Data Set Information
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| DATA_SET_NAME |
GRAIL MOON LGRS DERIVED GRAVITY SCIENCE DATA PRODUCTS V1.0
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| DATA_SET_ID |
GRAIL-L-LGRS-5-RDR-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
Data Set Overview : The Gravity Recovery and Interior Laboratory (GRAIL) Lunar Gravity Ranging System (LGRS) Reduced Data Record (RDR) archive includes data products generated from gravity investigations conducted by members of the GRAIL Gravity Team. Gravity RDRs include spherical harmonic models and acceleration maps of those models. A team at JPL, under the direction of Alex Konopliv, and another team at the Goddard Space Flight Center (GSFC), under the direction of Frank Lemoine, independently generated those products. The DATA_SET_ID 'GRAIL-L-LGRS-5-RDR-V1.0' includes the following components: Instrument host (i.e., 'GRAIL') Target (i.e., 'L' for Lunar) Instrument (i.e., 'LGRS' for Lunar Gravity Ranging System) CODMAC Data processing level number (i.e., '5') Description (i.e., 'RDR' for Reduced Data Record) Version number (i.e., 'V1.0') The data upon which these results were derived were collected between March and December 2012. The Science Phase of the mission was conducted from a near-circular, near-polar orbit with a mean altitude of 55 km. There were three different mapping cycles during the Science Phase, each covering a sidereal month (27.32 days). The first mapping cycle started while the science orbit had low periapsis altitudes with an orbiter separation distance of approximately 85 kilometers. Over the course of the first mapping cycle, and into the second mapping cycle, the periapsis altitudes of the science orbit increased, and the mean separation distance slowly drifted to 225 kilometers. A small Orbit Trim Maneuver (OTM) was performed during the second mapping cycle to decrease the separation drift rate. Following this OTM to the end of the third mapping cycle, the periapsis altitudes decreased, and the mean separation between the orbiters slowly drifted from 225 km back to 65 km. DSN coverage was nearly continuous. GRAIL proposed (and NASA approved) an Extended Mission, since there was sufficient fuel in the two spacecraft to acquire additional science data. The mean spacecraft altitude was lowered by about a factor of 2 to increase the sensitivity of the gravity measurements, and GRAIL defined a new set of science objectives. As in the Science Phase, the spacecraft separation distance was variable. DSN coverage was comparable. Parameters : Spherical harmonic models are tables of coefficients GM, Cmn, and Smn -- as in equation (1) of [TYLERETAL1992]. These can be used to represent gravitational potential of the Moon, for example. Both ASCII (data type SHA) and binary (data type SHB) formats are defined, with the latter being preferred for large files which also include covariance terms. Each file contains up to four 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); a names table, giving the order in which coefficients appear; a coefficients table (degree m, order n, coefficients Cmn and Smn, and their uncertainties); and a covariances table giving the covariances of CijCmn, SijSmn, CijSmn, and SijCmn. Radio Science Digital Map files are image representations of gravity and other parameters. Free air gravity, geoid, Bouguer anomaly, isostatic anomaly, and topographic values may be displayed using this data type. Data are formatted as PDS image objects. The 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. Processing : Spherical harmonic models and maps are derived from raw radio tracking data in several steps. The LGRS data are processed in large orbit determination programs that integrate the equations of motion (Mirage at JPL [MOYER2000], and GEODYN at NASA GSFC [PAVLISETAL2007]), and model mathematically the radio science observables (ramped Doppler and range data). The observations are related to the geophysical parameters through the numerical integration and the detailed mathematical modeling of the radio science observables, and of all forces acting on the spacecraft trajectory, including planetary and third body gravity, solar radiation pressure, planetary radiation pressure, atmospheric drag, solid body tides, and relativity. The gravity field coefficients are obtained by accumulating normal equations from often hundreds of data arcs, and solving these systems of linear equations with thousands of unknowns. The unknowns include arc parameters, particular to one data arc (such as the spacecraft state, radiation pressure scale factors, atmospheric drag scale factors, etc.) and common parameters. Radio tracking data are processed in arcs delimited by propulsive maneuvers, occultations, etc. The Moon orbiting spacecraft perform regular angular momentum desaturation (AMD) maneuvers to