| DATA_SET_DESCRIPTION |
This description was written by J. Kissel, J. Silen, B. Semenov,
and C. Acton.
Data Set Overview
=================
This data set contains raw time-of-flight spectrum data, which
are called ``events'' and are Level 1 data, and associated
ancillary data produced by the Stardust Cometary and Interstellar
Dust Analyzer Instrument (CIDA), a time-of-flight mass
spectrometer. The data were obtained during two mission episodes:
flyby of comet Wild-2, and cruise, which includes all other times
except the flyby. Each package of ``event'' and ancillary data is
telemetered to the ground as an Experiment Data Frame (EDF).
The term ``event'' is used to refer to any type of non-ancillary
data returned from the CIDA instrument. Some of these events are
test frames, generated by telecommands to ensure continued
correct operation of the instrument. Some events are the result
of a CIDA re-boot, which may have been commanded or may have been
a result of some other spacecraft condition. Some events are
known to have been generated by noise within the CIDA
electronics. All of these are considered non-scientific data and
are distinguished from scientific data by TARGET_NAME set to
``NON SCIENCE'' in the data labels and the data set index file.
459 of 535 (86%) EDFs in this data set contain non-scientific
data.
The remainder are events that may or may not contain spectra
resulting from actual particle hits; it is only through detailed
analysis that the user may make a determination of the cause of
the event and the resulting spectra may be interpreted. These
EDFs are distinguished by TARGET_NAME in the labels and index file
set to either ``81P/WILD 2 (1978 A2)'' (31 of 535 EDFs) or
``INTERSTELLAR PARTICLES'' (45 of 535 EDFs).
While included for completeness, the CIDA housekeeping and other
ancillary data are NOT needed for generation or interpretation of
CIDA spectra.
The CIDA event files include selected observation geometry
parameters, derived from the then-current SPICE kernels and
allied SPICE Toolkit software. These SPICE kernels are available
in a separate PDS Stardust data set, SDU-C-SPICE-6-V1.0.
The CIDA event data are supplemented with a PDS index file
providing a set of parameters computed for every CIDA event; this
information may be easily loaded into a database or spreadsheet
to facilitate searches for CIDA data meeting certain
user-specified observing conditions.
Data Collection Periods
=======================
Cruise Collection Period
------------------------
During the cruise from earth to Wild-2 and after the Wild 2
encounter the CIDA instrument was operating during the
following times:
Start Stop
------------------- -------------------
1999-02-22 1999-07-30
1999-09-13 2000-08-30
2000-10-10 2001-08-16
2002-11-02 2002-11-02
2003-02-04 2003-06-17
2003-07-16 2004-01-02T14:08:24
2004-01-03T01:23:08 2004-03-08
There were a number of short OFF times during these periods as
a result of the spacecraft going into safe-mode, spacecraft
maneuvers, and other reasons. The one day window on November 02,
2002 was during the Annefrank asteroid flyby, during which
no particle hits were detected.
Wild 2 Encounter Collection Period
----------------------------------
During the Wild-2 encounter the CIDA instrument was operating
during the following time:
Start Stop
------------------- -------------------
2004-01-02T14:27:06 2004-01-03T01:10:20
Data Calibration
================
The ``calibration'' of time-of-flight mass spectrometer data is in
fact the essence of the data analysis process. ``Calibration'' of the
data numbers contained in each event, resulting in a determination of
if a particulate impact actually occurred, and if so, of the
composition of the particle, may be straightforward, but may instead
be complex and subjective.
This data set includes a document, CALEXAMPL.PDF, providing a
complete description of the ``calibration'' of a laboratory test
event where the composition of the particle is well known. The
document also includes a similar ``calibration'' example for an
in-flight event obtained during the Wild 2 flyby.
Data Product Type and Format Overview
=====================================
CIDA data files provided in this archive are divided into two
main categories:
-- Spectrum Experiment Data Files (Spectrum EDFs), and
-- Housekeeping Experiment Data files (HK EDFs).
Spectrum EDFs contain the raw CIDA time-of-flight spectrum data.
Each Spectrum EDF file is sufficient for analysis in itself.
HK EDFs contain temperature, voltage and other engineering data
that might prove useful in reviewing the operating
characteristics of the instrument, but are NOT needed to
interpret the spectrum data.
There is only one type of Spectrum EDF, but there are five
different types of HK EDFs:
-- housekeeping parameters
-- configuration parameters
-- calibration parameters
-- global variable values
-- interrupt variable values
All CIDA data files are plain ASCII text files containing an
attached PDS label. The data are in the form of one (for HK EDFs)
or a few (for Spectrum EDFs) PDS-style, fixed-width column,
comma-delimited tables, the format and contents of which are
defined in the CIDASIS.TXT document included in the archive.
Each table contained in the file is identified in the attached
label by a separate TABLE object pointing to an external table
format file specifying individual table columns. The label format
and contents are described in detail in the ONLABELS.TXT file
included in the archive.
Data Processing
===============
The Stardust CIDA instrument output consisted of a variety of
binary data blocks called binary Experiment Data Files (EDFs),
each of which contained a set of spectrum or housekeeping data.
On board the spacecraft EDFs were packetized by the spacecraft's
flight software and downlinked within packets in the spacecraft
telemetry stream. For small housekeeping EDFs, multiple EDFs were
contained in one spacecraft telemetry packet while for large
spectrum EDFs the EDF was split between a few spacecraft packets.
