readme.txt

该包是根据DE405提供的国际天球矩形参考框架的基本位置和速度方面的资料

 JPL PLANETARY AND LUNAR EPHEMERIDES 

    Export Information  [December 6, 2005]

                                      E M Standish, JPL

INTRODUCTION
------------

  The JPL Planetary and Lunar Ephemerides are available to outside users upon 
  request.  The package allows an EXPERIENCED user to obtain the RECTANGULAR
  COORDINATES (x,y,z) of the sun, moon, and nine major planets by
  means of a simple subroutine written in standard fortran.

  Note: this package does NOT provide other coordinates, such as right
  ascension and declination, azimuth and altitude, longitude and
  latitude, etc.  It provides ONLY rectangular positions and velocities
  with respect to the International Celestial Reference Frame.

  We suggest for the more casual user, JPL's interactive website and telnet
  service, "Horizons", which provides a wide variety of astronomical 
  information and which uses the full precision of our ephemerides.  See 
  the website,  "http://ssd.jpl.nasa.gov/".

  In fact, for information about many different kinds of ephemerides 
  (interactive, self-contained, high precision, etc.) see the following website:

         "http://ssd.jpl.nasa.gov/iau-comm4"

  and click on "Where to obtain ephemerides".  

  For those who truly need the high-precision, basic JPL ephemerides, there 
  are two methods of acquiring the ephemerides: 1) from this site via ftp and 
  2) via a CRrom from the publisher, Willmann-Bell (see Appendix B).

  The final goal of the installation process is the successful execution 
  of the main program "TESTEPH.F".  This program reads and interpolates 
  planetary and lunar coordinates from a binary direct-access ephemeris file 
  and compares these results against corresponding numbers produced at JPL.  
  "TESTEPH.F" uses the subroutines which are of eventual interest to the user.

  It is strongly suggested that a potential user first read through this
  README in its entirety.  This will provide an idea of what is involved in
  both the installation and in the usage of the ephemeris package.

This README contains the following sections;

  Introduction
  Location of the files
  What to do (ftp and install)
  Unix users vs. other users
  Contents to be retrieved by the user (which files to get via ftp)
  Brief item description: what each retrieved item is for
  Available ephemerides (which ones; what years are covered)
  Ephemeris sizes (how big the files are)
  References (publications describing the ephemerides)
  Software description (the subroutines which provide ephemeris information)
  Software Usage (calling sequences, etc.)
  Constants on the Ephemeris Files : what ephemeris constants are on the files
  Assistance (only in case of emergency)
    Appendix A : The internal format of the ephemeris files
    Appendix B : CDrom available from Willmann-Bell
    Appendix C : Corrections to the software on the CDroms
    Appendix D : Documentation of DE405 and DE406
    Appendix E : Versions of the software in various languages (from
                 outside sources)


*******************************************************************************

LOCATION
--------

The ephemeris package is available over Internet from the anonymous ftp server:

   ftp://ssd.jpl.nasa.gov//pub/eph/export/DE405/

******************************************************************************

WHAT TO DO
----------

  Retrieve the items, listed in the next sections, from the anonymous ftp site.

  Read the "usrguide", especially the parts about "NRECL" and "KSIZE"
   
  [Note: For UNIX-based users, the ephemeris files are available in binary 
  form, ready for immediate installation on the user's computer.  For all 
  others, the ephemeris is supplied in ASCII format and must be converted 
  (a one-time only process) into binary format for installation; software 
  is supplied for this conversion.  (Sorry, we have tried to export binary 
  files for other types of platforms, but the lack of uniformity from one 
  computer and/or compiler to the next made this too difficult.)  However, 
  I have received the following:

     "I have been able to read the unix binary files with no problem
     on my Mac, and I suspect that any machine that formats floating 
     point numbers in IEEE-754 (1985) format will be able to read them."]

******************************************************************************

CONTENTS TO BE RETRIEVED BY THE USER
------------------------------------

 ***  UNIX users: retrieve the following 7 items: 

          /pub/eph/export/usrguide
          /pub/eph/export/fortran/testeph.f
          /pub/eph/export/fortran/selcon.f
          /pub/eph/export/fortran/binmerge.f
          /pub/eph/export/fortran/binshort.f
          /pub/eph/export/unix/unxSYYYY.XXX  (multiple files)
          /pub/eph/export/test-data/testpo.XXX

     where "SYYYY" is the starting year of each particular ephemeris block 
     ("S" is the sign : "p" for + and "m" for -) and "XXX" is the ephemeris 
     number: 200, 403, 405 or 406.  See choices below for the different 
     ephemerides.

     The UNIX binary files come in 50-year blocks (3.8-4.7 Mbytes each, 
     depending upon the ephemeris).  Once they are installed on the user's 
     computer, contiguous blocks may be merged together to form a single 
     ephemeris file; this is done using "binmerge.f".

