3.6 Coordinate Reference Frame [Reference_Frame]

This keyword replaces Coordinate_Source starting with Cycle 14 Calibration and all Cycle 15 programs. Select one of the following Reference_Frame values for each target.

ICRS

To be used if the coordinate reference frame is tied to the International Celestial Reference System (ICRS). Catalogs tied to the ICRS include: HST Guide Star Catalog 2 (GSC2), Hipparcos Catalog and the Tycho-2 Catalog.

GSC1

To be used if the coordinate reference frame is tied to the HST Guide Star Catalog 1. The Plate ID of the special catalogs (those with an ID ZZZx, where x=0-9, a-z) must be included with your coordinates.Other

To be used if the coordinates are not GSC1 or ICRS.