MESSENGER Software Interface Specification for the Gamma Ray Spectrometer Experiment Data Record Version 4.8 Prepared by Raymond Espiritu Erick Malaret Pierluigi Guasqui Applied Coherent Technology Corporation 112 Elden St, Suite K Herndon, VA 22304 http://www.actgate.com Patrick Peplowski Johns Hopkins University Applied Physics Laboratory 11100 Johns Hopkins Road Laurel, MD 20723 Document Review This document and the archive it describes have been through PDS Peer Review and have been accepted into the PDS archive. Patrick Peplowski, MESSENGER GRNS Scientist, has reviewed and approved this document. Susan Slavney, PDS Geosciences Node Representative, has reviewed and approved this document. Susan Ensor, MESSENGER Science Operations Center Lead, has reviewed and approved this document. Change Log DATE SECTIONS CHANGED REASON FOR CHANGE REVISION 6/2/11 N/A Add change log. 4.2 6/2/11 1.4, 1.5.4.3 Describe 9/2/10 GRS FSW update for fast neutron detection, updated GRS shield sensor product, and associated label change. 4.2 6/2/11 1.17, 1.18, 1.19 Add note that original GRS_SHIELD format applies to products before 9/17/10. Add format information for GRS_SHIELD_2 products starting 9/17/10. 4.2 6/2/11 Appendix/format descriptions Change "periherm" to "apoherm" in orbit start time descriptions 4.2 6/10/11 Document Review Replaced signature page with document review information per agreement with PDS 4.3 5/25/12 Applicable Documents, Archive release schedule Change "Data Management and Science Analysis Plan" to "Data Management and Archiving Plan" and update references. Replace archive release schedule table with reference to Data Management and Archiving Plan. 4.4 9/26/13 1.3, 1.4, 1.5.4.4, 1.20 Describe 25/2/13 GRS FSW update to optimize neutron detection, updated GRS shield sensor products, and associated label changes. 4.5 11/14/13 1.4, 1.5.4.4, 1.20 Edits resulting from review of new shield sensor products. 4.6 7/7/15 5.4.3,6.4, 6.5 Note use of clock partitions in time tags in product labels following January 8, 2013 S/C clock reset. Update reference to PDS file naming standard (was 27.3 now 36.3). Update GRS EDR data archive volume estimate for mission. Make correction to document style heading 1 so that all 8 document sections are present (not just one section). 4.7 7/13/15 Table of Contents, 5.1, 5.4.1, 6.5 Updated with minor formatting corrections 4.8 Table of Contents 1 PURPOSE AND SCOPE OF DOCUMENT 6 1.1 Purpose 6 1.2 Scope 6 2 APPLICABLE DOCUMENTS 6 3 RELATIONSHIPS WITH OTHER INTERFACES 6 4 ROLES AND RESPONSIBILITIES 7 5 DATA PRODUCT CHARACTERISTICS AND ENVIRONMENT 7 5.1 Instrument Overview 7 5.2 Data Product Overview 8 5.3 Data Processing 10 5.3.1 Data Processing Level 10 5.3.2 Data Product Generation 11 5.3.3 Data Flow 11 5.3.4 Labeling and Identification 14 5.3.4.1 HPGe Raw Spectra PDS Label 14 5.3.4.2 HPGe AC Spectra PDS Label 15 5.3.4.3 Shield Spectra PDS Label 15 5.3.4.4 Shield Count Rate PDS Label 16 5.3.4.5 Microphonics Time Series PDS Label 17 5.3.4.6 Software Counter PDS Label 18 5.3.4.7 Status PDS Label 18 5.3.4.8 FPGA ADC PDS Label 19 5.3.4.9 Command Echo PDS Label 20 5.4 Standards used in Generating Data Products 20 5.4.1 PDS Standards 20 5.4.2 Coordinate Systems 21 5.4.3 Time Standards 21 5.4.4 Data Storage Conventions 21 5.5 Data Validation 21 6 DETAILED DATA PRODUCT SPECIFICATION 22 6.1 Data Product Structure and Organization 22 6.2 Data Format Description 22 6.3 Label and Header Descriptions 22 6.3.1 Table Object Keyword Definitions 24 6.4 File Naming Conventions 24 6.5 Archive Volume and File Size 25 6.6 Directory Structure and Contents 25 6.7 Directory Contents 25 7 ARCHIVE RELEASE SCHEDULE TO PDS 26 8 APPENDICES 27 8.1 GRS_HPGE_RAW.FMT 27 8.2 GRS_HPGE_AC.FMT 29 8.3 GRS_SHIELD.FMT 31 8.4 GRS_SHIELD_2.FMT 32 8.5 SHIELD_2 Content Description 34 8.6 GRS_SCR.FMT 36 8.7 GRS_MICRO.FMT 39 8.8 GRS_SWC.FMT 41 8.9 GRS_STATUS.FMT 45 8.10 GRS_FPGA.FMT 68 8.11 GRS_CMDECHO.FMT 77 8.12 SPICE Kernel Files used in MESSENGER Data Products 78 8.13 CODMAC/NASA Definition of Processing Levels 79 8.14 MESSENGER Acronym List 79 1 Purpose and Scope of Document 1.1 Purpose This Software Interface Specification (SIS) document provides users of the Mercury: Surface, Space Environment, Geochemistry and Ranging (MESSENGER) Gamma Ray Spectrometer (GRS) data products with a basic description of the GRS instrument and Experiment Data Records (EDRs). The GRS EDR data products are deliverables to the Planetary Data System (PDS) and the scientific community that it supports. This document is both an EDR data product SIS and an EDR archive volume SIS. Note that the Gamma Ray and Neutron Spectrometer (NS) instruments are generally referred to together as the Gamma Ray and Neutron Spectrometer (GRNS) instrument. However they are two separate sensors, each with its own Event Processing Unit (EPU), and the data products are described within the specific Software Interface Specification (SIS) of each sensor. 1.2 Scope This SIS document is of a limited scope due to the EDRs being of a very low processing level. It does not provide a description or understanding of the GRS instrument or its EDRs at a detailed level. It is not intended for general use by data analysts outside of the MESSENGER project and it is not intended for the typical science user to access the EDRs routinely. Rather, it is mainly useful as an input to producing the Calibrated Data Record (CDR) and Reduced Data Record (RDR) products. There is a separate PDS data archive for the CDR and RDR products, and these products are described by a separate SIS document. 