Data Set Information
DATA_SET_NAME DAWN SPICE KERNELS V1.0
DATA_SET_ID DAWN-M/A-SPICE-6-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview ================= This data set includes the complete set of DAWN SPICE data files (``kernel files''), which can be accessed using SPICE software. The SPICE data contain geometric and other ancillary information needed to recover the full value of science instrument data. In particular SPICE kernels provide spacecraft and planetary ephemerides, instrument mounting alignments, spacecraft orientation, and data needed for relevant time conversions. This data set is contained on a single virtual volume, DAWNSP_1000, including data from all mission phases and covering from launch, 2007-09-27T12:40:49.832, through the end time of the latest spacecraft trajectory file supplied in the data set. Until the end of the spacecraft lifespan this data set is accumulating with new data added approximately every three to six months. Data Types (SPICE kernel types) =============================== SPK kernels contain ephemerides for spacecraft, planets, satellites, comets and asteroids as well as for moving or fixed spacecraft and instrument structures. They provide position and velocity, given in a Cartesian reference frame. SPK files are located under the ``data/spk'' directory of this data set. PCK kernels contain certain physical, dynamical and cartographic constants for target bodies, such as size and shape specifications, and orientation of the spin axis and prime meridian. PCK files are located under the ``data/pck'' directory of this data set. IK kernels (Instrument description kernels) give descriptive and operational data peculiar to a particular scientific instrument, such as internal timing relative to the spacecraft clock and field-of-view model parameters. IK files are located under the ``data/ik'' directory of this data set. CK kernels describe pointing, containing a transformation traditionally called the C-matrix which is used to determine time-tagged pointing (orientation) angles for a spacecraft structure upon which science instruments are mounted. CK files are located under the ``data/ck'' directory of this data set. EK (Events) kernels are derived from the integrated sequence of events used to produce actual spacecraft commands. EK files are located under the ``data/ek'' directory of this data set. LSK (Leapseconds) kernels contain the leapseconds and the values of other constants required to perform a transformation between Universal Time Coordinated (UTC) and Ephemeris time (ET). LSK files are located under the ``data/lsk'' directory of this data set. SCLK (Spacecraft Clock) kernels contain on-board clock calibration data required to perform a mapping between Ephemeris time (ET) and spacecraft on-board time (SCLK). SCLK files are located under the ``data/sclk'' directory of this data set. FK (Frame Definitions) kernels contain information required to define reference frames, sources of frame orientation data and connections between these frames and other frames supported within the SPICE system. This includes mounting alignment information for each instrument. FK files are located under the ``data/fk'' directory of this data set. DSK (Digital Shape) kernels contain information about the shape of the Dawn mission targets. DSK files are located under the ``data/dsk'' directory of this data set. Kernel File Details =================== A brief overview of the different types of DAWN kernels included in this data set is provided in the CONFIDENCE_LEVEL_NOTE section of this file while details specific to individual files are found in the ``*info.txt'' files in the corresponding data directory. The most detailed description of the data in each file is provided in metadata included inside the file -- in the description area of text kernels or in the comment area of binary kernels. Software ======== The SPICE Toolkit contains software modules needed to read SPICE kernel files. SPICE software is highly documented via internal headers. Additional documentation is available in separate ASCII text files called Required Reading files. For example, the S- and P- Kernel (SPK) Required Reading File, named SPK.REQ, describes use of the SPK kernel file readers and contains sample programs. The latest SPICE Toolkit for a variety of computer platforms such as PC, Mac, SUN, etc. is available at the NAIF Node of PDS electronically (via anonymous FTP and WWW servers). Refer to information in ``software/softinfo.txt'' for details regarding obtaining this software. Each version of the Toolkit is also archived at the NASA National Space Science Data Center. Loading Kernel Files into a SPICE-based Application =================================================== The easiest way to make data from a collection of SPICE kernels available to a SPICE-based application is to list these kernels in a meta-kernel and load it into the program using the high level SPICE data loader routine FURNSH. This data set provides such meta-kernel(s) under the ``extras/mk'' directory. For more information about the DAWN meta-kernel(s), see the file ``extras/mk/mkinfo.txt''.
