Dawn Vesta Gravity Science Derived Data Bundle Description ========================================================== References ========== - Asmar, S.W., R.G. Herrera, and T. Priest, Radio Science Handbook, JPL D-7938 Vol. 6, Jet Propulsion Laboratory, Pasadena, CA, 1995. - Asmar, S.W., and N.A. Renzetti, The Deep Space Network as an Instrument for Radio Science Research, Jet Propulsion Laboratory Publication 80-93, Rev. 1, 1993. - Bini, A., I. Ficai-Veltroni, S. Pieraccini, G. Cherubini, M. Benetello, and M. Giustini, Instrument system description, VID-GAF-RP-002, 2005. - Deep Space Network Telecommunications Link Design Handbook, JPL-E-810-005 Jet Propulsion Laboratory, Pasadena, CA, 2013. - H.&B.S. Jeffreys, Methods of Mathematical Physics, Third Edition. Cambridge University Press, 1962, 269 p. - Deep Space Mission System (DSMS) External Interface Specification (820-013, JPL D-16765), Radio Science Receiver Standard Formatted Data Unit (SFDU), Jet Propulsion Laboratory, Pasadena, CA, 2001. - Konopliv, A.S., S.W. Asmar, B.G. Bills, N. Mastrodemos, R.S. Park, C.A. Raymond, D.E. Smith, and M.T. Zuber, The Dawn Gravity Investigation at Vesta and Ceres, Space Science Reviews, 163, 461-486, 2011. - Konopliv, A.S., S.W. Asmar, R.S. Park, B.G. Bills, F. Centinello, A.B. Chamberlin, A. Ermakov, R.W. Gaskell, N. Rambaux, C.A. Raymond, C.T. Russell, D.E. Smith, P. Tricarico, and M.T. Zuber, The Vesta gravity field, spin pole and rotation period, landmark positions, and ephemeris from the Dawn tracking and optical data, Icarus 240, 103-117, doi:10.1016/j.icarus.2013.09.005, 2014. - Moyer, T.D., Mathematical Formulation of the Double-Precision Orbit Determination Program (DPODP), TR 32-1527, Jet Propulsion Laboratory, Pasadena, CA, 1971. - Prettyman, T.H., W.C. Feldman, F.P. Ameduri, B.L. Barraclough, E.W. Cascio, K.R. Fuller, H.O. Funsten, D.J. Lawrence, G.W. McKinney, C.T. Russell, S.A. Soldner, S.A. Storms, C. Szeles, and R.L. Tokar, Gamma-ray and neutron spectrometer for the Dawn mission to 1 Ceres and 4 Vesta, IEEE Trans. Nucl. Sci., Volume 50, Issue 4, pp. 1190-1197, August 2003, doi:10.1109/TNS.2003.815156 - Prettyman, T.H., W.C. Feldman, H.Y. McSween, Jr., R.D. Dingler, D.C. Enemark, D.E. Patrick, S.A. Storms, J.S. Hendricks, J.P. Morgenthaler, K.M. Pitman, R.C. Reedy, Dawn's Gamma Ray and Neutron Detector, Space Sci. Rev. (2011) 163:371-459, doi:10.1007/s11214-011-9862-0 - Rayman, M.D., T.C. Fraschetti, C.A. Raymond, and C.T. Russell, Dawn: A mission in development for exploration of main belt asteroids Vesta and Ceres, Acta Astronautica 58, 605-616, 2006. - Raymond, C.A., Dawn Science Plan, JPL D-31827, 2007. - Russell, C.T., and C.A. Raymond, The Dawn Mission to Vesta and Ceres, Space Science Reviews, 163, 3-23, 2011. - Schroeder, S.E. and P. Gutierrez-Marques, Calibration Pipeline, MPS report DA-FC-MPAE-RP-272, Issue 2, Rev. a, 20 July 2011. - Thornton, C.L. and J.S. Border, Radiometric Tracking Techniques for Deep Space Navigation, John Wiley and Sons, Hoboken, NY, 2003. - Tyler, G.L., G. Balmino, D.P. Hinson, W.L. Sjogren, D.E. Smith, R. Woo, S.W. Asmar, M.J. Connally, C.L. Hamilton, and R.A. Simpson, Radio Science Investigations with Mars Observer, Journal of Geophysical Research, 97, 7759-7779, 1992. Collections Overview ==================== The Dawn Vesta Gravity Archive Data Collection of Science Data Products (SDP) includes data products generated from gravity investigations conducted by members of the Dawn Gravity Team while the spacecraft was in orbit around the asteroid Vesta. Radio measurements were made using the Dawn spacecraft and Earth-based stations of the NASA Deep Space Network (DSN). Gravity SDPs include spherical harmonic models of Vesta's gravity field, maps or images of those models, and possibly line-of-sight acceleration profiles. A group at the Jet Propulsion Laboratory JPL under the direction of Sami Asmar produced spherical harmonic models and maps. These results were derived from raw radio tracking data. At Vesta, the mission was divided into three science orbits. All the orbits were polar. The Survey orbit was performed at a nominal altitude of 2735 km. The High Altitude Mapping Orbit, or HAMO, was performed at a nominal altitude of 685 km. The Low Altitude Mapping Orbit, or LAMO, was performed at a nominal altitude of 200 km. The spacecraft spent 20 days in Survey orbit, 34 days in HAMO-1, 141 days in LAMO, and another 40 days in HAMO-2. Between these science orbits, the spacecraft was in a transfer phase using the electric ion engines (Russell & Raymond, 2011). Parameters ========== Spherical harmonic models are tables of coefficients GM, Cmn, and Smn -- as in equation (1) of (Tyler et al., 1992). These can be used to represent gravitational potential of Vesta, for example. ASCII (data type SHA) formatted spherical harmonics are defined. 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). 