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  TITLE OF RELEASE

  GOODS/ISAAC Survey Release

19 May 2004

  TECHNICAL SUMMARY

  CURRENT RELEASE
  Survey:              GOODS
  Telescope:           ESO/VLT
  Instrument:          ISAAC
  Program IDs:         LP168.A-0485; 64.O-0643; 66.A-0572; 68.A-0544
  Origin:              ESO/EIS
  Number of regions:   1
  Region:              CDF-South
  Number of Fields:    21
  Number of passbands: 2 (J, Ks)
  EIS Release Number:  18
  Version:             1.0
  Release Date:        May 2004
  Release prepared by: GOODS & EIS teams

  PRODUCTS
  Product Type:        Mosaic, Mosaic Tiles
  Number of Tiles:     44
  Number of Mosaics:   2
  Number of images:    46
  Number of catalogs:  0
  Number of XML files: 0

  PREVIOUS RELEASE
  Origin:              ESO/EIS
  Number of regions:   1
  Region:              CDF-South
  Number of Fields:    8
  Number of passbands: 3 (J,H, Ks)
  EIS Release Number:  14
  Version:             0.5
  Release Date:        9 April 2002

  PRODUCTS
  Product Type:        Stacked Images
  Number of images:    24
  Number of catalogs:  0
  Number of XML files: 0
  Total Volume:        0.2 Gb

  ABSTRACT

  As part of the Great Observatories Origins Deep Survey (GOODS),
  infrared imaging observations of the Chandra X-ray Observatory Deep
  Field South (CDF-S) are being carried out in J-, H- and Ks- bands, 
  using the ISAAC instrument mounted at the Antu Unit Telescope (UT1)
  of the VLT at the ESO Cerro Paranal Observatory, Chile.

  These data are being obtained as part of the ESO Large Programme:
  LP168.A-0485(A) (Principal Investigator: C. Cesarsky). Data 
  covering 4 ISAAC fields in J- and Ks- bands are also available 
  from the ESO programmes 64.O-0643, 66.A-0572 and 68.A-0544 with 
  E. Giallongo as the principal investigator.

  Since ISAAC observations are still ongoing, this release consists 
  of J and Ks images of fields that have already been completed and 
  are available in the ESO Science Archive Facility up to the end of 
  ESO observing period 72 (effectively 9 March 2004). This data 
  release includes 21 fully reduced VLT/ISAAC fields in J- and Ks- 
  passbands (but see notes on fields 25/25n and 26/26n in the 
  COMPARISON TO PREVIOUS/LATER RELEASE(S) section of this document), 
  covering 131 square arcminutes of the GOODS/CDF-S region, as well 
  as 2 mosaics in the J- and Ks- passbands.

  As part of the overhaul of the EIS web service, commenced during 
  2003, the transfer of survey products to the ESO Science Archive
  Facility and the EIS web publishing mechanism has been wholly 
  automated. Any errors that may have been introduced during this 
  procedure shall be addressed in due course, and in response to 
  notifications from the EIS user community.   
  
  As with all ESO public surveys, survey raw data become public 
  immediately to registered users of the ESO Science Archive Facility,
  while reduced data and survey products are made available as soon as
  processed via the EIS survey system.


  CONTENTS OF THIS RELEASE

  This release is the second associated with the GOODS survey. It
  revises and significantly extends the previous (first) release
  (version 0.5) of 9 April 2002. The first release consisted of 8
  fields in J, H and Ks.

  The present release includes astrometrically calibrated, 
  photometrically calibrated and appropriately re-scaled 
  individual tiles (see STANDARD EIS DEFINITIONS, CONVENTIONS AND 
  DATA FORMATS section of this document) which, when co-adjoined, 
  form 2 large-scale mosaics, corresponding to 21 (13 new) 
  fields in J-band and 23 (15 new) fields in Ks-band.

  This release also contains the resultant 2 large-scale (J-band 
  and Ks-band) mosaics, with accurate astrometric solutions and 
  uniform photometric zero points (see DATA REDUCTION section of this
  document) formed by co-adjoining individual tiles in the same 
  passband.
 
