Data Set Information
|
| DATA_SET_NAME |
CASSINI COSMIC DUST ANALYZER CALIBRATED/RESAMPLED DATA
|
| DATA_SET_ID |
CO-D-CDA-3/4/5-DUST-V1.0
|
| NSSDC_DATA_SET_ID |
|
| DATA_SET_TERSE_DESCRIPTION |
Dust data from the Cosmic Dust Analyzer of the Cassini
Orbiter, not including the High Rate Detector.
|
| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set includes all data from the Cassini Orbiter Cosmic Dust
Analyzer (CDA), with the exception of the High Rate Detector (HRD) data
which will be included in a separate data set. All data
products in this data set are in tabular format. Each of the data
products (or product types) are described below. CDA Area Table - The
sensitive area of the CDA Impact Ionization Detector (IID) and Chemical
Analyzer Target (CAT) is tabulated as a function of the incident angle
with respect to the instrument axis. CDA Status History - Cassini
mission and CDA configuration, tests and other events. Records are
triggered by change in status affecting the sensitivity of the different
CDA subsystems and mission events. CDA events Table - Detector responses
and derived quantities from the Cassini dust detector as well as
spacecraft geometry information for noise or dust events. CDA Spectra
Table - Time-of-flight mass spectra peaks for individual impact events.
CDA MP Signal Tables - (multiple files) Time-of-flight mass spectra
signals for individual impacts. CDA QI Signal Tables - (multiple files)
Ion signals for individual impacts. CDA QT Signal Tables - (multiple
files) Electron signals for individual impacts as detected on the IID
target. CDA QC Signal Tables - (multiple files) Electron signals for
individual impacts as detected on the CAT target CDA QP Signal Tables -
(multiple files) Induced charge signal for individual impacts at the
entrance grid. CDA Table Settings - Table of voltages corresponding to
voltage level codes and Coulomb threshold settings. CDA Counter Table -
CDA impact counter time history file. There are 19 possible counter
values. Each event is evaluated on-board by the flight software and
receives one counter value. During the mission, successive improved
versions of the flight software were uploaded. Hence, the event
evaluation by the counter values evolved with time, allowing a better
classification of the events.
Calibration Issues
==================
1. Calibration of the Impact Ionization Detector
The calibration principle of the impact ionization detector is similar
to the Galileo instrument and Ulysses instrument
[GRUENETAL1992A],[GRUENETAL1992B] (see CDAREFS.CAT). The calibration of
the velocity-dependence of the signal rise times as well as the
calibration of the mass-velocity-dependence of the plasma charge yields
is based upon impact experiments in ground based laboratory
accelerators. In such facilities, impacts of particles with known mass
and velocity onto the flight spare unit can be studied. Besides
laboratory experiments, in-flight measurements in the well-understood
environment at 1 AU as well as measurements of Jovian stream particles
contributed to the instrument calibration. Up to now the interference of
the inner target (CAT) with the outer target (IID) is not entirely
understood. Therefore, future calibration work will be focused on this
issue.
2. Calibration of the Mass Analyser
The calibration of the TOF mass spectrometer is still preliminary. In
order to determine the mass resolution as well as the instrument
characteristics, particles of known composition were shot in the
Heidelberg dust accelerator onto the flight spare unit. Calibration data
for both subsystems, will be provided in subsequent deliveries.
Amplification Changes
=====================
The amplification factors of three instrument channels changed. Affected
are the channels QC (Electron signal, Chemical Analyser Target), QA
(Ion signal, Chemical Analyser Grid) and QT (Electron signal, Impact
Ionisation Target). The amplification factor determines the amount of
measured impact charge and is given by the conversion from dn-values
to charge values (Coulomb).
QT channel
----------
In total, two amplification changes were observed. The amplification
droped by a factor of 195 at a time between 2008-039T14:13:55 and
2008-039T19:50:15 (noise analysis of channel QT). The time of
2008-039T18:00:00 is taken for the change in conversion. A second
change in amplification occured in the timeframe 2009-224T18:30:00 and
2009-224T23:30:00 (noise analysis). The drop factor after this time
range is 22. The time of this change for archiving purposes is set to
2008-224T22:00:00.
Possible background/explanation:
--------------------------------
A RPXing occured at 2008-039T17:51 at 3.46 Saturn radii distance. On
day 224T21:06 the Enceladus flyby occured (E4, rev 80) with an
altitude of only 50 km above the surface.
