| DATA_SET_DESCRIPTION |
Data Set Overview
=================
The Mars Global Surveyor (MGS) Solar Conjunction Raw Data Archive
is a time-ordered collection of raw data acquired during the
Solar Conjunction in 2000, while MGS was in its Mars Mapping (MAP)
mission phase.
Two types of measurements were conducted during MAP; these
are known as closed-loop and open-loop recordings. The closed-
loop system used a phase-lock loop in the receiver to track the
downlink signal, reporting both amplitude and frequency at
rates typically of 1-10 times per second. In the open-loop
system, the signal was simply converted to a baseband frequency
range; the entire passband was sampled and recorded for later
processing. Typical open-loop sampling rates for MGS were
5000 samples per second. Closed-loop data are efficient for
characterizing slowly changing signals; open-loop data
(because of their much higher volume) are collected only
when the signal is very dynamic -- such as during an
occultation.
The data set includes two primary data types. Archival Tracking
Data Files (ATDFs or TDFs) are the most primitive (and most
voluminous) product of the closed-loop system. Original Data
Records (ODRs) are the primary data type from the open-loop system.
Parameters
==========
The ATDF is the primary output from the MGS closed-loop system.
ATDFs have 150 fields, though not all had been assigned during
the MGS era. Each ATDF 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 data fields include:
Range
High- or low-rate Doppler
High or low-rate downlink phase
Differential Range vs Integrated Doppler (DRVID)
Allan deviation
Smoothed noise
Uplink 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.
Open loop data records (ODRs) contain 8- or 12-bit samples of
receiver output. Each block of (typically) 1000 data samples
is accompanied by a 166 byte header. Each ODR is accompanied
by a full PDS label which describes both the content and format
of the file at the bit level. Header information includes:
Date and time of the first data sample
Sample rate and channel assignments
Receiver local oscillator (POCA) frequency
Attenuator settings
RMS voltages at several stages in the receiving chain
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).
ODS packets were converted to the older ODR (Original Data Record)
format for consistency in subsequent processing and archive.
Headers applied by the Ground Data System (GDS) during packet
handling have not been retained; they contained no additional
information about the data acquisition. The resultant data
accurately represent the output of the DSCC Spectrum Processing
(DSP) Subsystem at the DSN station. A full PDS label accompanies
each ODR file and gives a bit level description of the content
and format.
Data
====
ATDFs are stored in the TDF directory on archival volumes.
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 single letter (beginning
with 'A') denoting the sequence in which files with the same
ydddeee were handled. Generally ydddeeeB.TDF is a revised
version of ydddeeeA.TDF. The PDS label has file name
ydddeeeC.LBL. The typical ATDF contains about 39 Mbytes.
Original Data Records (ODRs) were produced whenever the DSP
was set to 'run' mode. These files are stored in the ODR
directory. In most cases, the entire DSP run was collected
into a single ODR file. But in other cases, it was more
convenient to subdivide the DSP data; queries were issued for
shorter time spans, and separate files were produced. File
names are of the form ydddhhmm.ODR where y is the one-digit
year of the first data, ddd is the day-of-year of the first
data, hh is the hour on which the first sample was taken, and
mm was the minute on which the first sample was taken. In
cases where two files had the same ydddhhmm (for example, two
DSN stations began recording at the same time, or a second query
was submitted for data which appeared suspicious after the
first query was processed), the less significant digit in mm
of the second file was converted to a letter ('0' became 'A',
'1' became 'B', ..., '9' became 'J'). In cases were three files
had the same ydddhhmm, the less significant mm digit was
converted to 'K', 'M', etc. The PDS label has file name
ydddhhmm.LBL.
Ancillary Data
==============
An extensive set of ancillary files is needed for proper
analysis and interpretation of the radio data (file types
TDF, and ODR). These are organized in parallel
directories and stored approximately chronologically.
Users should refer to the INDEX/CUMINDEX.TAB listing to
locate ancillary files.
