How HST Is Scheduled
After an observer submits a Phase II program to STScI, a Program Coordinator checks the proposal into a database at STScI. If the proposal is acceptable and if suitable guide stars (if necessary) can be found, the observations (called visits) in a proposal are assigned scheduling windows by the Long Range Planning (LRP) group. These windows range in width from a half day to eight weeks and represent times that an observation could be conducted on HST. They are subject to change, but STScI does try to hold to these windows whenever possible.
The actual observations onboard HST are scheduled on week-long calendars, starting every Monday, 00 Universal Time. Using a pool of observations already prepared for scheduling by the Program Coordinator Team, the Short Term Scheduling group begins to construct a given week's calendar three weeks prior to the start of its execution onboard HST. The actual command loads used to operate the HST spacecraft and its instruments are generated from these calendars.
Approximately five days before the start time of a calendar's execution, the command loads to be uplinked to HST are sent to Goddard Space Flight Center for final checking and verification.