of the above mentioned
        It is at this moment not clear which of them may actually be observed
        at the time of the impacts and which will be too weak to be
        observable, even with the largest and best telescopes.
        This is first of all due to the fact that it has not been possible to
        measure the sizes and masses of the individual cometary fragments and
        thereby to estimate the amount of energy which will be liberated at
        the collisions. Only rough estimates, based on the behaviour of the
        fragments and a comparison with other comets, are available. It is
        generally agreed that the smallest fragments measure at most a few
        hundred metres across, but there are divided opinions about the size
        of the largest. Conservative estimates put them at around 1, perhaps 2
        kilometres in diameter, more optimistic guesses quote figures of 4 - 5
        kilometres. Moreover, the internal constitution of the fragments is
        completely unknown. It clearly makes a difference, whether they are
        rather compact objects, or if they consist of very loose material; the
        first will penetrate much deeper into the atmosphere before they
        disintegrate than the second.
        Despite intensive observations, no gas has yet been detected in any of
        the fragments. We only see clouds of dust around them which completely
        hide them from our view. The amount of the dust has been steadily
        decreasing; this is because the dust production from the individual
        fragments - which began when the parent body broke up at the time of
        the near-collision with Jupiter in July 1992 - is slowly diminishing
        with time.
        Some of the smaller nuclei have recently disappeared from view,
        probably because they have ceased to produce dust. It is not clear,
        however, whether this also implies that they no longer exist at all,
        or whether they are just too small to be seen with available
        3.3 Why is this event of interest ?
        This event offers a unique opportunity to obtain new and exciting
        information about the colliding objects and the collision process
        itself. It is in fact a "cosmic experiment" of a type that has never
        before been observed by astronomers. Since very little is known about
        the actual effects that will be observed, the scientists have prepared
        themselves for different scenarios. There may be complete surprises,
        or the predicted effects may be too weak to perform accurate
        measurements. Whatever happens, new knowledge about this dramatic
        phenomenon will be collected.
        Here are the main subjects which will be studied.
        The structure of cometary nuclei:
        The internal structure and composition of cometary nuclei, often
        likened to "dirty snowballs", is still completely unknown. The images
        of the nucleus of comet Halley and other measurements of this famous
        comet, obtained from spacecraft and by ground-based telescopes in
        1986, never allowed a view below the surface of the very dark, 15-km
        The disintegration process of the fragments of comet Shoemaker-Levy 9
        in Jupiter's atmosphere will depend on their inner structure and
        observations of the associated phenomena may therefore allow some
        conclusions about this structure. Any new information on this subject
        will be extremely valuable for cometary physics and our understanding
        of these old objects, which we believe to harbour material that has
        remained unchanged since the very beginnings of the solar system,
        about 4600 million years ago.
        The deeper layers of Jupiter's atmosphere:
        If a comet fragment penetrates far down into the Jupiter atmosphere,
        the resulting, rising column of hot gases may contain elements of this
        atmosphere which could never have been observed otherwise. It may even
        become possible to prove the existence of complex molecules (possibly
        organic) which have not been seen before. Likewise, the time profile
        of the disintegration process (what happens at which altitude ?) may
        give us clues to the layering and structure of these parts of the
        It is expected that approximately half of the released energy will be
        transferred to the surrounding atmosphere (as a "shock") and result in
        wave motions, very similar to seismic waves in the Earth. Some of the
        waves will move along the upper atmosphere and spread like rings on
        the water. Others will traverse Jupiter's inner regions, before they
        again reach the surface, far from the impact sites. The observations
        of these waves will provide important clues to the deeper layers of
        the atmosphere as well as the inner structure of Jupiter.
        The inner structure of Jupiter:
        Jupiter's inner structure is in fact completely unknown to us. While
        it is expected that the main components are hydrogen and helium, it
        cannot be excluded that Jupiter has an inner core of heavy elements
        (metals) like the Earth. It may also be that there exists a shell of
        "metallic" hydrogen, surrounding a central core of very highly
        compressed helium.  The observation of the seismic waves may now for
        the first time give us definite clues to Jupiter's inner structure.
        The effects of comet collisions:
        Never before has the collision of a comet with another celestial body
        been directly observed.  The related computer simulations are
        extremely complex and with the present state of art they must be
        considered rather uncertain. The real effects of such a collision are
        therefore largely unknown.
        We are now in the unique situation of being able to watch such an
        event at distance. In addition to the effects that will be observed at
        Jupiter, a very central issue is that this may allow us to better
        estimate the possible effects of such a collision, when it happens at
        the Earth.
        There is no doubt that comet collisions with the Earth have taken
        place in the past; it is possible that the Tunguska event in 1908 was
        of this kind. It occured in central Siberia and resulted in a blast
        with an equivalent strength of approximately 20 - 50 Megatons. It is
        equally certain that such impacts will again happen. Still, the
        estimated frequency is rather low - perhaps one major catastrophe per
        30 million years.
        3.4 How will the collisions be observed ?
        All professional astronomers agree that nobody knows for sure, how
        dramatic the effects of the impacts will actually be. It is obvious,
        however, that unless we are prepared to observe them, we may lose a
        great chance for advancing our knowledge that is unlikely to come back
        in many years, if ever.
        For this reason, the observers have adopted a flexible policy. By
        carefully considering the optimal types of observations, a great
        variety of instruments and methods will be deployed at the large
        telescopes of the world's observatories. Each instrument, be it a CCD
        camera, a high-speed photometer, a long-slit spectrograph or a special
        receiver at a radio telescope, will work continuously during and after
        the impacts and the data will be looked at at short
        intervals. Moreover, all observers and their theoretically oriented
        counterparts at the computers will be in close contact during these
        days, continuously exchanging the latest information.
        This ensures that unexpected developments will be quickly detected,
        analysed and announced so that other observers can react to them in
        the shortest possible time. In this way, the observations will always
        be optimized.
        3.5 Could this event have implications for us on Earth ?
        Apart from new knowledge about what happens by a collision with a
        comet, the present event has no direct implications for life here on
        There have been wild and unfounded speculations in some places about
        possible, very dramatic effects, for instance that the orbit of
        Jupiter would be significantly changed, or that thermonuclear
        reactions may start on that planet. It has been alleged that this
        might in turn influence the Earth.
        The mass of Jupiter is 318 times that of the Earth and at least 10
        million million times larger than that of the comet, amply ensuring
        that the collisions will introduce no discernible change in Jupiter's
        orbit.  The temperatures which will be reached in the atmosphere, even
        if they are much higher (a few thousand degrees) than those normally
        prevailing, are way below what is needed to ignite a thermonuclear
        reaction, that is, several million degrees. None of the above effects
        are therefore possible.
        The collisions take place when Jupiter is about 770 million kilometres
        from the Earth. This enormous distance may be illustrated by the fact
        that it takes light, travelling at 300,000 km/sec through the very
        nearly empty space between us and the planet, no less than 43 minutes
        to reach us.  The corresponding delay is about 1 second from the Moon.
        Whatever happens at Jupiter is therefore very, very far from us and
        absolutely unlikely to have the slightest influence on the Earth and
        the life on this planet.
      4. Basic Information and Tables
        4.1 Comet Shoemaker-Levy and its orbit
        Comet Shoemaker-Levy 9 is the ninth short-period comet discovered by
        American astronomers Eugene and Carolyn Shoemaker and David Levy. It
        was first seen on a photographic plate obtained on 18 March 1993 with
        the 18-inch Schmidt telescope at the Mount Palomar Observatory,
        California. It was close in the sky to Jupiter and orbital
        calculations soon showed that it moves in a very unusual orbit. While
        other comets revolve around the Sun, this one moves in an elongated
        orbit around Jupiter with a period of just over 2 years. It was
        obvious that it must have been "captured" rather recently by the
        gravitational field of the planet.
        It was also found that Shoemaker-Levy 9 unlike most other comets
        consists of several individual bodies which move like "pearls on a
        string" in a majestic procession.  It was later determined that this
        is because the comet suffered a dramatic break-up due to the strong
        attraction of Jupiter at the time of an earlier close passage, only
        20,000 kilometres (that is less than 1/3 of the radius of Jupiter)
        above the cloud deck of this planet on July 8, 1992.
        High-resolution Hubble Space Telescope images have shown the existence
        of up to 21 individual fragments (also termed "sub-nuclei"), whose
        diameters probably range between a few kilometres and a few hundred
        metres. There is also much cometary dust visible around these
        sub-nuclei; it is probably a mixture of grains of different sizes,
        from sub-millimetre sand up to metre-sized boulders.
        Subsequent observations have showed changes in the relative brightness
        of the individual fragments, and many of them developed individual
        comet "tails". However, despite intensive spectroscopic observations,
        no gas has so far been detected in any of the nuclei, but this is not
        unusual for a comet at a distance of nearly 800 million kilometres
        from the Sun. We only see the dust clouds around the sub-nuclei and
        they are completely hidden from our view within these clouds. The
        amount of the dust has been steadily decreasing; this is because the
        dust production from the individual fragments -- which began when the
        parent body broke up at the time of the near-collision with Jupiter in
        July 1992 - is slowly diminishing with time.
        The fragments have been numbered from A to W. The largest are E, G, H,
        K, L and W. A is the first to impact on Jupiter, W is the last.  Some
        of the smaller fragments (J, M and O) have recently disappeared from
        view, probably because they have ceased to produce dust.
        In addition to the observations of the physical and chemical
        properties of the individual nuclei, astrometric (positional)
        observations have been carried out at several observatories. They have
        allowed to determine the orbits of the individual fragments and serve
        to make accurate predictions for the impact times. Nevertheless, it
        has not been possible to extrapolate the orbit backwards in time
        beyond the near-collision in July 1992 and the earlier orbit and
        origin of this comet is completely unknown. It is however likely that
        it has spent a very long time (probably since the birth of the solar
        system) in the outer regions of the system, until its orbit was
        recently perturbed, after which it had its fateful 1992 encounter with
        Predicted positions of three fragments 
        Computations by D.K. Yeomans and P.W. Chodas / JPL (June 24, 1994)
        The following tables give geocentric ephemerides for the fragments A,
        Q, and W.  These ephemerides are based on our latest orbital
        solutions, using astrometric data through 1994 June 16 and planetary
        ephemeris DE-245. 1 AU = 149.6 million kilometres.
