ASPECT (Jun99) ASTROE ASPECT (Jun99)
NAME
aspect -- calculate the mean pointing for an attitude file.
USAGE
aspect infile outfile verbose
DESCRIPTION
This tool calculates the mean pointing for a given attitude file.
In reality the calculation is more complex than a simple mean. The
algorithm is to first create a histogram of the amount of time
spent at each R.A. and Dec, then to pick the bin with the largest
time and calculate the mean R.A., Dec. and Roll Angle of the
spacecraft axes while the Z axis was in this bin.
This method avoid problems when the attitude is stable for most of
the observation, but has a large motion at the beginning or end of
the file due to settling or slewing.
In general telescope axes are not aligned perfectly with the
spacecraft axes. The tool is able to read an optional misalignment
matrix, in which case the result is orientation of a set of axes
offset from the spacecraft axes.
PARAMETERS
attfile [string]
This is the name of the attitude file to be read.
alignfile [string]
If this parameter is set to "NONE" then the results will give
the mean orientation of the spacecraft axes. If name of a file
containing a misalignment matrix is given, then the results
will be the mean orientation of axes offset from the spaceraft
axes. The format for the misalignment matrix is the same as for
TELDEF files (i.e. used ALIGNnm keywords in the primary header).
(nbins = 100) [integer]
Number of bins to use in attitude histogram. Since the
histogram is two dimensional the total number of bins is
nbins*nbins
(binsize = 0.01) [real]
Ideal size of a bin in degrees. This value should ideally be
set close to the error in the pointing stability.
(maxrot = 0.01) [real]
Maximum rotation angle between adjacent attitude "point" when
binning the attitude in degrees. Smaller values will cause the
program to run more slowly, but higher values may represent
quick motions incorrectly. The best value is close to binsize.
(ra) [real]
The mean Right Ascension is written to this parameter in
decimal degrees.
(dec) [real]
The mean Declination is written to this parameter in decimal
degrees.
(roll) [real]
The mean Roll Angle is written to this parameter in decimal
degrees.
EXAMPLES
BUGS