2 Applicable Documents The Messenger GRS EDR SIS is responsive to the following Documents: * Planetary Data System (PDS) Standards Reference, February 27, 2009, Version 3.8. JPL D-7669, Part-2. * Planetary Data System Archive Preparation Guide, April 1, 2010, Version 1.4, JPL D-31224. * GRS Flight Software Specification, Draft Dec. 15, 2003. * MESSENGER Data Management and Archiving Plan. The Johns Hopkins University, APL. Document ID number 7384-9019. * MESSENGER Mercury: Surface, Space Environment, Geochemistry, Ranging; A mission to Orbit and Explore the Planet Mercury, Concept Study, March 1999. Document ID number FG632/99-0479. * Appendix 7 to the discovery program Plan; Program Level Requirement for the MESSENGER Discovery project; June 20, 2001. * The MESSENGER Gamma-Ray and Neutron Spectrometer, Space Science Reviews 131, 339-391, 2007. 3 Relationships with Other Interfaces The GRS EDR data products are stored on Hard Disk and in a SQL (Structured Query Language) relational database for rapid mission access during mission operations. The data products are electronically transferred to the PDS Geosciences Node according to the delivery schedule in the MESSENGER Data Management and Archiving Plan. The data in the EDR files themselves are stored in PDS binary table objects with the exception of the GRS Status, Software Counter, and Command Echo EDRs. These three EDRs consist of data stored in PDS ASCII table objects. 4 Roles and Responsibilities The roles and responsibilities of the instrument teams, Applied Physics Lab (APL), Applied Coherent Technology (ACT), and the Planetary Data System (PDS) are defined in the MESSENGER Data Management and Archiving Plan. 5 Data Product Characteristics and Environment 5.1 Instrument Overview The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission is designed to orbit Mercury following one Earth flyby, two of Venus, and three of Mercury. It launched in August 2004 and achieved orbit insertion around Mercury on 18 March 2011. Initial data collection began during the three flybys of Mercury and consists primarily of global mapping and measurements of the surface, atmosphere, and magnetosphere composition. The nominal one-Earth-year long mission ended on 17 March 2012. This was immediately followed by the start of a one-year-long extended mission. MESSENGER is currently in a two-year-long second and final extended mission. MESSENGER orbital observations provide data to answer questions about the nature and composition of Mercury's crust, tectonic history, structure of the atmosphere/magnetosphere, and the nature of the polar caps. The Gamma Ray Spectrometer (GRS) instrument onboard the MESSENGER spacecraft is designed to observe the spectrum of gamma rays emitted from Mercury's surface in the energy range from 0.1 MeV to 10 MeV. Gamma rays are produced either directly from radioactive decay (of K, Th, U) or indirectly when activated by the cosmic ray background. The relatively low absorption rate of these gamma rays allows the estimation of the surface composition to depths of ~10's of cm, depending on the energy of the gamma ray. The GRS primarily consists of a high-purity Germanium (HPGe) cylinder surrounded by a shield of borated plastic scintillator, BC-454. The HPGe cylinder is suspended within the shield by Kevlar strings inside three nested gold-coated cans. This is done to provide thermal isolation for operation at cryogenic temperature. When a gamma ray interacts with the bulk HPGe, a charge is generated. The electric charge is amplified, measured, and then digitally converted into one of 16,384 (214) channels, or bins. After a specified amount of time, a histogram is produced, which shows the distribution of events (number of strikes) as a function of energy (channel number). Because of the low count rates usually encountered, accumulation times of minutes to hours are normal. The raw science data product (HPGe Raw EDR, section 5.2) is the counts in each of the 16384 bins after this accumulation period. This histogram is counted as one gamma ray spectrum. The HPGe required a mechanical cryocooler to maintain the required ~90K temperatures in order to detect gamma rays. The cryocooler failed on 15 June, 2012 after approximately 9,000 hours of operation. This exceeded the expected 8,000 hour lifetime of the cooler. Following the cooler failure, new flight software was uploaded to the GRS on 25 February 2013 for the purpose of optimizing the instrument for neutron and charged particle measurements with the BC-454 shield. These changes included the addition of a high time cadence measure of the local particle flux, which is useful for characterizing the charged particle environment near Mercury. The GRS uses the plastic scintillator as a shield against detection of cosmic rays. In a scintillator, the interaction of the gamma ray results in a brief fluorescence, with an intensity proportional to the energy. The light pulse is amplified by a photo-multiplier tube and then buffered, shaped and digitized from the HPGe. The shield scintillator has a much lower energy resolution than the HPGe, so detected events in the shield (SHIELD EDR, section 5.2) are binned to only 1024 channels by the EPU. If events are found to occur in both detectors within some short time interval (of order microseconds), a coincidence condition is flagged. This may have been caused by a single high-energy particle (cosmic ray) depositing energy in both detectors as it passed through, or by secondary photons created after an initial gamma ray or neutron interaction, or by two independent events occurring simultaneously (false coincidence or "accidental"). In any case, the energies measured cannot be related to the initial event without additional interpretation. A separate spectrum (HPGe AC EDR, section 5.2) is maintained