Building Sequence Database Files for the Hopkins Ultraviolet Telescope

3.1 2 Information Checking

The SDF files allow a number of "sanity" checks to be made without having to search through numerous separate files for the necessary information. For instance, the 1950 coordinates of each target from the SCIPLAN file are the "official" coordinates used for making the observations. These entries should be double checked against the coordinate entries from the guide star work (e.g. Target_RA,GS_Program and Target_Dec,GS_Program) to verify that the object was correctly located by the Guide Star Program (GSP). Differences of a few arcsec are unimportant. Differences up to 10 arcsec could indicate proper motion of your target or that a nearby object was mistakenly identified as your target. Any coordinate errors larger than this should definitely be resolved, and corrected coordinates supplied to MSFC for future planning. (Note: the offsets for potential guide stars are referred to the GSP coordinates. Hence, any discrepancy between the GSP coordinates and those being used by MSFC will cause the guide star fiducials to appear in the wrong place on the HUT TV.) The GSP also checks whether the Target_V_Mag entered by the user is consistent with the value found from the HST GS Catalog, and flags discrepant values.

Another check that can be made is whether the roll angle requested for a specific observation agrees with the actual roll angle selected by the MSFC planners when they searched for IPS guide stars. The SDF entry called "HUT_roll_angle" refers to any requested roll angle that was made with the official SCIPLAN submission to MSFC. (Note: "-99.99" indicates no angle was requested. A flag can be set that indicates whether the roll must be met exactly as given or whether \(+-180\(de is ok; usually \(+-180\(de has no impact.) The entry "PI_roll_angle" is entered into the SDF automatically when a file returns to us from MSFC with the actual planned roll angle for the observation. (This angle has the \(+-180\(de ambiguity removed.) Hence, the user can check whether the requested roll angle was satisfied or not. Note that these angles are simply astronomical "position angles" (degrees East of North=0\(de) of the "-@Y sub HUT@" end of the HUT aperture. Figure 1 shows a picture of the HUT TV field projected onto the sky with two examples. Our experience has been that requested roll angles can readily be accommodated by the IPS, but occasionally fields at high galactic latitude are limited in the choice of actual roll angles.

This document was translated by mm2html v1.3 on 13.07.94. Jon