attitude HEADAS help file

NAME

attitude -- Produces a statistical summary of the satellite pointing from a given ASCA attitude file.

USAGE

         attitude datafile attfile outfile pointing [ranom, decnom]

DESCRIPTION

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:

(1) The satellite direction defined as the Z-axis or boresight,
(2-5) The origin of each detector image in sky coordinates, which is: slightly difference to the Z-axis and to each other,
(6-9) The optical axis of each of the four telescopes which also points: in individual direction, and,
(10) A conveniently defined 'mean detector' or 'operation' pointing,: which is approximately the mean of the detector origins.

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.

PARAMETERS

attitude [string]: The ASCA Attitude file to be processed.
attpath [string]: The path to the Attitude file or 'default'. If 'default' is selected, the value stored in the defATTpath parameter (see below) will be used.
outfile [string]: An optional output file name, 'default', or 'none'. Each row in the output ASCII file contains the TIME (sec) offset from TSTART, the computed three boresight EULER ANGLES (deg), the linear X and Y offsets (arcmin) from the aspect point, and the SENSOR flag (see attitude file header for details). This file can be read into QDP to create a formatted plot of these values.
pointing [string]: The pointing choice: ATT/USER (see text above).
ranom [real] (prompted for if pointing=USER): The aspect sky point R.A.
decnom [real] (prompted for if pointing=USER): The aspect sky point DEC.
atimecol [string] (hidden parameter): Attitude file column name.
qcol [string] (hidden parameter): Attitude file quaternion column name.
qstat [string] (hidden parameter): Attitude file quality flag column name.
verbose [logical] (hidden parameters): The verbose flag: run time information updates.
summary [logical] (hidden parameters): The summary flag: produce a one line summary line.
defATTpath [string] (hidden parameters): The path pointing to the Attitude file.
valid [boolean] (hidden parameters): Is the following data valid? Set to 'no' at the beginning of the run and reset to 'yes' following successful completion.

euler1/2/3 [real] (hidden parameters): Computed mean Euler1/2/3 angle for file (degrees)
ra/dec/roll/offset_ave [real] (hidden parameters): Computed mean RA/DEC/ROLL/OFFSET for file (degrees; OFFSET in arcmin)
ra/dec/roll/offset_sig [real] (hidden parameters): Computed mean RA/DEC/ROLL/OFFSET RMS for file (degrees; OFFSET in arcmin)
mode [string] (hidden parameters): Parameter file interaction mode

EXAMPLES

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

BUGS

Please report problems/comments to ascahelp

AUTHOR

Eric Gotthelf.