to accumulate the anti-coincidence HPGe events (eliminating those background events likely due to cosmic rays). The 25 February 2013 flight software upload included the addition of a new data product, called "shield count rate". This product measures the total count rate at high time cadence (10 ms) in order to provide new insights into the charged particle environment around Mercury, particularly the energetic electron events. The total count rate on the detector is measured every 10 ms and stored in a 16,384 channel long array. For short integration periods, this array is too large and the remaining values are set to zero. When a data integration period would require more than 16,384 channels, the values past this length aren't stored. The GRS data rate is driven by the integration time for the HPGe raw and anticoincidence spectra, since these EDRs constitute by far the largest amount of data. Since the orbital gamma-ray flux is low, the smallest integration times are determined by surface mapping spatial resolution and thermal electronics energy smearing at the lowest altitudes. Assumption of a reasonable 60-second integration time at low altitudes and correspondingly larger integration times at higher altitudes yields an estimated data rate of 13 Mbits per earth day. Further information on the GRS instrument can be found in the MESSENGER instrument paper. 5.2 Data Product Overview There are ten EDR data products produced by the GRS instrument. A single EDR data file contains the observations with a time tag corresponding to a given Earth day. They are as follows: Data Product Product Description HPGE RAW * Detached PDS label file * Spectra data file - HPGe raw data in binary table. HPGE AC * Detached PDS label file * Spectra data file - HPGe anti-coincident data in binary table. SHIELD * Detached PDS label file * Spectra data file - SHIELD data in binary table. SHIELD (SH2) * Detached PDS label file * Spectra data file - SH2 data in binary table. SHIELD COUNT RATE (SCR) * Detached PDS label file * Count rate data file - SCR data in binary table. MICROPHONICS * Detached PDS label file * Time series data file - Microphonics data in binary table. SW COUNTER * Detached PDS label file * ASCII table file - software rate counter data. STATUS * Detached PDS label file * ASCII table file - critical state information provided by GRS status packet FPGA ADC * Detached PDS label file. * Diagnostic information stored in binary table. COMMAND ECHO * Detached PDS label file. * ASCII table file - Contains commands executed by GRS. The detached (separate) PDS label file describes the content of the data file. The label file defines the start time and end of the records in the data file (start time is the UTC time tag of the first record in the data file, and end time is the UTC time tag of the last record in the data file), product creation time, etc. The "science" data - HPGE_RAW, HPGE_AC, SHIELD, MICROPHONICS - are contained in data files where the data are arranged in binary tables. The first three are spectra described in Sec. 5.3.4. The Microphonics data are binned time series of fluctuations generated electronically that are associated with cryocooler vibrations. When fed through an acoustic speaker, they sound very much like cooler vibrations; hence the term "microphonics". The microphonics data are used to help determine if the cooler is developing vibration problems, such as bearing noise. The GRS flight software (FSW) was changed on September 17, 2010 to incorporate fast neutron detection in the GRS shield sensor. Measurement of the fast-neutron flux near the GRS is needed to reduce the uncertainty in the spacecraft contribution to important elemental lines in the GRS gamma-ray spectrum. The previous shield spectrum data product (Column 9 in the GRS_SHIELD.FMT file) was a full 1024 bins and extended well beyond the region of interest. This data product was subdivided into several new data products related to the measurement of thermal and fast neutrons. The first half (512 bins) is devoted to a buffer of raw events (up to 126 raw events plus an 8-word header), where each raw event contains full resolution information on each interaction that meets on-board requirements for candidate neutrons. The remaining available 512 bins contain five spectral data products that result from on-board binning of the raw events that meet selected criteria: Shield All Events Spectrum (128 bins) Shield Thermal Events Spectrum (128 bins) HPGe Thermal Events Spectrum (64 bins) Shield Fast Events Spectrum (128 bins) HPGe Fast Events Spectrum (64 bins) The GRS_SHIELD_2.FMT file describes the content of the GRS_SHIELD EDR for data taken after the September 17, 2010 FSW update (see Appendix 8.4 for more description on this format file). The GRS_SHIELD.FMT file describes the content of GRS_SHIELD EDRs before the FSW update (see Appendix 8.3 for more description on this format file). The four Thermal and Fast Events Spectra are all obtained using coincidence events with the HPGe detector in the 478-keV region of the HPGe spectrum. The 478-keV region contains the gamma-ray emitted in a thermal neutron capture reaction with 10B present in the borated-plastic shield. It was found that the spectra of these coincidence events best isolated the neutron signal, while minimizing the gamma-ray background, but it is not certain what fraction of these events are actually neutrons or gamma-rays. The buffer of unbinned raw events (up to 126 events per accumulation period) allows for enhanced analysis techniques, which if successfully developed may help to reduce these uncertainties. The two Thermal Events Spectra contain events within a narrow +/- 0.1 microsecond