IPP Software Navigation Tools IPP Links Communication Pan-STARRS Links

Changeset 5119


Ignore:
Timestamp:
Sep 25, 2005, 10:03:35 AM (21 years ago)
Author:
eugene
Message:

updated mosastro text

File:
1 edited

Legend:

Unmodified
Added
Removed

  • trunk/Ohana/doc/www/html/Elixir-Tools/mosastro.htm

    r4726 r5119  
     1<meta name=file  content=gastro>
     2<meta name=title content=gastro>
     3<meta name=page  content=gastro>
     4
     5<p>
     6mosastro takes a collection of data from mosaic CCD images, all
     7individually astrometrized, and determines a single global astrometric
     8solution for the complete system.  In this process, it determines a
     9distortion model for the telescope arising from the optical system, as
     10well as mapping solutions relating the coordinate systems of the
     11individual chip pixels to the focal plane.  Both of these
     12transformations may involve up to 3rd order polynomials. 
     13
     14<p>
     15The suggested operation is to use gastro (or gastro2) to determine
     16linear astrometric solutions for the individual chips before running
     17mosastro.  Mosastro requires the individual chip astrometry have an
     18accuracy of roughly 1 arcsec or better in order to select the match
     19between the observed stars and the astrometric reference catalog.   
     20This two stage approach allows a more robust linear solution for the
     21individual chips, which may have too few reference star matches to
     22define reliable high-order solution.  The mosaic analysis determines a
     23single distortion model representing the physical contribution of the
     24telescope optics.
     25
     26Mosastro is run assuming the user has a collection of Elixir-style
     27astrometry / photometry files in one of the CMP/SMP/SMF set of
     28formats.  Mosastro will auto-detect the data format and load the
     29stellar astrometric and photometric measurements.  The collection of
     30data is assumed to consist of one file per chip, with names which are
     31sufficiently consistent that they can be identified with a single
     32filename including wild-cards.
     33
     34<p>
     35The user command looks like:
    136<pre>
     37mosastro (glob) (ext) (phu)
     38</pre>
    239
    3   mosastro ()
     40The first argument is an expression containing wild-cards which
     41expands into the collection of files containing the astrometric data.
     42The mosastro program must receive the wild-card expression
     43<em>without</em> expansion by the shell.  The user call needs to
     44protect the wild-card against expansion, which can usually be done by
     45placing the expression within double-quote marks.  The second argument
     46is the new output extension.  The stellar photometry will be written
     47out to files using the same names as the input, replacing the final
     48filename extension with the provided extension.  The standard input
     49extensions are one of the following: 'cmp', 'smp' (used for dophot or
     50sextractor output files in raw text format), 'cmf, 'smf' (used for
     51dophot or sextractor output files in fits table format).  The
     52recommended output extensions replace the 'c' or 's' with 'x': 'xmp'
     53for raw text format, or 'xmf' for FITS table format.  The final
     54argument is the name of the output 'primary header unit' file.  The
     55standard usage here is to use the filename root (without chip
     56identifiers) with the extension 'phu'.  The output telescope boresite
     57and optical distortion terms are written to this primary header entry,
     58which is constructed from the first of the chip files (true?). 
    459
    5   perform mosaic astrometry on a collection of FITS images.  The input
    6   consists of SMP files (see gastro) which have valid astrometric
    7   solutions.  Mosastro determines a complete mosaic astrometry
    8   solution, including a polynomial term for the telescope optical
    9   distortion and individual polynomials for each chip.
     60<em> future expansions: allow input list of files from a file, allow
     61input MEF collection of chip astrom/photom </em>
    1062
     63<p>
     64In the following discussion, we refer to conversions between
     65several coordinate frames.  We use the term 'project' to describe the
     66projection of the celestial coordinates to the linear (focal plane or
     67chip) coordinates; we use the term 'deproject' to describe the
     68conversion from the linear chip or focal-plane coordinates to the
     69spherical celestial coordinates.
     70
     71<p>
     72mosastro performs the following steps in the analysis. 
     73<ul>
     74<li> Load the raw stellar astrometry data from the chip files
     75<li> Deproject the stars using the approximate chip astrometry
     76<li> Determine the RA and DEC range of the observed star measurements
     77<li> Define the initial guess telescope boresite / distortion model
     78<li> Project the observed star coordinates to the focal plane
     79<li> Load the astrometric reference catalog.
     80<li> Project the reference catalog to the focal plane
     81<li> Match obs and ref on the focal plane
     82<li> Measure the local gradient of the matched star coordinate in the
     83tangent plane as a function of focal plane coordinate. 
     84<li> Fit the local gradient values as a function of focal plane coordinates
     85<li> Use the measured gradient model to modify the distortion model
     86<li> Fit low-order solution for the chip model
     87<li> Clip outlier matches
     88<li> Fit high-order solution for the chip model
     89<li> Perform several clip / fit iterations
     90<li> Write out the new solutions / data to the output file
     91</ul>
     92
     93<h3> options </h3>
     94
     95The following command-line options are available to the user:
     96
     97<ul>
     98<li> -help or -h : print summary help information
     99<li> -v : turn on verbosity
     100
     101<li> -dump (selection) : write out matched stars data at some
     102processing stage.  The selection specifies where in the analysis to
     103write out the result.  The following options are available:
     104<ul>
     105<li> rawstars : write out the raw input observed star positions, after
     106the initial projection
     107<li> refcat   : write out the reference catalog data (after initial
     108projection).
     109
     110<li> rawmatch : write out the obs and ref stars after the first match,
     111before any fit is performed
    11112 
     113<li> fitgrads : write out the obs and ref stars after correction for
     114the local gradient
     115 
     116<li> fitchips_unclip : write out the obs and ref stars after fitting
     117the initial chip term
     118
     119<li> fitchips : write out the obs and ref stars after the clipping
     120iterations.
     121</ul>
     122
     123<li> -save-residuals : save table of obs and ref star matches, with
     124coordinates in the multiple frames, as an extension to the PHU file.
     125
     126<li> -chips : load the initial chip focal-plane mapping (not yet implemented)
     127
     128<li> -field : load the inital field rotation, boresite, plate-scale
     129from reference file
     130
     131<li> -order : define the polynomial order of the telescope distortion
     132model (default is 0).
     133
     134-chiporder : define the polynomial order of the chip mapping model
     135(default is 1).
     136</ul>
     137
     138<h3> Elixir Configuration Data </h3>
     139
     140
    12141</pre>
     142
     143
     144
     145
     146
     147
     148
Note: See TracChangeset for help on using the changeset viewer.