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Spitzer Observing Rules

4         Modification of AORs

To accommodate the inevitable need of investigators to modify and refine their approved observations, procedures are established to allow for this process.  The intent of these procedures is to allow adequate flexibility in modifying a Spitzer observing program to maximize the scientific value of an approved observation.  The guiding principles underlying these procedures are:


·         All programs executed by the Spitzer Space Telescope are properly reviewed and approved.  The approval process described below is intended to ensure that the modified program, as executed, is approved and avoids duplicate observations.


·         All modifications shall be such that the program stays within its originally allocated observing time.


The procedures described here exclude the procedures that will be followed in the catastrophic loss of a major instrumental or telescope function.

4.1       Types of Modifications

The Principal Investigator, according to the precepts and schedule outlined below, can modify an Astronomical Observation Request (AOR) in the Science Operations Database (SODB) electronically.  Once an AOR has been scheduled for observation, typically five to eight weeks before execution, it cannot be modified without approval (which will be rare) of the SSC Director’s office.


All requests for modification of approved AORs must be approved by the SSC Science User Support Team, which will characterize the request as one of two types.  Minor modifications consist of small changes of target parameters, typically a few arcseconds in celestial coordinates, or small changes in AOR execution time (< 20%), subject to the total observing time in an investigation remaining constant.  Minor modifications could also include small changes of other parameters in the AOR (e.g., change to high-dynamic mode in the IRAC AOR), as long as the changes do not alter the scientific content or intent of the original AOR.


Major modifications to an individual AOR consist of those changes that would substantially alter the scientific content or intent of the AOR. Examples of major modifications include:


·         Changing the execution time of an AOR by 20 percent or more, thereby increasing the probability that duplicate observations might arise.

·         Changing the sensitivity by a factor of 1.5 or more.

·         Changing the target coordinates, or boundary area, by an astronomically significant amount.

·         Changing the target to a different target judged by the investigator to be scientifically equivalent to the original target.


The execution of an approved observation may become infeasible (§11) or prove to be scientifically useless because of unanticipated circumstances.  If these events occur, and if an observer can a priori demonstrate that the approved AOR will yield useless data, the Principal Investigator can submit a request to make major modifications to the AOR.  The proposed modifications must be consistent with the original scientific intent of the approved observation and the observing time granted.  In addition, it cannot duplicate any other approved observation, and must be approved by the SSC Director.


Requests for major modifications to any approved observing program or AOR must be made to the SSC Science User Support Team through the Helpdesk (, and must be accompanied by adequate justification.  Modifications are contingent upon approval by the SSC Director, or designee.  Once the request for a modification is approved, the requestor may modify the AOR/program, with assistance provided by SSC Science User Support Team.  The latter is responsible for insuring that the modifications are implemented as approved.

4.2       Blackout Period

There is a blackout period during which no major modifications to approved AORs or programs are normally allowed.  The contents of the Reserved Observations Catalog (ROC) are frozen, and major modifications are not permitted while a solicitation for proposals for a new observing Cycle is active. This time period runs from the date the Call for Proposals is issued until the proposal submission date passes.