| DATA_SET_DESCRIPTION |
Data Set Overview
=================
The Cassini Radio Science Titan Bistatic and Occultation
experiment (TBOC2) Raw Data Archive is a time-ordered collection
of radio science raw data acquired on May 20, 2006,
during the Tour subphase of the Cassini mission.
The DATA_SET_ID 'CO-SSA-RSS-1-TBOC2-V1.0' includes the following
components:
Instrument host (i.e., 'CO' for CASSINI ORBITER)
Target (i.e., 'SSA' for Saturn's Satellite)
Instrument (i.e., 'RSS' for Radio Science Subsystem)
Data processing level number (i.e., '1')
Description (i.e., 'TBOC2')
Version number (i.e., 'V1.0')
Two types of measurements were obtained; these are known
as closed-loop and open-loop recordings. The closed-loop
system uses a phase-lock loop in the receiver to track the
downlink signal, reporting both amplitude and frequency 10
times per second. In the open-loop system, the signal is
simply converted to a baseband frequency range; the entire
passband is sampled and recorded at 16000 samples per second.
The data set includes three primary data types. Tracking and
Navigation Service Data Files (TNFs) are the most primitive (and
most voluminous) product of the closed-loop system. Orbit Data Files
(ODFs) are compressed versions of TNFs, specifically targeted to
spacecraft navigators and scientists interested in gravity fields.
Radio Science Receiver (RSR) files are the primary data type from
the open-loop system.
Parameters
==========
The TNF is the primary output from the Cassini closed-loop system.
Each TNF in the data set is accompanied by a PDS minimal label.
TNF data fields include:
High- or low-rate Doppler
Range
Uplink frequencies (ramps)
Differential Range vs Integrated Doppler (DRVID)
Allan deviation
Smoothed noise
Other information in TNF data records includes sample 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 a product of the closed-loop system;it contains the most
important information (range, Doppler and frequency ramps) needed by
spacecraft navigators, and investigators interested in determining
gravitational fields. Each ODF is accompanied by a full PDS label
which describes both the content and format of the associated file.
ODF data fields include:
One-way Doppler (Hertz)
Two-way Doppler (Hertz)
Three-way Doppler (Hertz)
SRA planetary operational discrete spectrum range (range
units)
The Radio Science Receiver (RSR) files are the primary output
from the Cassini open-loop system and they contain 16-bit samples
of receiver output. Each RSR file is accompanied by a full PDS label
which describes both the content and format of the file at the
bit level.
Processing
==========
The closed-loop Tracking and Navigation Service Files (TNFs)
and the Orbit Data Files (ODFs) for the Cassini TBOC2 are
constructed so that each file contains the data for each day.
ODFs are constructed by the RMDCT; they are constructed so that
each file contains the data for each day.
The open-loop Radio Science Receiver (RSR) files are screened for
gaps. No gaps were found in the RSR files for TBOC2.
Primary Data
============
The primary data are stored on DVD volumes in subdirectories TNF,
ODF and RSR in per-day directories TBOC2_ddd (where ddd specifies
the day of year based on the start time of the data). Users should
refer to the INDEX/CUMINDEX.TAB listing to locate primary data
files.
TNFs are stored in the TNF directory on archival volumes.
File names are of the form sssttaayyyy_ddd_hhmmxuuwVn.TNF,
where 'sss' is the sequence/orbit id (e.g., S19), 'tt' is the
target id (e.g., TI),'aa' is the activity/experiment id (e.g., BI),
'yyyy_ddd_hhmm' is the date and time for the start of included data
(e.g., 2006_077_2358), 'xuu' is the transmitter band and uplink
station (e.g., X25 or NNN for no uplink), 'w' is the ground mode
or 'way' (e.g.,1 for 1-way mode) and Vn is the file version
(e.g., V0).
The PDS label has file name sssttaayyyy_ddd_hhmmxuuwVn.LBL.
The typical TNF contains about 100 Mbytes.
ODFs are stored in the ODF directory on archival volumes.
File names are of the form sssttaayyyy_ddd_hhmmxuuwVn.ODF.