DATA_SET_RELEASE_DATE 2012-09-06T00:00:00.000Z
START_TIME 2007-09-27T12:40:49.832Z
STOP_TIME 2018-10-31T05:39:29.716Z
MISSION_NAME DAWN MISSION TO VESTA AND CERES
MISSION_START_DATE 2007-09-27T12:00:00.000Z
MISSION_STOP_DATE 2018-10-31T12:00:00.000Z
TARGET_NAME 1 CERES
MARS
4 VESTA
TARGET_TYPE ASTEROID
PLANET
INSTRUMENT_HOST_ID DAWN
INSTRUMENT_NAME SPICE KERNELS
INSTRUMENT_ID SPICE
INSTRUMENT_TYPE N/A
NODE_NAME navigation and ancillary information facility
ARCHIVE_STATUS
CONFIDENCE_LEVEL_NOTE This data set contains SPICE kernel files created during mission operations and after mission data reconstruction and analysis. Some general information about this collection follows here, but the prospective user is also referred to extensive descriptions about each file that are stored inside each kernel file. These metadata provide detailed information regarding the information source from which the data were derived, the type of processing applied to the source data, applicability of the data, etc. Metadata are located in the ``comment area'' for binary kernel types (SPK, CK, ESQ), accessible using either the COMMNT or SPACIT utility program found in the NAIF Toolkit. Metadata are located after ``\begintext'' markers within the text kernel types (PCK, IK, FK, LSK, SCLK, MK), accessible by using any available text file display tool such as a word processor, text editor, or the unix ``more'' or ``cat'' commands. Where there are questions about data accuracy or ``confidence'' not addressed herein the reader is invited to contact the NAIF node of the Planetary Data System for possible further information. SPK Files ========= Three kinds of SPK files are provided in this archive: SPK files for the spacecraft orbit, SPK files for the Solar System planets and asteroids, and SPK files for the relative locations of selected spacecraft structures. Each kind of file is briefly described below; more information is available in the file ``data/spk/spkinfo.txt''. The majority of spacecraft orbit SPK files contain the reconstructed spacecraft trajectory determined by the DAWN Navigation (NAV) Team, JPL. The informal 1-sigma uncertainty for the DAWN spacecraft reconstruction during the Vesta Survey from 2011-08-02 to 2011-08-31 was 700 m along track, 40 m radial, and 70 m crosstrack. During Vesta HAMO from 2011-09-28 to 2011-11-02, the informal 1-sigma estimate was 70 m along track, 7 m radial, and 8 m crosstrack. During Vesta LAMO from 2011-12-10 to 2012-05-01, the informal 1-sigma uncertainty was 3 m in the along track, radial, and crosstrack directions. No formal or informal uncertainty estimates were provided by the NAV team for the Ceres orbital phase. Additional spacecraft orbit SPK files for selected periods of the Vesta and Ceres orbital phases contain the reconstructed spacecraft trajectory determined by the Solar System Dynamics (SSD) group, JPL and DAWN Gravity Team, JPL. The uncertainty information for these SPKs is provided in the articles referenced in the internal SPK comments. This data set also includes the orbit number files generated during the mission using the NAIF's ORBNUM utility program. These files are not SPICE kernels; for this reason they are provided in the ``extras/orbnum'' directory. For more information about the DAWN orbit number files, see the file ``extras/orbnum/orbinfo.txt''. The DE421 and DE432 planetary ephemeris SPK files included in this data set contains ephemeris data for the Solar System planet barycenters, Sun, Mercury, Venus, Earth, Moon, and Mars. These versions of ephemerides were officially used by the project during mission operations and post mission data processing. The internal comments included these SPK files provide detailed accuracy information. The asteroid SPK files included in this data set contain ephemeris data for Vesta and Ceres produced by the NAV team, SSD, and the Gravity team. The informal 1-sigma uncertainty of the NAV Vesta reconstruction from 2011-08-01 to 2012-06-28 was 1.5 km in the along track and radial directions and 5.0 km in the crosstrack direction. The uncertainty for other target SPKs is provided in their comment areas. The DAWN structures SPK file included in this archive provides relative locations of the High Gain Antenna (HGA) and Solar Array (SA) components. The data included in the file are based of the dimensions from the spacecraft engineering drawings. CK Files ======== Five kinds of C-kernel files are provided