Ionosphere Calibration Files (ION Directory)
---------------------------------------------------
Ionosphere Calibration files were produced by the Tracking
System Analytic Calibration (TSAC) Group at JPL. They
documented and predicted Earth ionospheric conditions.
These are ASCII files of variable length records. Each
record is delimited by an ASCII line-feed (ASCII 10).
File names have the form ydddeeeC.ION where y is
the one-digit year of the first data in the file, ddd is
the day-of-year of the first data in the file, eee is the
day-of-year of the last data in the file, and C is a
character denoting sequence when more than one file with the
same ydddeee is handled. C starts from 'A' and progresses
to 'B', 'C', etc. with increasing numbers of similar coverage
files. ION files were usually released at one week
intervals to cover a single month; ydddeeeA.ION would be
the file released during the first week, ydddeeeB.ION would
be the file released during the second week, etc. Each ION
file is accompanied by a PDS minimal label with file name
ydddeeeC.LBL. Typical file sizes are less than 50 kB.
Channelized DSN Monitor Data Files (MCH Directory)
---------------------------------------------------
Channelized DSN Monitor Data files were produced by the MGS
query server, operating on DSN Monitor packets stored in the
MGS Central Data Base (CDB). These are binary files, usually
representing the collection of DSN Monitor data received from
a 24 hour period; they are not readily interpretable by end
users. File names have the form ydddeeeC.MCH where y is
the one-digit year of the first data in the file, ddd is
the day-of-year of the first data in the file, eee is the
day-of-year of the last data in the file, and C is a
character denoting sequence when more than one file with the
same ydddeee is handled. C starts from 'A' and progresses
to 'B', 'C', etc. with increasing numbers of similar coverage
files. Each MCH file is accompanied by a PDS minimal label
with file name ydddeeeC.LBL. File sizes can be as large as
30 MB. In general, an MCH file can be derived from the
corresponding MPK file using MGS-provided software and a
decommutation map.
Also in some MCH directories are ASCII tables of extracted
channel values--channelized state vectors, or CSV files.
These are values for a limited number of potentially
useful MCH channels that have been saved in tabular form.
CSV files in the MCH directory have names of the form
CSVydddC.MCH where y, ddd, and C are the same as for
the corresponding MCH file. Each CSV file is accompanied
by a detached PDS label with name CSVydddC.LBL which
completely describes the format and content of the CSV file.
Monitor Channel Tables (MCT Directory)
--------------------------------------
Monitor Channel Tables were derived from MCH CSV files at
Stanford. Each table lists a single Monitor channel versus
time in an ASCII PDS TABLE format. File names have the form
XXXydddC.MCT where XXX is a three-character mnemonic for
the channel, y is the one-digit year, ddd is the three-
digit day-of-year, and C is a single character (starting
with 'A') denoting the version. Each MCT file is
accompanied by a PDS label with file name XXXyddC.LBL which
completely describes both the content and the format of the
table. Examples of MCT files include:
XXX Description
--- ---------------------------------------------
AGC AGC level from M-0349 (Ant A, Rcv A)
DSS DSS antenna ID from M-0300
ELA Elevation angle from M-0304 (Ant A)
TSY System temperature from M-0725 (Ant A, Rcv A)
TSZ System temperature from M-0725 (Ant A, Rcv B)
Sequence of Events Files (SOE Directory)
---------------------------------------------------
Sequence of Events Files were produced by the MGS Mission
Control Team. These are ASCII files of variable length
records. Until 1998-08-20 SOE files were produced in a
special format that allowed use with the MGS-provided soeedt
program. After 1998-08-20, files were produced in a straight
ASCII format that required no special software; these may be
identified by the '.tsoe' suffix in the ORIGINAL_PRODUCT_ID.
