On this page, we list the main changes that affected the instrument and its current status.

  • 04/09/2015: The AG slide of XSHOOTER (doing the move between the slot, pinhole, acquisition mirror, IFU) will have to be repaired.  An intervention is foreseen in the coming months with about a week of unavailability of the instrument.
  • An article was recently published about the spectro-astrometry technique performed with XSHOOTER. It shows the limits of the instrument and pipeline on this kind of observations. The article is available here: Whelan et al., 2015, 579, A48.
  • 19/08/2015: The user manual for P97 phase 1 is now available. A document about the historical wavelength shift between arms has been released. It presents the problems in data, their origin, and the corrective actions that were performed. It is available with the manuals and other reports in the manuals page.
  • As announced, 2 new mapping templates (slit and ifu modes) are offered in P96 and described in the user manual P96 v2. In addition in this version we recall the offsets convention used at Paranal and we give advices in the use of the imaging mode to decrease the thermal background of the AGCCD.
  • In April 2015, a new pipeline version will be released. It corrects some bugs in the wavelength calibration due to non optimal correction of the flexures leading to offsets of a few km/s. In addition the problem of the non correct centring during the acquisition implied that the object was not observed perfectly in the center of the slits. There are small residuals in the radial velocity depending on the position in the slit (which still need to be fully characterized but they appear much smaller than the offsets that was due to the pipeline issue).
  • In P96, there is a new ETC taking into account the proper image quality making the difference with the seeing.
  • In P96, 2 new mapping templates should become available (follow this news page for their release). They will allow to perform proper mapping observations and data reduction than with the Generic-offset templates.
  • During 2015, a study about the repair of the ADCs is started. If successful, the repaired ADCs could be made available in 2016.
  • Due to a software issue, the target centering was inaccurate in the y direction by 0.25" for g_prime and U band filter acquisitions between Dec 2013 and 2 Sep 2014.  The centring was possibly not optimum at some point between 2008 and 2013 for all filters with a shift of 0.17".
  • In Period 94 X-shooter is offered again on UT2. For this reason the instrument will be dismounted from the Cassegrain focus of UT3  early September 2014. The last night of operation on UT3 will take place on September 1. The re-commissiong of the instrument on UT2 is scheduled on October 13 to 15. X-shooter will be operational in service mode starting on October 16.
  • Recently some tests were performed of a potential new instrument mode for X-shooter. This is the diaphragm mode that allows to observe very bright objects by diaphragming the entrance of the instrument. A small report is available here and some reduced data obtained during the technical night are available there. The observed stars are Achernar, HD196171, alpha Centauri, Antares, eps Scorpii, eta Scorpii, Fomalhaut.
  • Since an upgrade of the VLT SW in January, 2014, the quality of the images taken during the spectroscopic acquisition is suboptimal and are noiser than they should. The engineers are investigating the causes of this problem to provide a SW patch asap. Note that the imaging mode is not affected at all by this problem and all obtained images with this mode are of optimal quality. 
  • XSHOOTER is now installed at UT3 (recommissioned on Oct. 10-12). It appears that the efficiency of the full system (telescope + instrument) is better by 5 to 10% in average in all arms.

  • In P93, the light imaging mode of XSHOOTER performed with the 4th channel (AG camera) will be offered. The user manual of P93 phase 1 already gives some clues but a more detailed documentdedicated to this imaging mode will be published as soon as this mode is fully characterized.
  • XSHOOTER will probably undergo an intervention lasting 6 months in Period 94 or 95, during which the instrument will not be available for operations. The aim of the intervention is to fix the ADC systems. Therefore no large programs are accepted in P93 on this instrument.
  • In P92, XSHOOTER will be moved from the UT2 to the UT3 Cassegrain focus.
  • The XSHOOTER pipeline version 2.2.0 has been released and its REFLEX 2.4 support as well. You may want to find it here.
  • In P91, the policy regarding the telluric standard stars observations will be modified. For the details, please have a look at the user manual.
  • IMPORTANT: ADCs problems Please have a look at the new version of the user manual P90/P91 with section 2.2.2 providing relevant updates about the observations with disabled ADCs. The user manual is available here . During the past few months the ADCs (atmospheric dispersion correctors) for the UVB and VIS arms in XSHOOTER have been occasionally failing. Unfortunately recently the rate of such failures has increased. There is an ongoing investigation to find the cause for this misbehaviour, but it is unlikely that the situation is back to normal for the next few months. A major intervention on XSHOOTER to fix this problem is under evaluation. Incorrect position of ADCs might lead to slit losses worse than if they are not used. Consequently, the ADCs were temporarily disabled, starting on August 1st, 2012.