          Explanation of Symbols:
          R.A. J2000  Dec. = Geocentric astrometric right ascension and declination
                             referred to the mean equator and equinox of J2000.
                             Light time corrections have been applied.
          Delta            = Geocentric distance of object in AU.
          r                = Heliocentric distance of object in AU.
          Theta            = Sun-Earth-Object angle in degrees.
          Beta             = Sun-Object-Earth angle in degrees.
          Moon             = Object-Earth-Moon angle in degrees.
        Ephemeris (with perturbations) for Comet S-L 9, fragment A 
          Date (UT)  h    R.A. J2000  Dec.       Delta    r    Theta Beta Moon
        1994 Jul  5 00  14 09 46.99 -12 21 17.9  4.944  5.402  111.6 10.1 156
        1994 Jul  5 12  14 09 51.75 -12 21 01.0  4.952  5.403  111.2 10.1 150
        1994 Jul  6 00  14 09 56.74 -12 20 44.5  4.959  5.403  110.7 10.1 144
        1994 Jul  6 12  14 10 01.95 -12 20 28.4  4.967  5.403  110.3 10.2 138
        1994 Jul  7 00  14 10 07.39 -12 20 12.7  4.974  5.404  109.8 10.2 132
        1994 Jul  7 12  14 10 13.07 -12 19 57.3  4.982  5.404  109.3 10.2 126
        1994 Jul  8 00  14 10 18.98 -12 19 42.2  4.989  5.405  108.9 10.3 119
        1994 Jul  8 00  14 10 18.98 -12 19 42.2  4.989  5.405  108.9 10.3 119
        1994 Jul  8 12  14 10 25.13 -12 19 27.3  4.997  5.405  108.4 10.3 113
        1994 Jul  9 00  14 10 31.53 -12 19 12.5  5.005  5.406  108.0 10.3 107
        1994 Jul  9 12  14 10 38.18 -12 18 57.8  5.012  5.406  107.5 10.3 100
        1994 Jul 10 00  14 10 45.10 -12 18 43.1  5.020  5.407  107.1 10.4  94
        1994 Jul 10 12  14 10 52.29 -12 18 28.3  5.028  5.407  106.6 10.4  87
        1994 Jul 11 00  14 10 59.76 -12 18 13.2  5.036  5.408  106.2 10.4  81
        1994 Jul 11 12  14 11 07.52 -12 17 57.8  5.044  5.408  105.7 10.4  74
        1994 Jul 12 00  14 11 15.59 -12 17 41.8  5.051  5.409  105.3 10.4  68
        1994 Jul 12 12  14 11 23.99 -12 17 25.0  5.059  5.409  104.8 10.5  61
        1994 Jul 13 00  14 11 32.75 -12 17 07.1  5.067  5.410  104.4 10.5  54
        1994 Jul 13 12  14 11 41.89 -12 16 47.7  5.075  5.411  103.9 10.5  47
        1994 Jul 14 00  14 11 51.46 -12 16 26.3  5.083  5.411  103.5 10.5  40
        1994 Jul 14 12  14 12 01.53 -12 16 02.1  5.091  5.412  103.1 10.5  34
        1994 Jul 15 00  14 12 12.18 -12 15 33.8  5.099  5.413  102.6 10.6  27
        1994 Jul 15 12  14 12 23.59 -12 14 59.4  5.108  5.414  102.2 10.6  20
        1994 Jul 16 00  14 12 36.07 -12 14 14.1  5.116  5.415  101.7 10.6  13
        1994 Jul 16 12  14 12 50.47 -12 13 04.2  5.124  5.416  101.3 10.6   6
        Ephemeris (with perturbations) for Comet S-L 9, fragment Q1
          Date (UT)  h    R.A. J2000  Dec.       Delta    r    Theta Beta Moon
        1994 Jul  5 00  14 09 19.40 -12 24 49.7  4.941  5.398  111.5 10.1 156
        1994 Jul  5 12  14 09 23.82 -12 24 36.0  4.949  5.398  111.1 10.1 150
        1994 Jul  6 00  14 09 28.44 -12 24 22.9  4.956  5.399  110.6 10.2 144
        1994 Jul  6 12  14 09 33.28 -12 24 10.4  4.964  5.399  110.2 10.2 138
        1994 Jul  7 00  14 09 38.32 -12 23 58.4  4.971  5.399  109.7 10.2 132
        1994 Jul  7 12  14 09 43.57 -12 23 47.1  4.979  5.400  109.2 10.2 126
        1994 Jul  8 00  14 09 49.03 -12 23 36.3  4.986  5.400  108.8 10.3 119
        1994 Jul  8 12  14 09 54.70 -12 23 25.9  4.994  5.401  108.3 10.3 113
        1994 Jul  9 00  14 10 00.59 -12 23 16.1  5.001  5.401  107.9 10.3 107
        1994 Jul  9 12  14 10 06.70 -12 23 06.8  5.009  5.401  107.4 10.3 100
        1994 Jul 10 00  14 10 13.03 -12 22 57.8  5.017  5.402  107.0 10.4  94
        1994 Jul 10 12  14 10 19.58 -12 22 49.3  5.024  5.402  106.5 10.4  87
        1994 Jul 11 00  14 10 26.36 -12 22 41.1  5.032  5.403  106.1 10.4  81
        1994 Jul 11 00  14 10 26.36 -12 22 41.1  5.032  5.403  106.1 10.4  81
        1994 Jul 11 12  14 10 33.36 -12 22 33.2  5.040  5.403  105.6 10.4  74
        1994 Jul 12 00  14 10 40.60 -12 22 25.6  5.048  5.403  105.2 10.5  67
        1994 Jul 12 12  14 10 48.08 -12 22 18.2  5.055  5.404  104.7 10.5  61
        1994 Jul 13 00  14 10 55.80 -12 22 10.9  5.063  5.404  104.3 10.5  54
        1994 Jul 13 12  14 11 03.77 -12 22 03.7  5.071  5.405  103.8 10.5  47
        1994 Jul 14 00  14 11 12.00 -12 21 56.5  5.079  5.405  103.4 10.5  40
        1994 Jul 14 12  14 11 20.50 -12 21 49.1  5.087  5.406  102.9 10.6  33
        1994 Jul 15 00  14 11 29.27 -12 21 41.5  5.095  5.406  102.5 10.6  27
        1994 Jul 15 12  14 11 38.32 -12 21 33.6  5.103  5.407  102.0 10.6  20
        1994 Jul 16 00  14 11 47.68 -12 21 25.0  5.111  5.408  101.6 10.6  13
        1994 Jul 16 12  14 11 57.36 -12 21 15.7  5.119  5.408  101.2 10.6   6
        1994 Jul 17 00  14 12 07.39 -12 21 05.3  5.127  5.409  100.7 10.6   3
        1994 Jul 17 12  14 12 17.79 -12 20 53.4  5.135  5.410  100.3 10.7   9
        1994 Jul 18 00  14 12 28.61 -12 20 39.5  5.143  5.410   99.8 10.7  16
        1994 Jul 18 12  14 12 39.91 -12 20 22.9  5.151  5.411   99.4 10.7  23
        1994 Jul 19 00  14 12 51.78 -12 20 02.3  5.159  5.412   99.0 10.7  30
        1994 Jul 19 12  14 13 04.38 -12 19 35.7  5.168  5.413   98.5 10.7  37
        1994 Jul 20 00  14 13 18.01 -12 18 58.9  5.176  5.414   98.1 10.7  44
        1994 Jul 20 12  14 13 33.45 -12 17 58.9  5.185  5.415   97.7 10.7  51
        Ephemeris (with perturbations) for Comet S-L 9, fragment W 
         Date (UT)   h   R.A. J2000  Dec.       Delta    r    Theta Beta Moon
        1994 Jul  5 00  14 09 09.71 -12 26 02.8  4.940  5.397 111.5 10.1 156
        1994 Jul  5 12  14 09 14.04 -12 25 50.0  4.948  5.397 111.1 10.1 150
        1994 Jul  6 00  14 09 18.56 -12 25 37.9  4.955  5.397 110.6 10.2 144
        1994 Jul  6 12  14 09 23.29 -12 25 26.4  4.963  5.398 110.1 10.2 138
        1994 Jul  7 00  14 09 28.22 -12 25 15.5  4.970  5.398 109.7 10.2 132
        1994 Jul  7 12  14 09 33.36 -12 25 05.2  4.978  5.398 109.2 10.2 126
        1994 Jul  8 00  14 09 38.70 -12 24 55.5  4.985  5.399 108.8 10.3 119
        1994 Jul  8 12  14 09 44.24 -12 24 46.4  4.993  5.399 108.3 10.3 113
        1994 Jul  9 00  14 09 50.00 -12 24 37.9  5.000  5.399 107.8 10.3 107
        1994 Jul  9 12  14 09 55.96 -12 24 29.8  5.008  5.400 107.4 10.4 100
        1994 Jul 10 00  14 10 02.14 -12 24 22.3  5.016  5.400 106.9 10.4  94
        1994 Jul 10 12  14 10 08.53 -12 24 15.3  5.023  5.400 106.5 10.4  87
        1994 Jul 11 00  14 10 15.14 -12 24 08.7  5.031  5.401 106.0 10.4  81
        1994 Jul 11 12  14 10 21.97 -12 24 02.6  5.039  5.401 105.6 10.4  74
        1994 Jul 12 00  14 10 29.02 -12 23 56.8  5.046  5.402 105.1 10.5  67
        1994 Jul 12 12  14 10 36.29 -12 23 51.4  5.054  5.402 104.7 10.5  61
        1994 Jul 13 00  14 10 43.79 -12 23 46.3  5.062  5.403 104.2 10.5  54
        1994 Jul 13 12  14 10 51.53 -12 23 41.5  5.070  5.403 103.8 10.5  47
        1994 Jul 14 00  14 10 59.50 -12 23 36.8  5.078  5.404 103.3 10.5  40
        1994 Jul 14 12  14 11 07.71 -12 23 32.3  5.086  5.404 102.9 10.6  33
        1994 Jul 15 00  14 11 16.17 -12 23 27.8  5.094  5.404 102.4 10.6  27
        1994 Jul 15 12  14 11 24.88 -12 23 23.3  5.101  5.405 102.0 10.6  20
        1994 Jul 16 00  14 11 33.86 -12 23 18.7  5.109  5.406 101.6 10.6  13
        1994 Jul 16 12  14 11 43.11 -12 23 13.8  5.117  5.406 101.1 10.6   6
        1994 Jul 17 00  14 11 52.65 -12 23 08.6  5.125  5.407 100.7 10.6   3
        1994 Jul 17 12  14 12 02.48 -12 23 02.7  5.133  5.407 100.2 10.7   9
        1994 Jul 18 00  14 12 12.63 -12 22 56.1  5.141  5.408  99.8 10.7  16
        1994 Jul 18 12  14 12 23.13 -12 22 48.4  5.149  5.409  99.4 10.7  23
        1994 Jul 19 00  14 12 34.00 -12 22 39.2  5.158  5.409  98.9 10.7  30
        1994 Jul 19 12  14 12 45.28 -12 22 28.1  5.166  5.410  98.5 10.7  37
        1994 Jul 20 00  14 12 57.04 -12 22 14.2  5.174  5.411  98.1 10.7  44
        1994 Jul 20 12  14 13 09.36 -12 21 56.4  5.182  5.412  97.6 10.7  52
        1994 Jul 21 00  14 13 22.41 -12 21 32.6  5.191  5.413  97.2 10.7  59
        1994 Jul 21 12  14 13 36.46 -12 20 58.7  5.199  5.414  96.8 10.7  66
        1994 Jul 22 00  14 13 52.31 -12 20 02.1  5.208  5.415  96.3 10.7  73
        Predicted length of train of fragments
        Due to the different gravitational pull in the individual fragments,
        the length of the train will increase with time. The increase is most
        rapid just before the impacts.
