Requirements for SDSS Data Management Systems

This document describes the functional specifications on the SDSS Science Archive, which is to develop into the public data archive.

The data management systems shall maintain all processed data from the SDSS and provide access by SDSS scientists and operators in order to maximize the ease of the following:

1. Operate the SDSS survey so as to maximize the efficiency of operations.
2. Perform Quality Analysis operations on the data so as to ensure its integrity. The operations will verify calibrations, target selection criteria and classifications, completeness and accuracy.
3. Provide SDSS scientists with access to the data and tools to permit selection of spectroscopic targets for certain categories (serendipity; stars).
4. Provide SDSS scientists with access to the data so as to enable scientific analyses.

Requirements for the Science Archive

The science archive shall consist of:

1. A science database that shall:
   • a. Retain calibrated object catalogs (photometric CCD output)
   • b. Retain parameters from spectroscopic pipeline
   • c. Enhanced goal: provide ability to recalibrate object catalogs
   • d. Retain references to atlas images and extracted spectra
   • e. Provide ability to carry out manual target selection for certain target categories
   • f. Provide ability to carry out offline QA activities
   • g. Provide ability for SDSS scientists to extract subsets of retained data.
   • h. Provide smooth transition to public distribution system.
   • i. Enhanced goal: Provide ability to retain scientist-derived data sets.
2. A set of files tracked by the science database.
3. A set of files not tracked by the science database.

Input to Science Archive

1. Survey Definition
   • a. A description of the North Imaging survey area
   • b. Survey progress: A description of sky inserted into database to date
2. Final Astrometric Calibration
   • a. List of r' band calibration coefficients on a frame-by-frame basis.
3. Final Photometric Calibraton
   • a. List of photometric calibration coefficients on a frame-by-frame basis.
4. Merged Object Lists
   • a. A list of calibrated objects and parameters from the Frames pipeline of photo
   • b. A list of objects masks from the Frames pipeline of photo
   • c. Run and Field information. Might be needed for recalibration
   • d. Star/Galaxy/QSO classifications
   • e. Cross-identifications to other catalogs
5. Target Selection
   • a. A list of all targetable objects with target selection categories
   • b. A list of all objects from (a) selected as targets with selection category
   • c. Tiling flags for all objects in (b)
   • d. Reports for all targets selected manually
6. Spectroscopic Pipeline
   • a. Redshifts and parameters of all targeted objects
   • b. Enhanced goal: Tile and plate information.
7. Enhanced goal: Scientist derived catalogs
8. Enhanced goal: Other input catalogs
9. Separate files tracked from Science Database
   • a. Atlas Images
   • b. 1-D spectra
10. Separate files not tracked or accessible from Science Archive
    • a. Compressed pixel map
    • b. Full corrected pixel map
    • c. Corrected spectroscopic frames
    • d. Unused data

Functional Goals

1. User will be able to carry out efficient queries to locate objects over one or more ranges of following attributes:
   • a. Longitude or latitude in several spherical coordinates
     • i) J2000 Ra and Dec
     • ii) B1950 Ra and Dec
     • iii) Enhanced goal: Ra and Dec of arbitrary epoch
     • iv) Galactic coordinates
     • v) Survey Coordinates
     • vi) Any combination of the two coordinates
   • b. Radius within a give point of the sky
   • c. u' g' r' i' z' (One set of magnitudes per object)
   • d. Any linear combination of c.
   • e. Object radius (one per object)
   • f. Surface brightness formed by c and d.
   • g. Star/Galaxy/QSO Classification flag
   • h. Object class (small/medium/big/mask)
   • i. Target Selection Category
   • j. Spectrum available flag
2. User will be able to carry out queries on any retained object parameter (subject to implementation constraints).
3. Enhanced Goal: All calibrated quantities can be recomputed using improved astrometric and photometric calibrations. Queries can be performed on the recalibrated quantities.
4. For all efficient queries, return an esimated number of objects to be located.
5. For all located objects, users shall be able to specify an arbitrary subset of stored parameters to be returned (subject to implementation constraints) plus the following derived quantities:
   • a. Number of located objects
   • b. Extra parameters
6. Users shall be able to perform the following functions:
   • a. Efficient repeated queries (e.g. get all objects within each of 10,000 QSOs in my favorite catalog).
   • b. Make simple plots, etc. of returned parameters.
   • c. Formulate new queries based on results of previous queries.

Technical Goals

1. User interface
   • a. User interface shall be developed in a TCL/Tk/TclDp environment.
   • b. User interface shall communicate with a query support layer via ASCII interface protocol.
   • c. Data shall be returnable to files, sockets, or pipes. Returned data shall use binary machine independent format (FITS binary, ASCII if appropriate, FITS ASCII, other?)
2. Distributability
   • a. A master copy of all data shall be maintained (the Master Science Archive)
   • b. Capability shall be present to replicate all or part of the Master Science Archive as local databases at SDSS institutions. Replication may consist of:
     • i) Science Database in its entirety
     • ii) All or part of separate files tracked by Science Database
     • iii) No capability shall be present to replicate an arbitrarily selected subset of the science database beyond that described by section 1.c of USER INTERFACE.
     • iv) Replication of databases shall be possible on all SDSS supported platforms.
   • d. No capability is required be present to replicate all or part of separate files not tracked by Science Database
3. Security
   • a. Master Science Archive shall be protected against corruption by SDSS participant users
   • b. Master Science Archive shall be protected against unauthorized access by non-SDSS participants.