    The plots below show the effects of the atmospheric dispersion (shift in arcsec) as a function of airmass for each arm.
    For the UVB arm with the ADCs disabled UVB arm AD
    For the VIS arm with the ADCs disabled VIS arm AD
    For the NIR arm that has no ADCs NIR arm AD

    Hence, to minimize the slit loss due to atmospheric dispersion we advise you to prepare your observing strategy as follows:
    1) Put the slit at parallactic angle (default value 9999), if possible.
    2) Observe the target close to the meridian.
    The mimimum airmass of your target will of course depend on its declination. As a reference a plot of the airmass vs. target declination corresponding to observing +/-2h from the meridian is shown on the VIMOS Phase 2 web page: VIMOS visibilities

    Soon a revised version of the user manual will be posted with more details about the consequences of the observations without ADCs and the characterization of such observing mode. You may want to find it at user manual
  • The XSHOOTER pipeline version 1.4.5 has been released and its first REFLEX support as well. You may want to find it here.
  • Some updates of the user manual were performed regarding the phase 2 for P89, please check it.In addition a new document describing the NIR readout mode, its regimes and their impacts is available here. Please read it too as it may affect the data quality. And please prepare with the new XSHOOTER ETC v3.2.13 your OBs, specially regarding the NIR DITs and NIR slits.
  • In July 2011 during the intervention the NIR slits wheel was replaced by a new one with 2 new slits of 0.6" and 0.9" with the K-band bloking filter allowing observations not dominated anymore by the thermal background in J and H bands (background reduced by factors 3 to 4) but by the sky. However, the measurements show that the readout noise is the new limiting factor for these 2 slits. However, the 1.5" slit was removed.In addition the TCCD performances were improved allowing a reduced pick-up noise and giving snapshot images of a better quality than before.
  • New templates are available for P88, 1 about the spectrophotometric observations in nodding mode, 2 other for doing additional AFC during an OB.
  • Recently an oscillation of the dichroic absorption band in the UVB and VIS arms was reported. The last UVB arm order and the first 4 orders of the VIS arm suffer of this oscillation. However, the NIR arm remains not affected. More information in the Known Problems webpage, (see here)
  • The stability of the spectrographs in radial velocity iscurrently investigated with calibration data. In addition, for testingXSHOOTER possibilities, a RV standardstar HIP34785, a star with an exoplanet HD73256, and a stellar binarysystem HIP34110 were observed on March 24 and March 26, 2011. Newquality control plots will be available and as soon as we getstatistical information a report will be published in XSHOOTERwebpages.
  • In July 2011 an intervention will take place leading to replace the 1.5" slit of the NIR arm by another slit with a K-band bloking filter.Thus the 1.5" slit will not be available anymore. Once commissionned and properly characterized the 2 new slits of 0.6" and 0.9" with the K-band bloking filter will be offered.
  • Last October 2010, the patterns problem in the VIS arm has been fixed for both readout modes. The readout noise stays the same (see VIS Health Check plots ).
  • There is a meeting devoted to the 1st year of XSHOOTER science (October 19-22, 2010). For all details, see the website.
  • XSHOOTER pipeline, current version 1.2.2 find it here.First public release of XSHOOTER pipeline, v1.0.0 (May 2010):
    DISCLAIMER: The current version has been tested by a limited number of users at ESO and in the user community, hence, we cannot exclude that some bugs are still present. Please signal them to the instrument scientist, the pipeline responsible (find them here) and to xshooterATeso.org. The use/validity of the pipeline produced 1D merged spectra for scientific analysis depends very much on each scientific application and its requirements. The final assessment can be made by the user only.
  • The ESO Archive Group has prepared the XSHOOTER instrument specific query form (Feb 2010). Request here XSHOOTER public data.
  • New SM operation requirements/constraints might be implemented with a new period. Please always check the User Manual and/or the instrument specific phase 2 requirements or phase 2 news. Please note that changes have been implemented already for P85.


  • On Nov 2008 and Jan 2009 the UVB and VIS arms have been commissioned at the UT3 Cassegrain focus (see, e.g., Messenger 134, 12 ). Data taken during the commissioning runs have shown that the instrument efficiency matches the predictions and the instrument physical model.
  • The NIR arm has been commissioned on March 2009.
  • XSHOOTER commissioning data (Nov 2008, Jan 2009, Mar 2009 and May 2009) are public. Click here to retrieve them.
  • Paranalization data (May 29 to Jun 1 2009) are public. Click here to retrieve them.
  • XSHOOTER science verification (SV) data (Aug and Sep 2009) are public. All the data (including mistakenly hidden SV1 Flux standard calibrations) can be found here.

News about Science Data Product Forum

We would like to draw your attention about the existence of the Science Data Products internet forum which can be found at: http://www.eso.org/sci/data-processing/forum.html