        Date          Angular length   Physical length
                 (arcsec)     (km)
        1993 Mar 25     49       158,000
             Jul 1      67       265,000
        1994 Jan 1     131       584,000
             Feb 1     161       669,000
             Mar 1     200       762,000
             Apr 1     255       893,000
             May 1     319         1,070,000
             Jun 1     400         1,366,000
             Jul 1     563         2,059,000
             Jul15     944         3,593,000
        Impact A      1286         4,907,000
        4.2 Jupiter and its moons.
        Jupiter is the largest planet in the solar system. It is one of the
        brightest natural objects in the sky (only the Sun, the Moon and Venus
        are brighter) and it has always been known by mankind. Galileo Galilei
        first pointed his new telescope towards Jupiter in January 1610 and
        immediately discovered the four major moons, Io, Europa, Ganymedes and
        Callisto. Continued astronomical observations have shown that Jupiter
        possesses at least 16 moons. Jupiter is also known to have a rather
        faint ring of dust particles, much less conspicuous than the one
        around Saturn.
        Jupiter is 318 times heavier than the Earth and about 1000 times
        lighter than the Sun. It is now clear that Jupiter has about the same
        composition as the Sun (mostly hydrogen and helium) and that it is
        actually a "failed" star. 
        When the solar system was created about 4,600 million years ago by
        contraction in an interstellar cloud of gas and dust, the young Sun
        emerged after a few million years at the center of a rotating disk of
        this material. The temperature inside the Sun rose rapidly and soon
        reached several million degrees, enough to ignite the atomic
        processes, mostly the transformation of hydrogen into helium, that now
        are responsible for the brightness and the enormous energy output from
        the Sun. Contrarily, Jupiter began as a much smaller concentration of
        matter in the outer part of the disk and due to its small mass, the
        contraction process never resulted in temperatures high enough to
        start chain reactions inside Jupiter.
        As far as is known, Jupiter (like the Sun) has no solid surface, and
        its apparent surface is simply the top layer of the clouds in its
        atmosphere.  There are three cloud layers; the uppermost one consists
        of ammonium particles, the next lower one of more complex ammonium and
        nitrogen compounds, while the lowest one is made up of frozen water
        particles (ice crystals). There may be other layers below these which
        are still unknown to us.
        Next to nothing is known about Jupiter's inner structure. It is
        conceivable that there are specific and well-defined layers of
        different composition similar to those in the Earth. Some models
        predict a central core of helium, surrounded by a shell of "metallic"
        hydrogen (a highly exotic state of this basic element which can only
        exist at extremely high pressures).
        Jupiter's moons come in many different sizes. While the four major
        ones are as big as, or bigger than our own Moon, all of the others are
        significantly smaller and are most likely captured asteroids.
        The moon Io is of particular interest; there are many active volcanoes
        on its surface which emit mostly sulphuric compounds. This activity is
        due to Jupiter's incessant gravitational pull in Io, which deposits
        much energy in its inner parts and thereby causes a heating effect.
        Some Jupiter Data
        Mean distance from the Sun    778.3 million km
        Orbital period around the Sun     11.86 years
        Mean orbital velocity         13.06 km/sec
        Orbital inclination to Ecliptica  1.30 degrees
        Mass                  1.9 10^27 kg (= 318 x Earth mass)
        Mass (relative to the Sun)    1/1047
        Equatorial radius         71,600 km    (= 11.23 x Earth radius)
        Mean density              1.314 kg/m^3
        Rotation period           9 hr 50 min
        The moons of Jupiter
        Name      Distance from Jupiter   Orbital period    Radius
        Metis       127,000 km      0.295 days       ~20 km
        Adrasteia   128,000 km      0.297 days        12 km
        Amalthea    181,000 km      0.489 days       135 km
        Thebe       221,000 km      0.670 days        55 km
        Io      422,000 km      1.77  days      1826 km
        Europa      671,000 km      3.55  days      1563 km
        Ganymedes     1,070,000 km      7.16  days      2638 km
        Callisto      1,880,000 km     16.7   days      2410 km
        Leda         11,100,000 km    240     days        ~5 km
        Himalia      11,500,000 km    251     days       ~90 km
        Lysithea     11,700,000 km    260     days       ~10 km
        Elara        11,700,000 km    260     days       ~40 km
        Ananke       20,700,000 km    617     days       ~10 km
        Carme        22,400,000 km    692     days       ~15 km
        Pasiphae     23,300,000 km    735     days       ~20 km
        Sinope       23,700,000 km    758     days       ~15 km
        The outermost four moons move in retrograde orbits, that is contrary
        to the motion of almost all other objects in the solar system.
        Jupiter's position in the sky
        Explanation of Symbols:
        R.A. J2000  Dec. = Geocentric astrometric right ascension and declination
                             referred to the mean equator and equinox of J2000.
                             Light time corrections have been applied.
        Delta            = Geocentric distance  in AU.
        r                = Heliocentric distance  in AU.
        Angular size     = The angular size of Jupiter's disk in arcseconds
        Date (0 UT)  R.A. J2000  Dec.   Delta    r    Angular size
        1994 Jul  4  14 11.9   -12:01  4.9412  5.4192    40  
        1994 Jul  5  14:11.9   -12:02  4.9554  5.4190    40  
        1994 Jul  6  14:11.9   -12:02  4.9697  5.4188    40  
        1994 Jul  7  14:12.0   -12:03  4.9841  5.4187    39  
        1994 Jul  8  14:12.0   -12:03  4.9986  5.4185    39  
        1994 Jul  9  14:12.1   -12:04  5.0132  5.4183    39  
        1994 Jul 10  14:12.2   -12:05  5.0278  5.4181    39  
        1994 Jul 11  14:12.3   -12:05  5.0426  5.4180    39  
        1994 Jul 12  14:12.4   -12:06  5.0574  5.4178    39  
        1994 Jul 13  14:12.5   -12:07  5.0722  5.4176    39  
        1994 Jul 14  14:12.6   -12:08  5.0872  5.4174    39  
        1994 Jul 15  14:12.8   -12:09  5.1021  5.4172    39  
        1994 Jul 16  14:12.9   -12:10  5.1172  5.4170    38  
        1994 Jul 17  14:13.1   -12:11  5.1323  5.4169    38  
        1994 Jul 18  14:13.2   -12:12  5.1474  5.4167    38  
        1994 Jul 19  14:13.4   -12:14  5.1626  5.4165    38  
        1994 Jul 20  14:13.6   -12:15  5.1778  5.4163    38  
        1994 Jul 21  14:13.8   -12:16  5.1930  5.4161    38  
        1994 Jul 22  14:14.0   -12:18  5.2083  5.4159    38  
        1994 Jul 23  14:14.2   -12:19  5.2236  5.4158    38  
        4.3 Predicted impact times and visibility from different sites
        The following table was prepared by Paul Chodas and Don Yeomans
        (JPL/Caltech) and gives the predicted impact times, based on orbital
        computations, taken into account all available observations up to July
        5. It is expected that further observations will reduce the indicated
        uncertainties substantially.
        The predictions for fragments E, G, H, K, L, Q, R, S, and W are the
        most accurate, as these have the best-known orbits; fragments T, U,
        and V have the most poorly-determined orbits, (especially U).
        The indicated "Earth Receive" times correspond to the moments when the
        events become observable from the Earth; the light travel time from
        Jupiter (about 43 minutes) has been taken into account. The
        uncertainties indicate the interval around the predicted moment during
        which there is an approx. 95 % chance that the event really happens.
        The best viewing conditions for each impact are indicated. Note,
        however, that they are significantly better from locations in the
        southern hemisphere than from the mentioned northern sites.
