The precision pointing required of the Hubble Space Telescope (HST) motivated the design of the Fine Guidance Sensors (FGS). These large field of view white light interferometers are able to track the positions of luminous objects with ~1 millisecond of arc precision. In addition, the FGS can scan an object to obtain its interferogram with sub-mas sampling. These capabilities enable the FGS to perform as a high precision astrometer and a high angular resolution science instrument which can be applied to a variety of objectives, including:
- Relative astrometry with an accuracy approaching 0.2 mas for targets with V < 16.8.
- Detection of close binary systems down to ~8 mas, and characterization of visual orbits for systems with separations as small as 12 mas.
- Measuring the angular sizes of extended objects.
- 40 Hz relative photometry (e.g., flares, occultations) with milli-magnitude accuracy.
For complete details on the FGS and its capabilities, please see the FGS Instrument Handbook.