10.6 Proposal Scheduling

10.6.1 Unschedulable or Infeasible Programs

After Technical Review, observations determined to be feasible are scheduled for execution. The scheduling process attempts to optimize the overall HST efficiency. STScI will not contemplate requests to advance or postpone the scheduling of individual programs based on other considerations, with the possible exception of compelling scientific arguments.

10.6.1 Unschedulable or Infeasible Programs

Proposers should be aware that after acceptance of a proposal, the actual execution of the observations may in some cases prove impossible. Possible reasons include:

•	The accepted observation may be found to be infeasible or extremely difficult for technical reasons only after receipt of the Phase II information; ToO and time-critical observations can be particularly complex to plan and execute, and will be completed only to the extent that circumstances allow.

•	The observing mode or instrument selected may not be operational.

•	Suitable guide stars or scheduling opportunities may not exist.

Hence: All HST observations are accepted with the understanding that there can be no guarantee that the data will actually be obtained.

The STScI Director reserves the right to disallow at any time any or all observations of an approved program if it is demonstrated that incorrect or incomplete information was provided in the Phase I proposal that may have significantly influenced the approval recommendation by the review panels or the TAC.