QC channel
----------
Amplification dropped by factor of 140 at a time which lies between
2008-283T16:02:41 and 2008-283T21:31:02. The time of change for
archiving is set to : 2008-283T20:00:00.
Background:
-----------
An Enceladus flyby occured at 2008-283T19:06 (E5, rev 88) with an
altitude of 25 km and FSW 12.2 was used. Status as of 212-2009: Drop
factor still 140 (amplitude of TP3 = 131 dn)
QA channel
----------
The noise level of channel QA changed as well. However, this channel
is not digitized and no raw data information is available. A noise
test showed, that channel QA became insensitive in the time range
between 2008-208 and 2008-261. For overall calibration this change
has no effect and no changes in data processing is required for DPS
work.
|
| DATA_SET_RELEASE_DATE |
2005-07-01T00:00:00.000Z
|
| START_TIME |
1997-03-25T12:00:00.000Z
|
| STOP_TIME |
N/A (ongoing)
|
| MISSION_NAME |
CASSINI-HUYGENS
|
| MISSION_START_DATE |
1997-10-15T12:00:00.000Z
|
| MISSION_STOP_DATE |
N/A (ongoing)
|
| TARGET_NAME |
DUST
|
| TARGET_TYPE |
DUST
|
| INSTRUMENT_HOST_ID |
CO
|
| INSTRUMENT_NAME |
COSMIC DUST ANALYZER
|
| INSTRUMENT_ID |
CDA
|
| INSTRUMENT_TYPE |
COSMIC DUST ANALYZER
|
| NODE_NAME |
Small Bodies
|
| ARCHIVE_STATUS |
LOCALLY ARCHIVED
|
| CONFIDENCE_LEVEL_NOTE |
Events table
-----------------
Some values described in the PDS label table could not be provided in
this volume and are set to their missing constant value. PLEASE CONTACT
THE CDA TEAM BEFORE USING THE DATA FOR AN UPDATE OF THE CONFIDENCE
LEVEL. Efforts will be made to have those data provided in the
subsequent delivery. The missing values are:
- Particle speed and particle speed error factor
The reliable determination of the impactors velocity depends on ground
calibrations. For technical reasons, calibrations could be performed
only with a limited amount of material. In particular, calibration data
for ice particles are not available. However, recent measurements of icy
E ring particles during the early Cassini tour reveal a strong
dependance of the impact velocity determination upon impactor material,
and allow in-flight calibration. Calibrated velocity data will therefore
be provided only in future delivery, when a better understanding of the
instrument response will be reached.
- Particle mass and particle mass error factor
As the mass determination of an impacting particle requires the
determination of its impact velocity, the particle mass can not be
derived accuratly right now.
- Target flag
This flag, indicating where a dust particle impacted on the target,
should be provided in a future delivery, as identification routines
become more reliable.
- Event quality
This flag, evalutating the quality of an event, should be provided in a
future delivery, as event evaluation routines become more reliable.
- Particle charge
This value will be provided in a future delivery.
- Particle charge error
This value will be provided in a future delivery.
While the counter value is provided for each event, as returned by the
flight software, a detailed documentation about the meaning of the
different counter values is missing. However, the CDA team plan to
provide this documentation a bit later. This comment is also valid for
the counter table.
CDASPECTRA table
-----------------
As of the delivery date, the data contained in this table can not be
provided. Some data (like the number and position of peaks in the TOF
spectra) need more time to be derived reliably, and do not belong to the
minimum PDS requirement, as level 2 data. However, they will be provided
in a future delivery.
|
| CITATION_DESCRIPTION |
Altobelli, N., S. Kempf, and R. Srama, Cassini Cosmic
Dust Analyser Data V1.0, CO-D-CDA-3/4/5-DUST-V1.0, NASA
Planetary Data System, 2005.
|
| ABSTRACT_TEXT |
The Cosmic Dust Analyzer (CDA) is an instrument on the Cassini Orbiter
that studies the physical properties of dust particles hitting the
detector. This data set includes all data from the CDA with the
exception of the High Rate Detector (HRD). Please refer to
[SRAMAETAL2004B] (see CDAREFS.CAT) for a detailed CDA description.
|
| PRODUCER_FULL_NAME |
NICOLAS ALTOBELLI
|
| SEARCH/ACCESS DATA |
Asteroid/Dust SBN Website
|
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