        Fragment  Earth Receive   Uncert.  Best viewing conditions from
                   Date /Time     interval  
                   July  (UT)      (+-min)     
         A = 21     16  19:53:40     17    Africa (except W. Africa), Middle East, Eastern Europe  
         B = 20     17  02:49:03     17    Eastern N. America, Mexico, Western S. America  
         C = 19     17  06:55:36     17    New Zealand, Hawaii  
         D = 18     17  11:41:50     17    Australia, New Zealand, Japan  
         E = 17     17  15:03:51     16    India, Southern China, S.E. Asia, Western Australia   
         F = 16     18  00:28:15     14    S. America  
         G = 15     18  07:28:00     11    New Zealand, Hawaii  
         H = 14     18  19:25:48     11    Africa (except W. Africa), Middle East, Eastern Europe  
         K = 12     19  10:17:58     12    Australia, New Zealand  
         L = 11     19  22:06:58     12    Brazil, W. Africa, Spain  
         N = 9      20  10:18:37     17    Australia, New Zealand  
         P2= 8b     20  15:05:10     14    India, Southern China, S.E. Asia, Western Australia  
         Q2= 7b     20  19:31:36     25    Africa (except W. Africa), Middle East, Eastern Europe
         Q1= 7a     20  19:59:04     14    Africa (except W. Africa), Middle East, Eastern Europe  
         R = 6      21  05:22:04     14    Hawaii, West coast N. America  
         S = 5      21  15:07:13     12    India, Southern China, S.E. Asia, Western Australia 
         T = 4      21  18:04:14     30    Africa (except W. Africa), Middle East, Eastern Europe  
         U = 3      21  21:47:00     32    Brazil, W. Africa, Spain  
         V = 2      22  03:57:25     24    Western U.S.A., Mexico  
         W = 1      22  07:53:17     18    New Zealand, Hawaii, Eastern Australia
        The difference in viewing conditions from the North and the South is
        illustrated by the following table. The altitude is the height (in
        degrees) of Jupiter in the sky above the horizon; the higher, the less
        the atmosphere will disturb astronomical observations.
                                            Munich, Germany   La Silla, Chile
        Geographical latitude                     +48              -30
        Jupiter maximal altitude after sunset      27               73
        Time between sunset and Jupiter set     3 hrs 55 min     7 hrs 45 min
        4.4 List of expected effects
        The fragments will deposit a large amount of energy in the Jupiter
        atmosphere when they burn up and explode at the impact. Many different
        phenomena may result. 
        The following list summarizes the supposedly most important effects,
        their probable duration and how they may be observed.  It should be
        stressed that it is very uncertain how strong these effects will
        actually be and therefore how easy or difficult it will be to observe
        Effect          Duration    Type of Observation
        Ablation Flash      few seconds     Reflection from satellite/ring 
        Rising Plume        1 - 2 hours Changes of atmospheric patterns
                            Spectral changes (new molecules ?)
        Sonic waves     several hours   Temperature increase (ring pattern)
        Oscillations        several days    Temperature variations
        Dust charging       several days    Magnetic field => Radio emission 
                            Changes in Io torus
        Dust => Ring        ~10 days    Changes in dust ring
        Dust in atmosphere  some days   Changes in colour of atmospheric 
        4.5 Ground- and space based observations
        There will be many different types of observations from the ground and
        from space. In general, they complement each other. Only by observing
        this unique event with the entire arsenal of modern astronomical
        equipment can we hope to obtain a satisfactory understanding of the
        associated phenomena.
        The following main types of observations are planned from the ground:
        - Accurate pre-impact astrometry (positions) of the individual comet fragments
        - Search for differences in the optical emission of the individual fragments
        - Imaging and surface polarimetry of the cometary dust
        - Fabry-Perot-interferometry of the gas in the comet fragments
        - High-speed photometry of light echoes on the moons and the ring
           from the impacts
        - Observations in the visual and infrared wavebands of Jupiter's surface
          after the impacts (imaging, spectroscopy)
        - Visual and infrared imaging of the Io Plasma Torus
        - Millimeter observations of post-impact molecules
        - Radio monitoring of (decametric) emission
        and from space:
        - HST:      Ultraviolet + visual high-resolution imaging
                Ultraviolet spectroscopy
        - Galileo:  Imaging of impact sites 
                Infrared mapping
                Radio monitoring
        - Voyager 2:    Radio monitoring
        - Ulysses:  Radio monitoring
        4.6 Participating observatories
        It is expected that virtually all major observatories in the world
        will participate in observations of this event, with the exception of
        the northenmost ones from where Jupiter is not well observable because
        of very low altitude above the horizon and the short summer nights.
        Since it is winter and the nights are long on the southern hemisphere
        and Jupiter will be 12 degrees south of the celestial equator, the
        observing conditions are best for the astronomical observatories
        located here, including the ESO La Silla observatory.
        In addition to the major southern observatories, ESO La Silla, the
        Cerro Tololo Interamerican Obervatory (both located in Chile), the
        Anglo-Australian Observatory (Siding Spring, Australia), the South
        African Aastronomical Observatory (Sutherland, South Africa), the main
        participating observatories are in the southern part of the United
        States of America (Kitt Peak National Observatory, the Palomar
        Observatory, the Mauna Kea Observatory), in Spain (La Palma, Calar
        Alto), Japan, China, India, Mexico, and in the CIS republics.
        Observations are also planned from the South Pole and with the
        high-altitude Kuiper Airborne Observatory over the South Pacific.
        4.7 International coordination
        As soon as it became clear in the autumn of 1993 that a collision
        between comet Shoemaker-Levy 9 Jupiter will indeed take place,
        astronomers from many countries began to plan the associated
        observational campaign. International coordination and rapid exchange
        of information between observers and theoreticians is of particular
        importance during such a campaign where unexpected events may happen
        and quick adjustment of the observing programmes is desirable.
        The astronomers are connected in various ways, but above all through
        the world-wide net of computer connections; here the "Internet"
        network plays the most important role. At various observatories and
        institutes "mail exploders" have been set up which automatically
        multiplies and sends on incoming messages to all subscribers. One of
        these, at the University of Maryland, serves all observers all over
        the world. Moreover, several institutions have set up "World-Wide-Web
        Portals" which provide easy and efficient access to new information,
        both text and images.
        Since there will only be a few hours observing time at each
        observatory, it is very important that new developments are passed on
        to those observers who are next in the line. For instance, the first
        impact will be best observable in South Africa, while the next one, a
        few hours later, will be very well placed for observations from South
        For this reason, the observers at the South African Astronomical
        Observatory at Sutherland will be in direct contact with those at
        ESO's La Silla observatory in Chile. They will in turn talk to those
        at Hawaii and Australia, who begin their observations when Jupiter
        approaches the horizon in Chile.
      5. ESO and observations at La Silla
        A major coordinated programme to observe the impact of comet
        Shoemaker-Levy 9 on Jupiter has begun at the ESO observatory at La
        Silla in the Atacama desert (Chile). This section contains detailed
        information about the ESO organisation and these programmes.
        5.1 The European Southern Observatory
        Some facts about ESO:
        - Intergovernmental Scientific Organization, supported by 8 members
          countries: Belgium, Denmark, France, Federal Republic of Germany,
          Italy, the Netherlands, Sweden, Switzerland; Portugal associated since
          1990. Other countries may join soon.  
        - Headquarters at Garching near Munich (Germany)
          - Office of the Director General; Administration
          -  VLT and Science Divisions
          -  Space Telescope/European Coordinating Facility (ESA/ESO)
          -  Image Processing Center (MIDAS, IHAP)
          -  Remote Control Center (for three telescopes at La Silla)
        - Astronomical Observatory at La Silla in the Southern Atacama desert (Chile)
          - 2400 m altitude 
          - More than 290 clear nights per year
          - 14 optical telescopes up to 3.6 m diameter 
          - 15 m submillimetre telescope (SEST) 
          - Full remote control from Europe of three telescopes 
          - 800 square km property for light and dust protection
        - Future VLT Observatory at Paranal in the Central Atacama desert (Chile)
          - 2660 m altitude
          - More than 330 clear nights per year
          - Now under development
          - 725 square km property for light and dust protection
        - Main Telescope Projects
          - 3.5-metre New Technology Telescope (NTT); entered into operation
                in late 1989
          - 16-m Very Large Telescope (VLT); under construction (1988 - 2000+)
        - ESO's Legal Basis, Membership, Budget, etc. 
          - 1962: Convention for the Establishment of ESO (with Financial Protocol)
          - 1964: Agreement between Government of Chile and ESO
          - 1974: Protocol of Privileges and Immunities of ESO
          - 1979: Headquarters Agreement between the Federal Republic of Germany
                and ESO
          - Council and various Committees: 
          - Annual budget approx. 123 million DEM (1994); hereof about 65 million 
                DEM for the VLT   
          - about 300 staff members in Germany and Chile
          - Information from ESO published in Annual Reports, The ESO
                Messenger (4 times a year), Press Releases, Scientific and Technical
                Notes and Preprints, Conference Proceedings, etc.
        5.2  Observation Programmes at the ESO La Silla Observatory
        The following table provides an overview of the planned observational
        programmes at the ESO La Silla observatory (as of July 5, 1994). They
        are listed according to the type of investigation and some of them
        have already been successfully carried out. 