  Thus, a total of 46 image products form the core of the this 
  release. In compliance with EIS standards (defined in the 
  STANDARD EIS DEFINITIONS, CONVENTIONS AND DATA FORMATS section 
  of this document) image products are available in FITS format. 
  Files have EIS-based, time-stamped names. Each FITS file 
  consists of 2 extensions: the first extension contains the 
  science-grade image; the second extension contains the 
  corresponding weight map, defined as a variance map (e.g. it 
  should be used with SExtractor using the parameters: 
  -WEIGHT_IMAGE weight_map.fits -WEIGHT_TYPE MAP_WEIGHT).

  Field names can be found in the OBJECT keyword of the FITS 
  header. For convenience, the GOODS team provides a translation 
  protocol to associate standard EIS products to each GOODS field.

  The World Coordinate System (WCS) information and accuracy of 
  the individual tiles is preserved in the mosaics. A uniform 
  zero point of 26.0 can be used (e.g. with SExtractor) across 
  the entire field. However, it is important to note that the 
  PSF varies from tile to tile within each mosaic. In the absence 
  of proper aperture corrections or PSF-matching procedures, this 
  would impact efforts to create multi-colour catalogs. These 
  mosaics have slightly different dimensions, however they can 
  be readily registered using the intrinsic WCS information. 
  More specific information can be found in supporting 
  documentation provided by the GOODS team:

http://www.eso.org/science/goods/releases/20040430/

  RETRIEVING EIS PRODUCTS: GENERAL
  
  Official EIS products can be retrieved via two alternate routes,
  both originating at the EIS home page:

  http://www.eso.org/science/eis/eis_home.html

  This page indexes all EIS surveys, listing some of their most 
  important characteristics and presents a navigation 
  menu, spanning the width of the browser window.
   
  From the indexed list of surveys at the EIS home page, the survey 
  of interest can be selected via a hypertext link embedded in  
  the survey name. This action accesses a more detailed description 
  of the survey, including information about differing strategies (if 
  applicable). Within this page, another horizontal navigation menu 
  can be found. Selecting the RELEASE link of this 
  menu connects to a reverse chronological index table of official 
  EIS data releases for the pre-selected survey. This table lists 
  the following entries (whenever available): (1) The (hyperlinked) 
  integer index number of the release; (2) a 
  composite of the release version (first 2 values separated by a
  point; see STANDARD EIS DEFINITIONS, CONVENTIONS AND DATA FORMATS
  below), appended where appropriate with the release revision 
  number (an integer value) trailing a second point; (3) the date 
  the products entered the ESO Science Archive Facility 
  repositories (effectively the date of public release); (4) the 
  total volume (in Gigabytes) of the complete release package;
  (5) an indication that the release products include catalogs; 
  (6) an indication that the release products include images;
  (7) an indication that the release products include a list of 
  astronomical targets classified to be of potential scientific 
  interest (e.g. clusters of galaxies, QSO candidates, brown dwarf  
  candidates, etc.) if applicable, drawn from the release survey 
  products (to be implemented); (8) a hyperlink to the content of the
  .README file which documents the selected release in detail. 
  Selecting the hyperlinked index number in column (1) presents the 
  final element of the data release infrastructure: a full list of 
  products available in the selected release from which all products,
  or individual products can be selected interactively (see 
  below for more details).

  Alternatively, from the navigation menu, spanning the width of the 
  browser window, selecting the SURVEY RELEASE link connects to a 
  reverse chronological index table of official EIS data releases for
  the pre-selected survey. This table while similar, is not identical
  to that described above, and lists the following entries (whenever 
  available): (1) The (hyperlinked) integer index of the release 
  (i.e. "EIS release number"); (2) a description of the product type 
  (e.g. data, software); (3) a description of the products (e.g. 
  survey name, software name) (4) a composite of the release version 
  (first 2 values separated by a point; see STANDARD EIS DEFINITIONS,
  CONVENTIONS AND DATA FORMATS below), appended where appropriate 
  with the release revision number (an integer value) trailing a 
  second point; (5) the date the products entered the ESO Science 
  Archive Facility repositories (effectively the date of public 
  release); (6) the total volume (in Gigabytes) of the complete 
  release package; (7) a hyperlink to the content of the .README file
  which documents the selected release in detail. As before, 
  selecting the hyperlinked index number in column (1) presents the 
  final element of the data release infrastructure: list of products 
  available in the selected release from which, where implemented, 
  all products, or individual products can be selected interactively.

