GRAIL LGRS Reduced Data Record (RDR)
RDR – Reduced Data Record
Instrument: Lunar Gravity Ranging System
PDS3 Data Set ID: GRAIL-L-LGRS-5-RDR-V1.0DOI: 10.17189/1519529
PDS4 Bundle:urn:nasa:pds:grail_gravity_derivedDOI: 10.17189/k98m-hj18
This bundle contains GRAIL gravity model data products and associated documentation migrated from the PDS3 volume. It contains gravity models in map, ASCII, and binary formats.
The Lunar Gravity Ranging System (LGRS) Reduced Data Record (RDR) data products are the lunar gravitational field data resulting from analysis of the GRAIL science data. The bundle includes three data collections: RSDMAP, SHADR, and SHBDR.
The Spherical Harmonics ASCII Data Record (SHADR) contains ASCII coefficients and/or an ASCII covariance matrix for a spherical harmonic expansion of the lunar gravity field. For more information, see the SHADR Product SIS.
The Spherical Harmonics Binary Data Record (SHBDR) contains binary coefficients and/or a binary covariance matrix for a spherical harmonic expansion of the lunar gravity field. For more information, see the SHBDR Product SIS.
Radio Science Digital Map Products (RSDMAP) are geoid, isostatic anomaly, Bouguer anomaly, or other digital maps derived primarily from GRAIL science results including the spherical harmonics models above. For more information, see the RSDMAP Product SIS.
This bundle also includes SPICE Spacecraft and Planet Ephemeris Kernels (SPK) created by the GRAIL SDS. SPICE SPKs are the physical realization of two logical elements of the SPICE system—the S-kernel (spacecraft ephemeris) and the ephemeris portion of the P-kernel (planet, satellite, asteroid and comet ephemerides). When read using an appropriate subroutine from the SPICE Toolkit, an SPK file will yield state vectors—Cartesian position and velocity—of one user-specified ephemeris object relative to another, at a specified epoch and in a specified reference frame. For more information, see the SPK Product SIS.
LGRS RDR files follow a variety of file naming conventions listed below dependent upon their type.
GTsss_nnnnvv_SHA.TAB- used for Spherical Harmonics ASCII Data Records (SHADR)
GTsss_nnnnvv_SHB_Lccc.DAT - used for Spherical Harmonics Binary Data Records (SHBDR)
GTsss_ffff_nnnn_cccc.IMG - used for Radio Science Digital Map Products (RSDMAP)
where
"G" denotes the generating institution
"J" for the Jet Propulsion Laboratory
"G" for Goddard Space Flight Center
"M" for Massachusetts Institute of Technology
"T" indicates the type of data represented
"G" for gravity field
"sss" is a 3-character modifier specified by the data producer. This modifier is used to indicate the source spacecraft or project, such as GRX for the pair of GRAIL spacecraft and MRO for the Mars Reconnaisance Orbiter.
"_" the underscore character is used to delimit modifiers in the file name for clarity.
"nnnnvv" is a 4- to 6-character modifier specified by the data producer. Among other things, this modifier may be used to indicate the target body, whether the SHADR contains primary data values as specified by "T" or uncertainties/errors, and/or the version number. For GRAIL, this modifier indicates the degree and order of the solution for the gravity field, topography or magnetic field.
"SHA" denotes that this is an ASCII file of Spherical Harmonic coefficients
"SHB" denotes that this is a Binary file of Spherical Harmonic coefficients and error covariance information
"Lccc" is a 2- to 4-character modifier specified by the data producer to indicate the degree and order to which degree (L) the gravity covariance has been truncated, if applicable.
".TAB" indicates the data is stored in tabular form.
".DAT" indicates the data is stored in binary format.
".IMG" indicates the data is stored as an image.
"ffff" is a 4- to 6-character modifier specified by the data producer to indicate the degree and order of the solution for the gravity field, topography or magnetic field.
"nnnn" is a 4- to 8-character modifier indicating the type of data represented
"ANOM" for free air gravity anomalies
"ANOMERR" for free air gravity anomaly errors (1)
"GEOID" for geoid
"GEOIDERR" for geoid errors (1)
"BOUG" for Bouguer anomaly
"ISOS" for isostatic anomaly
"TOPO" for topography
"MAGF" for magnetic field
"DIST" for gravity disturbances
"DEGSTR" for degree strength
Note:(1) Geoid and gravity anomaly errors are computed from a mapping of the error covariance matrix of the gravity field solution.
"cccc" is a 2- to 4-character modifier specified by the data producer to indicate the degree and order to which the potential solution (gravity, topography or magnetic field) has been evaluated. In the case of the error maps for the gravity anomalies or geoid, this field indicates to which maximum degree and order the error covariance was used to propagate the spatial errors
In ODE, LGRS products have the following product IDs:
GTSSS_NNNNVV_SHA.TAB, for SHADR
GTSSS_NNNNVV_SHB_LCCC.DAT, for SHBDR
GTSSS_FFFF_NNNN_CCCC.IMG, for RSDMAP
For more information about LGRS products, see the Data Product SIS.