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 :ip-address "130.167.1.125"
 :ip-name "www.stsci.edu"
 :tcp-port 210
 :database-name "hst-aec-catalog"
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 :cost-unit :free 
 :maintainer "reppert@stsci.edu"
 :keyword-list (
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 :description "

               Archived Exposures Catalog README File
               ======================================

The Archived Exposures Catalog (AEC) is comprised of two separate lists:

         (1) Fixed Targets        (file: AEC.CATALOG) 
         (2) Solar System Targets (file: AEC_SS.CATALOG)  

Exposures are included here after they have been archived by the STScI 
Data Management Facility (DMF), and the current version of the AEC is
complete through April 21, 1993.  Please note that FGS observations are 
not included here; users interested in FGS data are requested to obtain the
desired information directly from STARCAT.  (STARCAT was described on page 20 
of the June 1991 issue of the STScI Newsletter; contact USB for further 
information.)

The AEC includes target name, position, scientific instrument configuration
and mode, spectral elements, exposure time, date of observation, program ID
number, DMF root name, and proprietary release date for the data.  The DMF
root name uniquely identifies the data for a given exposure and can be used
when requesting the data or when retrieving more detailed information about
the exposure from STARCAT.  The file AEC.CATALOG is sorted by target 
position, and the file AEC_SS.CATALOG is sorted by target name.  Each file
is 132 characters wide.  The format of these files was changed in January 1993
to include additional spectral element information.

The AEC contains several invalid entries.  These will be fixed in the DMF, 
and hence in this catalog, as soon as we are able to fix the sources of the
problems and rerun the HST data through the data-archiving procedures with new
DMF software.  The invalid catalog entries are identified with '???' in the
corresponding fields.  The problems include: 

     (1) Exposures with invalid coordinates (R.A. and/or declination).
     (2) Exposures with an invalid observation date.
     (3) Exposures with an invalid exposure time.
     (4) Exposures with no scientific instrument, mode, or spectral element.

Note also that some very short exposures with non-zero exposure time in fact
have exposure times much larger than indicated in the catalog.  Other exposures
have listed exposure time entries that are much larger than the actual exposure
times.  These problems have not been flagged with '???' (since they are
difficult to trace), but they will also be fixed when the other problems are
fixed. 

It is important to recognize that there is a wide variety of data qualities
represented among the exposures listed in the AEC.  There is no simple
mechanism for flagging failed observations, focus runs, calibration tests,
observations made with off-nominal mirror positions, or early instrument tests.
In fact, many exposures that have proprietary release dates that follow soon
after the date of observation are in fact 'failed' observations, 'bad' data, or
empty fields.  However, there are still many exposures that do not fit these
descriptions but simply have early release dates by policy; these data are of
good quality.  Hence, it is essential that the user exercise critical judgement
in assessing the value of different exposures, which will in fact require the
user to examine the relevant data for quality. 

The AEC files will be updated roughly every month.

K.Borne and T.Kimball
4/23/93

keywords:

	Hubble Space Telescope  
	HST 
	Space Telescope Science Institute

Server created with WAIS release 8 b5 on Apr 19 14:11:35 1993 by jackson@stsci.edu
The files of type dash used in the index were:
   observer/completed_observations/wais-AEC.CATALOG
   observer/completed_observations/wais-AEC_SS.CATALOG

"
 )
