Dawn Mission to Vesta and Ceres L-2 Data from Vesta and Ceres Gravity Science Instrument Archive Volume Software Interface Specification Dustin Buccino Jet Propulsion Laboratory, California Institute of Technology Version 2.1 May 31, 2017 (c) 2017 California Institute of Technology. Government sponsorship acknowledged. CHANGE LOG =========================================================================== DATE CHANGES REASON REVISION 12/30/16 Original 02/15/17 Improved clarity 1 03/23/17 Combined Vesta and Ceres in same SIS 2 05/31/17 PDS Peer Review 2.1 =========================================================================== Table of Contents =========================================================================== 1. INTRODUCTION 4 1.1 Purpose and Scope 4 1.2 Content Overview 4 1.3 References 4 2. REDUCED DATA RECORD ARCHIVE OVERVIEW... 5 2.1 Instrument Overview 5 2.2 Data Product Overview 5 2.2.1. Detailed Descriptions 5 2.3 Data Processing 6 2.4 Software 6 2.5 File Naming Conventions 7 2.6 Data Product Labels 7 2.7 Standard Keyword Values 7 3. ARCHIVE ORGANIZATION 7 3.1 Root Directory 8 3.2 CATALOG Directory 8 3.3 DOCUMENT Directory 8 3.4 INDEX Directory 8 3.5 DATA Directory 9 4. RELEVANT DATA ARCHIVED AT OTHER SITES. 9 4.1 NAIF Node 9 5. PERSONNEL 9 6. ACKNOWLEDGMENTS 9 ACRONYMS AND ABBREVIATIONS ASCII American Standard Code for Information Interchange CEGR Ceres Gravity DOY Day of Year DSC Dawn Science Center DSN Deep Space Network GS Gravity Science GSI Gravity Science Instrument JPL Jet Propulsion Laboratory NAIF Navigation Ancillary Information Facility NASA National Aeronautics and Space Administration PDS Planetary Data System RDA Raw Data Archive RDR Reduced Data Record RS Radio Science RSDMAP Radio Science Digital Map RSS Radio Science Subsystem RSSG Radio Science Systems Group SIS Software Interface Specification VEGR Vesta Gravity 1. INTRODUCTION 1.1. Purpose and Scope This Software Interface Specification (SIS) describes the format and content of the Dawn Mission to Vesta and Ceres (Dawn) Gravity Science (GS) Reduced Data Record (RDR) Archive for the Vesta and Ceres phase of the mission. The Dawn Vesta Gravity (VEGR) RDR represents the complete archive of raw data from gravity science investigations conducted using the radio link between the Dawn spacecraft and the Deep Space Network (DSN) tracking stations. The Dawn Ceres Gravity (CEGR) RDR represents the archive of reduced data from gravity science investigations conducted using the radio link between the Dawn spacecraft and the Deep Space Network (DSN) tracking stations. The archives are generated by the Dawn Gravity Science Team and the Dawn Science Center (DSC). It is maintained and distributed by the Planetary Data System (PDS). Gravity Science is a subset of Radio Science, and because of this, the terms Gravity Science (GS) and Radio Science (RS) are used interchangeably in this archive; as are the terms the Gravity Science Instrument (GSI) and Radio Science Subsystem (RSS). 1.2. Content Overview This archive contains data products derived from raw Dawn Gravity Science tracking data. The radio observations were carried out using the Dawn spacecraft and Earth-based receiving stations of the NASA Deep Space Network. This SIS describes the format and content of the Dawn GS RDR archive. The data are generated and assembled into archives by the Gravity Science Team and delivered to the Dawn Science Center (DSC). The DSC delivers the completed archive to PDS. The specific data products included in this archive are: Gravity field model coefficients (SHADR): The spherical harmonic coefficients of the gravity field derived from the tracking data Gravity field model coefficients and covariance (SHBDR): The spherical harmonic coefficients of the gravity field and respective covariance derived from the tracking data Gravity field maps (RSDMAP): Global maps of the gravity 1.3. References [1] 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. [2] 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. 2. REDUCED DATA RECORD ARCHIVE OVERVIEW 2.1. Instrument Overview The gravity science instrument utilizes the deep space transponder onboard the Dawn spacecraft and Doppler tracking equipment at the Deep Space Network to perform radio science investigations to determine the gravitational field of celestial bodies. For the full description of the Gravity Science instrument, please refer to the INST.CAT and DATASET.CAT files in the CATALOG directory. 