Each record is delimited by a carriage-return (ASCII 13)
line-feed (ASCII 10) pair, which may need to be removed
before the file is used on the local machine. File names
have the form ydddeeeC.SOE where y is the one-digit year
of the first data in the file, ddd is the day-of-year of
the first data in the file, eee is the day-of-year of the
last data in the file, and C is a character denoting
sequence when more than one file with the same ydddeee is
handled. C starts from 'A' and progresses to 'B', 'C',
etc. with increasing numbers of similar coverage files.
Each SOE file is accompanied by a PDS minimal label with
file name ydddeeeC.LBL. Typical file sizes are less than
1 MB.
Spacecraft/Planetary Ephemeris (SPK) Files (SPK Directory)
----------------------------------------------------------
Spacecraft/Planetary Ephemeris Files (also known as SP
kernels or SPK files) were produced by the MGS Navigation Team
(NAV). These files give spacecraft and planetary ephemerides.
These are ASCII files of variable length records in
a special NAIF 'transfer' format. Each record is delimited
by a carriage-return (ASCII 13) line-feed (ASCII 10)
pair, which may need to be removed before the file is used on
the local machine. After delimiter conversion (if needed)
the file would ordinarily be passed through the NAIF utility
SPACIT or TOBIN to convert it to the local binary format.
File names have the form ydddeeeC.SPK where y is the
one-digit year of the first data in the file, ddd is the
day-of-year of the first data in the file, eee is the
day-of-year of the last data in the file, and C is a
character denoting sequence when more than one file
with the same ydddeee is handled. C starts from 'A' and
progresses to 'B', 'C', etc. with increasing numbers of
similar coverage files. Each SPK file is accompanied by a
PDS minimal label with file name ydddeeeC.LBL. Typical file
sizes are less than 5 MB. Typical SPK files during MAP
included one day of orbit reconstructions followed by several
days of orbit predictions.
Troposphere Calibration Files (TRO Directory)
---------------------------------------------------
Troposphere Calibration files were produced by the
Tracking System Analytic Calibration (TSAC) Group at JPL.
They documented and predicted Earth tropospheric conditions.
These are ASCII files of variable length records. Each
record is delimited by an ASCII line-feed (ASCII 10).
File names have the form ydddeeeC.TRO where y is
the one-digit year of the first data in the file, ddd is
the day-of-year of the first data in the file, eee is the
day-of-year of the last data in the file, and C is a
character denoting sequence when more than one file with the
same ydddeee is handled. C starts from 'A' and progresses
to 'B', 'C', etc. with increasing numbers of similar coverage
files. TRO files were typically released at the beginning of
a month and covered the previous month. Each TRO file is
accompanied by a PDS minimal label with file name
ydddeeeC.LBL. Typical file sizes are less than 50 kB.
DSN Weather Files (WEA Directory)
---------------------------------
DSN Weather files were produced by the Tracking System
Analytic Calibration (TSAC) Group at JPL. Files give weather
calibration information for DSN complexes. These are ASCII
files of variable length records. Each record is delimited
by an ASCII line-feed (ASCII 10). File names have
the form ydddeeeD.WEA where y is the one-digit year of
the first data in the file, ddd is the day-of-year of the
first data in the file, eee is the day-of-year of the last
data in the file, and D is a single digit denoting the
DSN complex at which the data were acquired ('1' for
Goldstone, '4' for Canberra, or '6' for Madrid). WEA files
were typically released weekly and contain all weather data
for the complex since 1 January. Each WEA file is
accompanied by a PDS minimal label with file name
ydddeeeC.LBL. The files grow at the rate of approximately
90 kB per month.
Coordinate System
=================
SPK ephemeris files were produced for the J2000 inertial
reference frame. Other data types are not dependent on
definition of a coordinate system.
Software
========
Software for parsing, reducing, and analyzing data such as
these has been developed at Stanford University, at JPL and
elsewhere. 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
Young Minds CD Studio or Yamaha/GEAR authoring system.
The CD-WO volumes conform to ISO 9660 standards.
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