  The data release infrastructure has been designed to generate 
  a hierarchical sequence of HTML pages to support the differing 
  strategies for a given survey --- and for a given strategy, the 
  range of survey products that may become available, such as 
  images/catalogs (reduced, stacked, mosaic, single passband, colour)
  and other nightly products (e.g. zero points) as well as advanced 
  survey products such as target lists (as will be exemplified in 
  future releases). The list of products available per release is 
  presented in tabular format in the final element of the data 
  release infrastructure, the first section of which consists of 
  "data release information" (which enables access to general 
  information such as the .README file documenting the selected 
  release in detail; confirms details such as the product 
  description, version, data volume; and reports total numbers of 
  files and fields forming the release). 


  RETRIEVING EIS PRODUCTS: THIS RELEASE

  In the case of the present release (involving image mosaics and the
  component image tiles) the "data release information section" is 
  followed by a section detailing the "contents" of the release, 
  listing: (1) a sequential index number (not to be confused with the
  "Product Identification number" which is reported elsewhere); (2) 
  the EIS standard field/region name with an associated hyperlink to 
  a single .JPEG format file showing up to three images of the 
  region/field for purposes of illustration and ratification. These 
  images are ordered by increasing central wavelength of the passband.
  Where images in more than one passband are available, they are 
  accompanied by a final "RGB" colour composite image (in which "R" 
  is assigned to Ks-band, "G" is assigned to J-band and "B" is also 
  assigned to J-band). The .JPEG format enables image properties such
  as saturation and intensity to be interactively modified as desired
  using color editors (e.g. within the "xv" UNIX/Linux utility). (3) 
  the relevant passband; (4, 5) the R.A. and Dec. position; (6) the 
  total integration time (in seconds) contributing to the final 
  product; (7) the total number of science exposures contributing to 
  the final product; (8) a grade (A to D) assigned as an indication 
  of cosmetic quality, during visual inspection of the product by the
  EIS team; (9) the total volume (in Megabytes) of the selected 
  product; (10) a hyperlink to to a comprehensive descriptive log of 
  the product. (Product logs are planned for phased introduction over
  a series of forthcoming releases). (11) an interactive check-box 
  which enables the individual product to be selected/de-selected 
  before finally submitting the selection to the ESO Science Archive 
  Facility using "Request Marked Products" at the foot of the page.


  COMMENTS SPECIFIC TO THIS RELEASE

  In the case of the interface between the GOODS and EIS teams, 
  inconsistencies are present between adopted usages which while 
  inconvenient, are unavoidable. The following discussion emphasizes 
  specific cases and explains their origin.

  Ideally, the convention that would normally be adopted by EIS is 
  to name a field when the survey is first defined, using the survey 
  name and/or region as the root, followed by a numerical suffix 
  generated by the particular algorithm used in the construction of 
  the "Observation Block" (OB) and the associated survey strategy (as
  defined by a set of pointings, instrument and passband).  In this
  way, all possible identifiers of a field utilized by the EIS system
  both internally and externally (e.g. OB name, object name, target
  name, field name) and their graphical representations on the EIS 
  web pages form a homogeneous set.

  Historically however, the conventions have evolved in time due 
  to several factors:

  * At their outset, prior to the introduction of a systematic 
    global approach, several surveys were defined case-by-case 
    and in isolation. 

  * Over time, some pre-existing and on-going surveys had their 
    geometries changed; methods for addressing positions were 
    reviewed; surveys were extended, amalgamated or otherwise 
    re-defined by altered algorithms --- with the consequent 
    revision of the framework(s) within which the survey(s) were 
    being managed. 
 