2.2. Data Product Overview The derived data are stored in the DATA folder in two subdirectories. The RSDMAP files are binary files with detached PDS labels describing the format. The SHADR files are ASCII files with detached PDS labels describing the format. The table below describes the data products contained in these directories. ============================================================================== File Abbrev. File Type Source of Files ------------------------------------------------------------------------------ Radio Science Digital Map RSDMAP Binary Dawn Gravity Team Spherical Harmonics ASCII Data Record SHADR ASCII Dawn Gravity Team Spherical Harmonics Binary Data Record SHBDR Binary Dawn Gravity Team ============================================================================== 2.2.1. Detailed Descriptions Radio Science Digital Map files 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. Radio Science Digital Map products are stored in the DATA/RSDMAP directory with file names of the form GTsss_ffff_nnnn_cccc.IMG where G denotes the generating institution, T indicates the type of data represented, sss is a 3-character modifier specified by the data producer, 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, nnnn is a 4- to 8-character modifier indicating the type of data represented, and 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. 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. Spherical Harmonics ASCII Data Record files Spherical harmonic models are tables of coefficients GM, Cmn, and Smn. These can be used to represent gravitational potential of a celestial body, for example. ASCII (data type SHA) formatted spherical harmonics are defined. Because of the low degree field, no binary files (data type SHB) are provided.  Each file contains up to three 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). ASCII spherical harmonic models are stored in the DATA/SHADR directory with file names of the form GTsss_nnnnvv_SHA.TAB where G denotes the generating institution, T indicates the type of data represented, sss is a 3-character modifier specified by the data producer, nnnnvv is a 4-to 6-character modifier specified by the data producer. 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. Spherical Harmonics Binary Data Record files The Spherical Harmonics Binary Data Record (SHBDR) contains binary coefficients and/or a binary covariance matrix for a spherical harmonic expansion of gravity fields. SHBDR products have variable length, depending on the degree and order of the model and the number of tables included. A model of degree and order N will include approximately N**2 terms and therefore the number of terms in the covariance matrix will be of order N**4. For 8-byte storage and N=50, the total SHBDR volume will be about 30 MB. For N=100, the total SHBDR volume will be approximately 416 MB ASCII 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, T indicates the type of data represented, sss is a 3-character modifier specified by the data producer, nnnnvv is a 4-to 6-character modifier specified by the data producer. 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.LBL. 2.3. Data Processing Data processing is performed by the Dawn Gravity Science Team at the Jet Propulsion Laboratory in Pasadena, CA. The raw radio tracking data are input into a gravity-specific version of the JPL Orbit Determination Program (ODP) called MIRAGE, which filters the data in a least-squares method to solve for parameters, including spherical harmonic coefficients describing the gravity field. For an overview of the method, see Reference [1] or [2] in Section 1.3. 2.4. Software No software is included in this archive. The PDS-provided NASAview software is useful for opening and viewing RSDMAP products. It is available from the Planetary Data System's website at: https://pds.nasa.gov/tools/nasaview.shtml The SPICE toolkit provides useful tools and algorithms for ancillary data processing that could help in the use of these products of and is located at the NAIF PDS node naif.jpl.nasa.gov. 2.5. File Naming Conventions See Section 2.2.1 for file naming conventions in the description of each file type. 2.6. Data Product Labels Every file in this archive is accompanied by a PDS label. The label is either attached (embedded in the file) or detached (separate file with same name except for extension ‘.LBL’). Depending on the file type, the detached label may provide the content and structure of the file. Labels are structured in the PDS KEYWORD=VALUE fashion. A description of the keywords may be found on the web at http://pds.nasa.gov/tools/ddlookup/data_dictionary_lookup.cfm http://pds.nasa.gov/tools/ddlookup/data_dictionary_lookup.cfm. . 