On JWST, observing time will be defined to represent the total amount of mission-elapsed time, including overheads, required to carry out an observation. As such, it will consist of the time that is spent pointing at a target position, as well as overheads associated with slewing to the target and any idle time necessary to carry out the observation.  Where the overheads vary in length because they depend on the specific order in which a series of observations by various observers are carried out, average values for the activity will be used as defined in the Call for Proposals.

There will occasionally be observations that fail or are substantially compromised or incomplete for a variety of reasons. STScI will generally repeat or complete observations, assuming it is technically feasible to do so, in cases where a significant portion of the program has been compromised and the observer could not have reasonably anticipated the problem, or when the cause was not due to incomplete or incorrect information provided by the observer. Hence, GTOs and GOs will be charged only for observations that are considered to be successfully completed. The definition of a successfully completed observation will be considered on a case-by-case basis and will be the responsibility of STScI. This completion policy and its implementation will be the same for GTOs and GOs. Failed observations which are repeated will be allocated zero exclusive access time.

Approved by:

Edward J. Weiler, Associate Administrator, Science Mission Directorate, NASA Headquarters.  1/5/2010

Paul Hertz, Chief Scientist, Science Mission Directorate, NASA Headquarters. 12/30/2009

Jon A. Morse, Director, Astrophysics Division, Science Mission Directorate, NASA Headquarters.   12/7/2009

Eric P. Smith, JWST Program Scientist, Science Mission Directorate, NASA Headquarters.  11/30/2009

In accordance with Contract NAS5-03127, Statement of Work, Section A.4, A.5, the following guidelines are policies promulgated by the NASA Associate Administrator (AA) for the Science Mission Directorate (SMD) with regard to the implementation of the JWST science mission. Any reference to JWST Program or Project refers to the NASA JWST Program or Project unless explicitly noted otherwise.