Data Set Overview : The Dawn Mission to Vesta and Ceres (DAWN) Gravity Science (GR) Raw Data Archive (RDA) is the set of raw and partially processed radio science data collected during the Dawn mission to Ceres. The earliest data in this data set were collected on 2015-01-02. The closed-loop system used a phase-lock loop in the ground receiver to track the downlink signal, reporting both amplitude and frequency at rates typically of 1-10 times per second. Closed-loop data are efficient for characterizing slowly changing signals and are the input to operational navigation and orbit-determination processes. The data set includes one type of primary data, the ODF. TNFs (Tracking and Navigation Service Data Files) are the output of the closed-loop receiver. Orbit Data Files (ODFs) are compressed versions of TNFs. ODFs are specifically targeted to spacecraft navigators and scientists interested in gravity fields. Typical users of these data might analyze range and Doppler measurements in ODFs to reconstruct the spacecraft trajectory. Relevant questions would include the measurement uncertainties in range and Doppler at different DSN antennas; the uncertainties could set constraints on any model of Ceres's gravity field developed later, for example. Parameters : The ODF is a minimally processed output of the closed-loop receiver. It contains the most important information (range, Doppler and frequency ramps) needed by spacecraft investigators, and investigators interested in determining gravity fields. Each ODF is accompanied by a full PDS label which describes both the content and format of the associated file. ODF data fields include: Narrowband spacecraft VLBI, Doppler mode (cycles) Narrowband spacecraft VLBI, phase mode (cycles) Narrowband quasar VLBI, Doppler mode (cycles) Narrowband quasar VLBI, phase mode (cycles) Wideband spacecraft VLBI (nanoseconds) Wideband quasar VLBI (nanoseconds) One-way Doppler (Hertz) Two-way Doppler (Hertz) Three-way Doppler (Hertz) One-way total count phase (cycles) Two-way total count phase (cycles) Three-way total count phase (cycles) PRA planetary operational discrete spectrum range (range units) SRA planetary operational discrete spectrum range (range units) RE(GSTDN) range (nanoseconds) Azimuth angle (degrees) Elevation angle (degrees) Hour angle (degrees) Declination angle (degrees) Processing : ODFs are abstracted from subsets of TNF data, the uncompressed output of the closed-loop receiver at the Deep Space Network. A full PDS label accompanies each ODF file and gives a bit level description of the content and format. Data : The data set contains primary data and secondary data. Primary data are those files which would normally be used to derive science products and investigation results. Secondary data are needed for the processing or interpretation of primary data but are not usually considered to have science value of their own. For gravity science, there is one type of primary data. Listings of primary and secondary files can be found in INDEX/INDEX.TAB for the data set (as of the most recent delivery). ODFs are stored in the ODF directory. ODFs contain the output of the closed-loop tracking system of the Deep Space Network. File names are of the form dawncegryyyy_ddd_hhmmXuuwVn.odf where 'dawncegr' identifies the mission and the data set; 'yyyy' is the four-digit year, 'ddd' is the three-digit day-of-year, 'hh' is the two-digit hour, and 'mm' is the two-digit minute at the beginning of the file; 'X' indicates an X-Band uplink ('N' denotes no uplink); 'uu' indicates the uplink station (set to 'NN' for no uplink or 'MM' for two or more uplinking stations during the time interval covered), 'w' indicates the downlink mode ('1', '2', '3', or 'M' for 1-way, 2-way, 3-way, or 'multiple', respectively), and 'Vn' indicates the version number of the file. Dates and times in the file name are UTC. The ODF label has file name dawncegryyyy_ddd_hhmmXuuwVn.lbl. The typical ODF contains about 100 Kbytes. A sample ASCII dump of an ODF file is available in the DOCUMENTS directory. Secondary Data : An extensive set of ancillary files is needed for proper analysis and interpretation of the data. In the paragraphs below 'yyyy_ddd_yyyy_ddd' gives the start and end dates of the data in the file. All dates in the file names unless otherwise specified are UTC dates. All ASCII files have records delimited by an ASCII carriage-return (ASCII 13) line-feed (ASCII 10) pair. In some cases (especially for NAIF files) the  may need to be converted to either  or  before the file is used on the local machine. Antenna Phase Center File (APC Directory) --------------------------------------------------- Antenna Phase Center files were produced by the JPL Dawn Gravity Science team for release. The