| DATA_SET_DESCRIPTION |
This description was written by J. Kissel, J. Silen, B. Semenov,
C. Acton and J. Ryno.
Data Set Overview
=================
This data set contains Level 2 and 3 time-of-flight spectrum 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 episodes of the
Stardust-NExT extended mission: flyby of comet Tempel 1; and cruise,
which includes all other times except the flyby ([VEVERKAETAL2011],
[KISSELETAL2003], [GREENETAL2004]).
The spectra are called 'events.' Each package of 'event' and
ancillary data was 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.
588 of 705 (83%) 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 '9P/TEMPEL 1 (1867 G1)' (80 of 705 EDFs) or
'INTERSTELLAR PARTICLES' (37 of 705 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 Wild 2 to Tempel 1 the CIDA instrument
was operating (in CRUISE mode) during the following times:
Start Stop
------------------- -------------------
2005-06-10 2005-07-07
2005-09-01 2005-11-18
2007-01-25 2007-01-25
2007-11-20 2008-10-14
2009-03-30 2009-08-05
2009-08-14 2009-10-21
2009-11-02 2009-11-09
2009-12-07 2010-02-17
2010-02-18 2010-05-03
2010-05-11 2010-05-25
2010-06-29 2010-06-29
2011-02-02 2011-02-02
2011-02-14 2011-02-15
There were a number of OFF times during these periods as
a result of the spacecraft going into safe-mode, spacecraft
maneuvers, and other reasons. Between 2009-10 and 2010-02
CIDA sensitivity against spacecraft operations was tested by
lowering the data acquisition trigger sensitivity. No correlation
between spacecraft activity and CIDA events was found.
Tempel 1 Encounter Collection Period
------------------------------------
During the Tempel-1 encounter the CIDA instrument was operating
(in ENCOUNTER mode) during the following time:
Start Stop
------------------- -------------------
2011-02-14T04:51:22 2011-02-15T05:49:01
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.LBL, 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 EDR and RDR 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.LBL/.ASC 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.
Parameters
==========
Spectral and Other Non-Ancillary Data
-------------------------------------
All events are stored as spectral data in PDS TABLEs, regardless of
TARGET_NAME. Each row of a spectrum TABLE represents one mass line
of a time-of-flight spectrum. Each mass line (TABLE row) contains
- five CIDA channel raw (EDR) counts, as data numbers (DN)
- five CIDA channel calibrated (RDR) charges, in picocouloumbs
As mentioned above, it is important to note that not all event data
stored as spectra in PDS TABLEs are actually spectra, because some
non-particle-impact phenomena triggered CIDA to take and store data
as 'events.'
Ancillary Data
--------------
Ancillary data are also stored in PDS TABLEs, with each row
containing data for a sample time. The times are stored in the
first column in the TABLEs. Ancillary data include a variety of
parameters (temperatures, voltages, states such as ON and OFF, &c),
too numerous to list here. Refer to the TABLE PDS labels for the
meaning of each parameter.
Sampling Intervals
------------------
There are no set intervals for data sampling in CIDA. CIDA
generated an event when an internal algorithm determined that a
particle may have hit the target. The recovery time to prepare
for the next event was about 80ms. Other events and housekeeping
data could be initiated by commands from the ground, automatic
processes on the spacecraft, or anomalous spacecraft events (e.g.
reboot, safing). For more details of the CIDA sampling algorithm,
and its dependence on operating mode (CRUISE or ENCOUNTER), see
[KISSELETAL2003] and [GREENETAL2004].
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, stripped 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 the 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 naif0009.tls
PCK pck00009.tpc
SCLK sdu_sclkscet_00186.tsc
FK sdu_v20.tf
SPKs sdu_tempel1_ssd_s154.bsp'
sdu_isp000.bsp'
sdu_l_1999.bsp'
sdu_l_2000.bsp'
sdu_l_2001.bsp'
sdu_l_2002.bsp'
sdu_l_2003_w2.bsp'
sdu_l_2004.bsp'
sdu_l_2005_return.bsp'
sdu_l_2006.bsp'
sdu_l_2007.bsp'
sdu_l_2008.bsp'
sdu_l_2009.bsp'
sdu_l_2010.bsp'
sdu_l_2011_t1.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
sdu_sc_rec_2004_v2.bc'
sdu_sc_rec_2005_v2.bc'
sdu_sc_rec_next.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 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.
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
Jouni Ryno, Stardust CIDA S/W Technical Lead
|
.png)
.png)
