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HST Call for Proposals and HST Primer for Cycle 24 |
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6.2 HST VisitsThe following recommended guidelines were put in place to ensure scheduling efficiency and flexibility, and to maximize the number of scheduling opportunities during the HST observing cycle:
3. Changes in HST pointing within an orbit should not exceed ~2 arcminutes. This can be due to an explicit change in target position (e.g., POS TARG, dither pattern, aperture change) or the use of a new target. Changes larger than 2 arcminutes introduce major slews which may be accommodated only if science goals dictate and conditions allow it.A new visit is required if any of the following conditions occur:If full frame ACS or WFC3 data are taken at the highest possible rate (~6 ACS/WFC or WFC3 images per nominal orbit, or ~12 images per CVZ orbit) for several consecutive orbits, it is possible to accumulate data faster than it can be transmitted to the ground. High data volume proposals will be reviewed and on some occasions, users may be requested to divide the proposal into different visits or consider using subarrays. Users can achieve higher frame rates by using subarrays, at the expense of having a smaller field of view; see the ACS Instrument Handbook or WFC3 Instrument Handbook for details.