Dawn spacecraft utilizes four antennas during operations (1 high gain antenna and 3 low gain antennas). The Antenna Phase Center files contain the start times and stop times when any of the low gain antennas were being used. During times not specified in these files, the high gain antenna is being used. These are ASCII format with a detached PDS label describing the format of the data. File names have the form dawncegr_yyyy_ddd_yyyy_ddd.apc. The accompanying PDS label describes the content and structure of the file. Ionosphere Calibration Files (ION Directory) --------------------------------------------------- Ionosphere Calibration files are ASCII files produced by the Tracking System Analytic Calibration (TSAC) Group at JPL. They provide historical and predicted Earth ionospheric conditions. File names have the form dawncegr_yyyy_ddd_yyyy_ddd.ION. Each ION file is accompanied by a PDS minimal label with file name dawncegr_yyyy_ddd_yyyy_ddd.lbl. Typical file size is 24 KB. Spacecraft Mass History Files (SCM Directory) --------------------------------------------------- Spacecraft Mass History files were produced by the Dawn Spacecraft Team. They contain the estimates of the spacecraft mass, center of mass, and propellant usage. These are ASCII files of variable length records. File names have the form dawncegr_yyyy_ddd.scm, where yyyy_ddd is the applicable start date of the file. Files are accompanied by a PDS label describing the format of the data. Typical file size is 8 KB. The accompanying PDS label describes the content and structure of the file. Small Forces File (SFF Directory) --------------------------------------------------- Small Forces Files were created from the Dawn spacecraft engineering telemetry stream. These are ASCII files of variable length records. File names have the form dawncegr_yyyy_ddd_yyyy_ddd.sff. Each SFF file is accompanied by a PDS minimal label with file name dawncegr_yyyy_ddd_yyyy_ddd.lbl. Typical file sizes are 2.5 MB. File content and structure is defined by DAWN_SFF_SIS in the DOCUMENT directory. Troposphere Calibration Files (TRO Directory) --------------------------------------------------- Troposphere Calibration files are ASCII files produced by the Tracking System Analytic Calibration (TSAC) Group at JPL. They provide historical and predicted Earth tropospheric conditions. File names have the form dawncegr_yyyy_ddd_yyyy_ddd.TRO. Each TRO file is accompanied by a PDS minimal label with file name dawncegr_yyyy_ddd_yyyy_ddd.lbl. Typical file size is 150 KB. DSN Weather Files (WEA Directory) --------------------------------------------------- DSN Weather files were produced by the Tracking System Analytic Calibration (TSAC) Group at JPL. Files give weather calibration information for DSN complexes. These are ASCII files of variable length records. File names have the form dawncegr_yyyy_ddd_yyyy_ddd_ss.WEA, where 'ss' is the DSN complex where weather data were acquired. WEA files are typically released weekly and contain all weather data for the complex since 1 January. The files retained in the archive cover 365 days in 2011 and 366 days in 2012. Each WEA file is accompanied by a PDS minimal label with file name dawncegr_yyyy_ddd_yyyy_ddd_ss.lbl. The files grow at the rate of approximately 90 KB per month. Relevant Data Archived At Other Sites : 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 * EK: Spacecraft events kernel * 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/ Coordinate System : For the APC and SCM files, unless otherwise specified, the coordinate system is the spacecraft-fixed coordinate frame as described in the Dawn instrument host catalog file. Other data types are not dependent on definition of a coordinate system. Software : Software for parsing, reducing, and analyzing data such as these has been developed at several institutions. Because such software must usually operate at the bit-level and is written for a narrow range of platforms, it is not suitable for general distribution. No software is included with this archival data set. Media/Format : These data have been delivered to the PDS Small Bodies Node electronically.

Overview : Data in this archival data set have been collected to support radio science investigations, including derivation of the gravity field of Vesta. These are similar to data collected using other spacecraft at different targets and are believed to be generally of good quality. Data Coverage and Quality : The ODFs in this archive contain data from all nominal Dawn passes suitable for gravity science. They are primarily for the gravity investigation of Vesta. Limitations : The limitations in this data set follow from the quality of the execution, which is described above under Data Coverage and Quality.