Data model: datasweep-index

General description: File describing the location of each field in the calibObj sweep files, to make spatial searches on the sweep faster. Versions exist for the galaxies, stars, and sky sweeps. Given an RA and Dec one can use this file to find the nearby fields and find what the lines of the relevant sweep files are that you need to read.

Naming convention: datasweep-index-[type].fits (where type is 'gal', 'star' or 'sky')

Approximate size: 100 Mbytes.

File type: FITS

Read by products: idlutils

Written by products: photoop

Required column names: (should be listed for Yanny and FITS)

• RUN (int32): drift scan run number
• RERUN (string): reprocessing rerun number
• CAMCOL (int32): camera column
• FIELD (int32): field number
• RA (float64): RA center of field, J2000 degrees
• Dec (float64): Dec center of field, J2000 degrees
• ISTART (int32): first entry within calibObj datasweep file for this RERUN/RUN/CAMCOL
• IEND (int32): last entry within calibObj datasweep file for this RERUN/RUN/CAMCOL
• NPRIMARY (int32): the number of entries in the calibObj datasweep file for this RERUN/RUN/CAMCOL that have RESOLVE_STATUS set to SURVEY_PRIMARY

For IDL users, idlutils has a routine "sdss_sweep_circle" which utilizes these sweep indices to do very fast spatial searches (you can retrieve all objects within 3 deg radius in less than a minute).

Example file: datasweep-index-gal.fits