remove the angular momentum that has accumulated in the spacecraft momentum wheels. On GRAIL, these AMD maneuvers occur usually every 2-3 days, and arcs may be delimited by these maneuvers. The times of the AMDs are specified in the LGRS instrument catalogs in this archive. Maps of free air gravity and other quantities are generated from the spherical harmonic model(s) evaluated at regular grid points. Useful references which describe the procedures applied in general to processing GRAIL orbiter tracking data include [YUANETAL2001], [LEMOINEETAL2013], and [KONOPLIVETAL2013]. [THORNTON&BORDER2003] is a general reference for Orbit Determination. Data : Data are available online through the Planetary Data System (http://pds.nasa.gov) and encompass the primary and extended mission phases. ASCII spherical harmonic models are stored in the SHADR directory with file names of the form GTsss_nnnnvv_SHA.TAB, 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 (the pair of GRAIL spacecraft). '_' 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. '_' the underscore character is used to delimit information in the file name for clarity. 'SHA' denotes that this is an ASCII file of Spherical Harmonic coefficients '.TAB' indicates the data are stored in tabular form. Bouguer gravity data products have the name 'Bouguer' following the degree and order identifier, i.e. GTsss_nnnnvv_BOUGUER_SHA.TAB. The gravity data product using the special topography-based constraint described in GOOSSENSETAL2019 has the name 'Lambda1', i.e., GGGRX_1200B_LAMBDA1_SHA.TAB. Each SHADR file is accompanied by a detached PDS label; that label is a file in its own right, having the name GTsss_nnnnvv_SHA.LBL. Binary spherical harmonic models are stored in the SHBDR directory with file names of the form GTsss_nnnnvv_SHB_Lccc.DAT where 'G' denotes the generating institution 'J' for the Jet Propulsion Laboratory 'G' for Goddard Space Flight Center 'C' for Centre National d'Etudes Spatiales '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 (the pair of GRAIL spacecraft). '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 SHBDR 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. '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. '.DAT' indicates the data are stored in binary format. Each SHBDR file is accompanied by a detached PDS label; that label is a file in its own right, having the name GTsss_nnnnvv_SHB_Lccc.LBL. Radio Science Digital Map products are stored in the RSDMAP directory with file names of the form GTsss_ffff_nnnn_cccc.IMG, where 'G' denotes the generating institution 'J' for the Jet Propulsion Laboratory 'G' for Goddard Space Flight Center 'S' for Stanford University 'T' indicates the type of mission 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 (the pair of GRAIL spacecraft). 'ffff' is a 4-character modifier specified by the data producer to indicate the degree and order of the solution for the gravity 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 (1) Geoid and gravity anomaly errors are computed from a mapping of the error covariance matrix of the gravity field solution. 'cccc' is a 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 error, this field indicates to which maximum degree and order the error covariance was used to propagate the spatial errors '.IMG' indicates the data are stored as an image. Each RSDMAP file is accompanied by a detached PDS label; that label is a file in its own right with name GTsss_ffff_nnnn_cccc.LBL. Spacecraft and Planet Ephemeris Kernels (SPK) files are stored in the SPK directory with file names of the form sssttaaYYYY_DDD_yyyy_ddd.SPK, where sss 3-character spacecraft identifier GRA GRAIL-A GRB GRAIL-B GRX both tt Target ID, e.g., LU : Moon aa Activity/Experiment ID, e.g. GF : gravity field YYYY start year DDD start day of year yyyy end year ddd end day of year Coordinate System : GRAIL Gravity RDR files use a lunar body-fixed frame as defined in the DE 421 planetary ephemeris [FOLKNER2009]. GRGM1200A, GRGM1200B, and GRGM1200L files use the DE 430 ephemeris [FOLKNERETAL2014]. See labels of specific gravity products for details. Software : The SPICE Toolkit contains software modules needed to read SPICE kernel files. SPICE software is highly documented via internal headers. Additional documentation is available in separate ASCII text files called Required Reading files. The S- and P- Kernel (SPK) Required Reading File, name SPK.REQ, describes the 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, 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. Media/Format : This data set is stored online at the Planetary Data System (http://pds.nasa.gov/) and may be downloaded using a web browser or FTP software. A copy may be requested on physical media if downloading is not possible. The Planetary Data System maintains backup copies of this data set on various media.
