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Cosmic Origins SpectrographInstrument Handbookfor Cycle 22 > Chapter 9: Scheduling Observations > 9.2 Generic Observatory Overheads

9.2
The first time that you acquire an object, you must include a 6-minute overhead for the HST guide-star acquisition. In all subsequent orbits of the same visit, you must include the 4-minute overhead for the guide-star reacquisition. If you are observing an object in the Continuous Viewing Zone (CVZ), then no guide-star re-aquisitions are required.
You must allocate additional time for each deliberate movement of the telescope; e.g., if you are performing a target-acquisition exposure on a nearby object and then offsetting to your target, or if you are taking a series of exposures in which you move the target on the detector (POS-TARG), then you must allow time for telescope motion. The time varies depending on size of the slew; see Table 9.2.
Table 9.2: Generic Observatory Overhead Times
10 arcsec < Offset < 1.5 arcmin1
1.25 arcsec Offset 10 arcsec
1
Spacecraft motions larger than ~ 1.5 arcmin are likely to result in the loss of guide stars.


Cosmic Origins SpectrographInstrument Handbookfor Cycle 22 > Chapter 9: Scheduling Observations > 9.2 Generic Observatory Overheads

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