PSC Corrections
Corrections to the 2MASS All-Sky Point Source Catalog




I. Introduction

Analyses of the provisional Point Source Catalog (PSC) have turned up several features that require correction before the Catalog can be released. Correction involves both deleting several classes of unreliable sources (artifacts of various sorts) that were not previously identified, and adding back in rows from the Point Source Working Database that were inadvertantly omitted by the criteria for source selection for the All-Sky PSC. Failure to correct these would result in the PSC failing to satisfy the stringent Level 1 Requirements for reliability and completeness.

  1. Sources to be Deleted from the PSC (Status: deletions made 12/4/02)


  2. Sources to be Added to the PSC (Status: additions made 12/12/02)

II. Procedure for Deleting Sources

Deleting rows from the provisional PSC database table is relatively low-risk and straightforward. The steps necessary to modify the PSC and prepare it for release are:

  1. Identify cntr values of rows to be deleted
  2. Delete rows from PSC table (Chiu)
  3. Validate deletion (Chiu)

III. Procedure for Adding Sources

By agreement, sources to be added will only be selected from scans in the release. The sources to be added will satisfy the edge-distant requirements for the source selection (dist_edge_ew > 10 AND dist_edge_ns > 10). No source will be added that already has an apparation within 2" of its location in the PSC. The pre-release steps for adding these sources are:

  1. Identify rows from WDB to be added
  2. Generate value-added (FPG) columns for the new sources
  3. Resolve internal duplicates in cu_psc2 table (Wheelock)
  4. Combine value-added rows into cu_psc2 table (Chiu)
  5. Merge cu_psc2 table with Working Database values for sources (C hiu)
  6. Do any final filtering of sources to be added
  7. Concatenate merged list of sources to be added with current PSC to construct fp_psc2 (Chiu)
  8. Update XSC pts_key values for any new PSC sources that have non-null values of ext_key (Evans)

IV. Procedure for Both

Once the sources are deleted from the PSC, and the new sources are concatenated to the PSC, then following pre-release steps are necessary:

  1. Re-index and rebuild stats for new PSC table (Chiu)
  2. Build new .xpf files for the new PSC table (Monkewitz)
  3. Modify DD for PSC to hide prox, pxpa, pxcntr fields ( Evans)
  4. Point GATOR to the new PSC table (Zhang)
  5. Validate (all)

V. Post-Release Steps

By agreement, production of the DVD will follow the on-line release. The on-line PSC release will initially be made without the prox, pxpa, pxcntr values. They will be added to the on-line version after new values are computed.

  1. Download ascii PSC table and send to UMASS
  2. Re-evaluate prox, pxpa, pxcntr for PSC entries
  3. Update prox, pxpa, pxcntr columns in on-line PSC
  4. Generate PSC DVD masters


Last Updated: 13 December 2002
R. Cutri (IPAC)