Dawn Ceres 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. - 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. - Konopliv, A.S., Asmar, S.W., Bills, B.G., Mastrodemos, N., Park, R.S., Raymond, C.A., Smith D.E., 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. Russel, 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, 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. - Park, R.S., A.S. Konopliv, B.G. Bills, N. Rambaux, J.C. Castillo-Rogez, C.A. Raymond, A.T. Vaughan, A.I. Ermakov, M.T. Zuber, R.R. Fu, M.J. Toplis, C.T. Russell, A. Nathues and F. Preusker, A partially differentiated interior for (1) Ceres deduced from its gravity field and shape, Nature 537, 515-517, doi:10.1038/nature18955, 2016. - Park, R.S., A.T. Vaughan, A.S. Konopliv, A.I. Ermakov, N. Mastrodemos, J.C. Castillo-Rogez, S.P. Joy, A. Nathues, C.A. Polanskey, M.D. Rayman, J.E. Riedel, C.A. Raymond, C.T. Russell, and M.T. Zuber, High-resolution shape model of Ceres from stereophotoclinometry using Dawn Imaging Data, Icarus, Volume 319, 812-827, doi:10.1016/j.icarus.2018.10.024, 2019. - Park, R.S., A.S. Konopliv, A.I. Ermakov, J.C. Castillo-Rogez, R.R. Fu, K.H.G. Hughson, T.H. Prettyman, C.A. Raymond, J.E.C. Scully, H.G. Sizemore, M.M. Sori, A.T. Vaughan, G. Mitri, B.E. Schmidt, and C.T. Russell, Evidence of non-uniform crust of Ceres from Dawn's high-resolution gravity data. Nature Astronomy 4, 748-755 (2020). https://doi.org/10.1038/s41550-020-1019-1 - Russell, C.T., and C.A. Raymond, The Dawn Mission to Vesta and Ceres, Space Science Reviews, 163, 3-23, 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 Ceres 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 Ceres. 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 Ceres' 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 Ryan Park produced spherical harmonic models and maps. These results were derived from raw radio tracking data. At Ceres, the mission was divided into different science orbits. All the orbits were polar. The RC3 orbit was conducted at an alitutde of 13500 km, The Survey orbit was performed at a nominal altitude of 4400 km. The High Altitude Mapping Orbit, or HAMO, was performed at a nominal altitude of 1450 km. The Low Altitude Mapping Orbit, or LAMO, was performed at a nominal altitude of 375 km. An extended mission phase XMO1 was conducted at the same altitude as LAMO. Additional extended mission phases of XMO2, XMO3 and XMO4 were conducted at altitudes of 1480 km, 7520-9350 km, and 20000 km. Between these science orbits, the spacecraft as 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 Ceres, 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. 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 Ceres Gravity Science Raw Data Archive. Useful references which describe the procedures applied in general to processing Ceres orbiter tracking data include (Park et al., 2016). (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 collection with file names of the form GTsss_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. # CERES70E SHADR File Description This file contains coefficients and related data for the CERES70E spherical harmonic gravity model of Ceres. CERES70E is a 70th degree and order model obtained from radiometric tracking (Doppler and range data) and optical landmarks of the Dawn spacecraft in orbit about Ceres. The gravity model includes Prime Mission data from the Approach phase to the end of the LAMO orbit. The data span is Feb 2, 2015 to Sept 2, 2016. Optical landmark tracking is included for LAMO and HAMO phases. The Doppler and landmark tracking is also included for the Extended Mission-2 phase from June 6, 2018 to October 31, 2018. This gravity field is consistent with the final SPC shape model of Ceres (Park et al. High resolution shape model of Ceres from stereophotoclinometry using Dawn imaging data, Icarus, 2019). More details can be found in Park, R.S., Konopliv, A.S., Ermakov, A.I. et al. Evidence of non-uniform crust of Ceres from Dawn's high-resolution gravity data. Nat Astron 4, 748-755 (2020). https://doi.org/10.1038/s41550-020-1019-1 Some details describing this model are: The spherical harmonic