coincidence window and likely represent mostly thermal neutrons. The two Fast Events Spectra contain events with positive coincidence times > 0.1 microsecond and likely represent mostly fast neutrons. The two 64-bin Thermal and Fast Events HPGe Spectra provide the corresponding 478-keV HPGe peak along with sufficient background channels on either side of the peak to allow background subtraction, while the two 128-bin Thermal and Fast Events Spectra contain the corresponding shield spectrum. The GRS flight software (FSW) was changed on 25 February 2013 to improve neutron detection capability in the Shield data product as well as to add a new "shield count rate" EDR. This product measures the total count rate at high time cadence (10 ms) in order to provide new insights into the charged particle environment around Mercury, particularly the energetic electron events. The total count rate on the detector is measured every 10 ms and stored in a 16,384 channel long array. For short integration periods, this array is too large and the remaining values are set to zero. When a data integration period would require more than 16,384 channels, the values past this length are stored in the final channel. The first approximately 50 entries of the shield count rate product are always zero, and reflect the 0.5-second-long interval at the beginning of the accumulation period during which the GRS electronics busy performing other tasks and are unable to processes the total shield count rates. The SW_COUNTER EDR contains the data from the software event counters and associated data in an ASCII table, where event data are accumulated independent of energy. Similarly, the information for STATUS EDR is also contained in ASCII tables. Status data monitors many engineering parameters, such as voltages, currents, temperatures, and modes, in raw units. The data are contained in ASCII tables to allow the instrument engineer to immediately view the data in commercial-off-the-shelf spreadsheet or document viewing applications. This allows the instrument engineer to easily evaluate the instrument and generate simple trending plots. The FPGA_ADC EDR is stored in binary tables to facilitate extraction of bit counters which contain information about the state of the instrument. This data stores many parameters associated with the Analog-to-Digital converter ADC) event processing in the associated Field-Programmable Gate Array (FPGA). The Command Echo EDR contains the time-tagged list of commands executed by the GRS instrument. It also records the success level of each command. 5.3 Data Processing 5.3.1 Data Processing Level There is one EDR archive volume for the GRS instrument. The data volume contains level 2 CODMAC data products or EDRs. Each product has a unique file name and conforms to the file naming convention in section 6.4. All EDR products are stored at the Applied Physics Laboratory/Science Operations Center (APL/SOC) during mission operations. In addition to the sensor spectral data products, scientific and engineering-housekeeping data are sampled by the GRS at a rate independent of the spectra sampling rate. The data volume is electronically transferred to the PDS Geosciences Node following the procedure in section 5.3.3. 5.3.2 Data Product Generation The Gamma-Ray Spectrometer EDR files are produced by the MESSENGER Science Operations Center (SOC) operated jointly by APL and ACT. Data downlink is telemetered through NASA's Deep Space Network (DSN) managed by the Jet Propulsion Laboratory in Pasadena, CA, and then forwarded to APL. Inputs to the SOC consist of telemetry in the form of CCSDS packets. Level-1 GRS raw spectral and engineering data is then broken out of the data stream and stored online at the SOC. The 'PIPE-GRS2EDR' software packages the Level 1 CODMAC data to the PDS formats defined in this SIS (section 5.3.4 and Appendices). The resulting files are designated as Level 2 CODMAC data or EDRs. The EDR data products are made available to the MESSENGER Science Team for initial evaluation and validation. At the end of the evaluation and validation period, the data are organized and stored in the directory structure described in section 6.6 for transmittal to the Geosciences Node. The transmittal process is described in section 5.3.3. 5.3.3 Data Flow The MESSENGER SOC operates under the auspices of the MESSENGER Project Scientist to plan data acquisition, generate, and validate data archives. The SOC supports and works with the Mission Operations Center (MOC), the Science Team, instrument scientists, and the PDS. The SOC is located at John's Hopkins University/Applied Physics Lab (JHU/APL). The Data Flow diagram in figure 1 shows the general flow of data within the MESSENGER project and data flow to the PDS. The MOC handles raw data flow to and from the MESSENGER spacecraft and the SOC converts the raw telemetry into EDRs. The Science Team validates the EDRs and notifies the SOC if corrections are needed. Documentation and EDRs are delivered to the PDS Geosciences Node. SPICE kernels are delivered to the PDS Navigation and Ancillary Information (NAIF) node. The MESSENGER SOC delivers data for the GRS EDR data volume to the PDS Geosciences Node in standard product packages. Each package comprises data and files organized into directory structures consistent with the volume design described in section 6.6. The following describes the electronic transfer process of releasing data to PDS. In the weeks prior to the delivery date the directory structure is compressed into a single "zip archive" file for transmittal to the PDS node. The zip archive preserves the directory structure internally so that it can be recreated after electronic delivery