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. Provided in this bundle are several map types including a map of radial acceleration using the VESTA20H field with the J2 coefficient removed. Processing ========== Spherical harmonic models, maps, and line-of-sight acceleration profiles are derived from raw radio tracking data in several steps. The tracking data are processed in large orbit determination programs that integrate the equations of motion (DPODP at JPL (Moyer, 1971)), 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, where applicable. 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 (such as the gravity coefficients, the planetary gravitational constant or GM). Radio tracking data are processed in arcs delimited by propulsive maneuvers, occultations, etc. The spacecraft periodically performed angular momentum desaturation maneuvers. These maneuvers allowed the reaction wheels to spin down to avoid damage, but they had be countered the use of thrusters. Arcs may be delimited by these maneuvers. The details of each of these maneuvers specified in the small forces file of the Dawn Vesta Gravity Science Raw Data Archive. Useful references which describe the procedures applied in general to processing Vesta orbiter tracking data include (Konopliv et al., 2014). (Thornton & Border, 2003) is a general reference for Orbit Determination. Data ==== Data are available online through the Planetary Data System (http://pds.nasa.gov). ASCII spherical harmonic models are stored in the data-shadr/ directory with file names of the form GTDWN_nnnnvv_SHA.TAB where: 'G' denotes the generating institution 'J' for the Jet Propulsion Laboratory 'T' indicates the type of data represented 'G' for gravity field 'DWN' all products use this. '_' the underscore character is used to delimit modifiers in the file name for clarity. 'nnnvvv' is a 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 Dawn, this specifies the degree and version of the 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 is stored in tabular form. 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.xml. Binary spherical harmonic models are stored in the data-shbdr/ directory with file names of the form GTsss_nnnnvv_SHB.DAT where: 'G' denotes the generating institution 'J' for the Jet Propulsion Laboratory 'T' indicates the type of data represented 'G' for gravity field 'DWN' all products use this. '_' the underscore character is used to delimit modifiers in the file name for clarity. 'nnnvvv' is a 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 Dawn, this specifies the degree and version of the field. '_' the underscore character is used to delimit information in the file name for clarity. 'SHB' denotes that this is an Binary file of Spherical Harmonic coefficients and covariance '.DAT' indicates the data is stored in a binary data file. 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.xml. Radio Science Digital Map products are stored in the maps/ directory with file names of the form GTsss_ffff_nnnn_cccc.IMG where: 'G' denotes the generating institution 'J' for the Jet Propulsion Laboratory 'T' indicates the type of mission data represented 'G' for gravity field 'DWN' all products use this. '_' the underscore character is used to delimit information in the file name for clarity. '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. '_' the underscore character is used to delimit information in the file name for clarity. '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) 'BOU' for Bouguer anomaly 'ISOS' for isostatic anomaly 'TOPO' for topography 'MAGF' for magnetic field (1) Geoid and gravity anomaly errors are computed from a mapping of the error covariance matrix of the gravity field solution. '_' the underscore character is used to delimit information in the file name for clarity. '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 is 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.xml. SHADR Files Descriptions ------------------------ # SHADR Header Table Description The SHADR header includes descriptive information about the spherical harmonic coefficients which follow in SHADR_COEFFICIENTS_TABLE. The header consists of a single record of eight (delimited) data columns requiring 137 bytes, a pad of 105 unspecified ASCII characters, an ASCII carriage-return, and an ASCII line-feed. # SHADR Coefficients Table Description The SHADR coefficients table contains the coefficients for the spherical harmonic model. Each row in the table contains the degree index m, the order index n, the coefficients Cmn and Smn, and the uncertainties in Cmn and Smn. The (delimited) data require 107 ASCII characters; these are followed by a pad of 13 unspecified ASCII characters, an ASCII carriage- return, and an ASCII line-feed. # JGDWN_VES20H_SHA File Description This file contains coefficients and related data for the VESTA20H