Pipeline processing described in Section IV is in reality only the first step towards preparing the final products for 2MASS. The second and equally important phase of data processing is Catalog Generation.
Pipeline scan processing generates Working Databases, which contain all "detections" of point and extended sources drawn from each scan of a Survey Tile. The scan processing detection thresholds are intentionally set low to insure the completeness of the Survey. Therefore, in addition to detections and measurements of valid astrophysical sources, the Working Point and Extended Databases contain:
The objective of Catalog Generation processing is to select only those sources from the Working Databases that will result in release Catalogs that satisfy the 2MASS Level 1 Science Requirements for uniformity, sensitivity, completeness and reliability.
The process of generating Catalogs from the Working Databases begins with the selection of observations of Survey Tiles that were taken under conditions of seeing, background level and structure and atmospheric transparency that yield data that nominally satisfy the requirements for sensitivity and uniformity for the Survey. Once the Tiles are selected for the release, then sources from those Tiles are selected that meet SNR and other quality thresholds that insure that the reliability of the catalog will be high enough, but not so strict that the completeness is compromised.
For inclusion in the Second Incremental Data Release Point Source Catalog, a candidate source must meet all of the following criteria:
To be included in the Second Incremental Data Release Extended Source Catalog, a candidate source must meet all of the following criteria:
The following sections provide more detailed descriptions of each of these Catalog Generation processing phases.
[Last Update: 1 March 2000, by R. Cutri]