  * In the absence of pre-determined standards, collaborative 
    surveys co-administered by independent groups exhibit differing
    notations. The interface to a 
    common scheme (when this requirement is inevitably identified)
    becomes particularly difficult.
                 
  Hence, in practice, the desired ideal case is not always attainable
  and requires some retroactive adaptations. The following noteworthy 
  discrepancies between the nomenclature adopted by the GOODS and 
  EIS teams in referring to ISAAC pointings within the CDF-S occur: 

  1) The convention adopted by EIS is to assign fields and/or regions
     consecutive numbers at the time of survey strategy definition 
     using an automatic procedure. Currently, EIS assigns regions 
     and/or fields at survey definition according to sequentially
     increasing R.A. and Dec. positions of the defined pointings. 
     However, this was not always the case. There exist surveys for 
     which addressing information was assigned in isolation
     at the survey outset and which were also assigned a sequential 
     value to be incorporated into, and referenced by the EIS system
     at a later date. For these surveys, while the multiple 
     nomenclatures persist simultaneously, sequentially numbered 
     fields and/or regions referred to in EIS indices do not 
     correspond to numerical values which may appear in region 
     and/or field names assigned prior to introduction of the EIS 
     system. Hence in the GOODS survey, for example, the field 
     indexed by the EIS system (including the web service) as "1" 
     does not necessarily correspond to the field name originally 
     defined to be "F01" in the GOODS survey. For example:

     http://www.eso.org/science/eis/surveys/strategy_GOODS_infrared_deep.html)
                     
  2) The current EIS terminology prefaces field numbers with root 
     names derived from the applicable survey name (in this case 
     "GOODS_") whereas the same field numbers are prefaced "F" 
     by the GOODS team. 
                     
  3) Sequential TILEID numbers (defined in the STANDARD EIS 
     DEFINITIONS, CONVENTIONS AND DATA FORMATS section of this 
     document) appearing in the FITS header of an EIS product are 
     automatically assigned by the EIS system when binding mosaic 
     images and their contributing tiles into a set of related products 
     for a given release. The binding depends on the geometry and 
     completeness of the contributing reduced data. Therefore TILEID
     numbers do not necessarily correspond to other indices such as 
     the "F" field identifiers used by the GOODS team, or the "GOODS_" 
     field identifiers employed by EIS algorithms.

  Due to the mosaic nature of the products, the form of the products
  in the current release departs somewhat from the established EIS 
  form and introduces a number of keywords to the FITS headers to
  accommodate mosaic information. The most notable features are:
   
  * The products in the current release consist of mosaics 
    and their individual contributing tiles. The reported 
    zero point values for all of the released products are 
    re-scaled to a common mosaic value of 26.0 magnitudes.
    This is in contrast with other EIS releases for which 
    zero points are derived and reported for each product 
    individually. The relevant FITS keywords introduced 
    to accommodate this are defined in the STANDARD EIS 
    DEFINITIONS, CONVENTIONS AND DATA FORMATS section of this 
    document.

  * In contrast to the Vega magnitude system normally used by 
    default in EIS products, the current data release is 
    calibrated in the AB magnitude system. 

  * For the large-scale (J-band and Ks-band) mosaic images,
    the integration time reported is the sum of integration
    times of the individual tiles contributing to the mosaic
    products. 


  COMPARISON TO PREVIOUS RELEASE(S)

  Note that the present release includes new reductions of the J- and
  Ks- fields released earlier. The main areas of improvements were:

  1) Techniques to remove cross-talk effects;
  2) Methods of building reduction blocks, i.e. sub-groups of frames 
     with homogeneous data quality which are stacked together.
  3) Uniform photometric calibration across the entire surveyed area.
  4) Improved accuracy of the astrometric solution, now fixed on the 
     World Coordinate System defined by the HST/ACS GOODS 
     observations.