The PDS label has file name sssttaayyyy_ddd_hhmmxuuwVn.LBL.
The typical ODF contains about 3 Mbytes.
RSR files are stored in the RSR directory on archival volumes.
File names are of the form sssttaayyyyddd_hhmmxuudrrPD.rcs,
(or sssttaayyyyddd_hhmmxuudrrPV.rcs for an RSR file that has
been coverted from a VSR - a VLBI Science Receiver file)
where 'sss' is the sequence, (e.g., S19), 'tt' is the target,
(e.g., TI), 'aa' is the activity, (e.g., BI), 'yyyy' is the
year, (e.g., 2006), 'hhmm' is the start time, (e.g., 1955),
'xuu' is the uplink band and uplinking station, (e.g., X14),
'drr' is the downlink band and receiving station, (e.g., K25
or NNN for no uplink), P is the polarization, (e.g., R for right
circular polarization), and 'rcs' is the RSR channel and
subchannel that were used to collect the data (e.g., 1A1 or
1N1 for an RSR file that has been coverted from a VSR -
a VLBI Science Receiver file).
The PDS label has file name sssttaayyyyddd_hhmmxuudrrPD.LBL.
The typical RSR file contains from about 100 Mbytes to about
500 Mbytes.
Secondary Data
==============
Secondary data are needed for proper analysis and interpretation
of the radio data (file type, RSR). Secondary data
that cover a time span of 24 hours or less are stored in
subdirectories of TBOC2_ddd (i.e., 158, PD1, PD2 and TLM).
Secondary data that cover a time span greater than 24 hours are
provided in subdirectories CKF, EOP, ION, SPK and TRO in the
TBOC2_ANCILLARY directory. Users should refer to the
INDEX/CUMINDEX.TAB listing to locate secondary data files.
0158-Monitor Files (158 Directory)
---------------------------------------------------
0158-Monitor files are ASCII files with names
sssttaayyyy_ddd_hhmm_hhmmrr.158 where 'hhmm_hhmm' is the start
and end time of the file and 'rr' is the receiving station.
They are channelized DSN Monitor Data files (new format) and
they are produced at JPL by a Query Server operating on DSN Monitor
packets stored in the JPL Telemetry Delivery System (TDS) Data
Base. Each 0158-Monitor file is accompanied by a PDS label
with file name sssttaayyyy_ddd_hhmm_hhmmrr.LBL. Typical file size
is about 15 MB.
Path Delay Files (PD1 and PD2 Directories)
-----------------------------------------------------------
Path Delay files are ASCII files and they are produced by the
RSSG at JPL. File names have the form
sssttaayyyy_ddd_hhmm_hhmmrr.PD1 (stored in the PD1 directory - the
'1' in 'PD1' indicates that the data have been collected from
Advanced Water Vapor Radiometer (AWVR) Unit 1) and
sssttaayyyy_ddd_hhmm_hhmmrr.PD2 (stored in the PD2 directory - the
'2' in 'PD2' indicates that the data have been collected from AWVR
Unit 2) where 'hhmm_hhmm' is the start and end time of the data
and rr is the receiving station. Each Path Delay file
is accompanied by a PDS minimal label with file name
sssttaayyyy_ddd_hhmm_hhmmrr.LBL. Typical file size is 135 KB.
Telemetry Files (TLM Directory)
---------------------------------------------------
Telemetry files are ASCII files with names
sssttaayyyy_ddd_hhmm_hhmm.TLM where 'hhmm_hhmm' is the start and
end time of the file. They are channelized DSN Telemetry Data files
and they are produced at JPL by a Query Server operating on DSN
Telemetry packets stored in the JPL Telemetry Delivery System (TDS)
Data Base. Each Telemetry file is accompanied by a PDS label
with file name sssttaayyyy_ddd_hhmm_hhmmrr.LBL. Typical file size
is about 80 MB.
C-Kernel Files (CKF Directory)
---------------------------------------------------
C-Kernel Files are in transfer format and they are produced by the
Cassini Attitude and Articulation Control Subsystem team (AACS).
