attitude -- Produces a statistical summary of the satellite pointing from a given ASCA attitude file.
attitude datafile attfile outfile pointing [ranom, decnom]
ATTITUDE is a utility program used in conjunction with ASCALIN to compute a common aspect point for all four detector images.
ATTITUDE reads an ASCA attitude file and displays pointing info- mation. Key pointing information is also written out to the parameter file.
There are 10 sky pointing direction to consider with ASCA aspecting:
ATTITUDE computes (1), (10), while (2-5) and (6-9) are determined in addition by ASCALIN for each instrument over the Science File times.
ATTITUDE gives the mean satellite boresight as a set of Euler angle using the (Z-X-Z) definition, displayed in a form compatible with the ASCA Observation Reports, as well as the angles these axes make with respect to the Sun. The Euler angles and their Solar angles are particularly useful since the Y-axis is perpendicular to the solar panel, the X-axis is related to the roll angle, and the Z-axis defines the satellite boresight.
ATTITUDE also gives the mean detector pointing (RA/DEC/ROLL), ranges and RMS errors, the mean Sun location, as well as the mean annual aberration correction.
ATTITUDE also compute the mean offset from the average file pointing to a sky reference point (mean tangent plane offset in arcmin). The sky reference point may be given as an input value RA/DEC, (USER) or the computed file average itself will be used (ATT), in which case no additional input is necessary.
The following information is displayed:
1) Full path name of input file (truncated to to 55 characters).
2) The attitude file start and stop times as given in the file header.
3) The start and stop time of the data file to be processed.
4) The time value of the first and last record used from this attitude file.
5) The total time interval spanned by this file.
6) The Mean boresight Euler angles averaged over the the attitude file.
7) a) The position of the Sun computed at the half way time (degrees),
b) The Annual Aberration angle correction at this time (arcsec).
8) The mean satellite X-Y-Z axis pointing and the angles they makes with the Sun (degrees).
9) The file average, minimum, maximum, and sigma for the RA, DEC, and ROLL angle, and the linear offset along the focal plane. For ATTITUDE, the averages are determines using the mean mis-alignment matrix; for ASCALIN, the averages are determines using the instrument specific ones. The offset is just the mean linear tangent plane deviation from the aspect RA/DEC during the file time.
The following information is written back into ATTITUDE's parameter file. The valid flag is set to 'no' at the beginning of the run and reset to 'yes' following successful completion:
(valid = yes) Is this data valid? (euler1 = 117.0856) Computed mean Euler1 angle for file (degrees) (euler2 = 3.837651) Computed mean Euler2 angle for file (degrees) (euler3 = 218.3658) Computed mean Euler3 angle for file (degrees) (ra_avg = 115.4760) Computed mean RA for file (degrees) (dec_avg = 85.90086) Computed mean DEC for file (degrees) (roll_avg = 129.9715) Computed mean ROLL for file (degrees) (offset_avg = 0.055577) Computed mean OFFSET for file (arcmin) (ra_sig = 0.153005) Computed mean RA RMS for file (degrees) (dec_sig = 0.001955) Computed mean DEC RMS for file (degrees) (roll_sig = 1.187530) Computed mean ROLL RMS file (degrees) (offset_sig = 5.075366) Computed mean OFFSET RMS for file (arcmin)
Notes:3) Meaningful for ASCALIN only.
2,4) Time units in this file.
4) An increment of 0.001 second has been added (subtracted) from the stop (start) time to allow for truncation error.
1) Summarize an attitude file in the current directory and compute mean offset relative to mean pointing, make an ASCII version of the attitude file:
attitude fa930422_0306.2314 . default ATT
2) Summarize an attitude file in the default attitude directory and compute the mean offset relative to mean pointing (no output file):
attitude fa930422_0306.2314 default none ATT
3) Summarize an attitude file in the directory '/usr/evg' and compute mean offset relative to a given RA and DEC (no output file):
attitude fa930422_0306.2314 '/usr/evg' none USER ranom=14.345 decnom=-48.964
Please report problems/comments to ascahelp