 ***  non-UNIX users: retrieve the following 9 items:

          /pub/eph/export/usrguide
          /pub/eph/export/fortran/testeph.f
          /pub/eph/export/fortran/selcon.f
          /pub/eph/export/fortran/asc2eph.f
          /pub/eph/export/fortran/binmerge.f
          /pub/eph/export/fortran/binshort.f
          /pub/eph/export/ascii/ascSYYYY.XXX  (multiple files)
          /pub/eph/export/ascii/header.XXX
          /pub/eph/export/test-data/testpo.XXX

     where "SYYYY" is the starting year of each particular ephemeris block
     ("S" is the sign : "p" for + and "m" for -) and "XXX" is the ephemeris
     number: 200, 403, 405, or 406.  See choices below for different 
     ephemerides.

     The ASCII files come in 20-year blocks (about 3.5 Mbytes each). The 
     blocks are converted into binary blocks on the user's computer, using 
     "asc2eph.f"; then, contiguous binary blocks may be merged together to 
     form a single ephemeris file using "binmerge.f".  An alternative
     method is to add all of the ascii blocks together and then
     convert that file into the binary ephemeris on the user's
     computer, using "asc2eph.f".

     A smaller portion of a binary ephemeris file may be extracted
     from a larger file using "binshort.f".

******************************************************************************

BRIEF ITEM DESCRIPTION
-----------------------

  "usrguide"     : User's Guide containing instructions for obtaining and using
                   the ephemerides, including the usage of the subroutines and 
                   the testing of the software package.
                      
  "testeph"      : Software Package containing a main program which uses the 
                   reading and interpolating subroutines.  This program 
                   compares the results with similar runs made at JPL in order 
                   to ensure that the ephemeris is installed and being read 
                   correctly.
                   
                   The reading and interpolating subroutines included in 
                   "testeph", along with the ephemeris file(s) themselves, are 
                   the items which are of eventual interest to the user.

  "testpo"       : Test results computed at JPL; these are input by the program
                   "testeph" and are used for testing the ephemeris 
                   installation.  There is a different "testpo" for each 
                   different ephemeris; they must match or the test will not 
                   work correctly.

  "binmerge"     : Program to merge two adjoining binary ephemerides.

  "binshort"     : Program to extract a portion of an ephemeris from a larger 
                   file.


  for UNIX users
  --------------

  "unxSYYYY.XXX" : Binary ephemeris files from JPL Ephemeris DEXXX, covering 50
                   years, starting in the year SYYYY ("p/m" for "+/-").  The 
                   pieces may be used separately, or the 50-year files 
                   (300-year files for DE406) may be merged into a single 
                   ephemeris file using the program, "binmerge.f".  Also, a 
                   shorter-span ephemeris may be extracted from a longer one 
                   using the program, "binshort.f".
                   

  for non-UNIX users
  --------------

  "asc2eph.f"    : A one-time conversion program which converts the ephemeris 
                   from ASCII format into binary form. 
                           
  "ascSYYYY.XXX" : ASCII ephemeris files from JPL Ephemeris DEXXX, each 
                   covering 20 years, starting in the year SYYYY ("p/m" for 
                   "+/-").  The 20-year blocks may be converted separately 
                   into binary ephemeris files using "asc2eph" or they may 
                   be combined into a single ASCII file and then converted 
                   into a single binary file.  Separate binary files
                   may be merged into a single ephemeris file using
                   the program, "binmerge.f".  Also, a shorter-span
                   ephemeris may be extracted from a longer one using
                   the program, "binshort.f".

  "header.XXX" : Header information for ephemeris deXXX, needed by "asc2eph.f".

******************************************************************************

AVAILABLE EPHEMERIDES
---------------------

DE200 : (includes nutations but not librations)

     JED 2305424.5 (1599 DEC 09)  to  JED 2513360.5  (2169 MAR 31)

     This ephemeris has been the basis of the Astronomical Almanac since 
     1984.  It is based upon the dynamical equator and equinox of J2000 
     (see Standish, 1982 and Standish, 1990).

DE403 : (includes both nutations and librations)

     JED 2433264.5 (1949 DEC 14)  to  JED 2469808.5 (2050 JAN 02)

     Kept available since it has been a standard for the IERS and has
     been used by others in the past.

DE405 : (includes both nutations and librations)

     JED 2305424.50  (1599 DEC 09)  to  JED 2525008.50  (2201 FEB 20)

     Our latest ephemeris; it is based upon the International Celestial 
     Reference Frame (ICRF).  (DE200 is within 0.01 arcseconds of the frame 
     of the ICRF).  DE405 was created in May-June 1997.

DE406 : the New "JPL Long Ephemeris" (includes neither nutations nor 
        librations)

     Note:  DE406 is available only in unix on the ftp site.  

