| DATA_SET_DESCRIPTION |
Data Set Overview
=================
The Mars Pathfinder (MPF) Radio Science (RS) data archive
contains both raw radio tracking data collected during the
surface lifetime of the MPF Lander and results derived from those
data. Results include rotation rate, rotation axis, and (jointly
with Viking Lander data) the change in rotation rate for Mars.
For more information on the investigations see
[FOLKNERETAL1997A].
The raw data include two primary data types. Archival Tracking
Data Files (ATDFs or TDFs) are the most primitive (and most
voluminous) product. Orbit Data Files (ODFs) are edited versions
of ATDF files generated for spacecraft navigators.
In addition to the ATDF and ODF binary data files, an ASCII
version of the edited Pathfinder data is included, along with an
ASCII version of the edited data from the Viking landers.
Investigation results are presented in the form of ASCII tables.
Parameters
==========
The ATDF is the primary output from the Deep Space Network
tracking system. ATDFs have up to 150 fields, though not all are
used for Pathfinder. Each ATDF file in the data set is
accompanied by a full PDS label which defines both the content
and the format (at the bit level) of the file. ATDF fields
include:
High- or low-rate Doppler
Uplink phase
Differential Range vs Integrated Doppler (DRVID)
Range
Allan deviation
Smoothed noise
High or low-rate downlink phase
Other information included in ATDF data records is date and time;
spacecraft ID; ground station and its configuration; status flags
and values reported by various ground systems; calibration
values, noise estimates, and tolerances (station delay,
transmitter power, etc.); and signal strength.
The ODF is an edited version of the ATDF; it is a smaller file,
issued more frequently than the ATDF. It contains the most
important information (range and Doppler) needed by spacecraft
navigators and investigators interested in determining
gravitational fields of bodies such as Mars. Each ODF is
accompanied by a full PDS label which describes both the content
and format of the associated file. ODF fields include:
Narrowband spacecraft VLBI, Doppler mode (cycles)
Narrowband spacecraft VLBI, phase mode (cycles)
Narrowband quasar VLBI, Doppler mode (cycles)
Narrowband quasar VLBI, phase mode (cycles)
Wideband spacecraft VLBI (nanoseconds)
Wideband quasar VLBI (nanoseconds)
One-way Doppler (Hertz)
Two-way Doppler (Hertz)
Three-way Doppler (Hertz)
One-way total count phase (cycles)
Two-way total count phase (cycles)
Three-way total count phase (cycles)
PRA planetary operational discrete spectrum range (range
units)
SRA planetary operational discrete spectrum range (range
units)
RE[GSTDN] range (nanoseconds)
Azimuth angle (degrees)
Elevation angle (degrees)
Hour angle (degrees)
Declination angle (degrees)
X angle (where +X is east) (degrees)
Y angle (where +X is east) (degrees)
X angle (where +X is south) (degrees)
Y angle (where +X is south) (degrees)
Partially reduced data include tables of Doppler and range
measurements for MPF and the Viking Landers.
Tables of results give position of each lander in cylindrical
coordinates (longitude, radius, and z), pole right ascension and
declination, precession, Mars rotation at J2000, rotation rate,
obliquity, various drift rates, and uncertainties.
Processing
==========
ATDFs are screened for 'bad' data points, which are removed
before the file is released by the JPL Radio Metric Data
Conditioning Team (RMDCT).
ODFs are abstracted from subsets of ATDF data.
Range and Doppler measurements are used to define the relative
position and velocity of each lander with respect to the DSN
tracking station on Earth. A aeries of such measurements allows
inference of Mars' rotation and determination of lander
locations. Details are given in [FOLKNERETAL1997A].
Data
====
Data are stored on CD-WO volumes chronologically -- early ATDFs
appear on the first volume, later ATDFs appear on the second
volume. All other files are repeated on both volumes.
ATDFs are stored in the TDF directory. File names are of the
form ydddeeec.TDF, where y is the one-digit year of the first
data, ddd is the three-digit day-of-year of the first data, eee
is the three-digit day-of-year of the last data, and c is a
letter denoting the sequence in which files with the same ydddeee
were handled (beginning with 'A'). Generally ydddeeeB.TDF is a
revised version of ydddeeeA.TDF. The PDS label has file name
ydddeeeC.LBL. Typical ATDF file sizes are 39 Mbytes.
ODFs were issued approximately weekly; in some cases special ODFs
were also created. Most of the ODFs which were released are
included in the archival data set. ODFs are stored in the ODF
directory. File names are of the form ydddeeec.ODF where y is
the one-digit year of the first data, ddd is the three-digit
day-of-year of the first data, eee is the three-digit day-of-year
of the last data, and c is a single letter denoting the sequence
in which files with the same ydddeee were handled (beginning with
'A').
Partially processed data appear in the REDUCED directory.
MPF_DOPP.TAB and MPF_RANG.TAB are tables giving Doppler and
ranging results for Mars Pathfinder Lander. VIK_DOPP.TAB and
VIK_RANG.TAB are the corresponding files for the Viking landers.
The RESULTS directory contains lander positions and pole and
rotation results. LANDER.TAB gives longitude, radius, and z
coordinate for MPF, Viking Lander 1, and Viking Lander 2.
MAR_RA_D.TAB gives pole right ascension at J2000 and rate in
degrees/century, declination at J2000 and rate, rotation at J2000
and rotation rate in degrees/day. MARS_ROT.TAB gives obliquity
and obliquity rate, longitude of node, precession rate, rotation
about the pole, rotation rate, annual sine and cosine variations,
and semi-annual sine and cosine variations.
Ancillary Data
==============
An extensive set of ancillary files is needed for proper analysis
and interpretation of the radio data (file types TDF and ODF).
These are organized in parallel directories. All Pathfinder
ancillary files appear on each CD-WO volume.
Files in the CALIB Directory
----------------------------
The CALIB directory includes files with station calibrations
for ranging passes, and calibrations for Earth troposphere and
ionosphere. Each file is accompanied by a PDS label.
Earth Orientation Parameter Files (EOP Directory)
-------------------------------------------------
Earth Orientation Parameter files are produced by the Time and
Earth Motion Precision Observation (TEMPO) Group at JPL. These
are ASCII files of variable length records. The file
EOP12_97.TXT covers past motion since about 1962 through
December 1997. The EOP file is accompanied by a PDS label with
file name EOP12_97.LBL.
Software
========
Software for parsing, reducing, and analyzing data such as these
has been developed at several institutions. Because such
software must usually operate at the bit-level and is written for
a narrow range of platforms, it is not suitable for general
distribution. No software is included with this archival data
set.
Media/Format
============
The archival data set is written on CD-WO media using the
QuickTOPIX software for Macintosh. The CD-WO volumes conform to
ISO 9660 standards.
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