to the PDS node. The zip archive file is transmitted to the PDS node via FTP to an account set up by the receiving node. Also transmitted is a checksum file created using the MD5 algorithm. This provides an independent method of verifying the integrity of the zip file after it has been sent. Within days of transmittal the PDS node acknowledges receipt of the archive and checksum file. If acknowledgement is not received, or if problems are reported, the MESSENGER SOC immediately takes corrective action to effect successful transmittal. After transmittal the PDS node uncompresses the zip archive file and checks for data integrity using the checksum file. The node performs any additional verification and validation of the data provided and reports any discrepancies or problems to the MESSENGER SOC. It is expected that the node performs these checks in about two weeks. After inspection has been completed to the satisfaction of the PDS node, the node issues to the MESSENGER SOC acknowledgement of successful receipt of the data. Following receipt of a data delivery the PDS node organizes the data into a PDS archive volume structure within its online data system. Newly delivered data are made available publicly from PDS once accompanying labels and other documentation have been validated. 5.3.4 Labeling and Identification For every EDR data file there exists a detached PDS label file. Detached means that the label file is separate from the data file, as opposed to being in the header portion of the data file. The following are examples of the detached PDS label file for each of the GRS EDRs. Details about the label format are specified later in section 6.3. Each PDS label file will contain a pointer to an external format file. This format file describes the table structure of the EDR data file. Details for each format file are found in the Appendices. 5.3.4.1 HPGe Raw Spectra PDS Label PDS_VERSION_ID = "PDS3" /*** FILE FORMAT ***/ FILE_RECORDS = 287 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 32792 /*** GENERAL DATA DESCRIPTION PARAMETERS ***/ PRODUCT_ID = "GRS_RAW2004316ZZZ_DAT" PRODUCT_VERSION_ID = "V1" PRODUCT_CREATION_TIME = 2006-03-13T22:03:3 PRODUCT_TYPE = "DATA" STANDARD_DATA_PRODUCT_ID = "GRS_HPGE_RAW_SPECTRA " SOFTWARE_NAME = "PIPE-GRS2EDR" SOFTWARE_VERSION_ID = "1.0" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = "GAMMA RAY SPECTROMETER" INSTRUMENT_ID = "GRS" DETECTOR_ID = "HPGE" DATA_SET_ID = "MESS-E/V/H-GRNS-2-GRS-RAWDATA-V1.0" MISSION_PHASE_NAME = "EARTH CRUISE" TARGET_NAME = "CALIBRATION" START_TIME = 2004-11-11 00:00:27.000 STOP_TIME = 2004-11-11 23:49:27.000 SPACECRAFT_CLOCK_START_COUNT = 8618421 SPACECRAFT_CLOCK_STOP_COUNT = 8704161 ^TABLE = "GRS_RAW2004316ZZZ.DAT" OBJECT = TABLE COLUMNS = 10 INTERCHANGE_FORMAT = BINARY ROWS = 287 ROW_BYTES = 32792 DESCRIPTION = " This table contains one set of raw spectra collected from the high purity Germanium (HPGe) detector, MESSENGER Gamma Ray Spectrometer (GRS). A set is defined as all data with MET timestamps corresponding to a given Earth day. The complete column definitions are contained in an external file found in the LABEL directory of the archive volume. Additional details are contained in the EDR SIS document. " ^STRUCTURE = "GRS_HPGE_RAW.FMT" END_OBJECT = TABLE END 5.3.4.2 HPGe AC Spectra PDS Label PDS_VERSION_ID = "PDS3" /*** FILE FORMAT ***/ FILE_RECORDS = 199 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 32792 /*** GENERAL DATA DESCRIPTION PARAMETERS ***/ PRODUCT_ID = "GRS_ANC2004316ZZZ_DAT" PRODUCT_VERSION_ID = "V1" PRODUCT_CREATION_TIME = 2006-03-13T21:05:5 PRODUCT_TYPE = "DATA" STANDARD_DATA_PRODUCT_ID = "GRS_HPGE_AC_SPECTRA " SOFTWARE_NAME = "PIPE-GRS2EDR" SOFTWARE_VERSION_ID = "1.0" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = "GAMMA RAY SPECTROMETER" INSTRUMENT_ID = "GRS" DETECTOR_ID = "HPGE" DATA_SET_ID = "MESS-E/V/H-GRNS-2-GRS-RAWDATA-V1.0" MISSION_PHASE_NAME = "EARTH CRUISE" TARGET_NAME = "CALIBRATION" START_TIME = 2004-11-11 01:28:27.000 STOP_TIME = 2004-11-11 23:49:27.000 SPACECRAFT_CLOCK_START_COUNT = 8623701 SPACECRAFT_CLOCK_STOP_COUNT = 8704161 ^TABLE = "GRS_ANC2004316ZZZ.DAT" OBJECT = TABLE COLUMNS = 10 INTERCHANGE_FORMAT = BINARY ROWS = 199 ROW_BYTES = 32792 DESCRIPTION = " This table contains one set of Anti-Coincident (AC) spectra collected from the high purity Germanium (HPGe) detector, MESSENGER Gamma Ray Spectrometer (GRS). A set is defined as all data with MET timestamps corresponding to a given Earth day. The complete column definitions are contained in an external file found in the LABEL directory of the archive volume. Additional details are contained in the EDR SIS document. " ^STRUCTURE = "GRS_HPGE_AC.FMT" END_OBJECT = TABLE END 5.3.4.3 Shield Spectra PDS Label The sample PDS label below has a STANDARD_DATA_PRODUCT_ID used for Shield EDRs created prior to the FSW update on September 17, 2010. EDRs created from data after the FSW update have a STANDARD_DATA_PRODUCT_ID = "GRS_SHIELD_SPECTRA_2" and refer to the table structure defined in "GRS_SHIELD_2.FMT". PDS_VERSION_ID = "PDS3" /*** FILE FORMAT ***/ FILE_RECORDS = 216 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 2070 /*** GENERAL DATA DESCRIPTION PARAMETERS ***/ PRODUCT_ID = "GRS_SHI2004314ZZZ_DAT" PRODUCT_VERSION_ID = "V1" PRODUCT_CREATION_TIME = 2006-03-13T22:16:57 PRODUCT_TYPE = "DATA" STANDARD_DATA_PRODUCT_ID = "GRS_SHIELD_SPECTRA" SOFTWARE_NAME = "PIPE-GRS2EDR" SOFTWARE_VERSION_ID = "1.0" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = "GAMMA RAY SPECTROMETER" INSTRUMENT_ID = "GRS" DETECTOR_ID = "SHIELD" DATA_SET_ID = "MESS-E/V/H-GRNS-2-GRS-RAWDATA-V1.0" MISSION_PHASE_NAME = "EARTH CRUISE" TARGET_NAME = "CALIBRATION" START_TIME = 