The FGS Instrument Handbook is the basic reference manual for observing with the FGS. It describes the FGS design, properties, performance, operation, and calibration. The Handbook is maintained by the Observatory Support Group at STScI, who designed this document to serve three purposes:

• To help potential FGS users decide whether the instrument is suitable for their goals, and to provide instrument-specific information for preparing Phase I observing proposals with the FGS.
• To provide instrument-specific information and observing strategies relevant to the design of Phase II FGS proposals (in conjunction with the Phase II Proposal Instructions).
• To provide technical information about the FGS and FGS observations.

The FGS Data Handbook provides complementary information about the analysis and reduction of FGS data, and should be used in conjunction with this Instrument Handbook. In addition, we recommend visiting the FGS World Wide Web pages for frequent updates on performance, calibration results, and methods of data reduction and analysis. These pages can be found at:
http://www.stsci.edu/hst/instrumentation/fgs