1. STScI
2. HST
3. FGS Transfer Mode Reference Targets

FGS Transfer Mode Reference Targets

The following tables describe the reference transfer functions for FGS 3 and FGS 1R, available here in polynomial representations. Table 1 lists the targets, their V magnitudes, B-V color indices, and references where appropriate for all targets for which reference Transfer Functions are available. Table 2a and Table 2b specify the actual reference Transfer Functions for FGS 3 and FGS 1R respectively.

We note that the filters available for astrometry with FGS 3 are listed in Table 5.6 of the FGS Instrument Handbook.

Further details about Transfer Mode observing and calibration can be found in Chapter 5 of the FGS Instrument Handbook.

Table 1. Reference Transfer Function Targets

In the reduction of their data, observers should use that reference Transfer Function (see Table 2) which is closest in time to their observed data, using the same filter on a target of similar color index and close in the field of view to their observation.

In Table 2, the rootname of the reference Transfer Function is given in Column 6. The actual reference files have names of the form ROOTx.poly and ROOTy.poly; and ROOTx.FIT and ROOTy.FIT. The POLY files contain the polynomial representations for the data, and the FIT files contain the polynomial fits evaluated at 1 milli-arcsecond bins. All the files are in ASCII format.

Column 1 gives the date the reference data was observed. The secondary mirror was moved in 1993 on Day 352 (1993.352) in conjunction with the First HST Servicing Mission. Consequently, data taken before 1993.352 should NOT make use reference data after that date. Similarly, data taken after 1993.352 should NOT make use of reference data taken before that date.

Table 2a. FGS 3 Reference Transfer Functions for Pickle Center

Table 2b. FGS 1R Reference Transfer Functions for Pickle Center