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| DATA_SET_RELEASE_DATE |
2013-10-11T00:00:00.000Z
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| START_TIME |
2012-03-01T12:00:00.000Z
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| STOP_TIME |
2012-12-18T12:00:00.000Z
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| MISSION_NAME |
GRAVITY RECOVERY AND INTERIOR LABORATORY
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| MISSION_START_DATE |
2011-09-10T12:00:00.000Z
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| MISSION_STOP_DATE |
2012-12-18T12:00:00.000Z
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| TARGET_NAME |
MOON
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| TARGET_TYPE |
SATELLITE
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| INSTRUMENT_HOST_ID |
GRAIL-B
GRAIL-A
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| INSTRUMENT_NAME |
LUNAR GRAVITY RANGING SYSTEM B
LUNAR GRAVITY RANGING SYSTEM A
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| INSTRUMENT_ID |
LGRS-B
LGRS-A
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| INSTRUMENT_TYPE |
RADIO SCIENCE
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| NODE_NAME |
Geosciences
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| ARCHIVE_STATUS |
ARCHIVED - ACCUMULATING
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| CONFIDENCE_LEVEL_NOTE |
Overview : Data in this archive have been reduced as part of mission data analysis activities of the GRAIL Gravity Team. Products of questionable validity have been flagged or omitted. Review : This archival data set was reviewed by the GRAIL Gravity Team prior to submission to the Planetary Data System (PDS). Data set design, documentation, and sample products have passed a PDS peer review. Prior to creation of the final version of the archival data set, key elements of the archive were distributed for preliminary review. These included electronic versions of example PDS labels, example data files, CATALOG files, and Software Interface Specifications. These materials were distributed to PDS personnel, the experiment investigator, and others, as appropriate. Data Coverage and Quality : This volume contains gravity models and maps generated from GRAIL data collected during the primary and extended mission. GGGRX_0660PM_SHA.TAB is an ASCII file of coefficients and related data for the GSFC Lunar gravity field GRGM660PRIM, a degree and order 660 spherical harmonic model. It is a GSFC gravity field that includes the entire nominal mission of GRAIL tracking data (March 1, 16:30 to May 29, 16:36, 2012). JGGRX_0420A_SHA.TAB and JGGRX_0660B_SHA.TAB are ASCII files of coefficients and related data for the JPL Lunar gravity fields GL0420A and GL0660B, respectively, 420th and 660th degree and and order spherical harmonic models. They are JPL gravity fields that include the entire primary mission of GRAIL tracking data (March 1, 16:30 to May 29, 16:36:00, 2012). GGGRX_0660PM_SHB_L50.DAT, GGGRX_0660PM_SHB_L180.DAT, GGGRX_0660PM_SHB_L420.DAT, and GGGRX_0660PM_SHB_L660.DAT are binary files of coefficients and related data for the GSFC Lunar gravity field GRGM660PRIM, a 660th degree and order spherical harmonic model. It is a GSFC gravity field that includes the entire nominal mission of GRAIL tracking data (March 1, 16:30 to May 29, 16:36, 2012). JGGRX_0660B_SHB_L50.DAT, JGGRX_0660B_SHB_L180.DAT, JGGRX_0660B_SHB_L420.DAT, and JGGRX_0660B_SHB_L660.DAT are binary files of coefficients and related data for the JPL Lunar gravity field GL0660B, a 660th degree and order spherical harmonic model. It is a JPL gravity field that includes the entire primary mission of GRAIL tracking data (March 1, 16:30 to May 29, 16:36:00, 2012). GGGRX_0660PM_ANOM_L320.IMG is a map of the gravity anomalies (in mGal) of the Moon at a resolution of 4 pix/deg by 4 pix/deg. It is based on a GRAIL gravity field of the Moon produced by NASA GSFC. The gravity field is a degree and order 660 spherical harmonic model, which includes the entire nominal mission of GRAIL tracking data (March 1, 16:30 to May 29, 16:36, 2012). The field was truncated to degree and order 320 for the expansion in the spatial domain, to reduce remaining artifacts. JGGRX_0660B_ANOM_L320.IMG is a map of the gravity anomaly derived from the JPL GL0660B model of the Moon's gravity field. Each point gives the Lunar gravity anomaly in milligals, which is the difference of the model gravity on the geoid from the gravity on a reference sphere with semi-major-axis : 1738.0 km, GM : 4902.8003055554 km**3/s**2, and zero rotation rate. The JGGRX_0660B_ANOM_320 gravity anomaly is computed from a truncated GL0660B solution (from degree 2 up to degree 320). See the SHADR, SHBDR, and RSDMAP directories for additional data products for the GRGM900C, GL0900C, GL0900D, GL1500E, GRGM1200A, GRGM1200B, and GRGM1200L models. Limitations : The limitations in this data set follow from the quality of the execution, which is described above under Data Coverage and Quality.
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| CITATION_DESCRIPTION |
KAHAN, D.S., GRAIL Moon LGRS Derived Gravity Science Data Products V1.0, GRAIL-L-LGRS-5-RDR-V1.0, NASA Planetary Data System, 2013.
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| ABSTRACT_TEXT |
This data set contains archival derived science data, acquired from the Lunar Gravity Ranging System (LGRS) on the two spacecraft comprising the Gravity Recovery and Interior Laboratory (GRAIL) mission. Measurements were made using the GRAIL spacecraft and Earth-based stations of the NASA Deep Space Network (DSN). The data set includes high-resolution spherical harmonic models of the Moon's gravity field, covariance matrices for some models, and maps for some models. It also contains a complete set of SPICE SPK Files ('kernel files'), which can be accessed using SPICE software. The SPK products in this data set differ from those archived by GRAIL navigation, as they were created by the GRAIL SDS and make use of the LGRS to provide a more refined solution of the spacecraft ephemerides than those provided by GRAIL navigation.
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| PRODUCER_FULL_NAME |
DANIEL S. KAHAN
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| SEARCH/ACCESS DATA |
Geosciences Web Services
Geosciences Online Archives
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