DATA_SET_ID = "CO-E/J/S/SW-CAPS-5-DDR-DERIVED-V1.0"
OBJECT = DATA_SET_INFORMATION
DATA_SET_NAME = "
CASSINI ORBITER SAT/SW CAPS DERIVED V1.0"
DATA_SET_COLLECTION_MEMBER_FLG = N
START_TIME = 2004-180T00:03:24
STOP_TIME = 2012-154T06:03:13
DATA_SET_RELEASE_DATE = 2013-077
PRODUCER_FULL_NAME = "JUDITH D. FURMAN"
DETAILED_CATALOG_FLAG = N
DATA_OBJECT_TYPE = "TABLE"
CITATION_DESC = "
Waite, J.H., Furman, J.D.,
CASSINI ORBITER SAT/SW CAPS DERIVED V1.0,
CO-E/J/S/SW-CAPS-5-DDR-DERIVED-V1.0,
NASA Planetary Data System, 2013."
DATA_SET_TERSE_DESC = "This data set consists of all of the
ion moments generated from the Cassini Plasma Spectrometer (CAPS)
singles (SNG) and time-of-flight (TOF) data."
ABSTRACT_DESC = "
This data set consists of all of the ion moments data generated from
the Cassini Plasma Spectrometer (CAPS) ion mass spectrometer
singles or time-of-flight uncalibrated data.
The data set contains the derived ion moments data as follows:
Ion Moments (ION_MOMT)
Density, Temperature, Average Flow Speed, Average Flow Velocity
Ions included are H+, H2+, and W+ (water group ions: O+, OH+, H2O+)
For times when CAPS is not producing data due to being turned off or
due to communication issues, the data set will not contain data.
Additionally, there will be no data during times when the calculations
are not possible."
DATA_SET_DESC = "
Data Set Overview
=================
This data set consists of all of the ion moments data generated from
the Cassini Plasma Spectrometer (CAPS) ion mass spectrometer
singles or time-of-flight uncalibrated data.
The data set contains the derived ion moments data as follows:
Ion Moments (ION_MOMT)
Density, Temperature, Average Flow Speed, Average Flow Velocity
Ions included are H+, H2+, and W+ (water group ions: O+, OH+, H2O+)
For times when CAPS is not producing data due to being turned off or
due to communication issues, the data set will not contain data.
Additionally, there will be no data during times when the calculations
are not possible.
ION Moment File Discussion
==========
The data provided in this file are the moments of the ion distribution
(density, temperature, and flow velocity) derived from measurements
from the CAPS/IMS (Ion Mass Spectrometer) [YOUNGETAL2004]. The final
adopted geometric factors, efficiencies, and other relevant instrument
parameters used to derive these moments are available in the CAPS PDS
User's Guide [WILSONETAL2012] and are slightly different than those
used in the study of Thomsen et al. [THOMSENETAL2010]. The final
values are based on calculations, laboratory calibrations, simulations,
and comparison of in-flight data with measurements from other
instruments, including CAPS/ELS (Electron Spectrometer [LEWISETAL2008,
LEWISETAL2010]) and RPWS (Radio and Plasma Wave Investigation
[GURNETTETAL2004]).
When the Ion Method Flag is 1, i.e., numerical integration of the
Singles (SNG) measurements, the partition of SNG counts into three
different species bins (H+, H2+, W+) is based on concurrent
measurements of the ion composition available from the Time-of-Flight
(TOF) data product from the same instrument (W+ represents the sum
of the 'water-group' ion species O+, OH+, H2O+, and H30+). This
partition and the numerical integration algorithm are described in
detail in Thomsen et al. [THOMSENETAL2010] and Thomsen and Delapp
[THOMSENETAL2005]. While the calculation of the moments (n,T,V) is
is done independently for each species [THOMSENETAL2010], for the PDS
submission we report only a single velocity vector, which is
calculated as a mass- and density- weighted average of the velocities
derived for the three species:
AveV = sum (m_i * n_i * V_i) / sum (m_i * n_i) where i=H+, H2+, W+
(note that the _ indicates that what follows is a subcript)
and where m_i and n_i are the ion mass and density of the ith species
(m_W+ is taken to be 16, although in practice it makes very little
difference whether one takes either extreme, i.e., 16 or 19). This
weighting is based on our experience [e.g., THOMSENETAL2010] that the
heavy-ion velocities are more reliable when they are available (hence
the weighting by m_i), but if they are not well-determined due to low
counts, the light-ion values are to be preferred (hence the weighting
by n_i). The reported temperatures represent averages of the values
perpendicular and parallel to the magnetic field.
