As data obtained from FGS is different than the other science instruments aboard HST, the reduction and analysis of FGS data requires specialized methods and software tools. Such software includes the reduction of multi-epoch Position Mode observations (used, for example, in the determination of an object's parallax), multi-epoch Transfer Mode observations (used to derive a binary system's orbital parameters), as well as the detailed inspection of the data from a single exposure or observation. The software (i.e. source code) for analyzing both Position Mode and Transfer Mode observations and pipeline products can be downloaded from the FGS Software Tools section of this Website. These tools are written in standard Fortran and/or C and operate in the UNIX environment. A significant amount of this software was provided to STScI by the Space Telescope Astrometry Science Team (STAT) at the University of Texas and Lowell Observatory. However, please note that many of the tools produce graphical displays by calls to the SM library, for which you may require a site license. STScI is working to replace the SM with a publicly licensed package. Until this is accomplished, if you need to use a non-SM graphics package, modest alterations to the source code will be necessary.
Chapters 2, 3 and 4 of the Data Handbook for FGS provide details on the reduction and analysis FGS data. For access to and information on FGS reference files, please see the Reference Files section of this Website.
We recommend a visit to STSCI for all first time users of FGS, in order to become better acquainted with the data and data reduction software.