spherical harmonic gravity model of Vesta. VESTA20H is a 20th degree and order model obtained from radiometric tracking (Doppler and range data) and optical landmarks of the Dawn spacecraft in orbit about Vesta. The gravity model includes data from the Approach phase to the end of the HAMO-2 orbit. The data span is July 13, 2011 to July 25, 2012. Optical landmark tracking is included for the Survey, HAMO and LAMO phases. Optical tracking is yet to be included for HAMO-2. Some details describing this model are: The spherical harmonic coefficients are fully normalized. The associated GM = 17.2882449693 km^3/s^2 The reference radius = 265.0 km The Vesta-fixed reference frame prime meridian and pole location in IAU coordinates is given by Right ascension = 309.05870 degrees (estimated) RA rate = -0.207 degrees/cty (fixed) Declination = 42.23190 degrees (estimated) Dec rate = -0.048 degrees/cty (fixed) Prime Meridian = 284.59521 degrees (fixed) Rotation rate = 1617.3331279 degrees/day (estimated) The pole location and rotation rate are estimated jointly with the gravity field. The motion of the pole in inertial space is given by the modeled precession and nutation for a homogeneous Vesta and is not estimated. The prime meridian epoch value is chosen to match the Vesta LAMO shape model from Bob Gaskell on June 1, 2012 (Claudia is rotated to 146 deg E). This shape model includes images from the HAMO-2 phase and fills the previous gap in the shape model of the northern polar region. The uncertainties of the pole and rotation rate (5x formal) for this solution are Right ascension = 0.000043 degrees Declination = 0.000031 degrees Rotation rate = 0.00000087 degrees/day The reference for this gravity field is Konopliv et al., The Vesta gravity field, spin pole and rotation, landmark positions, and ephemeris from the Dawn tracking and optical data, Icarus, 2013, http://dx.doi.org/10.1016/j.icarus.2013.09.005. (Konopliv et al., 2014). The original published gravity field is in the Claudia coordinate system with the prime meridian location defined by the Claudia crater. To be consistent with IAU standards, this version of the VESTA20H gravity field has been rotated by 210 degrees to be similar to the Claudia double-prime coordinate system. The difference between the Claudia coordinate system and Claudia double-prime coordinate system is documented in the document collection, VESTA_COORDINATES_131018.PDF. Note that because the pole and spin rate are jointly estimated with the gravity field, the coordinate system used in this map differs slightly from the official Claudia double-prime coordinate system. For details about the gravity coordinate frame, see the details above. Observations for the gravity field consist of Doppler and range measurements from Deep Space Network (DSN) tracking. The count time for the Doppler observations is 60 seconds. The typical accuracy for the Doppler is 0.02 mm/s for the 60 second sample time. The range accuracy is about 2 meters and is limited by the station calibration accuracy. The actual rms scatter is less than 0.3 meters in spacecraft position. This product is a set of two ASCII tables: a header table and a coefficients table with 252 coefficients and a GM value. Definitions of the tables follow. The VESTA20H gravity model is delivered as a Spherical Harmonics Gravity ASCII Data Record (SHADR) and is produced by the JPL Dawn Gravity Science Team (Alex Konopliv, Ryan Park, Sami Asmar). # JGDWN_VES26J_SHA File Description This file contains coefficients and related data for the VESTA26J spherical harmonic gravity model of Vesta. VESTA26J is a 26th degree and order model obtained from radiometric tracking (Doppler and range data) and optical landmarks of the Dawn spacecraft in orbit about Vesta. The gravity model includes data from the Approach phase to the end of the HAMO-2 orbit. The data span is July 23, 2011 to July 25, 2012. Optical landmark tracking is included for the Survey, HAMO, HAMO-2 and LAMO phases. Some details describing this model are: The spherical harmonic coefficients are fully normalized. The associated GM = 17.2882844211 km^3/s^2 The reference radius = 265.0 km The Vesta-fixed reference frame prime meridian and pole location in IAU coordinates is given by Right ascension = 309.06110 degrees (estimated) RA rate = -0.225213 degrees/cty (estimated with MOI) RA acceleration = 0.000298 degrees/cty^2 (estimated with MOI) Declination = 42.232386 degrees (estimated) Dec rate = -0.052184 degrees/cty (estimated with MOI) Dec acceleration= 0.0001118 degrees/cty (estimated with MOI) Prime Meridian = 284.6430975804534 degrees (estimated) Rotation rate = 1617.33312922 degrees/day (estimated) The pole location and rotation rate are estimated jointly with the gravity field. The motion of the pole in inertial space is given by the modeled precession and nutation for a Vesta with polar moment of inertia (MOI) C = 0.4208 (estimated). The prime meridian epoch value is estimated with the Claudia landmark longitude fixed to zero. The uncertainties of the pole and rotation rate for this solution are Right ascension = 0.00031 degrees Declination = 0.000068 degrees Rotation rate = 0.00000013 degrees/day Observations for the gravity field consist of Doppler and range measurements from Deep Space Network (DSN) tracking. The count time for the Doppler observations is 60 seconds. The typical accuracy for the Doppler is 0.02 mm/s for the 60 second sample time. The range accuracy is about 2 meters and is limited by the station calibration accuracy. The actual rms scatter is less than 0.3 meters in spacecraft position. This product is a set of two ASCII tables: a header table and a coefficients table with 252 coefficients and a GM value. Definitions of the tables follow. The VESTA26J gravity model is delivered as a Spherical Harmonics Gravity ASCII Data Record (SHADR) and is produced by the JPL Dawn Gravity Science Team (Ryan Park and Alex Konopliv). More details about VESTA26J can be found in: Park, R.S., A.I. Ermakov, A.S. Konopliv, A.T. Vaughan, N. Rambaux, B.G., Bills, J.C. Castillo-Rogez, R.R. Fu, S A. Jacobson, S.T. Stewart, and M.J. Toplis, “A small core in Vesta inferred from Dawn’s observations,” Nature Astronomy, 2025. https://doi.org/10.1038/s41550-025-02533-7 SHBDR Files Descriptions ------------------------ # SHBDR Header Table Description The SHBDR Header includes descriptive information about the spherical harmonic coefficients which follow in SHBDR_COEFFICIENTS_TABLE. The header consists of a single record of nine data columns requiring 56 bytes. The Header is followed by a pad of binary integer zeroes to ensure alignment with RECORD_BYTES. # SHBDR Names Table The SHBDR Names Table contains names for the solution parameters (including gravity field coefficients) which will follow in SHBDR_COEFFICIENTS_TABLE. The order of the names in SHBDR_NAMES_TABLE corresponds identically to the order of the parameters in SHBDR_COEFFICIENTS_TABLE. Each coefficient name is of the form Cij or Sij where i is the degree of the coefficient and j is the order of the coefficient. Both indices are three- digit zero-filled right-justified ASCII character strings (for example, C010005 for the 10th degree 5th order C coefficient, or S002001 for the 2nd degree 1st order S coefficient). The eighth byte in the table is an ASCII blank used to ensure that the row length is equal to RECORD_BYTES. Names of other solution parameters are limited to 8 ASCII characters; if less than 8, they will be left-justified and padded with ASCII blanks. The Names Table itself will be padded with ASCII blanks, if necessary, so that its length is an integral multiple of RECORD_BYTES. # SHBDR Coefficients Table The SHBDR Coefficients Table contains the coefficients and other solution parameters for the spherical harmonic model. The order of the coefficients in this table corresponds exactly to the order of the coefficient and parameter names in SHBDR_NAMES_TABLE. The SHBDR Coefficients Table will be padded with double precision DATA_TYPE zeroes so that its total length is an integral multiple of RECORD_BYTES. # SHBDR Covariance Table The SHBDR Covariance Table contains the covariances for the spherical harmonic model coefficients and other solution parameters. The order of the covariances in this table is defined as columnwise vector storage of the upper triangular matrix formed by the product of the SHBDR Names Table with its transpose. For example, if the Names Table has four entries A, B, C, and D, then the covariances are given by the column vectors in the upper triangular matrix of | A | [ A B C D ] = | AA AB AC AD | | B | | BA BB BC BD | | C | | CA CB CC CD | | D | | DA DB DC DD | That is, the covariance table will list (in this order) AA, AB, BB, AC, BC, CC, AD, BD, CD, and DD. The SHBDR Covariance Table will be padded with double precision DATA_TYPE zeroes so that its total length is an integral multiple of RECORD_BYTES. # JGDWN_VES20H_SHB Description This file contains the covariance and related data for the JPL Dawn Vesta gravity soluttion VESTA20H, a 20th degree and order spherical harmonic model and covariance. For a description of the solution and spherical harmonic coefficents, see the ascii pds label file for the VESTA20H spherical harmonic gravity coefficients in DATA/SHADR/JGDWN_VES20H_SHA.LBL VESTA20H is a 20th degree and order model obtained from radiometric tracking (Doppler and range data) and optical landmarks of the Dawn spacecraft in orbit about Vesta. The gravity model includes data from the Approach phase to the end of the HAMO-2 orbit. The data span is July 13, 2011 to July 25, 2012. Optical landmark tracking is included for the Survey, HAMO and LAMO phases. Optical tracking is yet to be included for HAMO-2. Some details describing this model