Single Star Guiding Information
In some cases, the Guide Star Acquisition process can only acquire a single guide star. In that case, there may be some degree of drift in roll which can happen over time. The degree can vary depending on factors such as the length of the exposure, time of an exposure or set of exposures, and the distance between the target and the guide star in the focal plane. This general principle applies to all instruments in the focal plane. For instrument-specific examples, see below.
Instrument-Specific Examples
More information can be found in the ACS Data Handbook: Section 5.2.3 Impact of Guide Star Failure.
Please see the ACS example for the general principle. Any additional COS-specific information will be added here at a future date.
Please see the ACS example for the general principle. Any additional STIS-specific information will be added here at a future date.
Please see the ACS example for the general principle. Any additional WFC3-specific information will be added here at a future date.