Except for constraints relaxation, major changes are not possible once the Phase 2 is finished and OBs are sent to the scheduler. However, during observation the SAs may adjust some parameters (like exposure time) to respond to the variable conditions, but the total time granted to a given program will remain unchanged. To relax the constraints after Phase 2 (in order to increase the probability of execution), the PI should contact the SOD first. If permission is granted, the PI should re-submit those OBs that were not executed yet.
Other changes are not allowed, except for special cases. If the user wants to change an original target, it should be discussed with the SOD first. It may be allowed if the science goal is unchanged, there is no conflict with other programs3.8, and there is a good reason. Changing filters should also be discussed with SOD first.