are: The spherical harmonic coefficients are fully normalized. The associated GM = 17.2882449693 km^3/s^2 The reference radius = 265.0 km The Vesta-fixed reference frame prime meridian and pole location in IAU coordinates is given by Right ascension = 309.05870 degrees (estimated) RA rate = -0.207 degrees/cty (fixed) Declination = 42.23190 degrees (estimated) Dec rate = -0.048 degrees/cty (fixed) Prime Meridian = 284.59521 degrees (fixed) Rotation rate = 1617.3331279 degrees/day (estimated) The pole location and rotation rate are estimated jointly with the gravity field. The motion of the pole in inertial space is given by the modeled precession and nutation for a homogeneous Vesta and is not estimated. The prime meridian epoch value is chosen to match the Vesta LAMO shape model from Bob Gaskell on June 1, 2012 (Claudia is rotated to 146 deg E). This shape model includes images from the HAMO-2 phase and fills the previous gap in the shape model of the northern polar region. The uncertainties of the pole and rotation rate (5x formal) for this solution are Right ascension = 0.000043 degrees Declination = 0.000031 degrees Rotation rate = 0.00000087 degrees/day The reference for this gravity field is Konopliv et al., The Vesta gravity field, spin pole and rotation, landmark positions, and ephemeris from the Dawn tracking and optical data, Icarus, 2013, http://dx.doi.org/10.1016/j.icarus.2013.09.005. (Konopliv et al., 2014). The original published gravity field is in the Claudia coordinate system with the prime meridian location defined by the Claudia crater. To be consistent with IAU standards, this version of the VESTA20H gravity field has been rotated by 210 degrees to be similar to the Claudia double-prime coordinate system. The difference between the Claudia coordinate system and Claudia double-prime coordinate system is documented in the document collection, VESTA_COORDINATES_131018.PDF. Note that because the pole and spin rate are jointly estimated with the gravity field, the coordinate system used in this map differs slightly from the official Claudia double-prime coordinate system. For details about the gravity coordinate frame, see the details above. The formal error covariance of VESTA20H is delivered in the Spherical Harmonics Gravity Binary Data Record (SHBDR) and is produced by the Dawn Gravity Science Team at JPL. # JGDWN_VES26J_SHB Description This file contains the covariance and related data for the JPL Dawn Vesta gravity solution VESTA26J, a 26th degree and order spherical harmonic model and covariance. VESTA26J is a 26th degree and order model obtained from radiometric tracking (Doppler and range data) and optical landmarks of the Dawn spacecraft in orbit about Vesta. The gravity model includes data from the Approach phase to the end of the HAMO-2 orbit. The data span is July 23, 2011 to July 25, 2012. Optical landmark tracking is included for the Survey, HAMO, HAMO-2 and LAMO phases. Some details describing this model are: The spherical harmonic coefficients are fully normalized. The associated GM = 17.2882844211 km^3/s^2 The reference radius = 265.0 km The Vesta-fixed reference frame prime meridian and pole location in IAU coordinates is given by Right ascension = 309.06110 degrees (estimated) RA rate = -0.225213 degrees/cty (estimated with MOI) RA acceleration = 0.000298 degrees/cty^2 (estimated with MOI) Declination = 42.232386 degrees (estimated) Dec rate = -0.052184 degrees/cty (estimated with MOI) Dec acceleration= 0.0001118 degrees/cty (estimated with MOI) Prime Meridian = 284.6430975804534 degrees (estimated) Rotation rate = 1617.33312922 degrees/day (estimated) The pole location and rotation rate are estimated jointly with the gravity field. The motion of the pole in inertial space is given by the modeled precession and nutation for a Vesta with polar moment of inertia (MOI) C = 0.4208 (estimated). The prime meridian epoch value is estimated with the Claudia landmark longitude fixed to zero. The uncertainties of the pole and rotation rate for this solution are Right ascension = 0.00031 degrees Declination = 0.000068 degrees Rotation rate = 0.00000013 degrees/day Observations for the gravity field consist of Doppler and range measurements from Deep Space Network (DSN) tracking. The count time for the Doppler observations is 60 seconds. The typical accuracy for the Doppler is 0.02 mm/s for the 60 second sample time. The range accuracy is about 2 meters and is limited by the station calibration accuracy. The actual rms scatter is less than 0.3 meters in spacecraft position. The VESTA26J gravity model is delivered as a Spherical Harmonics Gravity Binary Data Record (SHBDR) and is produced by the JPL Dawn Gravity Science Team (Ryan Park and Alex Konopliv)." More details about VESTA26J can be found in: Park, R.S., A.I. Ermakov, A.S. Konopliv, A.T. Vaughan, N. Rambaux, B.G., Bills, J.C. Castillo-Rogez, R.R. Fu, S