        More detailed information about the others, especially those during
        the critical period from July 16 - 22, 1994, will be found in section
        Program no.  Telescope  Instrument Dates           No.      Allocation
        PI                                          Observer(s) 
           1         ESO 1.52m  B&C spec.  Apr. 12 - Apr. 15   3            ESO
        Spectroscopy of individual SL9 nuclei
        Heike Rauer                 Heike Rauer
        Max-Planck-Institut fuer Aeronomie
        D-37189 Katlenburg-Lindau
        Max-Planck-Str. 2
        Tel.: +49-5556-979-394
        Fax.: +49-5556-979-240
           2         NTT        EMMI       June 30 - July  2   2            ESO
        Direct imaging and spectroscopy of individual SL9 nuclei
        Rita Schulz                 Rita Schulz
        Max-Planck-Institut fuer Aeronomie      Joachim A. Stuewe
        Postfach 20
        D-37189 Katlenburg-Lindau
        Tel.: +49-5556-979-219
        Fax.: +49-5556-979-240
           3         2.2m   Foc. Red. MPAe  Apr. 1 - 7      6           MPIA
        Narrow-band Fabry-Perot interferometry and imaging of the Io torus
        Klaus Jockers                   Klaus Jockers
        Max-Planck-Institut fuer Aeronomie (MPAe)
        Postfach 20
        D-37189 Katlenburg-Lindau
        Tel.: +49-5556-979-293
        Fax.: +49-5556-979-240
           4         1m     Foc. Red. MPAe  Apr. 25 - May 1  6      ESO
        Narrow-band (Fabry-Perot) and wide-band imaging of comet SL 9
        Klaus Jockers                   Klaus Jockers
        Max-Planck-Institut fuer Aeronomie (MPAe)
        Postfach 20
        D-37189 Katlenburg-Lindau
        Tel.: +49-5556-979-293
        Fax.: +49-5556-979-240
           5         DK 1.54 m  CAM/CCD    Apr. 30 - Jul 15?     ? x 1hour       ESO/DK
        Astrometry of individual SL-9 nuclei
        Olivier Hainaut                  Olivier Hainaut 
        European Southern Observatory
        Karl-Schwarzschild-Strasse 2
        D-81827 Garching bei Muenchen
        Tel. : +4989-32006306
        Fax  : +4989-3202362
           6         1 m        Special    July 15 - July 25   10            ESO
        Fast multi-channel UBVRI photometry of Jovian satellites
        Heinz Barwig                     Heinz Barwig
        Universitaets-Sternwarte Muenchen        Otto Baernbantner
        Scheinerstr. 1
        D-81679 Muenchen
        Tel.: +49-89-922094-45
        Fax.: +49-89-922094-27
           7         DK 1.54 m  Spec/CCD   July 17 - July 24   8            ESO
        Fast CCD photometry of the satellites and CCD imaging of Jupiter's disk
        Bruno Sicardy                        Laurent Jorda
        Observatoire de Paris-Meudon
        5, place Jules Janssen
        F-92195 Meudon Cedex
        Tel.: +33-1-4507-7962
        Fax.: +33-1-4507-7469
           8         Boch. 60cm CCD        July 10 - July 25   15           Bochum
        CCD imaging of Jupiter
        Uri Carsenty                     Uri Carsenty
        DLR                      S. Mottola
        NE-PE                        E. Bratz
        D-82234 Wesling
        Tel.: +49-8153-281328
        Fax.: +49-8153-2467
        email: "28842::carsenty"
           9         Dutch 90cm CCD    16-22 July       4 x 1/2 night   Dutch
        CCD imaging of Jupiter
        Keith Horne                                  Keith Horne
        Astronomical Institute                       Remco Shoemakers
        Postbus 80000                                
        NL-3508 TA Utrecht
        The Netherlands
        Tel. : +30-31-535234
        Fax  : +30-31-535201
          10         CAT 1.4m   CES       July 18 - July 25   7             ESO
        High-resolution spectra of Jupiter (detection of water vapour)
        Anne Marie Lagrange                          Anne Marie Lagrange
        Laboratoire d'Astrophysique                  Olivier Hainaut
        Observatoire de Grenoble
        414, rue de la Piscine
        F-38041 Grenoble Cedex
        Tel. : +33-76514788
        Fax  : +33-76448821
          11         2.2m      IRAC2B     July 16 - 24        8         MPIA
        Near-IR imaging of comet SL 9 and Jupiter's atmosphere
        Klaus Jockers                   Klaus Jockers
        Max-Planck-Institut fuer Aeronomie
        Postfach 20
        D-37189 Katlenburg-Lindau
        Tel.: +49-5556-979-293
        Fax.: +49-5556-979-240
          12         NTT    IRSPEC    July 16 - July 28   12 x 1/2      ESO
                          July 30 - July 31    1 x 1/2      ESO
        Near-IR spectroscopy of Jupiter
        Therese Encrenaz                Therese Encrenaz,
        DESPA - Observatoire de Paris           Guenter Wiedemann
        F-92195 Meudon
        Tel.: +33-1-4507-7691
        Fax.: +33-1-4507-2806
        email: "meudon::encrenaz"
          13         NTT    IRSPEC    July 16 - July 28   12 x 1/2      ESO
                          July 30 - July 31    1 x 1/2      ESO
        Near-IR spectroscopy of Jupiter
        Rita Schulz                 Rita Schulz
        Max-Planck-Institut fuer Aeronomie      Joachim A. Stuewe
        Postfach 20
        D-37189 Katlenburg-Lindau
        Tel.: +49-5556-979-219
        Fax.: +49-5556-979-240
          14       3.6 m    TIMMI     July 16 - July 28   12 x 1/2      ESO
                          July 30 - July 31    1 x 1/2      ESO
        Far-IR imaging and spectroscopy of Jupiter (atmosphere)
        Timothy A. Livengood                Tim Livengood
        NASA/Goddard Space Flight Center        Theodor Kostiuk
        NASA/GSFC                   Hans Ulrich Kauefl
        Code 693
        Greenbelt, MD 20771
        Tel. : +1-301-286-1552
        Fax  : +1-301-286-1629
          15       3.6 m    TIMMI     July 16 - July 28   12 x 1/2      ESO
                          July 30 - July 31    1 x 1/2      ESO
        Far-IR imaging and spectroscopy of Jupiter (seismology)
        Benoit Mosser                   Benoit Mosser
        Institut d'Astrophysique                    Pierre O. Lagage
        98, bd. Arago
        F-75014 Paris
        Tel. : +33-1-4320-1425
        Fax  : +33-1-4329-8673
          16       DK 1.54 m    Spec/CCD   July 17 - July 24   8        ESO
        CCD imaging of Io torus and Jupiter ring
        Nicolas Thomas                  Nicolas Thomas
        Max-Planck-Institut fuer Aeronomie
        Max-Planck-Str. 2
        D-37189 Katlenburg-Lindau
        Tel. : +49-5556-979-437
        Fax  : +49-5556-979-240 or 141
          17       SEST     350 GHz    July 18 - July 23 5 shifts     ESO
        Molecular lines
        Daniel Gautier                  Pierre Colom
        Observatoire de Paris-Meudon            Dominique Bockelee-Morvan
        Observatoire de Meudon                      Didier Despois
        F-92195 Meudon
        Tel. : +33-1-4507-7707
        Fax. : +33-1-4507-7469
        Program no.: La Silla SL9/Jupiter Program No.
        Telescope  : Telescope allocated
        Instrument : Instrumental configuration
        Dates      : Time allocated (noon to noon for optical telescopes)
        No.        : Nos. of nights (optical telescopes) or shifts (SEST)
        Allocation : Time allocation authority
        PI     : Name and address of Principal Investigator
        Observer(s): Name(s) of observer(s)
        Title      : Brief description of the purpose of this program
        5.3 Brief descriptions of individual programmes at La Silla
        The following descriptions of the programmes which will be carried out
        at La Silla have been prepared by the participating astronomers.
        The programme numbers refer to the table in section 5.2, which also
        list the addresses of the Prinicipal Investigators, as well as the
        names of the observers who are expected to be at La Silla. The
        acronyms used are explained in section 1.2.
        As experience will be gained from the first impacts, it cannot be
        excluded that some of the indicated observational procedures and goals
        will be adjusted in the course of this campaign.
        Programmes 2 and 13
        3.5-metre New Technology Telescope with the EMMI and IRSPEC instruments
        June 30 - July 02, 1994 (Programme  2)
        July 16 - July 28, 1994 (Programme 13)
        July 30 - July 31, 1994 (Programme 13)
        Rita Schulz (Max-Planck-Institute fuer Aeronomie, Katlenburg-Lindau,
        Germany; PI)
        We shall monitor the individual fragments of comet Shoemaker-Levy 9
        with the NTT in different spectral ranges before (June 30 - July 2,
        1994) and during their impacts on Jupiter (July 16 - 28, 1994).
        The colour and the spatial distribution of the dust that surrounds the
        individual fragments will be analysed by means of CCD images taken in
        the visual range with different filters; this may uncover possible
        differences between the individual fragments. At the same time, we
        will also obtain spectra of the fragments to search for emission bands
        of the various gaseous species which are normally present in comets.
        Near-infrared spectroscopical monitoring of the impacts will provide
        information about the composition of the individual fragments of the
        comet.  It is expected that large amounts of water will be
        released. Ion chemistry calculations thereby predicts the formation of
        several ions which can be observed in the near-IR.
        Moreover, the effects of Jupiter's magnetosphere on the cometary dust
        will be analysed in detail on images obtained in wavebands that
        correspond to one of the methane absorption bands, both in late June
        and during the week of the impacts.
        Programme 5
        Danish 1.5-metre telescope with a CCD camera (and other telescopes)
        April 30 - July 15, 1994 (intermittently)
        Olivier Hainaut (ESO; PI) and Richard M. West (ESO)
        The individual fragments of comet Shoemaker-Levy 9 move in very
        complex orbits around Jupiter. They are mainly influenced by the
        gravitational pull of the Sun and Jupiter, and to some extent by the
        moons of this giant planet.  During the last few days before the
        impacts, the fragments will experience a rapid acceleration to about
        60 km/sec; this is, however, strongly dependent on their actual
        locations relative to Jupiter and unless the orbits are extremely well
        known, it is therefore difficult to make very accurate predictions of
        the impact times.
        The determination of these orbits is based on positional measurements
        of the individual fragments at different times. This is done by means
        of images obtained with large telescopes and sensitive CCD cameras.
        The positions of the comet fragments are compared with those of stars
        with accurately known positions, that are seen on the same images.
        In order to know in advance as well as possible when the impacts
        occur, it is necessary to continue astrometric observations up to the
        very last moment, in practice a few days, perhaps the last day, before
        the first impact.  However, such observations are difficult for
        several reasons.
        First, when the fragments are very close to Jupiter, the strong
        straylight from the planet will flood the CCD camera and make it
        difficult to see the images of the fainter ones. Next, the fragments
        are moving away from each other and already the "string of pearls" is
        so long that several exposures are necessary to image them all. And
        most important, in order to achieve the highest possible accuracy, the
        positions of the fragments must be compared with those of stars with
        very well determined positions ("astrometric standards") of which
        there are so few in the sky that none can be expected to be located on
        the same exposures as the comet.  This problem is overcome by first
        measuring the accurate positions of some of the fainter stars seen on
        the CCD images with the comet on available large-field photographic
        plates which also show some of the astrometric standard stars.
