PDS_VERSION_ID          = PDS3
RECORD_TYPE             = STREAM

OBJECT                  = TEXT
   INTERCHANGE_FORMAT   = ASCII
   PUBLICATION_DATE     = 2013-03-28
   NOTE                 = "Cassini SP-Kernel Covariance Table Information"
END_OBJECT              = TEXT

END


Covariance Tables
=================

   This directory contains covariance table files describing the formal
   position uncertainties of Cassini's reconstructed ephemeris provided
   in the SPK files produced by the CASSINI NAV Team.

   These table files have the same names as the corresponding SPK files
   with an additional suffix set to the NAIF ID of the body with
   respect to which the uncertainties are given. All table file names
   have extension ``.txt''.

   For example, the table file ``060213R_SCPSE_05348_06005_606.txt''
   describes the formal position uncertainties of Cassini's
   reconstructed ephemeris provided in the reconstructed SPK file
   ``060213R_SCPSE_05348_06005.bsp'' with respect to Titan (NAIF ID
   606) as a function of time.

   Each covariance table file contains a single header record showing
   the field (column) names and one or more covariance matrix term data
   records, each comprising seven fields (columns). The first column
   labeled ``UTC'' contains the UTC time of the record. The columns
   labeled ``Rad'', ``Trans'', and ``Norm'' contain the covariance
   matrix diagonal terms, whereas the columns labeled ``Rad-Trans'',
   ``Rad-Norm'', and ``Trans-Norm'' list the covariance matrix
   off-diagonal terms. The ``Rad'' term is directed along the vector
   from body to Cassini, the ``Norm'' term is directed along the
   Cassini orbit angular momentum vector relative to body, and the
   ``Trans'' term is directed along the vector formed by ``Rad'' cross
   ``Norm''.

   Covariances can be assembled from the terms in each row (each time)
   as follows:

      Rad             Rad-Trans       Rad-Norm
      Rad-Trans       Trans           Trans-Norm
      Rad-Norm        Trans-Norm      Norm

   The square-root of each diagonal term is the one-sigma formal
   uncertainty along that direction. Dividing a non-diagonal term by
   the product of the square-roots of the diagonal terms in the
   corresponding row and column produces the correlation coefficient
   between the two directions.

   The covariance matrix terms represent formal one-sigma statistics.
   To account for possible systematic errors, scaling the uncertainties
   by a factor of three (scaling each row and each column of the
   covariance matrix by three) is advised in order to obtain a better
   portrayal of realistic uncertainties.

   Tables for some SPKs are missing and, if provided by the NAV team,
   will be added to the data set at a later time.

   A few tables have coverage shorter than the coverage of the
   corresponding SPK file. There is currently no plan to regenerate
   these tables to provide the complete coverage.


Contact Information
===================

   Regarding Cassini project specific information provided in this data set
   and for general information about SPICE system:

      Boris Semenov
      (818)-354-8136
      Boris.Semenov@jpl.nasa.gov

   address:

      Navigation and Ancillary Information Facility (NAIF)
      Jet Propulsion Laboratory
      MS 301-125L
      4800 Oak Grove Drive
      Pasadena CA 91109 USA