What is the ESO/ST-ECF DSS application?

The ESO/ST-ECF Digitized Sky Survey [DSS] application is a client program that extracts random sky section from the DSS image server installed at ESO. The extracted images are delivered in standard FITS format and contain all header keywords needed to visualize proper celestial coordinates for any pixel position.

At IRA the client is available on Linux Computer

Two scripts are available to access dss fields: "dss1" and "dss2".

DSS1

If used without argument dss1 will be interactive and will enter a loop; displaying a prompt in the following form:

Enter data for first field:

There are two possible set of responses here:

  • <image-name>  <ra> <dec> <X-size> <Y-size>  (e.g.,  mystar 1 2 3.4 +5 6 7.8 10 10 will produce a FITS image 10x10 arcminutes and centered on ra=1h 2m 3.4 sec and dec=+5deg 6min 7.8sec).
  • [<object name>] <image-name> <X-size> <Y-size> (e.g., [m 33] m33 10 10 will produce a 10x10 arcmin FITS image centered on the SIMBAD position of  Messier 33.

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    The other option is to use the batch mode:  In this case the list of pointings to be retrieved have to be recorded in a file following the syntax above. For example:

    f001  1 2 3 4 5 6 7 10 10
    f002  8 9 10 -11 12 13.4   7 8
    f003  15 16 17.18 -19 20 21.22 20 20
    etc...

    Assuming the file is called dss1.in, the dss1 application has therefore to be called in the following way:

    $ dss1 -i dss1.in

    After execution, the following files will be available in the current working directory:

    f00106z6.fits   f0020446.fits   f00301c9.fits
     

    DSS2

    The new dss2 scripts has only to take one extra parameter: the color. At the moment, only two are possible: 'red' or 'blue'.

    The syntax is otherwise absolutely identical. The batch mode also works, provided 'red' or 'blue' has been provided as a first parameter to the dss2 command. For example:

    $ dss2 blue -i /tmp/dss2.in
     

    The service is also available through a Web interface. This is best suited for small amount of fields. The purpose of this client application is to enable the creation of batch jobs to retrieve at once large number of fields, or to be integrated into other application software, scripts or automated observing tools and telescopes.

    The application is based on the original software developed at the Space Telescope Science Institute to retrieve any random part of either:
     
     

    The First Digitized Sky Survey DSS-1 25 micron scans  On-line on magnetic disks 100% complete
    The Second Digitized Sky Survey DSS-2 red 15 micron scans On-line on 63 DVDs in a juke box 95% complete
    The Second Digitized Sky Survey DSS-2 blue 15 micron scans On-line on 17 DVDs in a juke box 25% complete

    The ESO/ST-ECF Archive has developed the DSS program further to
     

  • make it work as network client and
  • to include SIMBAD name resolving as an alternative to coordinate-only retrieval.

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    The DSS application essentially takes coordinates and field of view specifications interactively or from an input  file and creates a FITS file that can be viewed, converted or analysed with any astronomical data analysis package.

    The ESO/ST-ECF DSS program (version 2.5) is currently supported on Solaris 2.5 & 2.6, SunOS 4.1.4, HP-UX 10.20 and also now on Linux (x86 CPUs).

    What is the Digitized Sky Survey?

    DSS-1


    The Digitized Sky Survey is a collection of Schmidt plates covering the entire sky. The plates are dated from various epochs within the past 30 years. Those have been scanned electronically and the data has been lossily compressed and made available on CD-ROMs. There are two groups of CDs available (102 CD-ROMs, compression 10x; 10 CD-ROMs compression 100x) from the Guide Star Survey group at the Space Telescope Science Institute. See below for more technical details regarding the production and scanning of the material.

    DSS-2

    In the framework of the preparation of the second version of the Guide Star Catalogue, a lot more plates have been scanned, providing multicolor, full sky coverage at a higher resolution with plates. This data collection is now slowly becoming available at a few selected sites. At the time of this writing, 98% of the red plates and 25% of the blue plates are available at the ESO/ST-ECF archive.

    More Details

    The digitization has been carried out using the STScI scanning microdensitometers resulting in a pixel size of 25 micron (15 micron for the second generation -DSS2).

    The plates for the southern data are from the SERC Southern Sky Survey and from the SERC J Equatorial extension. These are deep (3600s) IIIa-J exposures obtained through a GG 395 filter, except for 94 short (1200s) V-band exposures mostly at low galactic latitudes (|b| <= 15 deg) plus 2 plates covering the LMC and 2 very short (300s) V-band exposures, each centered on one of the Magellanic Clouds.

    The northern data (dec >= +6 deg) was obtained from the 1950-1955 epoch Palomar Sky Survey. These are deep 103-E exposures obtained through a red plexiglass filter.

    The digitized images have been compressed by a factor of 10, on average, and are extremely faithful to the original data both photometrically and astrometrically.

    The Second Digitized Sky Survey consists in the higher resolution scans of several more plate collection in the red, blue, visible and near infrared. When complete, these collections will help produce a 2-billion object catalog, with multiple colors and proper motions. The DSS2 scans have similarly been compressed and written onto CD-Rs for distribution to a few selected sites. Each color requires approximately 400 CDs. The ESO/ST-ECF archive has copied those onto DVD-Rs.

    What is the typical use of DSS?

    The most frequent use of DSS is to generate finding charts, prior to, or during observing runs. Other applications also involve search for optical counterparts of objects discovered at other wavelengths or any scientific statistical projects, just to cite a few examples.

    How is the entire sky available on-line?

    With today's storage technologies, it has become possible to maintain the entire DSS1 on-line, on fast magnetic disks.

    We have also copied the DSS-2 CD-Rs onto DVD-Rs and placed them into a fast DVD jukebox which was acquired early 1999. A picture of this installation is shown.

    We added a few features to the retrieval software such as: specifying a region around an object name rather than a coordinate pair. This feature was implemented thanks to the SIMBAD interface developed by the CDS in Strasbourg France. We also patch the image headers to include World Coordinate System (WCS) keywords so that a suitable FITS viewer will be able to show celestial rather than pixel coordinates.

    Copyright Notice

    The DSS program is a modification by ESO/ST-ECF of the "getimage" program which is, together with the data, copyrighted by the Space Telescope Science Institute (STScI Digitized Sky Survey, (c) 1993, 1994, AURA, Inc. All rights reserved).

    If the Digitized Sky Survey southern data was helpful for your research work, the following acknowledgment would be appreciated:

    Based on photographic data obtained using The UK Schmidt Telescope. The UK Schmidt Telescope was operated by the Royal Observatory Edinburgh, with funding from the UK Science and Engineering Research Council, until 1988 June, and thereafter by the Anglo-Australian Observatory. Original plate material is copyright (c) of the Royal Observatory Edinburgh and the Anglo-Australian Observatory. The plates were processed into the present compressed digital form with their permission. The Digitized Sky Survey was produced at the Space Telescope Science Institute under US Government grant NAG W-2166.