        We have begun such measurements and thanks to the kind help of the
        scientists involved in the ESA Hipparcos programme, we have obtained
        pre-publication lists of extremely accurate astrometric standards near
        the comet path across the sky. This has enabled us to mesure the
        positions of all the fragments of comet Shoemaker-Levy 9 with high
        precision (0.2 - 0.3 arcseconds, corresponding to about 200 kilometres
        near Jupiter) and herewith to contribute substantially to the
        improvement of the prediction of the impact times.
        Programme 6
        1-meter telescope with multi-channel high-speed photometer
        July 15 - 25, 1994
        Heinz Barwig (PI), Hermann Boehnhardt, Karl-Heinz Mantel and Otto
        Baernbantner (Universititaets-Sternwarte Muenchen, Germany)
        We will attach the special multi-channel high-speed photometer of the
        Universitaets-Sternwarte Muenchen to the ESO 1-metre telescope in
        order detect light echoes from the Jovian moons. Since the impacts
        themselves are not directly visible from Earth, we will use suitable
        Jovian moons as mirrors behind Jupiter to reflect the flashes caused
        during the entry of the comet fragments into Jupiter's atmosphere.
        However, these light echoes are rather difficult to detect against the
        bright sunlight also reflected from the moons' surfaces.  Light echoes
        from moons, which are in the shadow of Jupiter, but still visible from
        the Earth, will be much easier to measure, but unfortunately only one
        impact is expected to occur during such a satellite eclipse, namely
        that of fragment K with Europa in eclipse.
        During our observations up to three Jovian satellites will be
        monitored simultaneously through broad-band filters (the standard
        U,B,V,R,I-colours).  The photometer works very rapidly (it provides a
        temporal resolution of a tenth of a second or better) and may
        therefore give a very accurate timing of the light echoes and
        therefore the impacts. If the flash from an impact is reflected from
        several moons, the reflected light will arrive at different times at
        Earth and we will observe these time delays.  In combination with the
        known positions of the moons, this will allow us to calculate the actual
        impact time at Jupiter.
        Our multi-colour measurements will at the same time provide an estime
        of the flash temperature and the energy released in the visual
        wavelength range at the moment of impact.
        The knowledge of the exact impact times is of particular interest,
        since this will make it possible to establish reliable reference
        points for the studies of the propagation of impact phenomena through
        the Jovian atmosphere and for the seismic observations. Furthermore,
        accurate impact times will help to select and to send back to Earth
        the most interesting images obtained by the Galileo spacecraft which
        has the privilege of looking directly at impacts sites on the rear
        side of Jupiter.
        Programme 7
        1.54-metre Danish telescope with a special CCD camera
        July 17 - 24, 1994
        Bruno Sicardy (Observatoire de Paris, Meudon, France; PI), Jean
        E. Arlot, F. Colas, W. Thuillot (Bureau des Longitudes, Paris,
        France), C. Buil (Centre National d'Etudes Spatiales, Paris, France)
        and J. Lecacheux (Observatoire de Paris, France).
        Our program will make use of an anti-blooming CCD camera to monitor
        some of the collisions of the fragments of comet P/S-L 9 with
        Jupiter. Although the impacts will not be directly visible from the
        Earth, they occur sufficiently close to the limb of Jupiter (about 10
        degrees or less) so that any plume that rises a few hundred kilometres
        above the impact point will be directly observable from the Earth a
        few minutes after the impact.
        A fast anti-blooming CCD has the advantage of being able to record up
        to 2-3 images/sec, while limiting the scattered light from the bright
        planet. From ESO, one of the best candidates to be observed is the
        impact of fragment F just after sunset on July 17. We will try to
        image the corresponding plume, in order to better estimate the exact
        time of impact, and also to be able to say something about the
        impactor mass and the plume formation.
        Another goal of particular interest is to attempt to catch the
        reflection of the impact light on the comet dust during the very entry
        of the corresponding fragment. It may also be that reflections will be
        observable on the small moon Amalthea. Such reflections will be very
        useful for determining the exact impact times and may give information
        about the first few seconds of the entry into the atmosphere.
        In the few hours following the impacts (in particular L and U), we
        will turn to imaging the cloud appearances at the impact points and
        record the evolution of these changes as the planet settles back to
        equilibrium. Various optical filters (corresponding to the continuum
        light and methane absorption bands) will allow us to probe different
        levels in Jupiter's atmosphere, and their respective reactions to the
        Programme 8
        Bochum 60-cm telescope with CCD camera
        July 10 - 25, 1994
        Uri Carsenty (PI), Stefano Mottola, Egon Bratz (DLR, Wesling, Germany)
        This programme differs from most of the others at La Silla in that it
        will start several days before the impacts will take place. This will
        give us sufficient time to trim the instrument and to gain experience
        which will be needed for the critical observations.
        We intend to monitor first the comet fragments as they approach
        Jupiter and later the impact zones, as they come into
        view. Last-minute changes in the fragments may be detected which will
        be important for the predictions of the relative strengths of the
        impacts.  It cannot be excluded that the strong gravitational effects
        of Jupiter will lead to further disintegration of the fragments.
        We shall do these observations through various optical filtres, some
        of which are sensitive to the emission from the cometary dust, and
        others which may show the presence of gas in the fragments, not
        detected until now. Changes in the clouds of Jupiter will be seen by
        comparison with images which were obtained during the preceding
        days. In this way, we hope to detect the effects of the impacts as
        quickly as possible and to alert other observers who may then
        concentrate their observational efforts on these phenomena.
        Programme 9 
        Dutch 0.9-metre telescope with  CCD camera
        July 16 - 22, 1994
        Keith Horne and Remco Schoenmakers (Astronomical Institute, Utrecht,
        The Netherlands)
        We will be using a CCD camera on the Dutch 0.9-metre telescope to take
        a movie showing the brightness and color variations of one or more of
        Jupiter's moons that happen to be located behind Jupiter at the times
        when the largest fragments of comet Shoemaker-Levy 9 are predicted to
        crash into the atmosphere on Jupiter's back side.
        Since we cannot monitor the crash site directly, we will be searching
        for faint traces of the crash in light that is reflected from the
        moons.  The predicted signature is a brief (5 second) flash in
        ultraviolet and optical light as the comet fragment passes through the
        transparent upper layers of the atmosphere, a short delay after it
        punches through the opaque cloud deck, and finally a slower (1 minute)
        pulse, first in red and then in infrared light, as the expanding and
        cooling fireball from the explosion rises back up to the surface.
        If we succeed in detecting these signatures, our data will allow us to
        determine the temperature and surface area as functions of time during
        the bolide and fireball phases. A comparison with the appropriate
        model calculations will then give information about the kinetic energy
        and hence the total mass of each comet fragment, its degree of
        fragmentation, the depth to which it penetrates, and the vertical
        structure of the Jovian atmosphere.
        We plan to use a modified version of a special observing technique
        that is normally used to monitor rapidly variable stars with 10 second
        time resolution.  During each exposure, we will set the telescope
        tracking rates so that the moon's image is trailed across the CCD
        detector.  This trailed image will give us a record of the time
        variations in the brightness of the moon.  In addition, we will place
        a low-dispersion prism in the filter wheel to separate the
        ultraviolet, visible, red, and infrared images of the moon in a
        direction perpendicular to the trailing direction.  This will allow us
        to determine the color and hence temperature changes as a function of
        When we are not monitoring the moons, we will take images of Jupiter
        in various filters to record changes in the cloud features that result
        from the comet impacts.
        Programme 10
        1.4-metre Coude Auxiliary Telescope with the Coude Echelle Spectrograph
        Anne-Marie Lagrange (PI) and J.-L. Bertaux (Observatoire de Grenoble,
        France), Olivier Hainaut (ESO)
        We will attempt to detect water vapour in the upper atmosphere of
        Jupiter above the clouds, which may be injected there during the
        impact of comet fragments, either from the evaporation/fragmentation
        of these fragments, or because the energy released by the impact will
        result in a huge, rising plume of water vapour from the Jovian water
        cloud at the 5 bar pressure level. The calculations of synthetic
        spectra have shown that it may be possible to detect water vapor
        absorption if there are more than 10^18 molecules/cm^2 along the line
        of sight. If this amount is distributed over a square area with a side
        of 3,500 km (this corresponds to one arcsec at the distance of
        Jupiter), the total quantity of water would corresponds to what is
        contained in an ice ball of 100 m radius. This is significantly less
        than the sizes now estimated for most of the fragments and may
        therefore give us a good chance of actually detecting this water.
        However, it must be emphasized that the water could also come from the
        clouds of Jupiter at the 5 bar pressure level, where the largest
        fragments are expected to explode and send upwards a large quantity of
        cometary and Jovian material.
        Whatever the origin of the water vapour observed above the visible
        layers of ammonia ices, it is expected that the original cloud will be
        spread horizontally by the general circulation of the atmosphere. Our
        spectral observations will be able to monitor the evolution of these
        impact-produced water vapour clouds.
        For this programme we will use the "long" camera at the CES/CAT to
        obtain long-slit spectra with the CCD with a slit width of 1 arcsec at
        very high spectral resolution (R = 100000, or about 0.1 nm).  We shall
        take high-resolution spectra of the disc of Jupiter in the
        near-infrared wavelength region, where numerous strong lines of water
        vapour are present. At the time of predicted impact the position of
        Earth and Jupiter will be quite favorable, giving a sufficient Doppler
        shift (about 26 km/sec) for the Jovian absorption lines to be well
        separated from the corresponding lines from the water vapour in the
        Earth's atmosphere.
        Programme 11
        MPI/ESO 2.2-metre telescope with IRAC2B camera
        July 16 - 24, 1994
        Klaus Jockers (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau,
        Germany; PI)
        Our observations will be carried out at the MPI/ESO 2.2m telescope on
        which will be mounted the ESO near-infrared camera IRAC2B. They will
        be conducted in the K-band, which covers wavelengths from 2.0 to 2.4
        Jupiter's atmosphere contains methane, which absorbs very strongly in
        this wavelength range and the disk of Jupiter is therefore very dark
        at this waveband. As we do not see a solid or liquid planetary surface
        (if it exists at all, it must be very deep inside the planet), it is
        common to measure the altitude in Jupiter's atmosphere from a
        reference level, where the pressure equals the pressure at the Earth's
        surface (1 bar = 10^5 Pascal = 10^5 Newton/m^2). The part of Jupiter's
        atmosphere that is accessible in the K band ranges from somewhat less
        than 50 km to about 400 km above this reference surface with pressures
        from a few tenths to one millionth of the surface pressure at the
        Earth. In the upper (outermost) part of this altitude interval, a
        small but significant part of the atmosphere is ionized (the atoms and
        molecules carry electric charge), so we call this region the
        "ionosphere" (a similar one exists at somewhat lower altitudes in the
        Earth's atmosphere).