coefficients are fully normalized. The associated GM = 62.628896902 km^3/s^2 The reference radius = 470.0 km The Ceres-fixed reference frame prime meridian and pole location in IAU coordinates are fixed to CERES18D values: Right ascension = 291.42763 degrees RA rate = 0.0 degrees/cty Declination = 66.76033 degrees Dec rate = 0.0 degrees/cty Prime Meridian = 170.309 degrees Rotation rate = 952.1532635 degrees/day The pole location, W0 and spin rate were determined in the CERES18D gravity field by fixing the y-value of the Kait landmark to zero. The uncertainties of the pole for CERES18D solution are Right ascension = 0.0002 degrees Declination = 0.0002 degrees The gravity field is constrained using a variable surface acceleration constraint based upon the degree strength of the gravity field for each longitude and latitude location. 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 0.02-0.03 mm/s for the 60 second sample time. The range accuracy is about 1-2 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 5037 coefficients and a GM value. Definitions of the tables follow. The CERES70E 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). # CERES70E_ISOSIG SHADR File Description This file contains coefficients and related data for the CERES70E spherical harmonic gravity model of Ceres. CERES70E is a 70th degree and order model obtained from radiometric tracking (Doppler and range data) and optical landmarks of the Dawn spacecraft in orbit about Ceres. The gravity model includes Prime Mission data from the Approach phase to the end of the LAMO orbit. The data span is Feb 2, 2015 to Sept 2, 2016. Optical landmark tracking is included for LAMO and HAMO phases. The Doppler and landmark tracking is also included for the Extended Mission-2 phase from June 6, 2018 to October 31, 2018. This gravity field is consistent with the final SPC shape model of Ceres (Park et al. High resolution shape model of Ceres from stereophotoclinometry using Dawn imaging data, Icarus, 2019). More details can be found in Park, R.S., Konopliv, A.S., Ermakov, A.I. et al. Evidence of non-uniform crust of Ceres from Dawn's high-resolution gravity data. Nat Astron 4, 748-755 (2020). https://doi.org/10.1038/s41550-020-1019-1 Some details describing this model are: The spherical harmonic coefficients are fully normalized. The associated GM = 62.628896902 km^3/s^2 The reference radius = 470.0 km The Ceres-fixed reference frame prime meridian and pole location in IAU coordinates are fixed to CERES18D values: Right ascension = 291.42763 degrees RA rate = 0.0 degrees/cty Declination = 66.76033 degrees Dec rate = 0.0 degrees/cty Prime Meridian = 170.309 degrees Rotation rate = 952.1532635 degrees/day The pole location, W0 and spin rate were determined in the CERES18D gravity field by fixing the y-value of the Kait landmark to zero. The uncertainties of the pole for CERES18D solution are Right ascension = 0.0002 degrees Declination = 0.0002 degrees The gravity field is constrained using a variable surface acceleration constraint based upon the degree strength of the gravity field for each longitude and latitude location. 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 0.02-0.03 mm/s for the 60 second sample time. The range accuracy is about 1-2 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 5037 coefficients and a GM value. Definitions of the tables follow. The CERES70E 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). # CERES70E_KAULA SHADR File Description This file contains coefficients and related data for the CERES70E_KAULA spherical harmonic gravity model of Ceres. CERES70E_KAULA is a 70th degree and order model obtained from radiometric tracking (Doppler and range data) and optical landmarks of the Dawn spacecraft in orbit about Ceres. The gravity model includes Prime Mission data from the Approach phase to the end of the LAMO orbit. The data span is Feb 2, 2015 to Sept 2, 2016. Optical landmark tracking is included for LAMO and HAMO phases. The Doppler and landmark tracking is also included for the Extended Mission-2 phase from June 6, 2018 to October 31, 2018. This gravity field is consistent with the final SPC shape model of Ceres (Park et al. High resolution shape model of Ceres from stereophotoclinometry using Dawn imaging data, Icarus, 2019). More details can be found in Park, R.S., Konopliv, A.S., Ermakov, A.I. et al. Evidence of non-uniform crust of Ceres from Dawn's high-resolution gravity data. Nat Astron 4, 748-755 (2020). https://doi.org/10.1038/s41550-020-1019-1 Some details describing this model are: The spherical harmonic coefficients are fully normalized. The associated GM = 62.6289111207 km^3/s^2 The reference radius = 470.0 km The Ceres-fixed reference frame prime meridian and pole location in IAU coordinates are fixed to CERES18D values: Right ascension = 291.42763 degrees RA rate = 0.0 degrees/cty Declination = 66.76033 degrees Dec rate = 0.0 degrees/cty Prime Meridian = 170.309 degrees Rotation rate = 952.1532635 degrees/day The pole location, W0 and spin rate were determined in the CERES18D gravity field by fixing the y-value of the Kait landmark to zero. The uncertainties of the pole for CERES18D solution are Right ascension = 0.0002 degrees Declination = 0.0002 degrees The gravity field is constrained using a Kaula power law constraint of 0.0012/n^2. 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 0.02-0.03 mm/s for the 60 second sample time. The range accuracy is about 1-2 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 5037 coefficients and a GM value. Definitions of the tables follow. The CERES70E_KAULA 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). # CERES18D Description This file contains coefficients and related data for the CERES18D spherical harmonic gravity model of Ceres. CERES18D is a 18th degree and order model obtained from radiometric tracking (Doppler and range data) and optical landmarks of the Dawn spacecraft in orbit about Ceres. The gravity model includes data from the Approach phase to the end of the LAMO orbit. The data span is Feb 2, 2015 to Sept 2, 2016. Optical landmark tracking is included for all phases. This gravity field is consistent with the final SPC shape model of Ceres (Park et al. High resolution shape model of Ceres from stereophotoclinometry using Dawn imaging data, submitted to Icarus, 2018). Some details describing this model are: The spherical harmonic coefficients are fully normalized. The associated GM = 62.6290536121 km^3/s^2 The reference radius = 470.0 km The Ceres-fixed reference frame prime meridian and pole location in IAU coordinates is given by Right ascension = 291.42763 degrees (estimated) RA rate = 0.0 degrees/cty (fixed) Declination = 66.76033 degrees (estimated) Dec rate = 0.0 degrees/cty (fixed) Prime Meridian = 170.309 degrees (estimated) Rotation rate = 952.1532635 degrees/day (estimated) The pole location, W0 and spin rate are estimated jointly with the gravity field by fixing the y-value of the Kait landmark to zero. The uncertainties of the pole for this solution are Right ascension = 0.0002 degrees Declination = 0.0002 degrees Note ceres18d is similar to ceres18c version 2 of the gravity field which has the corrected location of the kait crater. This is a rotation of -0.064074 deg about the z-axis versus the previous version of the gravity field. 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 0.02-0.03 mm/s for the 60 second sample time. The range accuracy is about 1-2 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 357 coefficients and a GM value. Definitions of the tables follow. Note: the defined constant uncertainty (in this case, the gravitational constant GM) is 1-sigma definition and is rounded. The additional zeros at the end are data formatting to be consistent with SHADR files in other gravity field archives. The SHBDR file contains a GM uncertainty that is not rounded. The CERES18D 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). 