in this archive: the spacecraft bus (SC) orientation CKs (reconstructed from TLM, reconstructed from image processing, and predicted), the solar array (SA) orientation CKs (reconstructed from TLM), the VIR Spectrometer (VIR) orientation CKs (reconstructed from VIR housekeeping TLM), the FC alignment CK files (reconstructed from OPNAV calibrations), and the FC2 updated pointing CKs based on gravity and shape determination. The s/c and SA reconstructed CK files were produced from engineering telemetry downlinked from the spacecraft. The predicted CKs included in this data set are intended to be used to fill gaps with nominal orientation by loading these predicted files simultaneously with (but with lower priority than) the reconstructed files. The reconstructed spacecraft bus (SC) CK files based on telemetry (TLM) were created by NAIF at JPL; the reconstructed SC CK files based on FC images were created by the FC Team at DLR; and the predicted spacecraft bus CK files were produced by the DAWN Spacecraft Team (SCT). The image-based and predicted SC CKs are included in the archive only for the periods when TLM-based SC CKs have gaps. The system pointing budget summary, in milliradians, from Orbital Sciences' pre-launch analysis, provided by the DAWN ACS team as an indicator of the reconstructed TLM-based CK accuracy, is: ----------------- ---- ---- ---- X Y Z ----------------- ---- ---- ---- FC Estimate 0.20 0.13 0.07 FC Requirement 0.25 0.25 0.25 VIR Estimate 0.21 0.14 0.08 VIR Requirement 0.25 0.25 0.25 ----------------- ---- ---- ---- An informal, one-sigma accuracy estimate for the spacecraft bus attitude provided in the reconstructed CK files, reported by the DAWN OPNAV team based on the star field calibration data taken during approach to Vesta, is approximately 85 microradians. The reconstructed solar array (SA) CK files were created by NAIF at JPL. The reconstructed VIR Spectrometer CK files were created by the VIR Team at INAF. The FC alignment CK files were created by NAIF at JPL using input from the DAWN OPNAV team. The FC2 updated pointing CKs based on gravity and shape derivation done by the DAWN Gravity Team, JPL. They provided FC2 orientation relative to inertial space only at the time of Ceres images used in the analysis. More information about DAWN CK files is available in the file ``data/ck/ckinfo.txt''. PCK Files ========= PCK files provide size, shape and orientation data for ``target'' bodies such as Vesta, Ceres, Mars, and Earth. A description of these data items and reference to their source is provided inside the PCK file, which is a simple text file that can be viewed using any word processor, text editor or text display utility. The set of Vesta PCK files provided in this data set includes the current PCK containing Vesta rotation constants for the ``Claudia Double-Prime'' coordinate system, which was used in products archived in the DAWN Vesta mission science data sets, and two obsolete PCKs containing Vesta rotation constants for the ``DAWN-Claudia'' and ``Claudia Prime'' coordinate systems used during project operations and for pre-peer-review archive deliveries. The two obsolete PCKs are superseded by the current PCK and are included in the data set only for the record. The generic PCK file included in this data set is based on the IAU/IAG/COSPAR values accepted in 2000. This PCK also provides Vesta rotation constants for the ``IAU-2000'' Vesta coordinate system, that are obsolete and superseded by the ``Claudia Double-Prime'' constants from the current Vesta PCK. The Ceres PCK files provided in this data set contain the constants used during operations at Ceres, the final official constants produced by the project at the end of the mission, and specific sets of constants provided by the Gravity Team, JPL and FC Team, DLR consistent with their corresponding shape models stored in the DSK files. More information about the PCK files included in this data set is available in the file ``data/pck/pckinfo.txt''. FK Files ======== Frames kernel files provide specifications for how one reference frame is defined relative to another frame. The DAWN FK provided in this data set contains the complete set of frame definitions for the spacecraft, its structures such as solar array and antennas, and all of its science instruments. Meta information provided in the comments included in this file consists of the frame definitions, description of the frame