  Detailed comparisons between the previous and new data sets will be
  presented elsewhere. At the moment it suffices to say that the new
  reductions supercede those of of the previous release (version 0.5)
  of 9 April 2002.

  For J- and Ks- band data, the present release supercedes the
  GOODS/EIS data release 0.5 performed on 9 April 2002 for the
  following fields: GOODS_09, GOODS_10, GOODS_11, GOODS_14, GOODS_15,
  GOODS_16 GOODS_20 and GOODS_21.

  In addition, this release introduces reduced J- and Ks- band data
  for the following 13 fields: GOODS_03, GOODS_04, GOODS_05, 
  GOODS_08, GOODS_13, GOODS_19, GOODS_22, GOODS_23, GOODS_24, 
  GOODS_25n, GOODS_26n, GOODS_30 and GOODS_31; and the fields 
  GOODS_25, GOODS_26 in Ks.

  Note the suffix "n" (new) for the fields GOODS_25n and GOODS_26n 
  is due to a re-arrangement of the ISAAC mosaic in the initial 
  stages of the survey to ensure maximum coverage of the GOODS/CDF-S 
  area within the observing time allocation (for ESO programme
  168.A-0485(A)). Reduced observations at the original field 
  positions (as part of ESO programme 168.A-0485(E)) are also 
  included in this release (Ks-band only in fields named GOODS_25 
  and GOODS_26). Thus the Ks-band data includes files associated 
  with both positions 25 and 25n, and both positions 26 and 26n. 
  The J-band data includes files associated with only positions 
  25n and 26n (i.e. files associated with positions 25 and 26 are 
  not included with the J-band data).

  In contrast to previous releases (in which the Vega magnitude 
  system is adopted), it should be emphasized that the current 
  release adopts AB magnitude system. Furthermore, the release of 
  re-scaled mosaics and component tiles, as in this release, may 
  not always be practicable (depending on the instrument used), 
  shall not be common EIS procedure. Together, these features 
  represent significant departures from the standard EIS procedure 
  being established (see the STANDARD EIS DEFINITIONS, CONVENTIONS 
  AND DATA FORMATS section of this document).


  DATA REDUCTION

  The ISAAC data were reduced using the EIS/MVM image processing
  library. This software package is publicly available and can be
  retrieved from the URL:

  http://www.eso.org/science/eis/survey_release.html
 
  Each field is the co-addition of a number of sky-subtracted frames
  (the TOT_IMAG keyword in FITS image header) grouped in a number of
  Reduction Blocks (RB). Images are registered using an accurate
  astrometric catalog extracted from a deep ESO Wide Field Imager (WFI)
  R-band image of the CDF-S and then warped onto a grid pre-defined 
  to be a convention common for all GOODS program data products. Thus 
  the native pixel scale of ISAAC is re-sampled to 0.15 arcseconds in
  the reduced products.

  ASTROMETRY

  The astrometric calibration was derived using a reference catalog
  generated from a deep ESO Wide Field Imager (WFI) R-band image 
  which was itself astrometrically calibrated using the GSC2.3 
  reference catalog. The astrometry has been compared by the GOODS 
  team with calibrated data from the Hubble Space Telescope (HST) 
  Advanced Camera for Surveys (ACS). These comparisons yield rms 
  scatter in astrometry of 0.1 arcseconds across the entire area. 
  All images have a pixel scale of 0.15 arcseconds, which is exactly 
  a factor of 5 larger than the pixel in the GOODS/ACS images.

  The WCS in the image header is reported using the CD-matrix
  notation. The projection adopted is TAN and the orientation is 
  north up and east to the left.