A. Jacobson, S.T. Stewart, and M.J. Toplis, "A small core in Vesta inferred from Dawn's observations," Nature Astronomy, 2025. https://doi.org/10.1038/s41550-025-02533-7 Map Projection Descriptions --------------------------- Note on value-added metadata: The PDS4 map products use updated projection values for upperleft_corner_x, upperleft_corner_y, pixel_resolution_x, and pixel_resolution_y. These values are based on proper cartographic parameters for equirectangular (simple cylindrical) projection. These values were provided by Trent Hare (PDS Imaging Node) and are documented in the figure equirectangular_map_projection_PDS4.pdf in the document collection; they supersede the values in the original PDS3 labels. # Description of the Digital Map of the Radial Gravity This file contains a digital map of the radial gravity derived from the JPL VESTA20H model of the Vesta gravity field. Each point gives the Vesta gravity radial acceleration in milligals on a 290-km x 265-km ellipsoid of revolution, which is the surface closest to Vesta that has minimal convergence errors for the spherical harmonic expansion. The JGDWN_VES20H_ACCEL gravity acceleration is computed from the full VESTA20H solution (from degree 2 up to degree 20) using the prime meridian given by W=284.59521 degrees. Because gravity will not converge on the geoid, gravity anomaly cannot be computed. Instead, the map is provided as radial acceleration on an ellipsoid, which is computed using the radial component of the spherical harmonic gravity potential. The JGDWN_VES20H_ACCEL_0020 gravity acceleration is computed from the full VESTA20H solution (from degree 2 up to degree 20), but without the J2 coefficient. The centrifugal acceleration due to the rotation of Vesta is not included in this map. The reference for this gravity field is Konopliv et al., The Vesta gravity field, spin pole and rotation, landmark positions, and ephemeris from the Dawn tracking and optical data, Icarus, 2013, http://dx.doi.org/10.1016/j.icarus.2013.09.005. (Konopliv et al., 2014). The original published gravity field is in the Claudia coordinate system with the prime meridian location defined by the Claudia crater. To be consistent with IAU standards, this version of the VESTA20H gravity field has been rotated by 210 degrees to be similar to the Claudia double-prime coordinate system. The difference between the Claudia coordinate system and Claudia double-prime coordinate system is documented in the document collection, VESTA_COORDINATES_131018.PDF. Note that because the pole and spin rate are jointly estimated with the gravity field, the coordinate system used in this map differs slightly from the official Claudia double-prime coordinate system. For details about the gravity coordinate frame, see JGDWN_VES20H_SHA File Description. The map is delivered as a Radio Science Digital Map (RSDMAP) product. Each pixel represents the radial acceleration on a simple cylindrical projection. Latitude and longitude are gridded and intersect one another at right angles. The map has 181 lines with 360 samples per line. For example, the first 8 bytes (PC_REAL) represent the first pixel at -180 degrees longitude and +90 degrees latitude. The last 8 bytes represent the last pixel at +179 degrees longitude and -90 degrees latitude. The map is produced at JPL by the Dawn Radio Science Team (Alex Konopliv, Ryan Park, Sami Asmar). # Description of the Digital Map of the Radial Gravity Error This file contains a digital map of the radial gravity error derived from from the JPL VESTA20H covariance of the Vesta gravity field. Each point gives the Vesta gravity radial acceleration error in milligals on a 290-km x 265-km ellipsoid of revolution, which is the surface closest to Vesta that has minimal convergence errors for the spherical harmonic expansion. The JGDWN_VES20H_ACCERR gravity acceleration error is computed from the full VESTA20H covariance (from degree 2 up to degree 20) using the prime meridian given by W=284.59521 degrees. The corresponding map of radial gravity acceleration is JGDWN_VES20H_ACCEL. The reference for this gravity field is Konopliv et al., The Vesta gravity field, spin pole and rotation, landmark positions, and ephemeris from the Dawn tracking and optical data, Icarus, 2013, http://dx.doi.org/10.1016/j.icarus.2013.09.005. (Konopliv et al., 2014). The original published gravity field is in the Claudia coordinate system with the prime meridian location defined by the Claudia crater. To be consistent with IAU standards, this version of the VESTA20H gravity field has been rotated by 210 degrees to be similar to the Claudia double-prime coordinate system. The difference between the Claudia coordinate system and Claudia double-prime coordinate system is documented in the document collection, VESTA_COORDINATES_131018.PDF. Note that because the pole and spin rate are jointly estimated