In case an alignment of the axes of a map in Right Ascension and Declination with the spacecraft axes is desired for observations with the detector arrays, observers should consider to use the spacecraft coordinate system instead of the equatorial system. This is only of concern during Phase 2 data entry. For scheduling, mapping is regarded as a single observation. Thus, a map, or a scan, will only be scheduled as a whole or not at all. The overhead to start a map observation is 180 sec.
Additional overheads accumulate due to moving from one point to the next one.
The slews between points in a map are usually much shorter than the slews for target acquisition. In contrast to the latter, these slews involve the same guide star and the control is different. They are called micro-slews. In the following a procedure is described how to calculate the overhead due to these micro-slews. The acceleration to the maximum speed and the deceleration to slow down to zero is 3 seconds each, the maximum slewing speed, called the coasting speed, within a map is arcsecsec .