A suite of software -- developed and run by the Stardust Data
Management and Archive Team (DMA) and collectively referred to
as CIDA Telemetry Processing Software (CTPS) -- retrieved packets
with CIDA data from the Telemetry Data Server(s)(TDS) used by the
Stardust Project, striped off ground system and spacecraft packet
headers, and placed the EDF data in a binary EDF collection file
for delivery to the CIDA science team. That binary file
essentially contained a ``chunk'' of a single stream of concatenated
EDFs.
The binary EDF collection files were then delivered to the CIDA
science Team, which used a set of software -- developed and run
by Finnish Meteorological Institute (FMI) and called
EDFPARSER/EDF2ASCII -- to combine ``chunks'' into a single
telemetry stream, extract individual binary EDFs from it, convert
binary data from individual EDFs into ASCII and save the ASCII
Spectrum EDF and ASCII HK EDF files in the format in which the
data are provided in this data set. For Spectrum EDF data the
conversion constituted simply printing byte values as ASCII
integers and did not involve any scaling and/or calibration of
the values. For the generic EDF header data and HK EDFs it in
some cases involved de-multiplexing fields and converting
ancillary fields containing count values into physical units --
temperatures, voltages, etc.
Ancillary Data
==============
Each Spectrum EDF file includes a table containing a number of
derived geometry parameters. These parameters were computed using
the following SPICE kernels archived in the Stardust SPICE data
set, SDU-C-SPICE-6-V1.0:
Kernel Type File Name
------------ ------------------------
LSK naif0007.tls
PCK pck00007.tpc
SCLK sdu_sclkscet_00080.tsc
sdu_sclkscet_00105.tsc
FK sdu_v17.tf
SPKs sdu_l_1999.bsp
sdu_l_2000.bsp
sdu_l_2001.bsp
sdu_l_2002.bsp
sdu_l_2003_w2.bsp'
sdu_w2_opnav.bsp
CKs sdu_sc_rec_1999_v2.bc
sdu_sc_rec_2000_v2.bc
sdu_sc_rec_2001_v2.bc
sdu_sc_rec_2002_v2.bc
sdu_sc_rec_2003_w2_v2.bc
sdu_sc_rec_w2_opnav.bc
------------ ------------------------
Coordinate System
=================
The geometry items provided in the geometry table of the Spectrum
EDF files are relative to either the ecliptic reference frame of
J2000 or the Stardust spacecraft reference frame. Refer to the
specification of the geometry table columns to see which
parameters are defined in which frame.)
The ecliptic reference frame of J2000 is defined as follows:
- +Z axis is along Ecliptic North at J2000 epoch
(2000 JAN 01 12:00 ET);
- +X axis is along vernal Equinox at J2000 epoch;
- +Y completes the right hand frame;
The Stardust reference frame is defined as follows:
- +X axis is along the longer side of the spacecraft bus and
points from the aerogel capsule side towards the dust shield
side;
- +Z is perpendicular to the deployed solar arrays surface and
points along the HGA pointing direction;
- +Y completes the right hand frame;
- the origin of this frame is at the center of the launch
vehicle interface ring attached to the shield side of the
spacecraft bus.
This diagram illustrates the spacecraft reference frame and CIDA
mounting with respect to it:
|| Dust Collector
|| Array
Solar Array Main ||
Shield +Z .-. Shield ||
.-. ^| | o
| |==========|====o===============o===============
`-' || |-------------------. . Solar
|| | |/| Array
|| | .-----. CIDA | |
<-------o| | | ' | | Return
+X +Y . __/ | | Capsule
| | `. `. |\|
| |--- `. `.---- -----' o---------
| | `. `. \_______/
`-' `.'`. Target
------> ------> ------> .' --------
Nominal . '
Incoming Particle `. ' 40 deg
direction during `.
Encounter `. Normal to
CIDA Target Plane
As seen on on the diagram CIDA is mounted on the +Y side of the
spacecraft bus. The CIDA target plane is parallel to the
spacecraft Y axis. The normal to the target plane is in the XZ
plane and 40 degrees from +X towards +Z.
The back of the opening between the target and the entrance to
the drift tube is shielded, not permitting particles coming from
the back (-X side) or top (+Z side) to hit the target. The
un-shielded part of the opening and non-planar geometry of the
target surface allow impacts by the particles coming from within
the angular range of a few degrees towards +Z and about 30
degrees toward -Z, measured from the +X axis.
Software
========
The data in this data set are in standard PDS format -- ASCII
text files with comma-delimited, fixed-width columns -- and,
therefore, can be viewed by PDS-provided programs or loaded into
commercial programs that support comma-delimited formats. For
this reason no special processing software is included in this
data set.
Unresolved Liens on the Data
============================
A request was made by the external peer reviewers to split the
data files into separate subdirectories for science and
non-science data. Resources were not available to make this
change and propagate it through the data set documentation. Users
should note that science and non-science data files are mixed in
a single directory, and can use the TARGET_NAME field to
discriminate among them as needed. The TARGET_NAME field is
included in the index provided with this data set.
Contact Information
===================
For any questions regarding the data in this archive, contact:
Dr. Jochen Kissel, Stardust CIDA Science Lead
Dr. Johan Silen, Stardust CIDA Science Team Member
Dr. Jouni Ryno, Stardust CIDA S/W Technical Lead
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