with the gravity field, the coordinate system used in this map differs slightly from the official Claudia double-prime coordinate system. For details about the gravity coordinate frame, see JGDWN_VES20H_SHA File Description. The map is delivered as a Radio Science Digital Map (RSDMAP) product. Each pixel represents the error in radial acceleration on a simple cylindrical projection. Latitude and longitude are gridded and intersect one another at right angles. The map has 181 lines with 360 samples per line. For example, the first 8 bytes (PC_REAL) represent the first pixel at -180 degrees longitude and +90 degrees latitude. The last 8 bytes represent the last pixel at +179 degrees longitude and -90 degrees latitude. The map is produced at JPL by the Dawn Radio Science Team (Alex Konopliv, Ryan Park, Sami Asmar). # Description of the Digital Map of the Bouguer This file contains a digital map of the Bouguer gravity derived from the JPL VESTA20H model of the Vesta gravity field. Each point gives the Vesta gravity radial acceleration minus the gravity derived from integration of Vesta shape assuming uniform density in milligals on a 290.0-km x 265.0-km ellipsoid of revolution, which is the surface closest to Vesta that has minimal convergence errors for the spherical harmonic expansion. The JGDWN_VES20H_BOU gravity acceleration is computed from the truncated VESTA20H solution (from degree 2 up to degree 15). Please note thtat the Bouguer anomaly map is computed up to degree 15, for detailed information see Section 4, Figure 5 of the below publication (Konopliv et al., 2014). At degree 15, the Bouguer spectrum and sigma curve of the gravity field become close for the Bouguer anomaly to be applicable. The reference for this gravity field is Konopliv et al., The Vesta gravity field, spin pole and rotation, landmark positions, and ephemeris from the Dawn tracking and optical data, Icarus, 2013, http://dx.doi.org/10.1016/j.icarus.2013.09.005. (Konopliv et al., 2014). The original published gravity field is in the Claudia coordinate system with the prime meridian location defined by the Claudia crater. To be consistent with IAU standards, this version of the VESTA20H gravity field has been rotated by 210 degrees to be similar to the Claudia double-prime coordinate system. The difference between the Claudia coordinate system and Claudia double-prime coordinate system is documented in the document collection, VESTA_COORDINATES_131018.PDF. Note that because the pole and spin rate are jointly estimated with the gravity field, the coordinate system used in this map differs slightly from the official Claudia double-prime coordinate system. For details about the gravity coordinate frame, see JGDWN_VES20H_SHA File Description. The map is delivered as a Radio Science Digital Map (RSDMAP) product. Each pixel represents the Bouguer gravity on a simple cylindrical projection. Latitude and longitude are gridded and intersect one another at right angles. The map has 181 lines with 360 samples per line. For example, the first 8 bytes (PC_REAL) represent the first pixel at -180 degrees longitude and +90 degrees latitude. The last 8 bytes represent the last pixel at +179 degrees longitude and -90 degrees latitude. The map is produced at JPL by the Dawn Radio Science Team (Alex Konopliv, Ryan Park, Sami Asmar). # Description of the Digital Map of the Vesta GEOID This file contains a digital map of the Vesta geoid derived from the JPL VESTA20H spherical harmonic model of the Vesta gravity field. Each point is the Vesta geoid height in meters above a reference ellipsoid (semi-major-axis = 281.0 km, GM = 17.2882449693 km**3/s**2, flattening = 0.195729537, and rotation rate = 0.00032671051138233364 rad/s). The prime meridian is given by W=284.59521 degrees. ** IMPORTANT NOTE ** The JGDWN_VES20H_GEOID is computed from the VESTA20H solution (from degree 2 up to degree 20). Note that the geoid is *not valid* for all points on the surface due to divergence of the spherical harmonics. The valid region is roughly between +- 60 degrees latitude. The reference for this gravity field is Konopliv et al., The Vesta gravity field, spin pole and rotation, landmark positions, and ephemeris from the Dawn tracking and optical data, Icarus, 2013, http://dx.doi.org/10.1016/j.icarus.2013.09.005. (Konopliv et al., 2014). The original published gravity field is in the Claudia coordinate system with the prime meridian location defined by the Claudia crater. To be consistent with IAU standards, this version of the VESTA20H gravity field has been rotated by 210 degrees to be similar to the Claudia double-prime coordinate system. The difference between the Claudia coordinate system and Claudia double-prime coordinate system is documented in the document collection, VESTA_COORDINATES_131018.PDF. Note that because the pole and spin rate are jointly estimated with the gravity