Data Set Information
|
DATA_SET_NAME |
NEAR SPICE KERNELS MATHILDE
|
DATA_SET_ID |
NEAR-A-SPICE-6-MATHILDE-V1.0
|
NSSDC_DATA_SET_ID |
96-008A-00A
|
DATA_SET_TERSE_DESCRIPTION |
This data set includes the complete set of SPICE data for one
NEAR mission phase in the form of SPICE kernels, which can be
accessed using SPICE software available to read these files.
|
DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set includes the complete set of SPICE data for one NEAR
mission phase in the form of SPICE kernels, which can be accessed
using SPICE software available to read these files.
The SPICE data contains geometric and other ancillary information
needed to recover the full value of science instrument data. In
particular SPICE kernels provide spacecraft and planetary
ephemerides, instrument mounting alignments, spacecraft orientation
and spacecraft sequences of events. Data needed for relevant time
conversions is also included.
This data set is possibly spread across multiple volumes, each
containing the complete set of SPICE kernels for two or more mission
phases, a single mission phase or a portion of a mission phase.
The volume coverages are summarized in the table:
VOLUME ID START TIME(YYDDD) STOP TIME(YYDDD)
----------- ------------------- -------------------
NGMATH_0001 1997176 1997178
Data Types (SPICE kernel types)
===============================
SPK kernels contain ephemerides for spacecraft, planets, satellites,
comets and asteroids as well as for moving or fixed spacecraft and
instrument structures. They provide position and velocity, given in
a Cartesian reference frame. SPK files are located under the
GEOMETRY/SPK directory.
PCK kernels contain certain physical, dynamical and cartographic
constants for target bodies, such as size and shape specifications,
and orientation of the spin axis and prime meridian. PCK files are
located under the GEOMETRY/PCK directory.
IK kernels (Instrument description kernels) give descriptive and
operational data peculiar to a particular scientific instrument,
such as internal timing relative to the spacecraft clock and
field-of-view model parameters. IK files are located under the
GEOMETRY/IK directory.
CK kernels describe pointing, containing a transformation
traditionally called the C-matrix which is used to determine
time-tagged pointing (orientation) angles for a spacecraft structure
upon which science instruments are mounted. CK files are located
under the GEOMETRY/CK directory.
LSK (Leapseconds) kernels contain the leapseconds and the values of
other constants required to perform a transformation between
Universal Time Coordinated (UTC) and Ephemeris time (ET). LSK files
are located under the GEOMETRY/LSK directory.
SCLK (Spacecraft Clock) kernels contain on-board clock calibration
data required to perform a mapping between Ephemeris time (ET) and
spacecraft on-board time (SCLK.) SCLK files are located under the
GEOMETRY/SCLK directory.
Software
========
The SPICE Toolkit contains software modules needed to read SPICE
kernel files. SPICELIB software is highly documented via internal
headers. Additional documentation is available in separate ASCII
text files called Required Reading files. For example, the S- and P-
Kernel (SPK) Required Reading File, named SPK.REQ, describes use of
the SPK kernel file readers and contains sample programs.
The latest SPICE Toolkit for a variety of computer platforms such as
PC, Mac, SUN, HP, SGI, VAX, DEC Alpha, NeXT, etc. is available at
the NAIF Node of PDS electronically (via anonymous FTP and WWW
servers). Each version of the Toolkit is also archived at the NASA
National Space Science Data Center.
|
DATA_SET_RELEASE_DATE |
2001-09-06T00:00:00.000Z
|
START_TIME |
1997-06-25T12:00:00.000Z
|
STOP_TIME |
1997-06-27T11:59:59.999Z
|
MISSION_NAME |
NEAR EARTH ASTEROID RENDEZVOUS
|
MISSION_START_DATE |
1996-02-17T12:00:00.000Z
|
MISSION_STOP_DATE |
2001-02-28T12:00:00.000Z
|
TARGET_NAME |
EROS
|
TARGET_TYPE |
ASTEROID
|
INSTRUMENT_HOST_ID |
NEAR
|
INSTRUMENT_NAME |
SPICE KERNELS
|
INSTRUMENT_ID |
SPICE
|
INSTRUMENT_TYPE |
UNKNOWN
|
NODE_NAME |
Small Bodies
|
ARCHIVE_STATUS |
SUPERSEDED
|
CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview
=========================
This volume contains SPICE kernel files created during mission
operations only. No post processing has been done on these data.
SPK Files
=========
Two kinds of SPK files are provided in this archive: SPK files for
the spacecraft orbit and SPK files for EROS, Earth and Sun.