        The cometary fragments will penetrate more deeply into the atmosphere,
        but this altitude range may be affected by the rising plume that is
        expected to develop soon after each impact. It is unlikely that the
        cometary fragments themselves will be bright enough to be observable
        in the K band just before their impact, when they are close to
        Jupiter's limb, but the following effects may be observable:
        1. A haze cloud of cometary debris may appear above the impact site,
        when it rotates to the visible side of Jupiter's disk. This cloud may
        be seen in addition to the polar haze which is always present in
        Jupiter's polar ionosphere.
        2. We expect a modification of the Jovian polar aurora. Narrow-band
        images of Jupiter, taken at wavelengths within the K-band where the
        H3+ ion radiates, show a strong brightening around Jupiter's polar
        caps. This is the Jovian aurora. Like the aurora observable in the
        arctic and antarctic regions of the Earth, the Jovian aurora is caused
        by energetic particles precipitating into the ionosphere and heating
        it. A similar heating may occur after the cometary impacts. Therefore,
        in addition to the always observable aurora, emission of H3+ ions
        heated by the plumes that result from the cometary impacts may be
        observable close to the impact sites.
        3. At the longwave border of the K band, the methane absorption is
        less strong and we can look more deeply into the atmosphere down to
        the ammonia cloud deck at 20 km altitude. Modifications (for instance
        evaporation) of the ammonia clouds by the impact may be observable.
        4. The strong methane absorption present in large parts of the K band
        has another advantage. As Jupiter's disk is dark, the straylight,
        which affects objects outside, but close to the visible limb, is
        strongly reduced.  Therefore it is possible to observe in the K-band
        Jupiter's faint ring that extends from 53000 to 60000 km above
        Jupiter's limb. Because of the favourable relative location of the
        Sun, the Earth and Jupiter during the impacts, a part of this ring (on
        the side where the impacts occur) is eclipsed by Jupiter's shadow. It
        may become illuminated by the light flash expected at the time of an
        impact. Therefore, we shall observe the ring at the time of an impact
        in order to determine the infrared characteristics of this flash.
        Programme 12
        3.5-metre New Technology Telescope with IRSPEC instrument
        July 16 - 28, 1994
        July 30 - 31, 1994
        Therese Encrenaz (PI) and P. Drossart (Observatorie de Paris, France),
        Rita Schulz and J.A.Stuewe (Max-Planck-Institute fuer Aeronomie,
        Katlenburg-Lindau, Germany), Guenther Wiedemann (ESO)
        The impact of the fragments of comet Shoemaker-Levy 9 on Jupiter may
        induce significant changes in both the troposphere and the
        stratosphere of the planet, provided the fragments are big enough to
        reach the level where the atmospheric pressure is 1 bar. The entire
        atmospheric region located above the deep water cloud level (P about 5
        bars) can be probed by near-infrared spectroscopy. In particular, the
        composition and the thermal structure of the troposphere can be
        studied at wavelengths around 4-5 microns, the ammonium cloud level (P
        about 0.5 bar) can be monitored in the near-infrared continuum (1.25
        microns) and the upper stratospheric haze can be mapped in the
        spectral regions of strong methane absorption.
        We plan to monitor the impact regions and the surrounding areas of the
        Jovian disk using the imaging spectrometer IRSPEC at the 3.5-metre NTT
        telescope of ESO between July 16 and 31, 1994. This instrument will
        record infrared spectra in the 1 - 5 microns range with a spectral
        resolving power of about 3000 and a pixel size of 2 arcsec.
        These observations should allow us to monitor the various cloud levels
        of the Jovian atmosphere and their short-term and long-term evolution
        after the impacts. The variations of the temperature profile at the
        impact location will be recorded. Some minor tropospheric gaseous
        species (NH3, PH3, CO, H2O,...) of the Jovian atmosphere might be
        carried to higher levels and become observable.
        Programme 14
        3.6-metre telescope with the Far-Infrared instrument TIMMI
        July 16 - 28, 1994
        July 30 - 31, 1994
        Tim A. Livengood (PI), Ted Kostyuk and P.N. Romani(NASA Goddard Space
        Flight Center, Greenbelt, U.S.A.), C.F. Chyba (National Research
        Council, Washington, U.S.A.), Hans Ulrich Kaeufl and Guenter Wiedemann
        Stratospheric phenomena on Jupiter will be observed from the ESO
        3.6-metre telescope, using the TIMMI thermal-infrared camera which
        will also be used at the same time to study possible seismic
        TIMMI is able to detect emission from warm gases in Jupiter's
        uppermost atmosphere, the stratosphere, and has already been used to
        study auroral emissions from Jupiter's poles.  Preliminary
        observations were conducted in March 1994.  Observations of the impact
        events will be sensitive to gases that are unique to Jupiter's deep
        atmosphere that the impacts may eject upwards into the stratosphere.
        We plan to study the alterations in Jupiter's stratospheric
        composition and temperature profile and the rate at which the modified
        atmosphere returns to its normal state.  We may also be able to track
        the drift of impact sites in the atmosphere in order to measure
        large-scale stratospheric wind speeds, similar to tracking the
        dispersal of gases thrown out by a volcano on Earth.  Dust in
        Jupiter's magnetosphere may affect the power delivered to the aurorae,
        which may produce a detectable change in auroral brightness.
        TIMMI observations of the impacts will give us information about two
        regions of the Jovian system that are normally difficult to study, the
        stratosphere and magnetosphere.  A good understanding of these regions
        is very important in preparing for planetary spacecraft missions and
        in understanding the physics of atmospheric processes.
        Programme 15
        ESO 3.6-metre telescope with the Far-Infrared TIMMI instrument
        July 16 - 28, 1994
        July 30 - 31, 1994
        Benoit Mosser (Institut d'Astrophysique, Paris, France;
        PI). F. Billebaud (Observatoire de Lyon, France), P.O. Lagage and
        M. Sauvage (Sap), France), P. Drossart and D. Gautier (DESPA, Meudon,
        France), Phillipe Lognonne (IPG, Paris, France)
        We shall use the TIMMI camera to monitor the seismic waves excited by
        the impact, which will allow us to probe the interior of Jupiter. The
        impacts will produce local shocks which will create various waves that
        propagate through the planetary interior, very much like seismic waves
        from earthquakes do through the Earth.
        High-frequency waves, or transient waves (also known as primary
        waves), will cross the entire planet in less than 2 hours. We hope to
        detect their arrival times by means of the thermal perturbations they
        induce when they arrive back in the upper troposphere and dissipate
        their energy there. Low-frequency waves will be trapped in the
        planetary interior and contribute to various modes of global
        oscillations. In the days following the impacts, such modes will be
        detectable through the thermal fluctuations associated with these
        The monitoring of the front wave of the high frequency waves will be
        conducted during the two hours following each impact, and will provide
        us with a measurement of the sound speed profile in the fluid
        envelope. The long-period modes will be continuously observed during
        at least four observing "nights" (at these infrared wavelengths we can
        also observe in the afternoon, before the Sun sets) after the
        impacts. They will probe the planetary core and the region of the
        envelope where hydrogen is in a fluid metallic phase.
        These seismological observations may provide the first measurement of
        the density profile in the interior, and will permit to discriminate
        between the currently rather poorly constrained models of the interior
        of Jupiter.  We shall be able to test the state of hydrogen and helium
        at pressures up to one megabar, and also how the giant planets were
        The observation of the long period modes at ESO will be coordinated
        with other observations conducted with similar cameras at the
        Canadian-French Hawaii Telescope at Mauna Kea and at the Nordic
        Optical Telescope at La Palma (Canarian Islands). This multi-site
        project will permit us to obtain a good resolution of the various
        seismological frequencies.
        Programme 16
        1.54-metre Danish telescope with Special CCD Camera
        July 17 - 24, 1994
        Nicolas Thomas (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau,
        Germany; PI)
        The volcanically active, inner moon Io is the major source of heavy
        ions (electrically charged atoms and molecules) in Jupiter's
        magnetosphere.  Approximately 1 ton/sec of mostly sulphur and oxygen
        atoms is removed continuously from the satellite and become ionized in
        Jupiter's magnetosphere where they form a torus of heavy ions
        encircling Jupiter near Io's orbit, known as the Io Plasma Torus, or
        the IPT). This torus has been studied by spacecraft and from the
        ground since the mid-1970s, but the detailed mechanisms remain
        obscure. It also seems that there must be an additional energy source
        whose nature still remains unknown.
        Comet Shoemaker-Levy 9's break-up in Jupiter's magnetosphere was first
        thought to introduce a large enough mass to have an extreme effect on
        the IPT.  However, it is now apparent that the mass loss from the
        comet will be too small by at least a factor of 1000 to affect the IPT
        by increasing its mass.  On the other hand, the comet may affect the
        unknown energy source which maintains the stability of the emissions.
        We will observe the IPT by imaging the ionized sulphur emissions at
        visible and near-infrared wavelengths through narrow-band interference
        filters, allowing to measure the electron temperature and density of
        the IPT. These observations permit a rapid assessment of the IPT
        during the comet encounter and would give the strongest indication
        from ground-based observations of variability due to cometary
        The Jovian ring was discovered by the Voyager 1 spacecraft in 1979. It
        was subsequently imaged from the ground on at least two occasions
        around 1980 at visible wavelengths. Observations are very difficult
        due to the ring's proximity to Jupiter (0.8 Jovian radii from
        Jupiter's surface) and are best performed in the IR at wavelengths
        near 2.2 microns. However, visible observations provide a higher
        spatial resolution and are also of interest.