field, the coordinate system used in this map differs slightly from the official Claudia double-prime coordinate system. For details about the gravity coordinate frame, see JGDWN_VES20H_SHA File Description. The map is delivered as a Radio Science Digital Map (RSDMAP) product. Each pixel represents the geoid height on a simple cylindrical projection. Latitude and longitude are gridded and intersect one another at right angles. The map has 181 lines with 360 samples per line. For example, the first 8 bytes (PC_REAL) represent the first pixel at -180 degrees longitude and +90 degrees latitude. The last 8 bytes represent the last pixel at +179 degrees longitude and -90 degrees latitude. The map is produced by Dawn Gravity Team (Alex Konopliv, Ryan Park, Sami Asmar) at JPL." # Description of the Digital Map of the Vesta GEOID Error This file contains a digital map of the Vesta geoid error derived from the JPL VESTA20H spherical harmonic covariance of the Vesta gravity field. Each point is the Vesta geoid height error in meters above a reference ellipsoid (semi-major-axis = 281.0 km, GM = 17.2882449693 km**3/s**2, flattening = 0.195729537, and rotation rate = 0.00032671051138233364 rad/s). The prime meridian is given by W=284.59521 degrees. The JGDWN_VES20H_GEOIDERR is computed from the VESTA20H covariance (from degree 2 up to degree 20). Note that the geoid is not valid for all points on the surface due to divergence of the spherical harmonics. The valid region is roughly between +- 60 degrees latitude. ** IMPORTANT NOTE ** The corresponding map of geoid height is JGDWN_VES20H_GEOID. Note that the geoid is *not valid* for all points on the surface due to divergence of the spherical harmonics. The valid region is roughly between +- 60 degrees latitude. The reference for this gravity field is Konopliv et al., The Vesta gravity field, spin pole and rotation, landmark positions, and ephemeris from the Dawn tracking and optical data, Icarus, 2013, http://dx.doi.org/10.1016/j.icarus.2013.09.005. (Konopliv et al., 2014). The original published gravity field is in the Claudia coordinate system with the prime meridian location defined by the Claudia crater. To be consistent with IAU standards, this version of the VESTA20H gravity field has been rotated by 210 degrees to be similar to the Claudia double-prime coordinate system. The difference between the Claudia coordinate system and Claudia double-prime coordinate system is documented in the document collection, VESTA_COORDINATES_131018.PDF. Note that because the pole and spin rate are jointly estimated with the gravity field, the coordinate system used in this map differs slightly from the official Claudia double-prime coordinate system. For details about the gravity coordinate frame, see JGDWN_VES20H_SHA File Description. The map is delivered as a Radio Science Digital Map (RSDMAP) product. Each pixel represents the error in geoid height on a simple cylindrical projection. Latitude and longitude are gridded and intersect one another at right angles. The map has 181 lines with 360 samples per line. For example, the first 8 bytes (PC_REAL) represent the first pixel at -180 degrees longitude and +90 degrees latitude. The last 8 bytes represent the last pixel at +179 degrees longitude and -90 degrees latitude. The map is produced by Dawn Gravity Team (Alex Konopliv, Ryan Park, Sami Asmar) at JPL. Coordinate System ================= Dawn Gravity SDP files use a Vesta centered body-fixed coordinate system similar to the IAU coordinate system. The values differ slightly because the the orientation of Vesta is estimated in the orbit determination process. See labels of specific gravity products for details. Software ======== None. CONFIDENCE LEVEL NOTE ===================== Overview ======== Data in this collection have been reduced as part of mission data analysis activities of the Dawn Gravity Team. Review ====== This archival collection was reviewed by the Dawn Gravity Team prior to submission to the Planetary Data System (PDS). Bundle design, documentation, and sample products have passed a PDS peer review. Data Coverage and Quality ========================= This collection contains gravity models and maps generated from Dawn data collected between July 2011 and July 2012. JGDWN_VES20H_SHA.TAB is an ASCII file of coefficients and related data for a 20th degree and order Vesta gravity field produced at the Jet Propulsion Laboratory. The name of this gravity model is VESTA20H. The model used is described in the file's detached label. JGDWN_VES20H_ACCEL_0020.IMG is a digital map of the Vesta radial acceleration due to gravity with the J2 coefficient removed. The radial accelerations are computed with the VESTA20H field described in the JGDWN_VES20H_SHA.TAB file. This Vesta gravity field was produced at the Jet Propulsion Laboratory. The model used is described in the file's detached label.