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NEAR Laser Ranger (NLR) Level 2 and 3 Data Archive (PDS)

NSSDCA ID: PSPG-00725

Availability: At NSSDC, Ready for Offline Distribution (or Staging if Digital)

Time span: 2000-03-05 to 2001-02-12

Description

This volume contains level 2 and level 3 NEAR Laser Rangefinder (NLR) data. The level 2 data consists of calibrated ranges and an observation log file that lists start times and basic parameters for the start of collection of each observation set by the NEAR NLR. The level 3 dataset is comprised of spherical harmonic models and gridded map products. The data volumes are stored on a single DVD volume.

The NLR Level 2 Data Products (NEAR-A-NLR-5-CDR-EROS/ORBIT-V1.0) include the along-track profiles of NLR data in SI units, together with spacecraft position, orientation, and timing data. Ranges from level 1 NLR data are the source of the level 2 data product. Precision orbits were generated at NASA-GSFC, and supplemented where appropriate by JPL navigation team orbits, ancillary timing and attitude information supplied by the NEAR SDC and instrument data derived from in-flight analysis. These data were merged to create the calibrated profile data. Each level 2 data product is a text format table corresponding to a daily level 1 EDR file, and is described by a detached label.

Profiles are tables of longitude, latitude, and radius at the laser bounce point, together with time stamps, the spacecraft position, and instrument threshold setting. Ranges are coverted from counts to meters of one-way range from NLR to 433 Eros as described in the calibration document NLRCALIB.TXT. Precision orbit data for the NEAR-Shoemaker spacecraft is provided by the NASA-GSFC analysis team and the JPL navigation team, and is archived in the form of SPICE format spacecraft ephemeris (SPK) files.

The NLR Level 3 Data Products (NEAR-A-NLR-6-EROS-MAPS-MODELS-V1.0) include spherical harmonic shape and gravity models, and gridded maps or images of those models. Spherical harmonic models are tables of coefficients GM, Cmn, and Smn. ASCII data type (SHA) formats are defined. Each file contains 2 tables: a header table containing general parameters for the model (gravitational constant, its uncertainty, degree and order of the field, normalization state, reference longitude, and reference latitude) and a coefficients table (degree m, order n, coefficients Cmn and Smn, and their uncertainties).

Gridded Digital Map files are image representations of shape and other parameters. Gravity and topographic values may be displayed using this data type. Data are formatted as PDS image objects. The level 2 NLR profiles in the 200 by 200 km orbital phases and lower are the source of the NLR shape models. The adjusted profiles are merged by binning observations within a given grid cell, uniformly spaced in longitude and latitude. The median value and the number of observations in each bin comprise the gridded data product. The gravity field coefficients were obtained by solving systems of equations. Radio tracking data in long arcs delimited by propulsive maneuvers, occultations, etc. were used in solutions that were obtained iteratively and by least squares.

The PDS data set IDs are NEAR-A-NLR-5-CDR-EROS/ORBIT-V1.0 and NEAR-A-NLR-6-EROS-MAPS-MODELS-V1.0. The data are contained on CD volumes NLEROS_2001 - NLEROS_2005, held on DVD volume NLEROS_3001. Total data volume is 2887.04 Mb.

Alternate Names

  • PDS NEAR NLR Data Archive 2/3
  • NEAR-A-NLR-5-CDR-EROS/ORBIT-V1.0
  • NEAR-A-NLR-6-EROS-MAPS-MODELS-V1.0

Disciplines

  • Planetary Science: Small Bodies
  • Planetary Science: Geology and Geophysics

Old NSSDCA ID

  • 96-008A-04B

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. David E. SmithGeneral ContactNASA Goddard Space Flight Centerdavid.e.smith@nasa.gov
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