PDS_VERSION_ID = PDS3
LABEL_REVISION_NOTE = "2001-09-17 SB: Grayzeck original"
RECORD_TYPE = STREAM
OBJECT = DATA_SET
DATA_SET_ID = "NEAR-A-NLR-5-EROS/SHAPE/GRAVITY-V1.0"
OBJECT = DATA_SET_INFORMATION
DATA_SET_NAME =
"NEAR EROS NLR DERIVED PRODUCTS - SHAPE MODEL V1.0"
DATA_SET_COLLECTION_MEMBER_FLG = "N"
DATA_OBJECT_TYPE = TABLE
START_TIME = 2001-04-30
STOP_TIME = 2001-08-27
DATA_SET_RELEASE_DATE = 2001-09-30
PRODUCER_FULL_NAME = "JAMES MILLER"
DETAILED_CATALOG_FLAG = "N"
DATA_SET_TERSE_DESC = "NEAR Eros shape/gravity science derived
data from NEAR NAV team at JPL."
DATA_SET_DESC = "
Data Set Overview
=================
This file contains a shape model for the
asteroid Eros derived from NEAR Laser Rangefinder observations.
The NLR measurements were made over the period 30 April 2000 to
27 August 2000 from orbits of 35 and 50 km.
The gravity model (16 x 16 elements) obtained from this shape model is
provided as a separate companion file ('GR_101.TXT') to this file.
The shape model (34 x 34) files and information regarding the file
formats and contents were kindly supplied by J.K. Miller of the NEAR
navigation team, in response to user requests made at the NEAR PDS
archive review.
Parameters
==========
SH_101.TXT A multi-part table giving X, Y, and Z vertices of the
shape model, the plate model, and parameters.
The shape table lists a serial number and coordinates for
each vertex comprising the plate model of the shape of Eros. The
vertex numbers are referenced in the following table.
NOTE that the first row of this table contains only a single
integer in the first column, giving the total number of vertices
in the table.
The index number of the vertex. This number is used in the plate table.
Following rows contain (x,y,z) position of the vertex
The shape table further defines the triangular plates comprising
the Eros shape model. For each plate three vertices are listed by
vertex number. The positions corresponding to each vertex number
are defined in the preceeding vertex table.
NOTE: The first row of this table contains only a single integer
indicating the total number of plates defined.
Subsequent rows have the index number for the triangular plate defined
along with the index numbers of the three vertices defining this plate
Then there is a single-row table contains two constants relating
to the table of harmonic coefficients:
first the degree of the harmonic solution. The total number
of coefficients in the solution is (NDEGREE+1)^2.
Second there is a Normalization flag. This value is '1', indicating
that the following solution has been fully normalized.
The last part of the table lists several parameters and the harmonic
coefficients constituting the shape model solution. The format, an
in-house format used by the NAV team, is not tied to logical records,
but rather makes use of a repeating, 3-column physical record structure
as needed to hold the various parameters. The contents of the rows of
the table are as follows:
The first two records contain the volume of the model and the vector
offset from the center of the shape model to the true center of
gravity:
Record 1:
Column 1 Volume in km^3
Column 2 -blank-
Column 3 -blank-
Record 2:
Column 1 Xcg in km
Column 2 Ycg in km
Column 3 Zcg in km
The next two record contain the coefficients for the inertia tensor.
Note that this is a symmetric matrix, so only the unique elements are
specified here:
Record 3:
Column 1 Ixx in km^2
Column 2 Iyy in km^2
Column 3 Izz in km^2
Record 4:
Column 1 Ixy in km^2
Column 2 Ixz in km^2
Column 3 Iyz in km^2
The subsequent records contain the shape model harmonic coefficients
Cij and Sij. All the Si0 are = 0, and are thus omitted from this file.
The remaining coefficients are stored three to a record, in this
logical sequence:
C00
C10 C11 S11
C20 C21 C22 S21 S22
C30 C31 C32 C33 S31 S32 S33
etc.
which becomes this physical sequence:
Record 5: C00 C10 C11
Record 6: S11 C20 C21
Record 7: C22 S21 S22
Record 8: C30 C31 C32
Record 9: C33 S31 S32
etc.
The total number of coefficients stored is (NDEGREE+1)^2, where
NDEGREE is found as the first integer (i.e., COLUMN 1) in the first
row of the HDR_TABLE, above,
The last record in the file contains only a single entry in the first
column.
GR_101.TXT ASCII coefficients for the gravity model.