Spacecraft Orbit SPK Files
--------------------------
SPK files are for the spacecraft are created by the NEAR JPL
Navigation team. The kernels in this archive are specifically
created for science users and distributed through the Science Data
Center. These kernels are merged from a series of operations SPK
kernels. The merged kernels remove all of the predicted data from
the operations kernel, except the final predicted segment in the
kernel. For science use they must be loaded sequentially by the
spice kernel load routines, so that the oldest are loaded first.
This will ensure that reconstructed values are used whenever
possible.
Solar System Body SPK Files
---------------------------
The solar system body SPK files were provided by the JPL Navigation
team by way of the NAIF group. The accuracies for the bodies in each
file can be obtained by inspecting the comment portion of each file
using the COMMNT utility from the SPICE toolkit, which is available
from NAIF. The asteroid SPK files were provided directly from the
JPL Navigation team. The comment portion of the Mathilde and Eros
SPK files provide detailed information regarding their usage and
accuracy.
CK Files
========
C-kernel files provide orientation of the spacecraft. With the
exception of NIS, the NEAR instruments have fixed orientation. MSI,
NIS, XGRS and NLR all nominally are oriented along the spacecraft
positive X-axis. The Solar panels and high gain antenna are
nominally oriented in the positive z-axis. The small difference of
instrument orientation from the X-axis are given in the instrument
kernel (IK) files. The data Ck files are taken directly from the
attitude telemetry produced by the spacecraft Flight Computer (FC).
The FC data is reformatted at full resolution into the Ck files. No
interpolation is done on these data.
EK Files
========
Events kernel files are often used to digitally represent an
experimenter's notebook( ENB EK's) or to list a summary of all
commands sent to a spacecraft, as is the case with Sequence EK's.
In the case of NEAR, E-kernels are used in a very different way:
to efficiently represent the shape of EROS. This representation is
often referred to as a 'shape' or 'plate' model. There are two plate
models of EROS in this delivery, one at a lower resolution, having
only 1566 plates and another at a higher resolution, having 7516
plates. These plate E-kernels are specifically designed for use with
the SPICE plate library, developed specifically for NEAR. This
library is used to perform geometric calculations related to fields
of view, observing geometry, etc. for shape models defined as a plate
E-Kernel. The plate library can be obtained by contacting NAIF.
PCK Files
=========
PCK files provide size, shape and orientation data for 'target'
bodies such as Mathilde and EROS. A description of these data items
and reference to their source is provided inside the text PCK files,
which is a simple text file that can be viewed using any word
processor, text editor or text display utility. The binary PCK files
contain a comment area for each file. SPICE Toolkit utilities like
SPACIT and COMMNT can be used to extract the comments from these
files.
IK Files
========
Instrument kernel files provide specifications for the mounting
alignment and where applicable field-of-view size, shape and
orientation for the named instrument. Metadata describing these
estimates are provided in each IK file included in this archive.
Parameter values were determined from pre-launch measurements or
from manufacturing blueprints.
SCLK Files
==========
Spacecraft Clock kernel files provide a tabulation of data needed
for converting time measurements between ephemeris time (ET) and
spacecraft clock time (SCLK). The SPICE SCLK file is produced by the
NEAR Mission Operations Center.
The time correlation accuracy provided in SCLK files is informally
reported by the MOPS team to be better 20 milliseconds during
orbital phases. This accuracy has been corroborated by independent
estimates to within 500ms.
SPICE software does not prohibit an SCLK file from being used for
time conversions occurring for 'future times' (or more accurately,
for epochs that occur later than the epoch of the last telemetry
data used in producing the last correlation coefficients found in
the SCLK file). Such 'predict' time conversions are likely to be
inaccurate (changed somewhat) once the epoch of interest has been
passed.
LSK Files
=========
Leapseconds kernel files provide a tabulation of 'leapseconds' and
some other terms used in converting time measurements between
ephemeris time (ET) and Universal Time (UTC). 'Spacecraft Event
Time' (SCET) is the commonly used name for UTC events measured at
the spacecraft.
Metadata describing how the LSK data are obtained or computed is
contained inside the LSK text file. The time conversion provided by
SPICE LSK files is accurate to approximately 0.000030 seconds.
|
CITATION_DESCRIPTION |
Citation TBD
|
ABSTRACT_TEXT |
This data set includes the complete set of SPICE data for one
NEAR mission phase in the form of SPICE kernels, which can be
accessed using SPICE software available to read these files.
|
PRODUCER_FULL_NAME |
NEAR SCIENCE DATA CENTER
|
SEARCH/ACCESS DATA |
SBN PSI WEBSITE
|
|