     JED 0624976.50 (-3001 FEB 04) to 2816912.50 (+3000 MAY 06)

     This is the same ephemeris as DE405, though the accuracy of the 
     interpolating polynomials has been lessened (interpolation on the 
     64-day mesh points remains exact, however).  For DE406/LE406, the 
     interpolating accuracy is no worse than 25 meters for any planet and 
     no worse than 1 meter for the moon.

     DE406 requires about 10 megabytes for each 300-year block.

******************************************************************************

EPHEMERIS SIZES (ftp blocks)
----------------------------
                                    de200    de403     de405     de406

UNIX binary (50-year blocks)  :     3.8 Mb   4.1 Mb    4.7 Mb

UNIX binary (300-year blocks) :                                  10.0 Mb

ASCII (20-year blocks)        :     5.2 Mb             6.4 Mb

ASCII (25-year blocks)        :              6.1 Mb

******************************************************************************

REFERENCES
----------

 Newhall, X X, Standish, E.M. and Williams, J.G.: 1983, "DE102: a numerically 
   integrated ephemeris of the Moon and planets spanning forty-four centuries",
   Astronomy & Astrophysics, vol. 125, pp. 150-167.

 Standish, E.M.: 1982, "Orientation of the JPL Ephemerides, DE200/LE200, to 
   the Dynamical Equinox of J2000", Astronomy & Astrophysics, vol. 114, 
   pp. 297-302.

 Standish, E.M.: 1990, "The Observational Basis for JPL's DE200, the 
   planetary ephemeris of the Astronomical Almanac", Astronomy & Astrophysics,
   vol. 233, pp. 252-271.

 Standish, E.M., Newhall, X X, Williams, J.G. and Folkner, W.F.: 1995, 
   "JPL Planetary and Lunar Ephemerides, DE403/LE403", JPL IOM 314.10-127.

 Standish,E.M.: 1998, "JPL Planetary and Lunar Ephemerides,
   DE405/LE405",JPL IOM  312.F-98-048. 

   [the preceding 2 references are available in PostScript on the
   following website: http://ssd.jpl.nasa.gov/iau-comm4/relateds.html]

******************************************************************************

SOFTWARE DESCRIPTION
--------------------

The software package (apart from the programs used to initially construct the
ephemeris, asc2eph, binmerge, and binshort) consists of a main test program 
which uses the reading and interpolating routines in order to retrieve the 
ephemeris data and to compare the results against the Test Data.  

Two of the subroutines called by testeph.f are of primary interest to the user:
"PLEPH" and "SELCON".  Three others, "CONST", "DPLEPH", and "STATE" may also be
useful.

   PLEPH  :  Get the state vector (position and velocity) of one body with 
              respect to another at any given time within the interval covered 
              by the ephemeris.

   SELCON :  Retrieve values of user-requested constants on the ephemeris file.
 
   CONST  :  Retrieve values of all of the constants on the ephemeris file.

   DPLEPH :  Same as PLEPH, but with increased precision in the input time.

   STATE  :  Read and interpolate the ephemeris file. (Called by PLEPH).

******************************************************************************

SOFTWARE USAGE
--------------

C  NOTE : Over the years, different versions of PLEPH have had a 5th argument:
C  sometimes, an error return statement number; sometimes, a logical denoting
C  whether or not the requested date is covered by the ephemeris.  We apologize
C  for this inconsistency; in this version, we use only the four necessary
C  arguments and do the testing outside of the subroutine.


**  PLEPH  ********  subroutine pleph( tdb, npl, nctr, pv)  **********

    Input
    -----
          tdb [d.p.]  : julian ephemeris date
          npl [int.]  : planet number
          nctr [int.] : center number

             identifications for "npl" and "nctr"
             ------------------------------------
              1 = mercury           8 = neptune
              2 = venus             9 = pluto
              3 = earth            10 = moon
              4 = mars             11 = sun
              5 = jupiter          12 = solar-system barycenter
              6 = saturn           13 = earth-moon barycenter
              7 = uranus           14 = nutations in longitude and obliquity
                                   15 = librations (if they exist on the file)
                 (for nutations and librations, nctr=0)
    Output
    ------
          pv(6) [d.p.]  : x,y,z,x-dot,y-dot,z-dot [au, au/day]
                  for nutations, d(psi), d(eps), d(psi)-dot, d(eps)-dot
                                  [rads, rads/day]
                  for librations, (Euler angles and rates, w.r.t. the ephemeris
                                  reference frame)   [rads, rads/day]


**  SELCON  ********  subroutine selcon ( nams, nmbr, vals)  **********

    Input
    -----
    nams(nmbr) [char*6] : names for which values are requested (the list of 
                          names is given below)
    nmbr [int.]         : the number of names in 'nams'

    Output