        A large quantity of smaller dust particles is present around the comet
        fragments. Although significant amounts of this material will miss
        Jupiter entirely, it will intersect the ring plane and impact the
        satellites near the ring. This could produce significant enhancements
        in the mass of material in the ring. We will observe the ring in an
        attempt to detect of perturbations in the ring due to the cometary
        These observations will rely on the anti-blooming CCD system of the
        Observatoire de Paris (see also Programme 7).
        Programme 17
        15-metre Swedish-ESO Submillimetre Telescope with radio receivers
        July 18 - 23, 1994
        Daniel Gautier (PI), Danielle Bockelee-Morvan and Pierre Colom
        (Observatoire de Paris-Meudon, France), D. Despois (Observatoire de
        Bordeaux, France), Jacques Crovisier, Therese Encrenaz, E. Lellouch
        and A. Marten (Observatoire de Paris-Meudon, France), Tobias Owen
        (University of Hawaii, U.S.A.), D. Strobel (John Hopkins University,
        The infalling fragments of comet Shoemaker-Levy 9 will evaporate in
        the upper atmosphere of Jupiter. The various elements contained in
        these fragments will then appear in gaseous form in the Jovian
        atmosphere, and will form new molecules different from those
        previously observed on the planet. If the fragments penetrate into the
        deep atmosphere before they detonate, they may also lift molecules
        which are formed in the interior of Jupiter and which have not yet
        been detected up to high altitudes where they may then become
        We have then two objectives, both based on a the possible modification
        of the atmosphere of Jupiter following the impacts. First, to
        determine the composition of the comet and secondly, to improve our
        knowledge of the composition of the planet.
        Observations by means of a radiotelescope of the radiation emitted by
        Jupiter is a very powerful tool for detecting gaseous species. The
        great sensitivity of the methods used in radioastromy will permit us
        to detect the specific emissions of molecules, even if they only are
        present in a very small numbers.
        This is reason why we shall use the 15-metre SEST radiotelescope to
        observe Jupiter immediately after the first impact and during the
        following days. In this respect, the SEST has a unique advantage when
        compared to other radiotelescopes in the world. Since Jupiter is
        presently situated south of the celestial equator, we will be able to
        perform much longer series of observations and at higher elevations
        above the horizon than other radiotelescopes which are all located in
        the Northen hemisphere. However, close coordination with groups
        working at other sites has been organized.
        5.4 The ST/ECF and observations with the Hubble Space Telescope
        The Space Telescope European Coordinating Facility (ST/ECF) was
        established in 1984 by the European Space Agency (ESA) in conjunction
        with the European Southern Observatory (ESO). It is a group of
        astronomers and computer scientists with the goal of helping European
        astronomers make best use of the Hubble Space Telescope (HST). This is
        achieved by providing specialist information and advice, developing
        computer software for processing data from the telescope and
        establishing and operating a full copy of the HST data archive.
        The HST is 2.4-metre aperture telescope in low earth orbit designed as
        a general purpose astronomical observatory for imaging and
        spectroscopy in the ultra-violet, optical and near infrared regions of
        the spectrum. It is a collaboration between NASA and the European
        Space Agency and European astronomers are guaranteed to receive at
        least 15% of the observing time for the duration of the ESA/NASA
        agreement (currently ten years after HST launch).
        HST was launched in 1990 by the Space Shuttle. Soon afterwards it was
        discovered that the primary mirror of the telescope had the wrong
        shape and that the performance was poorer than expected. The ST-ECF
        was active in helping to produce computer software which allowed a
        partial correction for this error. In late 1993 a repair mission of
        the Space Shuttle very successfully installed corrective optics in the
        telescope and the performance is now in most respects as good as the
        original specification.
        The Hubble Space Telescope will be among the most important of the
        telescopes which will study the collision of comet Shoemaker-Levy 9
        with Jupiter. Its position in orbit around the Earth allows very high
        resolution images to be made both of the comet itself and the effects
        on Jupiter after the collision.
        Observations of the comet before impact will allow the orbits of the
        fragments and their sizes to be better determined and hence allow
        improvements of the estimates for the times of impact and likely size
        of the subsequent explosions. Images already obtained have shown that
        some of the fragments which appeared single from the ground are
        actually double or multiple. The actual impacts will not be observable
        with HST any more than from ground-based telescopes although a major
        fireball may be seen rising above the edge of the planet's disc.
        After the collision the effects on the atmosphere, rings, satellites
        and environment of Jupiter will be studied over an extended period
        using the HST. Six science programs will be executed and they will use
        all four of HST's science instruments, two spectrographs and two
      6. ESOs Services to the Media
        There are many signs that the upcoming collision between comet
        Shoemaker-Levy 9 and giant planet Jupiter has caught the imagination
        of the public. Numerous reports in the various media during the past
        weeks and months describe the effects expected during this event.
        In view of the unique nature of this event and the associated
        astronomical observations, ESO has decided to provide special services
        to the media. In particular, it is the intention to ensure that the
        media will be able to follow the developments at La Silla closely and
        in near-real time, and at the same time will be kept informed about
        the observational results at other observatories all over the world.
        This service will be available from the ESO Headquarters in Garching
        near Munich, Germany, but special arrangements will also be made for
        the media in Chile.  In view of the complex and critical nature of
        these observations, it will not be possible to arrange direct access
        to the La Silla observatory during the observing period.
        ESO will obtain all new information directly from the observers at La
        Silla via the permanent satellite link to the ESO Headquarters in
        Garching (Germany). For this, ESO is setting up the necessary internal
        communication lines at La Silla which will allow this transfer to be
        done at the shortest possible notice. While the observers cannot be
        disturbed during the actual observations, they will communicate their
        results and observational progress at regular intervals, and very
        quickly, if and when "dramatic" events are observed.
        ESO furthermore has complete and permanent access to the world-wide
        communication net between all observers of this event, especially set
        up for this purpose. The information available from this source will
        first of all serve to alert the observers about the results in other
        places and to warn them about new and unexpected developments.
        Moreover, the Space Telescope European Coordinating Facility, the
        ESA/ESO group that is responsible for the Hubble Space Telescope use
        by European astronomers and which is housed at the ESO Headquarters,
        will contribute with information regarding the observations with this
        major observational facility.
        With these important sources of information at its disposal, ESO is
        therefore in a prime position to inform about and comment on the
        latest developments at the shortest possible notice.
        6.2 Specific arrangements
        In practical terms, ESO's services to the media will be provided in
        several steps.
        The present Information Package marks the beginning of the "hot"
        phase, during which the final preparations for the observations are
        Beginning on July 10, ESO will issue short daily bulletins with the
        latest predictions and other news, related to these preparations of
        observations at La Silla and elsewhere in the world. They can be
        accessed via the ESO WWW Portal and they will be sent by fax to those
        who request this service (see the addresses below).
        The main event will be a Press Conference at the ESO Headquarters in
        Garching which will commence on Saturday 16 July, 1994, at 20:00
        (CEST). This will be just before the first impact is expected to
        happen and will provide an excellent opportunity to inform the media
        about the very latest developments.
        The conference will begin with an in-depth briefing, followed by voice
        contact to South Africa, from where we shall learn about the
        observations of the first impact, which will be well visible from
        there. The preparations at La Silla will be described by some of the
        observers there (image telephone), and we will hear from the Space
        Telescope Science Institute in Baltimore about the observations with
        that telescope.
        We expect that some of the media representatives will opt to pass the
        night at the ESO Headquarters and to follow the first observations at
        La Silla at distance (food and beverages will be provided).
        Unexpected and "spectacular" events, should they happen, will be
        announced and commented as quickly as possible. We will also contact
        the La Silla observers immediately after the end of their observations
        (in the early morning hours at Garching) and request live commentaries
        about the initial results. At the same time, the latest images will be
        transferred and made available.
        There will be Press Conferences each day at 11:00 (CEST) on 17 - 22
        July 1994, summarizing the previous night's results. Selected images
        obtained at ESO the night before will be available on these occasions.
        In Chile, ESO will publish a Spanish version of this Information
        Package as soon as possible. The same images that will be at disposal
        to the press in Europe will also be sent to Chile and made available
        there. There will be a major Press Conference at the ESO Office in
        Vitacura in the morning of July 17, 1994, with a presentation by ESO
        astronomers of the first results from the night before. It is expected
        that further Press Conferences will be held during the following days;
        these will be announced in due time.
        6.3 Contact addresses
        Media representatives, who are interested in participating in the
        Press Conference in Garching in the evening of July 16 and who would
        like to stay at ESO during the following night, must obtain a personal
        invitation by contacting Mrs. E.  V\"olk of the ESO Information
        Service (Tel.: +4989-32006276; Fax: +4989-3202362), before noon on
        Wednesday, July 13, 1994. Otherwise access to the ESO Headquarters
        cannot be guaranteed.
        Participation in the activities in Chile should be arranged by
        contacting the ESO Office in Santiago, Alonso de Cordova 3107,
        Vitacura (Tel.: 228-5006).
        6.4 Computer access to information from ESO
        The World-Wide Web is a high-level tool for accessing information and
        navigating between sites on the Internet.  It is publicly available,
        and has become very widely used in the last one or two years.  To
        access it, a "browser" is used.  Examples are Mosaic (which can be
        used on a computer system with good graphics capabilities) and Lynx
        (which allows for line-mode access).
        ESO's address on the World-Wide Web is: 
        Accessing this address gives access to various areas, one of which
        relates to ESO's activities in regard to the SL9/Jupiter event.  This
        information is kept constantly up to date, and will continue to be so
        during the entire period of the collision between comet and planet.
        Information from ESO will also be available on CompuServe (GO SPACE,
        and then access the Astronomy Forum).
        6.4. List of Available Images (July 5, 1994)
         - Recent picture of the fragments of comet Shoemaker-Levy 9, obtained
             with the Danish 1.5-metre telescope at La Silla (ESO Press Photo
         - Aerial view of the La Silla observatory (ESO Press Photo SL9J/94-02)
         - ESO special instrument TIMMI which will used to observe the SL9
             event (ESO Press Photo SL9J/94-03)
         - The Munich Fast Photometer (mounted at the Wendelstein observatory),
             another instrument  which will used to observe the SL9 event
             (ESO Press Photo SL9J/94-04)
         - The ST/ECF group at ESO (ESO Press Photo SL9J/94-05)