File names have the form sssttaayyyy_ddd_yyyy_ddd.CKF where
'yyyy_ddd_yyyy_ddd is the start and end time of the file. Each
C-Kernel file is accompanied by a PDS minimal label with file name
sssttaayyyy_ddd_yyyy_ddd.LBL. Typical file size is 20 MB.
Earth Orientation Parameter files (EOP Directory)
---------------------------------------------------
Earth Orientation Parameter files are ASCII files and they are
produced by the Kalman Earth Orientation Filter (KEOF) Group
at JPL. File names have the form sssttaayyyy_ddd_yyyy_ddd.EOP.
Each EOP file is accompanied by a PDS minimal label with file
name sssttaayyyy_ddd_yyyy_ddd.LBL. Typical file size is 24 KB.
Ionosphere Calibration Files (ION Directory)
---------------------------------------------------
Ionosphere Calibration files are produced by the Tracking
System Analytic Calibration (TSAC) Group at JPL. They provide
historical and predicted Earth ionospheric conditions.
File names have the form sssttaayyyy_ddd_yyyy_ddd.ION.
Each ION file is accompanied by a PDS minimal label with file
name sssttaayyyy_ddd_yyyy_ddd.LBL. Typical file size is 23 KB.
Spacecraft/Planetary Ephemeris (SP-Kernel) Files (SPK Directory)
----------------------------------------------------------
Spacecraft/Planetary Ephemeris Files (also known as SP kernels
or SPK files) are produced by the Cassini Navigation Team
(NAV). These files give spacecraft and planetary ephemerides.
File names have the form sssttaayyyy_ddd_yyyy_ddd.SPK.
Each SPK file is accompanied by a PDS minimal label with file
name having the form sssttaayyyy_ddd_yyyy_ddd.LBL. Typical
file size is 20 MB.
Troposphere Calibration Files (TRO Directory)
---------------------------------------------------
Troposphere Calibration files are produced by the
Tracking System Analytic Calibration (TSAC) Group at JPL.
They provide historical and predicted Earth tropospheric
conditions. File names have the form sssttaayyyy_ddd_yyyy_ddd.TRO.
Each TRO file is accompanied by a PDS minimal label with file name
sssttaayyyy_ddd_yyyy_ddd.LBL. Typical file size is 120 KB.
Files in the CALIB Directory
=============================
The CALIB directory contains a Leapsecond kernel file, a Spacecraft
Clock Conversion file, a USO Characterization Report and a
Boresight Calibration Report. All files in the CALIB directory are
ASCII text files with variable length records delimited by
ASCII carriage-return line-feed pairs. All file names in this
directory contain the string 'yymmdd', where yy, mm, dd
indicate the year, month and day of the file creation.
Leapsecond kernel files are a record of leap seconds (past and
predicted) that allow proper conversion between ephemeris time
and UTC. File names are of the form:
LSK_yymmdd.TLS
Each file LSK_yymmdd.TLS is accompanied by a PDS detached minimal
label with name LSK_yymmdd.LBL.
Spacecraft Clock Conversion files allow time measured by the
spacecraft clock to be converted to other time systems (e.g.,
ephemeris time or UTC). File names are of the form:
TSC_yymmdd.SCK
Each file TSC_yymmdd.SCK is accompanied by a PDS detached minimal
label with name TSC_yymmdd.LBL.
The Boresight Calibration Report and the USO Characterization Report
are produced by the Radio Science Systems Group (RSSG) at JPL.
The naming convention for these files is:
BORESIGHT_yymmdd.TXT
USO_yymmdd.TXT
Coordinate System
=================
SPK files are produced in the J2000 inertial
reference frame. Other data types are not dependent on any
definition of a coordinate system.
Software
========
Software for parsing, reducing, and analyzing data such as
these has been developed 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 unsuitable for
general distribution. As such, no software is included with
this archival data set.
Media/Format
============
The archival data set is written on DVD-R media. The DVD-R volumes
conform to the 'UDF_ISO-9660_BRIDGE' structure as required by PDS.
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