2004-11-09 06:02:19.000 STOP_TIME = 2004-11-09 23:57:19.000 SPACECRAFT_CLOCK_START_COUNT = 8467334 SPACECRAFT_CLOCK_STOP_COUNT = 8531834 ^TABLE = "GRS_SHI2004314ZZZ.DAT" OBJECT = TABLE COLUMNS = 9 INTERCHANGE_FORMAT = BINARY ROWS = 216 ROW_BYTES = 2070 DESCRIPTION = " This table contains one set of raw spectra collected from the SHIELD detector, MESSENGER Gamma Ray Spectrometer (GRS). A set is defined as all data with MET timestamps corresponding to a given Earth day. The complete column definitions are contained in an external file found in the LABEL directory of the archive volume. Additional details are contained in the EDR SIS document. " ^STRUCTURE = "GRS_SHIELD.FMT" END_OBJECT = TABLE END 5.3.4.4 Shield Count Rate PDS Label PDS_VERSION_ID = "PDS3" /*** FILE FORMAT ***/ FILE_RECORDS = 990 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 32792 /*** GENERAL DATA DESCRIPTION PARAMETERS ***/ PRODUCT_ID = "GRS_SCR2013244ZZZ_DAT" PRODUCT_VERSION_ID = "V1" PRODUCT_CREATION_TIME = 2013-11-13T20:22:34 PRODUCT_TYPE = "DATA" STANDARD_DATA_PRODUCT_ID = "GRS_SHIELD_COUNTER" SOFTWARE_NAME = "PIPE-GRS2EDR" SOFTWARE_VERSION_ID = "1.1" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = "GAMMA RAY SPECTROMETER" INSTRUMENT_ID = "GRS" DETECTOR_ID = "ACS" DATA_SET_ID = "MESS-E/V/H-GRNS-2-GRS-RAWDATA-V1.0" MISSION_PHASE_NAME = "MERCURY ORBIT YEAR 3" TARGET_NAME = "MERCURY" START_TIME = 2013-09-01T00:00:01.000 STOP_TIME = 2013-09-01T23:30:21.000 SPACECRAFT_CLOCK_START_COUNT = "2/20317601" SPACECRAFT_CLOCK_STOP_COUNT = "2/20402221" ^TABLE = "GRS_SCR2013244ZZZ.DAT" OBJECT = TABLE COLUMNS = 10 INTERCHANGE_FORMAT = BINARY ROWS = 990 ROW_BYTES = 32792 DESCRIPTION = " This table contains one set of high-time-resolution count rate measurements in the GRS anti-coincidence shield. Each entry contains a 16384-channel-long array that is populated with values corresponding to the total number of events registered by the GRS Anti-Coincidence Shield (ACS) in 10-ms-long increments. When the accumulation period is insufficient to populate all 16384 channels, the remaining entries are assigned values of zero. When the number of measurements exceeds 16384, the last channel records the sum of all subsequent events. A set is defined as all data with MET timestamps corresponding to a given day." ^STRUCTURE = "GRS_SCR.FMT" END_OBJECT = TABLE END 5.3.4.5 Microphonics Time Series PDS Label PDS_VERSION_ID = "PDS3" /*** FILE FORMAT ***/ RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 65548 FILE_RECORDS = 7 /*** GENERAL DATA DESCRIPTION PARAMETERS ***/ PRODUCT_ID = "GRS_MID2004315ZZZ_DAT" PRODUCT_VERSION_ID = "V1" PRODUCT_CREATION_TIME = 2006-03-03T16:01:1 PRODUCT_TYPE = "DATA" STANDARD_DATA_PRODUCT_ID = "GRS_MICROPHONICS" SOFTWARE_NAME = "PIPE-GRS2EDR" SOFTWARE_VERSION_ID = "1.0" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = "GAMMA RAY SPECTROMETER" INSTRUMENT_ID = "GRS" DETECTOR_ID = "MICROPHONICS" DATA_SET_ID = "MESS-E/V/H-GRNS-2-GRS-RAWDATA-V1.0" MISSION_PHASE_NAME = "EARTH CRUISE" TARGET_NAME = "CALIBRATION" START_TIME = 2004-11-10 16:22:59.000 STOP_TIME = 2004-11-10 23:47:13.000 SPACECRAFT_CLOCK_START_COUNT = 8590973 SPACECRAFT_CLOCK_STOP_COUNT = 8617627 ^TABLE = "GRS_MID2004315ZZZ.DAT" OBJECT = TABLE COLUMNS = 6 INTERCHANGE_FORMAT = BINARY ROWS = 7 ROW_BYTES = 65548 DESCRIPTION = " This table contains the parameters and spectra associated with one set of raw microphonics time series collected by the MESSENGER Gamma Ray Spectrometer (GRS). A set is defined as all data with MET timestamps corresponding to a given Earth day. The complete column definitions are contained in an external file found in the LABEL directory of the archive volume. Additional details are contained in the EDR SIS document. " ^STRUCTURE = "GRS_MICRO.FMT" END_OBJECT = TABLE END 5.3.4.6 Software Counter PDS Label PDS_VERSION_ID = "PDS3" /*** FILE FORMAT ***/ FILE_RECORDS = 72 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 355 /*** GENERAL DATA DESCRIPTION PARAMETERS ***/ PRODUCT_ID = "GRS_SWC2004319ZZZ_TAB" PRODUCT_VERSION_ID = "V1" PRODUCT_CREATION_TIME = 2006-03-09T15:03:3 PRODUCT_TYPE = "ANCILLARY" STANDARD_DATA_PRODUCT_ID = "GRS_SOFTWARE_RATE_COUNTERS" SOFTWARE_NAME = "PIPE-GRS2EDR" SOFTWARE_VERSION_ID = "1.0" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = "GAMMA RAY SPECTROMETER" INSTRUMENT_ID = "GRS" DATA_SET_ID = "MESS-E/V/H-GRNS-2-GRS-RAWDATA-V1.0" MISSION_PHASE_NAME = "EARTH CRUISE" TARGET_NAME = "CALIBRATION" START_TIME = 2004-11-14 00:09:29.000 STOP_TIME = 2004-11-14 23:49:29.000 SPACECRAFT_CLOCK_START_COUNT = 8878161 SPACECRAFT_CLOCK_STOP_COUNT = 8963361 ^TABLE = "GRS_SWC2004319ZZZ.TAB" OBJECT = TABLE COLUMNS = 30 INTERCHANGE_FORMAT = ASCII ROWS = 72 ROW_BYTES = 355 DESCRIPTION = " This table contains one set of software rate counter telemetry information gathered by the MESSENGER Gamma-Ray Spectrometer (GRS). A set is defined as all data with MET timestamps corresponding to a given Earth day. The complete column definitions are contained in an external file found in the LABEL directory of the archive volume. Additional details are contained in the EDR SIS document. " ^STRUCTURE = "GRS_SWC.FMT" END_OBJECT = TABLE END 5.3.4.7 Status PDS Label PDS_VERSION_ID = "PDS3" /*** FILE FORMAT ***/ FILE_RECORDS = 1079 RECORD_TYPE = "FIXED_LENGTH" RECORD_BYTES = 1127 /*** GENERAL DATA DESCRIPTION PARAMETERS ***/ PRODUCT_ID = "GRS_STA2005175ZZZ_TAB" PRODUCT_VERSION_ID = "V1" PRODUCT_CREATION_TIME = 2006-03-09T15:19:58 PRODUCT_TYPE = "ANCILLARY" STANDARD_DATA_PRODUCT_ID = "GRS_STATUS" SOFTWARE_NAME = "PIPE-GRS2EDR" SOFTWARE_VERSION_ID = "1.0" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = "GAMMA RAY SPECTROMETER" INSTRUMENT_ID = "GRS" DETECTOR_ID = "HPGE" DATA_SET_ID = "MESS-E/V/H-GRNS-2-GRS-RAWDATA-V1.0" ISSION_PHASE_NAME = "EARTH CRUISE" TARGET_NAME = "CALIBRATION" START_TIME = 2005-06-24 06:01:20.000 STOP_TIME = 2005-06-24 23:59:20.000 SPACECRAFT_CLOCK_START_COUNT = 28080024 SPACECRAFT_CLOCK_STOP_COUNT = 28144704 ^TABLE = "GRS_STA2005175ZZZ.TAB" OBJECT = TABLE COLUMNS = 167 INTERCHANGE_FORMAT = ASCII ROWS = 1079 ROW_BYTES = 1127 DESCRIPTION = " This table contains one set of status telemetry information gathered by the MESSENGER Gamma-Ray Spectrometer (GRS). A set is defined as all data with MET timestamps corresponding to a given Earth day. The complete column definitions are contained in an external file found in the LABEL directory of the archive volume. Additional details are contained in the EDR SIS document. " ^STRUCTURE = "GRS_STATUS.FMT" END_OBJECT = TABLE END 5.3.4.8 FPGA ADC PDS Label PDS_VERSION_ID = "PDS3" /*** FILE FORMAT ***/ FILE_RECORDS = 7213 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 64 /*** GENERAL DATA DESCRIPTION PARAMETERS ***/ PRODUCT_ID = "GRS_ADC2004320ZZZ_DAT" PRODUCT_VERSION_ID = "V1" PRODUCT_CREATION_TIME = 2006-03-09T04:52:26 PRODUCT_TYPE = "ANCILLARY" STANDARD_DATA_PRODUCT_ID = "GRS_FPGA_ADC" SOFTWARE_NAME = "PIPE-GRS2EDR" SOFTWARE_VERSION_ID = "1.0" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = "GAMMA RAY SPECTROMETER" INSTRUMENT_ID = "GRS" DATA_SET_ID = "MESS-E/V/H-GRNS-2-GRS-RAWDATA-V1.0" MISSION_PHASE_NAME = "EARTH CRUISE" TARGET_NAME = "CALIBRATION" START_TIME = 2004-11-15 16:54:50.000 STOP_TIME = 2004-11-15 18:55:02.000 SPACECRAFT_CLOCK_START_COUNT = 9024881 SPACECRAFT_CLOCK_STOP_COUNT = 9032093 ^TABLE = "GRS_ADC2004320ZZZ.DAT" OBJECT = TABLE COLUMNS = 31 INTERCHANGE_FORMAT = BINARY ROWS = 7213 ROW_BYTES = 64 DESCRIPTION = " This table contains one set of FPGA ADC diagnostic information gathered by the MESSENGER Gamma-Ray Spectrometer (GRS). A set is defined as all data with MET timestamps corresponding to a given Earth day. The complete column definitions are contained in an external file found in the LABEL directory of the archive volume. Additional details are contained in the EDR SIS document. " ^STRUCTURE = "GRS_FPGA.FMT" END_OBJECT = TABLE END 5.3.4.9 Command Echo PDS Label PDS_VERSION_ID = "PDS3" /*** FILE FORMAT ***/ FILE_RECORDS = 8 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 125 /*** GENERAL DATA DESCRIPTION PARAMETERS ***/ PRODUCT_ID = "GRS_CMD2004320ZZZ_DAT" PRODUCT_VERSION_ID = "V1" PRODUCT_CREATION_TIME = 2008-12-05T19:42:49 PRODUCT_TYPE = "ANCILLARY" STANDARD_DATA_PRODUCT_ID = "GRS_COMMAND_ECHO" SOFTWARE_NAME = "PIPE-GRS2EDR" SOFTWARE_VERSION_ID = "1.0" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = "GAMMA RAY SPECTROMETER" INSTRUMENT_ID = "GRS" DATA_SET_ID = "MESS-E/V/H-GRNS-2-GRS-RAWDATA-V1.0" MISSION_PHASE_NAME = "EARTH CRUISE" TARGET_NAME = "CALIBRATION" START_TIME = 2004-11-15 06:25:10.000 STOP_TIME = 2004-11-15 18:55:01.000 SPACECRAFT_CLOCK_START_COUNT = 8987101 SPACECRAFT_CLOCK_STOP_COUNT = 9032092 ^TABLE = "GRS_CMD2004320ZZZ.DAT" OBJECT = TABLE COLUMNS = 7 INTERCHANGE_FORMAT = ASCII ROW_BYTES = 125 ROWS = 8 DESCRIPTION = " This table contains one set of the commands executed by the MESSENGER Gamma-Ray Spectrometer (GRS). A set is defined as all data with MET timestamps corresponding to a given Earth day. The complete column definitions are contained in an external file found in the LABEL directory of the archive volume. Additional details are contained in the EDR SIS document. " ^STRUCTURE = "GRS_CMDECHO.FMT" END_OBJECT = TABLE END 5.4 Standards used in Generating Data Products 5.4.1 PDS Standards The GRS EDR data products are constructed according to the data object concepts developed by the PDS. By adopting the PDS format, the data products are consistent in content and organization with other planetary data collections. In the PDS standard, the EDR data file is grouped into objects with PDS labels describing the objects. Each EDR data product consists of the following: * A data file containing an ASCII or binary table object, in fixed field format. ASCII table objects are additionally in comma separated value (CSV) format. This makes the ASCII data extremely easy to read by many commercial off-the-shelf programs. See section 5.2 for a listing of the data products and whether the data is contained in an ASCII or binary table object. * A label file, which is a high-level description of the parameters that correspond to the data file. The label file contains a pointer to an external format file which details the structure of the table object in the data file. 5.4.2 Coordinate Systems SPICE kernels are archived at the PDS NAIF node. Coordinate systems are included in the CDR-RDR-DAP SIS document. 5.4.3 Time Standards The MET field in the GRS EDR tables matches the spacecraft time in integer seconds that is transmitted to MESSENGER subsystems by the Integrated Electronics Module (IEM). This is referred to by the MESSENGER project as Mission Elapsed Time (MET). MET = 0 is August 3, 2004, at 05:59:16 UTC, which is 1000 seconds prior to the MESSENGER launch. Relativistic effects and circumstances occurring during the mission would result in MET not being a true account of seconds since launch. Following a planned spacecraft clock reset on January 8, 2013, partition numbers (1/, or 2/) were added to product labels to disambiguate MET seconds after the spacecraft clock reset (if partition number is not present, SPICE defaults to partition 1/). For this reason the MESSENGER spacecraft clock coefficients file is archived at the PDS Navigation and Ancillary Information Facility (NAIF) Node. This file is used in conjunction with the leapseconds kernel file in order to calculate the conversion