The gravity model table starts as one row with three integer parameters:
The degree of the harmonic solution presented and two processing flags.
The degree of the harmonic solution, i.e., the number of harmonic
cooefficient stored in this file is (NDEGREE+1)^2.
The first flag indicating that the result has been normalized.
It is equal to '1'. A second flag as an internal processing flag,
equal to '1'
Next this table lists the various parameters and harmonic
coefficients of the gravity solution. The format, an in-house format
used by the NAV team, is not based on logical records, but rather
makes use of a repeating, 3-number physical record structure as
needed to hold the various parameters. The contents of the rows of
the table are as follows.
The first two records contain general model parameters:
Record 1:
Column 1 Volume in km^3 of the model
Column 2 Density in g/cm^3 (assumed constant)
Column 3 Mass in kg
Record 2:
Column 1 The gravitational potential, GM, in km^2/s^3
Column 2 R0, the average radius used in the model - in this case
selected to be the maximum radius
Column 3 -blank-
The next two records contain the coefficients for the inertia tensor.
Note that this is a symmetric matrix, so only the unique elements are
specified here:
Record 3:
Column 1 Ixx in km^2
Column 2 Iyy in km^2
Column 3 Izz in km^2
Record 4:
Column 1 Ixy in km^2
Column 2 Ixz in km^2
Column 3 Iyz in km^2
The subsequent records contain the gravitational harmonic coefficients
Cij and Sij. All the Si0 are = 0, and are thus omitted from this file.
The remaining coefficients are stored three to a record, in this
logical sequence:
C00
C10 C11 S11
C20 C21 C22 S21 S22
C30 C31 C32 C33 S31 S32 S33
etc.
which becomes this physical sequence:
Record 5: C00 C10 C11
Record 6: S11 C20 C21
Record 7: C22 S21 S22
Record 8: C30 C31 C32
Record 9: C33 S31 S32
etc.
The total number of coefficients stored is (NDEGREE+1)^2, where
NDEGREE is found as the first integer in the first row of the file
(that is, in column 1 of the INTEGER_TABLE defined above).
The last record in the file contains only a single entry in the first
column.
Processing
==========
The shape model include both a triangular plate model and a set
of spherical harmonics. The plate model is comprised of two lists:
a list of (x,y,z) vertex positions relative to the center of the
model; and a list of the triples of vertices defining each of the
triangular plate.
The spherical harmonics are provided as a set of coefficients
with corresponding values for volume, center-of-gravity offset
and the inertia tensor (KONOPLIVETAL2001, MILLERETAL2002).
The gravity model obtained by integrating this shape model is
provided as a separate companion file ('gr_101.dat') to this
file in the same form as the shape model.
Ancillary Data
==============
None.
Coordinate System
=================
The Eros coordinate system is defined as follows: prime meridian fixed
at 326.06 deg, IAU 1994 right ascension at 11.369 deg, declination at
17.227 degrees, and rotation rate at 1639.38885 deg/day.
Software
========
None.
Media/Format
============
CD "
CONFIDENCE_LEVEL_NOTE = "
Overview
========
Data in this archive have been reduced as part of mission data
analysis activities of the NEAR Navigation Team. Data of
questionable validity have been omitted from the solutions.
Review
======
This archival data set was not reviewed by the NEAR NLR or RSS
Teams prior to submission to the Planetary Data System (PDS).
It was not one of the data sets included in a comprehensive
review by the PDS Small Bodies Node in August 2001. Instead
a separate onlinbe review was performed for PDS acceptance.
Data Coverage and Quality
=========================
The data included in this archive were collected during the
NEAR orbital phase from 2000-04-30 to 2000-08-27.
Limitations
===========
None."
END_OBJECT = DATA_SET_INFORMATION
OBJECT = DATA_SET_TARGET
TARGET_NAME = EROS
END_OBJECT = DATA_SET_TARGET
OBJECT = DATA_SET_HOST
INSTRUMENT_HOST_ID = NEAR
INSTRUMENT_ID = NLR
END_OBJECT = DATA_SET_HOST
OBJECT = DATA_SET_REFERENCE_INFORMATION
REFERENCE_KEY_ID = "KONOPLIVETAL2001"
END_OBJECT = DATA_SET_REFERENCE_INFORMATION
OBJECT = DATA_SET_REFERENCE_INFORMATION
REFERENCE_KEY_ID = "MILLERETAL2002"
END_OBJECT
END_OBJECT
END