Q: What target coordinate accuracy is needed for use with the
smallest format?
A: The smallest F/96 format (256x256) is only 3.6 arcseconds across.
With an average guide star error of almost 1 arcsecond, this leaves
less than 0.8 arcseconds of error for the target coordinates. For
this reason, an INTeractive ACQuisition is mandatory to insure that
the target does not fall outside the small format. This adds 1
orbit to the observing program, but insures that the target is
actually observed.
Q: What is the overhead time for acquiring bright objects?
A: A new Bright Object Acquisition procedure has been developed
for the FOC to observe any target brighter than 9th magnitude.
This new procedure does not rely on any real time
interaction and checks the filter positions automatically
prior to taking any exposures. Since it is completely
automated, it adds just under one minute to the overhead
of the image, rather than a complete orbit which the
old procedure required.
This new procedure can be implemented by adding the following
Optional Parameter to the necessary exposures:
Optional_Parameters: CHECK-FILTER = YES
This parameter only needs to be attached to the exposures with
unique filter combinations, not to every exposure even though
the filters don't change. For example, images taken of a
bright star would use the CHECK-FILTER parameter as follows:
Exposure 1: F275W,F278M,F4ND, CHECK-FILTER=YES
Exposure 2: F275W,F278M,F4ND
Exposure 3: F275W,F278M,F4ND
Exposure 4: F275W,F307M,F4ND, CHECK-FILTER=YES
Exposure 5: F275W,F307M,F4ND