2.7. Standard Keyword Values The Dawn Gravity Science RDA uses the following standard keywords and values, consistent across the archive: =============================================================================== Keyword Dawn Standard Values ------------------------------------------------------------------------- DATA_SET_ID DAWN-A-RSS-5-VEGR-V1.0; DAWN-A-RSS-5-CEGR-V1.0 DATA_SET_NAME DAWN VESTA GRAVITY SCIENCE DERIVED SCIENCE DATA V1.0; DAWN CERES GRAVITY SCIENCE DERIVED SCIENCE DATA V1.0 INSTRUMENT_HOST_ID DAWN INSTRUMENT_HOST_NAME DAWN INSTRUMENT_ID RSS INSTRUMENT_NAME GRAVITY SCIENCE INSTRUMENT INSTRUMENT_TYPE RADIO SCIENCE MISSION_NAME DAWN MISSION TO VESTA AND CERES TARGET_NAME 1 CERES; 4 VESTA VOLUME_ID DWNCGRS_2; DWNVGRS_2 VOLUME_SERIES_NAME DAWN VOLUME_SET_ID USA_NASA_PDS_DAWN_GRS_L2 VOLUME_SET_NAME DAWN GRAVITY SCIENCE INSTRUMENT DERIVED L-2 DATA VOLUME_VERSION_ID VERSION 1 ================================================================================ 3. ARCHIVE ORGANIZATION The Dawn Gravity Science Raw Data Archive for Ceres has the following directories: Root directory CATALOG DOCUMENT DATA ---RSDMAP ---SHADR ---SHBDR INDEX The contents of the directories are described below. 3.1. Root Directory This directory is the core directory on which the rest of the archive is built. It contains the following files: 1. AAREADME.TXT: Human readable description of the archive contents 2. ERRATA.TXT: Human readable list of corrections and other comments regarding the archive 3. VOLDESC.CAT: Description of the contents of the volume 3.2. CATALOG Directory This directory contains descriptions of the dataset, mission, instrument, and spacecraft. They are all ASCII stream files. It contains the following files: 1. CATINFO.TXT: Description of the directory 2. DATASET.CAT: Overview of the RDA 3. INST.CAT: Overview of the Gravity Science Instrument 4. dawninsthost.cat: Overview of the Dawn spacecraft 5. dawnmission.cat: Overview of the Dawn Mission to Vesta and Ceres 6. DSMAP.DAT: Overview of the Radio Science Digital Map files 7. PERSON.CAT: Contributors to the archive and contact information 8. REF.CAT: References for the archive 3.3. DOCUMENT Directory This directory contains the corresponding documentation to help the end user use and interpret the data included in this archive. The following documents are included: ============================================================================== File Type Contents ------------------------------------------------------------------------------ DOCINFO.TXT text Description of the directory DAWN_GRAV_RDR_SIS Word, PDF, html This document RSDMAP html Description of the contents and format of the Radio Science digital map files SHADR html Description of the contents and format of the Spherical Harmonic ASCII data record files SHBDR html Description of the contents and format of the Spherical Harmonics Binary data record files =============================================================================== 3.4. INDEX Directory This directory contains the following files: 1.INDEXINFO.TXT: Description of the directory 2. INDEX.LBL: Detached label describing INDEX.TAB 3. INDEX.TAB: Table listing all data products in the RDR archive 3.5. DATA Directory The DATA directory contains the primary data. It contains the following subdirectories and file types: ================================================================================ Directory File Type Contents -------------------------------------------------------------------------------- RSDMAP Radio Science Digital Map Contains maps of an evaluated gravity field, such as gravity anomaly SHADR Spherical Harmonics ASCII Data Record Contains the spherical harmonic coefficients of the gravity field of the specified body SHBDR Spherical Harmonics Binary Data Record Contains the spherical harmonic coefficients and covariance of the gravity field of the specified body ================================================================================ 4. RELEVANT DATA ARCHIVED AT OTHER SITES 4.1. NAIF Node The Navigation and Ancillary Information Facility (NAIF) is the navigation node of the PDS. NAIF provides the archives for spacecraft navigation, attitude, events, clock conversion, and planetary ephemerides for most NASA missions. Additionally, NAIF provides the SPICE toolkit, containing useful algorithms to utilize and manipulate data NAIF provide. Relevant to gravity science are the following types: CK: Spacecraft and solar array attitude orientation files FK: Reference frame specification SCLK: Conversion between spacecraft time and ephemeris time SPK: Spacecraft and Planetary ephemeris data The NAIF PDS archive for Dawn is located at: naif.jpl.nasa.gov/pub/naif/pds/data/dawn-m_a-spice-6-v1.0/ 5. PERSONNEL Ryan S. Park, Chair of the Dawn Gravity Science Working Group, NASA Jet Propulsion Lab Alex S. Konopliv, Dawn Gravity Science Co-Investigator, NASA Jet Propulsion Lab Dustin R. Buccino, Dawn Radio Science Analyst, NASA Jet Propulsion Lab 6. ACKNOWLEDGMENTS The work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.