IPAC 2MASS Working Group Meeting #76 Minutes

IPAC 2MASS Working Group Meeting #76 Minutes, 10/10/95

Attendees: C. Beichman, R. Cutri, T. Evans, J. Fowler, L. Fullmer, D. Kirkpatrick, G. Kopan, B. Light, C. Lonsdale, H. McCallon


  1. Distortion Map
  2. SDS Review/Mail Schedule
  3. SDS Glossaries
  4. SDS Online Storage


  1. Distortion Map -- H. McCallon reported that certain aspects of handling the focal-plane distortion maps were not clear in the existing guidelines covering software interface and subsystem documentation. The distortion correction method is not yet fully defined; past discussions have indicated that it is needed in different forms in different subsystems, but it should nevertheless be maintained in a single central location.

    It was suggested that a relatively low-order polynomial model of the mapping from pixel space to undistorted true-angle space should suffice. In PICMAN, the model will need to be implemented in an extremely efficient form, e.g., a specific polynomial with coefficients read from a data base, since a general-purpose function called every time distortion correction is needed would generate far too much CPU usage. In PROPHOT, a separate function call might be acceptable; this would be desirable, since it would decouple the details of distortion correction from the inner workings of PROPHOT.

    It became clear that the distortion correction process is best designed with its relationship to the overall mapping of scan coordinates to true-sky coordinates in mind. Since the three arrays have generally independent scale and twist-angle properties, each band will have to mapped to an ideal coordinate system somewhere along the pipeline. This will be done according to where the needed information is available and when the mapping is needed. After some discussion, the baseline approach is as follows:

  2. SDS Review/Mail Schedule -- The schedule for the technical-subsystem SDS's previously identified as required for the upcoming November review is as follows. Draft versions are to be delivered to /proj/2mass/doc/design/sds, printed, and hardcopy distributed to IPAC 2MASS personnel by Monday, October 16. Reviews and rewrites should be finished in time for a mailing to UMASS on Thursday, October 19.

  3. SDS Glossaries -- C. Beichman requested that all SDS's include a glossary. All 2MASS/IPAC-peculiar jargon used in the SDS should be defined in the glossary, as should any new terminology developed for the subsystem described in the SDS. The glossary may be placed at the end of the document without a section or appendix identifier.

  4. SDS Online Storage -- The online repository for SDS's (before being put into the web area) is /proj/2mass/doc/design/sds/XXXX, where XXXX represents the name of a subsystem. In a previous memo, J. Fowler indicated the contents desired, namely the SDS in native wordprocessor format, an ASCII format version (if different from the native wordprocessor version), and a postscript version. The new aspects are that separate subdirectories for each subsystem are to be used, and any linked or embedded files are also to be delivered (e.g., RoboChart native- format files).