relationships, source of and accuracy of the mounting alignment information, etc. This data set also includes Vesta- and Ceres-specific frames kernels. Each kernel contains the definition of the body-fixed frame for the respective asteroid. More information about the DAWN FK files is available in the file ``data/fk/fkinfo.txt''. IK Files ======== Instrument kernel files provide specifications for geometric parameters and--where applicable--field-of-view size, shape and orientation for the named instruments. Metadata describing these estimates are provided in each IK file included in this archive. Parameter values were determined from pre-launch measurements, instrument parameters specification documents, and in some cases from analysis of in-flight calibration data. The accuracy estimates for these data vary from instrument to instrument and, where available, are included in the IK internal comments. This data set includes IK files for instruments on the DAWN spacecraft, including the Framing Camera, the Gamma Ray and Neutron Detector (GRaND), the Visible and Infrared Mapping Spectrometer (VIR), antennas, star trackers, and other structures. Because the sets of geometric parameters included in the IKs vary from instrument to instrument users are encouraged to carefully examine the IKs before using them. More information about DAWN IK files is available in the file ``data/ik/ikinfo.txt''. SCLK Files ========== Spacecraft Clock kernel files provide a tabulation of data needed for converting time measurements between ephemeris time (ET) and spacecraft clock time (SCLK). The DAWN SPICE SCLK files were made from similar files--SCLK/SCET files, or SCLKvSCET files--produced by another mission entity. Each newly made SCLK file fully replaces the previous SCLK file. For DAWN, the time correlation accuracy provided in the SCLK kernel files for the Vesta orbital operations time period is informally reported to be better than 20 milliseconds, while the accuracy for the cruise to Vesta time period is significantly worse, with errors occasionally growing to 200-300 milliseconds. SPICE software does not prohibit an SCLK file from being used for time conversions occurring for ``future times'' (or more accurately, for epochs that occur later than the epoch of the last telemetry data used in producing the last correlation coefficients found in the SCLK file). Such ``predict'' time conversions are likely to be inaccurate (changed somewhat) once the epoch of interest has been passed. More information about the DAWN SCLK files is available in the file ``data/sclk/sclkinfo.txt''. LSK Files ========= Leapseconds kernel files provide a tabulation of ``leapseconds'' and some other terms used in converting time measurements between ephemeris time (ET) and Universal Time (UTC). ``Spacecraft Event Time'' (SCET) is the commonly used name for UTC events measured at the spacecraft. Metadata describing how the LSK data are obtained or computed is contained inside the LSK text file. The time conversion provided by SPICE LSK files is accurate to approximately 0.000030 seconds. More information about the LSK files is available in the file ``data/lsk/lskinfo.txt''. DSK Files ========= Digital Shape kernel (DSK) files provide target object shape data in a variety of digital shape representations, such as triangular plate models or digital elevation models. The DSK files included in this data set provide triangular plate shape models for Ceres and Vesta produced by the Gravity Team, JPL and FC Team, DLR. More information about the DSK files is available in the file ``data/dsk/dskinfo.txt''. EK Files ======== The DAWN project did not produce any EK files; therefore, no EKs are included in this data set.
CITATION_DESCRIPTION Krening, S.C., B.V. Semenov, C.H. Acton, and A.M. Bailey, DAWN SPICE KERNELS V1.0, DAWN-M/A-SPICE-6-V1.0, NASA Planetary Data System, 2012. https://doi.org/10.17189/1520119
ABSTRACT_TEXT This data set includes the complete set of DAWN SPICE data files (``kernel files''), which can be accessed using SPICE software. The SPICE data contain geometric and other ancillary information needed to recover the full value of science instrument data. In particular SPICE kernels provide spacecraft and planetary ephemerides, instrument mounting alignments, spacecraft orientation, and data needed for relevant time conversions.
PRODUCER_FULL_NAME ALYSSA M. BAILEY
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