  PHOTOMETRY

  The photometric calibration of the present data was performed by 
  the GOODS team using a mosaic assembled from SOFI images of the 
  EIS-DEEP and DPS infrared surveys conducted over the same region. 
  The SOFI images (5 x 5 arcminutes) encompass a number of tiles 
  within the ISAAC mosaic (2.5 x 2.5 arcminutes each), yielding a 
  more robust relative calibration across the entire surveyed area.
  A zero point for each ISAAC field was determined from the SOFI 
  images using a sample of circa 50 stars identified in HST/ACS 
  images. All ISAAC and SOFI images were first PSF-matched to the 
  common value of 0.9 arcseconds (worst seeing in SOFI images), then 
  aperture magnitudes of these stars were used to determine a 
  zero point for each individual image in the AB system. This 
  procedure yielded zero points with typical rms scatters of 0.03 
  magnitudes in J-band and 0.05 magnitudes in Ks-band. However, note 
  that to provide a homogeneous photometric zero point across the 
  entire GOODS mosaic, all images have been re-scaled to the same 
  zero point of 26.0 in the AB system. Corresponding keywords (see 
  the STANDARD EIS DEFINITIONS, CONVENTIONS AND DATA FORMATS section 
  of this document for definitions) in the FITS headers have been set 
  accordingly, ZPMOSAIC = 26.0, ZPMOSSYS = 'AB' while ZPMOSERR has 
  been set to the aforementioned rms values for J- and Ks- bands.  
  The integration times are also normalized to unity, EXPTIME = 1, 
  so that AB magnitudes in all released images, including the 
  mosaics, can be obtained as: mag(AB) = -2.5*log10(flux) + ZPMOSAIC.

  To determine systematic errors in this calibration procedure,
  independent/crossed photometric calibrations are needed on the SOFI
  and ISAAC data. The SOFI zero points were found to be consistent
  (within a few percent) with 2MASS photometry of a limited number of
  stars in the field. The evaluation of zero points from observations
  of photometric standard stars (available in the ESO Science Archive
  Facility) is planned for future releases.

  There remains a suggestion that a zero point offset of up to 0.1
  magnitudes might be present in one field only (see the REMARKS ON
  INDIVIDUAL PRODUCT(S) section of this document).


  DATA QUALITY ASSESSMENT

  Before being released images are examined by eye and graded by the
  EIS team, with the grade range being from A (best) to D
  (worst). This grade refers only to the visual aspect of the data
  (e.g. background, cosmetics). For this release, there are 40 grade 
  A images and 6 grade B images. The latter are all in Ks-passband
  and typically reflect the presence of somewhat enhanced background
  features.
 
  The widespread reporting of graded
  data shall undergo a phased introduction over a series of
  forthcoming product releases. Eventually, the grade will also
  include a larger set of quality control parameters (QCP) and will 
  be available for each survey product via corresponding product
  logs. The distribution of grades will also become available through
  the EIS WEB service (via STATISTICS accessible from the release
  page).


  REMARKS ON INDIVIDUAL PRODUCT(S)

  GOODS_16 - A comparison with an independent reduction and
  calibration performed on EIS/SOFI data by the K20 collaboration
  (Cimatti et al. 2002) in a limited area suggests that the zero point
  in field GOODS_16 might have an offset of up to 0.1 magnitudes in
  the Ks-band (the zero point in this release being fainter). We
  encourage the community to communicate to the GOODS/EIS team any
  relevant information on this topic.


  NEXT RELEASE(S)

  Anticipated future EIS/GOODS releases include: the reduced H-band
  data; the remaining 9 ISAAC/GOODS fields (GOODS_01, GOODS_02,
  GOODS_06, GOODS_12, GOODS_17, GOODS_18, GOODS_28, GOODS_29,
  GOODS_32); Zero points evaluated from observations of photometric
  standard stars and source catalogs and the phased introduction of
  comprehensive product logs.


  STANDARD EIS DEFINITIONS, CONVENTIONS AND DATA FORMATS
  
  The EIS survey system is designed to administer and document (via
  integration with a robotically maintained web service) multiple
  surveys and strategies in their entirety, from survey definition to
  release of science-grade products by nominally operating in
  unsupervised mode. Achieving this requires the introduction of 
  well-defined procedures to enable adaptive, automatic and 
  sequential addressing of information. These procedures may 
  occasionally lead to conventions (e.g. field/region
  names) which may not always be intuitive, but are driven by the
  specific process involved. The most relevant conventions are 
  defined below:
    
