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Knowledgebase: Spot and Leopard
Why does Spot not let me visualize an AOR on the date it was executed? The data were taken early in the mission.
Posted by z-Schuyler Van Dyk on 02 December 2008 10:51 AM
There are two things that create this effect. In either case, if your object was observed at the edge of its visibility window, you might not be able to visualize it.

(1) To allow faster slews, we changed the definition of the OPZ in early 2004. It reduced by 2.5 degrees -- the inner limit changed from 80 to 82.5 degrees.

(2) As we proceed with the mission, Spitzer's location in orbit changes, so the Operational Pointing Zone (OPZ) changes slightly in time. This 'creep' in the orbit as Spitzer moves further away from the Earth manifests itself by a shifting OPZ within Spot. Users will start to notice that if they try to visualize AORs in Spot for targets very near the OPZ back in say Dec 2003 or Jan 2004 (when perhaps, their observations actually occurred) that Spot may now not let them. The target may now be outside the CURRENT OPZ of Spitzer.

The only alternative is to visualize the AOR at a date as close to the observation date as Spot allows. Observers can still use Spot to get background estimates of the target on a specific date whether or not Spitzer can actually see the target at that time.