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_CER18D_SHB SHBDR File Description This file contains the covariance and related data for the JPL Dawn Ceres gravity soluttion CERES18D, a 18th degree and order spherical harmonic model and covariance. Some details describing this model are: The spherical harmonic coefficients are fully normalized. The associated GM = 62.6290536121 km^3/s^2 The reference radius = 470.0 km The Ceres-fixed reference frame prime meridian and pole location in IAU coordinates is given by Right ascension = 291.42763 degrees (estimated) RA rate = 0.0 degrees/cty (fixed) Declination = 66.76033 degrees (estimated) Dec rate = 0.0 degrees/cty (fixed) Prime Meridian = 170.309 degrees (estimated) Rotation rate = 952.1532635 degrees/day (estimated) The pole location, W0 and spin rate are estimated jointly with the gravity field by fixing the y-value of the Kait landmark to zero. The uncertainties of the pole for this solution are Right ascension = 0.0002 degrees Declination = 0.0002 degrees Note ceres18d is similar to ceres18c version 2 of the gravity field which has the corrected location of the kait crater. This is a rotation of -0.064074 deg about the z-axis versus the previous version of the gravity field. For a description of the solution, see the ascii pds file for the CERES18D spherical harmonic gravity coefficients. The error covariance of CERES18D is delivered in the Spherical Harmonics Gravity Binary Data Record (SHBDR) and is produced by the Dawn Gravity Science Team at JPL. 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 CERES18D model of the Ceres gravity field. Each point gives the Ceres gravity radial acceleration in milligals on a 482.0-km x 445.9-km ellipsoid of revolution, which is close to the surface of Ceres. The hydrostatic coefficients J2 and J4 are not included. The JGDWN_CER18D_ACCEL_0018 gravity acceleration is computed from the full CERES18D solution (from degree 2 up to degree 18). 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 the JPL CERES18D model of the Ceres gravity field. Each point gives the Ceres gravity radial acceleration error in milligals on a 482.0-km x 445.9-km ellipsoid of revolution, which is close to the surface of Ceres. The hydrostatic coefficients J2 and J4 are included. The JGDWN_CER18D_ACCERR gravity acceleration error is computed from the full CERES18D solution covariance (from degree 2 up to degree 18). 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 CERES18D model of the Ceres gravity field. Each point gives the Ceres gravity radial acceleration minus the gravity derived from integration Ceres shape assuming uniform density in milligals on a 482.0-km x 445.9-km ellipsoid of revolution, which is close to the surface of Ceres. The hydrostatic coefficients J2 and J4 are not included. The JGDWN_CER18D_BOU_0018 gravity acceleration is computed from the full CERES18D solution (from degree 2 up to degree 18). 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 Ceres GEOID This file contains a digital map of the Ceres geoid derived from the JPL CERES18D spherical harmonic model of the Ceres gravity field. Each point is the Ceres geoid height in meters above a reference ellipsoid (semi-major-axis = 482.0 km, GM = 62.6273588067 km**3/s**2, flattening = 0.074896, and rotation rate = 0.000192340387006239 rad/s). The JGDWN_CER18D_GEOID_0018 is computed from the CERES18D solution (from degree 2 up to degree 18). 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 Ceres geoid uncertainty derived Cfrom the covariance matrix for the spherical harmonic coefficients of the JPL CERES18D Ceres gravity field. Each point is the Ceres geoid height error in meters above a reference ellipsoid (semi-major-axis = 482.0 km, GM = 62.6273588067 km**3/s**2, flattening = 0.074896, and rotation rate = 0.000192340387006239 rad/s). The JGDWN_CER18D_GEOIDERR_0018 is computed from the CERES18D solution (from degree 2 up to degree 18). The map is produced by Dawn Gravity Team (Alex Konopliv, Ryan Park, Sami Asmar) at JPL. Coordinate System ================= Dawn Gravity SDP files use a Ceres centered body-fixed coordinate system similar to the IAU coordinate system. The values differ slightly because the the orientation of Ceres is estimated in the orbit determination process. See the coordinate system document in the Dawn Mission Bundle: - dawn-mission/document-rss/CERES_COORD_SYS_180628.PDF and the 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). Data set 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 January 2015 and August 2016.