                         User manual to get_apriori_eop
 
 
                                Leonid Petrov
 
 
                                2005.04.01
 
 
                                Abstract
 
   Program  get_apriori_eop  is for creation a priori Earth orientation files
which can be used as input for Calc and Solve
 
 
Questions and comments about this guide should be sent to:
 
Leonid Petrov ( sgdass@lists.nasa.gov )
 
 
                                Table of contents:
 
 
1 ................ Overview
 
 
2 ................ How to use
 
 
3 ................ Configuration file
 
   3.1 ........... Format of configuration file
   3.2 ........... Example of configuration file
 
________________________________________________________________________________
 
        1 Overview
        ==========
 
   Program  GET_APRIORI_EOP  retrieves the file with apriori, either
file finals.all from the United States Naval Observatory (USNO) or
IERS C04 from the International Earth Rotation Service using
program wget for automatic files retrieval via ftp. Optionaly,
it downloads the second external EOP file which overwrites the values
defiend in the first exteronal EOP file. Optionally, it finds the
differences between the retrieved EOP series and the  EOP series in
erp format used by Solve as the Earth orientation mod-file, finds
parameters of linear regression of the differences in UT1, X pole
coordinates, Y pole coordinates, then (optionally) subtracts parameters
of linear regression from the external EOP series of UT1 and polar
motion. Finally, the subroutine get_apriori_eop re-formats resulting
EOP file to 1) ut1pm.dat and to 2) erp-format for Calc and Solve
for using it as an Earth orientation mod-file.
 
Program requires a parameter: configuration file.
 
        2 How to use
        ============
 
   Usage:  get_apriori_eop <configuration_file>
 
   It is convenient to run get_apriori_eop scheduled by cron every night.
 
        3 Configuration file
        ====================
 
  The configuration file controls the work of get_apriori_eop.
It contains directives which are specific for you Analysis Center
and assumed not to be changed frequently. The name of the
configuration file is passed as an argument to get_apriori_eop.
 
                3.1 Format of configuration file
                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
   Configuration file contains records of three type:
1) comments: any line which beginning from ##
 
2) directives for get_priori_eop: the line which starts from
# and which is not a comment line.
Directive consists of three or more words separated by one or more
blanks.
 
   Word1 -- symbol # -- directive attribute
   Word2 -- keyword
   Word3,4...  value(s) of the keyword.
 
   Configuration file should contain definition of all keywords and
   all variables listed in the next subsection.
 
   Descriptions of directives of get_apriori_eop configuration file.
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
  EXTFMT:   Format of the external file.
            One of USNO_FINALS or IERS_C04.
            Comment: USNO_FINALS file contains *two* sort of parameters
            grouped in left columns (1:134) and in right columns
            (135:185). Get_apriori_eop gets parameters from the left
            columns only.
 
  URLEXT:   URL of the external file which is to be browsed.
 
  URLEXT2:  URL of the second external file which is to be browsed.
            The external EOP series may be represented by two files.
            The second file overwrites the values defined in the
            first. The values defined only in the second file are
            kept untouched. THe length of the output file is
            determined by the first file. If the EOP should be
            represented with only one file, this field should be NONE.
 
  FILEXT:   local name of the external file after it is browsed to
            the local machine.
 
  FILEXT2:  local name of the second external file after it is
            browsed to the local machine. If URLEXT2 is NONE, then
            FILEXT2 should be NONE as well.
 
  FILERP:   File name of the reference erp file. This erp file should
            be in erp modfile format.
 
  FILOUT:   local name of the output file in erp modfile format.
 
  FILUPM:   local name of the output file in binary ut1pm format.
            Program Calc, dbedit and apriori can use files in this
            format.
 
  WGET_EXE: Filename with path of program wget. Program wget should
            be installed before calling get_apriori_eop.
 
  FL_ROT:   Flag whether to apply transformation of the external
            file. The value is one of TRUE or FALSE.
 
  ROT_FROM: Date of the left boundary of the dates range for which
            computation of linear regression is done. The right
            boundary is the date of the last observation which has
            been reference used for deriving reference EOP series.
            Format: yyyy.dd.mm, for example 2000.01.29 for
            January 29, year 2000.
 
  WEIGHTS:  Flag: which weights should be used for computation of
            regression coefficients. One of EQUAL or IN are allowed.
            EQUAL means that all weighs are 1. IN means that the
            weight is 1/DSQRT ( sig_x**2 + sig_r**2 ) where sig_f
            stands for formal uncertainty of external EOP and sig_r
            stands for formal uncertainty of reference EOP.
 
                3.2 Example of configuration file
                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
#############################################################################
##                                                                         ##
##  Configuration file for retrieving USNO finals Earth orientation        ##
##  parameter series to the Goddard Space Flight Center from the United    ##
##  States Naval observatory.                                              ##
##                                                                         ##
##                                       Last update: 01-APR-2005 16:35:06 ##
##                                                                         ##
#############################################################################
# URLEXT:   ftp://maia.usno.navy.mil/ser7/finals.all
# URLEXT2:  ftp://maia.usno.navy.mil/ser7/finals.daily
# FILEXT:   /tmp/usno_finals.fil
# FILEXT2:  /tmp/usno_daily.fil
# FILOUT:   /data1/save_files/last_usno_final.erp
# FILERP:   /data1/save_files/last.erp
# FILUPM:   /data1/save_files/ut1pm.dat
# WGET_EXE: /users/pet/bin/wget
# FL_ROT:   TRUE
# ROT_FROM: 2000.01.01
# WEIGHTS:  IN
 
