Mosaics In Two Gyro Mode

Mosaics that require more than ~20 orbits to construct should be designed taking into consideration of the scheduling requirements. As a rule, mosaics can be constructed with images taken at orientations differing by 90 degrees. This provides scheduling flexibility, resulting in more days per year when these observations can be taken. In Two Gyro mode, we will generally be restricted to only one or two of these orientations. The scheduling aids available on the website can help you determine which orientations are available for your target, and how many days each provides to the schedulers. Dividing the orbits required for the mosaic by the available days gives a rough indication of the scheduling difficulty for the program. Programs that require less than 1 orbit per available day are generally easy to schedule, those that require more than 3 orbits per available day are difficult to schedule and may collide with other programs.

The amount of scheduling time available can depend strongly on the absolute orientation angle chosen for the mosaic. There can be scientific reasons for choosing a particular orientation for a mosaic, such as alignment with the object, or matching prior data sets. Proposers should examine whether orientations that provide more observing days are acceptable. It is particularly useful to indicate in the proposal how much flexibility there is in selection of the orientation of the mosaic. Providing even 10 or 15 degrees of flexibility can ease problems during program implementation. This is particularly helpful in resolving scheduling conflicts between accepted programs that inadvertently compete for the same observing days. These conflicts will be more common in Two Gyro mode.