PLATE_SOLUTION

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Last Updated Jan 2001

Copyright © 2001 The Association of Universities for Research in Astronomy, Inc. All Rights Reserved.

Purpose :

Compute an Astrometric Plate Solution (Replaces task ASTROSOL).

Procedure :

This program takes the specified astrometric catalogue and reads the RA, Dec coordinates and pixel positions on the plate from the MCO file. It then computes the coefficients of the plate model. There are options to apply the effect of refraction and to use either a gnomonic or an equidistant projection.
This routine determines the astrometric plate coefficients. The task APPLY_CALIB uses these coefficients and astrometrically calibrates an objects in an oop file. PLATE_SOLUTION is an adaption of ASTROSOL with the added ability to apply the effects of refraction and to use an equidistant projection (instead of the classical gnomonic projection). Other tasks (in the future) will create a mask (probably a series of magnitude masks) and APPLY_CALIB will use apply these masks to further improve the positions.
Whenever the program runs into an abort mode (usually not enough information is provided) then a file called region_plate_solution.abort is created, the reason for the abort is written to the file, and the program stops. This is useful when running a script file with many different task to be run one right after the other. Before if plate_solution aborted the script continued with the next task. Now the script has been adapted so that the existence of the abort file - halts the batch job.

Updates (5/99)

The ablity to pre-correct for refraction is stil in the testing phase. Do not run it in this mode.
A few more varibles were added to the GSH header to support the dermination of the astrometric errors by apply_calib.
REJECTION CODES.
Stars can be rejected from the solution for a number of reasons. The rejection codes have the following meaning:
A. -2 = Reject object because of its classification (it was not a star). The qualifier /ONLY_STARS controls this feature. To turn it off type /NOONLY_STARS.
B. -3 = Reject object because it did not fall inside the X,Y or Magnitude range specified by the qualifiers /Xrange, /Yrange, or /Magrange, respectively.
C. -4 = Reject object because the delete flag was set.
D. >0 = Reject object because it falls outside the least squares residual tolerance range.
CAUTIONS,CAVEATS, FUTURE PLANS
  • The equidistant projection will have problems for objects near the pole. A change to the code will be made ASAP (as soon as I figure out how to do it).
  • I am still in the process (3/5/98) of creating, updating and improving the GSCII_HOUR_ANGLE.DAT file. A number of double checks have been performed on the hour angle values, however the hour angles still may not be correct so please let Jane Morrison (morrison@stsci.edu) know if you have a problem with Plate_Solution and you think it is an incorrect hour angle. Do not touch the GSCII_HOUR_ANGLE.DAT file!

    • Calling Sequence :

    PLATE_SOLUTION MCO filename
    [/CATALOG_CODE= 3 letter code {default = PPM}]
    [/USERMCO=filename]
    [/XRANGE=(lx,ux)]
    {default entire plate}
    [/YRANGE=(ly,uy)]
    {default entire plate}
    [/MAGRANGE=(lm,um)]
    {all magnitudes}
    [/[no]ONLY_STAR]
    Only use objects classified as stars
    [/FINAL_CLASS]
    Use the final class field to make the decision for the /ONLY_STAR decision
    [/DECISION_TREE]
    {default} Use the decision_tree classification to make the decision for the /ONLY_STAR decision
    [/MODEL=type]
    (3TERM, 6TERM, 10TERM, LINEAR, QUAD, CUBIC)
    {default, 10term}
    [/[no]REFRACTION]
    Apply refraction {default /norefraction}
    [/PROJECTION = gnomonic, equidistant]
    {default = gnomonic}
    [/ITERATE=([MAX_ITER=n{def=5}],[SIGMA=n{def=2.5}],[DELTA_SIGMA=n{def=0.25}])
    [/[no]ANNOTATE]
    {default /ANNOTATE} write to DID file
    [/[no]UPDATE_GSH]
    {default /UPDATE_GSH} update GSH calibration keywords
    [/[no]DUMPFILE]
    {default /DUMPFILE} create a dumpfile
    [/PLOT=plot_q]
    GS2150_POST, GS_POST, 4N_POST, X, NOPRINT{def})
    [/PRINT=print_q]
    (GS_ANSI{def}, GS2150_ANSI, 4N_ANSI, TTA3)
    [/VERBOSE]
    [/COMMENT="String"] write to DID file
    [/DEBUG]
    [/LIMIT RADIUS] **NOT IMPLEMENTED**
    [/DEBLENDED] **NOT IMPLEMENTED**
    [/REF NUM] **NOT IMPLEMENTED**

    Availability :

    • GSSS AXP - yes
    • GSSS VAX - yes
    • PIXELS - mo

    History/Author :

  • Original Implementation - Brian McLean (ASTROSOL)
  • Adapted to GSCII pipeline (removal of NAG dependency - 11/97) - Jane Morrison
  • Added refraction and equidistant projection (1/98) - Jane Morrison

    Things to add in the future

  • The refraction terms will be read in from the GSH header.
  • Add a flag to not use deblended (children) in the reduction.
  • Add a restrictions on which stars to use as reference stars: based on location on plate (/limit radius) and number of reference stars (/ref num).