Building Sequence Database Files for the
Hopkins Ultraviolet Telescope
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