Because the ion flows within the Saturnian magnetosphere are typically
transonic, an accurate measurement of the plasma properties requires
that the flow be in the field of view. Analysis of CAPS measurements
has determined that the magnetospheric flows typically lie near the
corotation direction [e.g., THOMSENETAL2010]. Therefore, the PDS file
includes a flag to tell whether or not the corotation direction lies
within the CAPS FOV. In addition, the numerical moments algorithm
does not work if the spacecraft is rolling or if the instrument is not
actuating. Under such conditions, the moments are flagged as 'bad'.
Therefore, there are three values for the quality flag: 'Not-bad;
corotation direction in FOV', 'Not-bad; corotation direction not in
the FOV', and 'Bad (s/c rolling and/or CAPS not actuating)'.
Data
====
The data are stored in multiple data files and have been organized
in folders, first by higher order data type and then by year. Each file
contains a maximum of 24 hours of data. Note that data is included in
the file based on the start time, and not the end time of the data.
Format of the data files can be found in the CAPS instrument archive
specification [FURMANETAL2013]. The format can also be found in the
.LBL files in the FM/HIGHERORDER/IONMOMT/YYYY specific directory,
co-located with the data.
Ancillary Data
==============
Ancillary data can be found in the ANC data file provided with the
CAPS UNCALIBRATED data set.
References
========
[FURMANETAL2005] CAPS standard data products and archive volume
software interface specification, Version 1.9, JPL SIS ID:
IO-AR-017, Southwest Research Institute, San Antonio, TX 78250,
2005.
[ARRIDGEETAL2009] The effect of spacecraft radiation sources on
electron moments from the Cassini CAPS electron spectrometer,
Planetary and Space Science, 57, 854-869,
doi:10.1016/j.pss.2009.02.011, 2009.
[GURNETTETAL2004] The Cassini Radio and Plasma Wave Investigation,
Space Sci. Rev. 114, 395-463, 2004.
[LEWISETAL2008] Derivation of density and temperature from the Cassini
Huygens CAPS electron spectrometer, Planetary and Space Science, 56,
901-912, doi: 10.1016/j.pss.2007.12.017, 2008.
[LEWISETAL2010] The calibration of the Cassini-Huygens CAPS Electron
Spectrometer, Plan. and Space Sci., 58, 427?436,
doi:10.1016/j.pss.2009.11.008, 2010.
[THOMSENETAL2005] Numerical moments computation for CAPS/IMS, Los
Alamos National Laboratory Report LA-UR-05-1542, 2005.
[THOMSENETAL2010] Survey of ion plasma parameters in Saturn's
magnetosphere, J. Geophys. Res., 115, A10220,
doi:10.1029/2010JA015267, 2010.
[WILSONETAL2012] PDS User's Guide for Cassini Plasma Spectrometer
(CAPS), 2012.
[YOUNGETAL2004] Cassini Plasma Spectrometer Investigation,
Space Sci. Rev. 114, 1-112, 2004."
CONFIDENCE_LEVEL_NOTE = "
Review
======
These data have been reviewed by the instrument team and are of the
highest quality that can be generated at this time. Science results
based on these data have been published in several journals (Science,
Nature, JGR, etc.). After submission to the PDS, these data will be
approved through the peer review process.
Data Coverage and Quality
=========================
Gaps
----
There are many gaps in the CAPS data stream and there are many
different sources for these gaps. Sources of gaps are as follows:
a. telemetry outages
b. data policing violations (CAPS data volume higher than
allocated)
c. incorrect spacecraft data management commanding
d. telemetry commanding during Cruise
e. instrument anomalies
f. instrument modes which don't return all data products
g. planned instrument power-off and/or sleep periods
h. instrument off due to bus imbalance/short issues
When there is no data for a time period, one of the above sources
is the reason behind the gap. There is no indicator to which of
the sources is responsible for the gap in data coverage.
Poor Data
---------
Even in environments that are condusive to moment generation, other
factors may influence the quality of the calculation. For each record
in the file, there is an associated quality flag that should be
examined to determine the teams confidence in the quality of the
calculation.
Limitations
===========
The main limitation for ION moments is that the data are only
generated during periods where the environment is condusive to moment
generation."
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