PDS_VERSION_ID                      = PDS3
RECORD_TYPE                         = STREAM
OBJECT                              = TEXT
  NOTE                              = "Description of the Lunar
     Prospector Level 0 Position data set file format"
  PUBLICATION_DATE                  = 1998-09-04
END_OBJECT                          = TEXT
END


            DESCRIPTION OF THE POSITION DATA SET FILE FORMAT

     This document describes the format of data product files of the
Position data set within the Lunar Prospector Level 0 archive.  The
format of this file type is not described with the PDS table object
because the information for each spacecraft position is stored on two
separate lines (records) within the file.  As such, the file you are
reading provides a discussion of the format of a Lunar Prospector
position file.

     In general, each spacecraft position file contains information
about the position of the spacecraft for a period of one day.
Position values are one minute apart.  The beginning of a sample
spacecraft position file is given below (Note that some spacing
between fields has been reduced to fit the line width of this file.):


19980116
DATE  JAN 16, 1998   0HRS   0MINS   .000SECS  (JULIAN DATE = 2450829.5000)
R 1837.725280 V 1.633686258 LAT -1.027664246 LON 42.09858986 HGT 99.72527992
DATE  JAN 16, 1998   0HRS   1MINS   .000SECS  (JULIAN DATE = 2450829.5007)
R 1837.695563 V 1.633720897 LAT -4.083539834 LON 42.05998070 HGT 99.69556307
DATE  JAN 16, 1998   0HRS   2MINS   .000SECS  (JULIAN DATE = 2450829.5014)
R 1837.667342 V 1.633747325 LAT -7.139519279 LON 42.02112939 HGT 99.66734168


     The first line of the file contains the starting date in the form
of yyyymmdd, where yyyy is the year, mm is the month, and dd is the
day of month.  The rest of the file contains pairs of lines.  Each
pair of lines contains one spacecraft position, along with spacecraft
velocity.  The first line of a given pair has the date and time of the
spacecraft position.  The time is given as UTC and as a Julian date.
The second line of the pair contains the spacecraft position and
velocity as follows:

R -       Spacecraft Radius:  The distance of the spacecraft from the
          center of the moon in km.

V -       Spacecraft Velocity:  The absolute velocity of the spacecraft
          in km/sec.

LAT -     Sub-spacecraft Latitude:  The selenographic latitude of the
          point directly beneath the spacecraft in degrees with north
          latitude as positive.

LON -     Sub-spacecraft Longitude:  The selenographic longitude of the
          point directly beneath the spacecraft in degrees with east
          longitude as positive.

HGT -     Spacecraft Altitude:  The distance of the spacecraft above the
          surface of the moon in km assuming that the moon is a sphere of
          radius 1738 km.