  REDUCED IMAGE: A "reduced image" is the "nightly" product of a 
                 reduction process of a so-called "Reduction Block" (RB).
                 By definition a RB is a group of raw images obtained
                 in the same night which share the same position, 
                 passband and form a sequence in time. The content of 
                 a RB is usually
                 identical to an executed "Observation Block" 
                 (OB) as used in the ESO Data Flow System (DFS). 
                 However, the system also allows RBs to be formed
                 by concatenation of similar sequentially 
                 executed OBs. In addition individual exposures 
                 can be discarded based on configurable 
                 constraints on their properties (e.g. background
                 counts, DIMM seeing values, integration time, 
                 etc.)   

  STACKED IMAGE: A "stacked image" is the product of an advanced
                 process in which "reduced images" sharing the 
                 same instrument, passband and position on the 
                 sky are grouped into so-called "Stack Blocks" 
                 (SB). In the assembly of SBs, individual 
                 "reduced images" can be discarded according to 
                 configurable constraints on their properties
                 (e.g. measured seeing, amplitude of PSF 
                 distortion, visual grade, OB completeness). The 
                 images of the thus assembled SB are re-scaled
                 and accumulated in a weighted co-addition 
                 procedure to generate a single final output 
                 product.

  MOSAIC IMAGE:  A "mosaic image" (or simply "mosaic") is an
                 image formed from several contiguous (reduced 
                 or stacked) "images" produced by the EIS 
                 survey system, which have been subsequently
                 re-scaled to share a common zero point and 
                 co-adjoined as "tiles" to form a single, 
                 large-scale product.

  MOSAIC TILE:   A "mosaic tile" (or simply "tile") is an image 
                 (reduced or stacked) produced by the EIS survey 
                 system which has been subsequently re-scaled 
                 such that it shares a zero point common to other
                 tiles and a large-scale "mosaic image" (or 
                 simply "mosaic") of which it forms a component. 

  VERSION:       The EIS concept of a release "version" 
                 represents a wholesale, global change: either 
                 introducing a new set of products, affecting or 
                 superceding the quality or properties of more 
                 than 5 per cent of previously release products.
   
  REVISION:      The EIS concept of a release "revision" 
                 represents localized changes which may affect 
                 individual products with a released data set, 
                 while leaving others unaffected. Individual 
                 products found to be anomalous may be removed 
                 or replaced. New products may be added. The 
                 total revisions must not alter more than 5 per 
                 cent of a pre-existing set of products. 

  ZPMOSAIC:      FITS header keyword ZPMOSAIC contains the value of 
                 the zero point (magnitudes) applied to the 
                 processed tiles in order to refer instrumental 
                 magnitudes to the common photometric system of the 
                 mosaic, MOSAICID. The value for ZPMOSAIC is 
                 determined by a re-scaling process in which 
                 individual reduced images are harmonized to become 
                 tiles sharing a common zero point for the entire 
                 mosaic.
  
  ZPMOSERR:      FITS header keyword ZPMOSERR contains the value of 
                 the uncertainty (magnitudes) associated with the 
                 determination of ZPMOSAIC. 

  ZPMOSSYS:      FITS header keyword ZPMOSSYS contains the 
                 photometric system in which ZPMOSAIC and
                 ZPMOSERR are expressed.   

  MOSAICID:      FITS header keyword MOSAICID contains the
                 the unique identity of the mosaic to 
                 which an individual tile belongs to.
  
  MOSTILES:      FITS header keyword MOSTILES contains the 
                 total number of individual tiles contributing to 
                 the larger mosaic, MOSAICID.

  TILEID  :      FITS header keyword TILEID contains the unique 
                 identity of the individual tile 
                 within the larger mosaic, MOSAICID. TILEID does not 
                 necessarily map directly to any other FITS keyword 
                 value (e.g. OBJECT).

  REFERENCES

  Cimatti, A., Daddi, E., Pozzetti, L. et al. 2002, 
  Astronomy and Astrophysics, 392, 395

  Vandame et al. 2004, in preparation.

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eis data account 2004-05-19