between MET and UTC. The conversion is easily done through the use of SPICE kernels and the CHRONOS Utility. CHRONOS is a utility included with the SPICE package that is distributed by the PDS NAIF node. The SPICE kernels are files that contain the information needed to perform the conversion. Two SPICE kernels are required. One is the Leapseconds Kernel (LSK) and the other is the MESSENGER Spacecraft Clock Kernel (SCLK). The SCLK file is used by CHRONOS to convert between spacecraft clock time and ephemeris time, while the LSK file is used to convert from ephemeris time to UTC time. The CHRONOS utility is self-documenting and the SPICE package itself contains full documentation on each of the utilities (including CHRONOS) and how they are used. 5.4.4 Data Storage Conventions The data are organized following PDS standards and stored on hard disk and an SQL (Structured Query Language) relational database for rapid access during mission operations. The MESSENGER SOC transfers data to PDS via electronic transfer and delivery methods as detailed in section 5.3.3. After verification of the data transfer PDS provides public access to MESSENGER science data products through its online data distribution system. 5.5 Data Validation The GRS EDR data products are validated by the GRS Instrument scientist for science content and for compliance with PDS archive standards [MESSENGER Data Management and Archiving Plan]. 6 Detailed Data Product Specification 6.1 Data Product Structure and Organization The MESSENGER GRS data set is archived at the PDS Geosciences node as a data archive volume. The GRS EDR products in the data archive volume store the data in a form closest to the raw telemetry data received from the spacecraft. There is only one GRS EDR data archive volume which was created at the first delivery to PDS. Subsequent deliveries to PDS update this data volume. If errors are discovered the data is replaced with corrected EDRs on the next scheduled delivery date. The EDRs are organized in the data archive volume according to the structure defined in section 6.6. First there is the top level directory. Then subsequent directories are organized into folders by year. In each year folder there are directories organized by month. The PDS START_TIME keyword in the EDR is used to determine the year and month directory in which the EDR is placed. 6.2 Data Format Description Data is stored in ASCII table format or in binary table format. A detached PDS label file provides a detailed description of the structure of each table. See section 5.2 for details on which EDR contains a binary table or an ASCII table. 6.3 Label and Header Descriptions The following are the keyword definitions for the detached PDS label file. The detached PDS label file has the same name as the data file it describes, except for the extension .LBL to distinguish it as a label file. The keywords are listed in the order in which they appear in the example PDS labels in Section 5.3.4. PDS_VERSION_ID Represents the version number of the PDS standards documents that is valid when a data product label is created. PDS3 is used for the MESSENGER data products. FILE_RECORDS Indicates the number of physical file records, including both label records and data records. RECORD_TYPE Indicates the record format of a file. The FIXED_LENGTH value is used for the table object in the MESSENGER GRS EDR data products. RECORD_BYTES The number of bytes in a physical file record, including record terminators and separators. PRODUCT_ID The product_id data element represents a permanent, unique identifier assigned to a data product by its producer. See also: source_product_id. Note: In the PDS, the value assigned to product_id must be unique within its data set. PRODUCT_CREATION_TIME Defines the UTC system format time when the product was created. PRODUCT_VERSION_ID Identifies the version of an individual product within a data set. Example: V1, V2, V3 Product_version_id will be incremented if a given EDR has to be regenerated and sent to PDS to replace a previously submitted EDR. PRODUCT_TYPE Identifies the type or category of a product within a data set. STANDARD_DATA_PRODUCT_ID Used to link a GRS EDR file to one of the 10 types of GRS data products defined within the GRS EDR SIS. SOFTWARE_NAME Identifies the data processing software used to generate the EDR products. SOFTWARE_VERSION_ID Indicates the version of the data processing software used to generate the EDR products from the spacecraft telemetry. INSTRUMENT_HOST_NAME The full name of the host on which an instrument is based. In this case it is the MESSENGER spacecraft. INSTRUMENT_NAME The full, unabbreviated name of the instrument: Gamma-Ray Spectrometer. INSTRUMENT_ID An abbreviated name or acronym which identifies an instrument (i.e. GRS). DATA_SET_ID The data_set_id element is a unique alphanumeric identifier for a data set or a data product. The data_set_id value for a given data set or product is constructed according to flight project naming conventions. There is only one data_set_id for the GRS EDRs. MISSION_PHASE_NAME Provides the commonly used identifier of a mission phase. TARGET_NAME The target of the observation START_TIME Provides the date and time of the beginning of an event or observation (whether it be a spacecraft, ground-based, or system event) in UTC system format. STOP_TIME Provides the date and time of the end of an observation or event (whether it be a spacecraft, ground-based, or system event) in UTC system format. SPACECRAFT_CLOCK_START_COUNT Mission Elapsed Time (MET) corresponding to the first record in the data table. SPACECRAFT_CLOCK_STOP_COUNT Mission Elapsed Time (MET) corresponding to the last record in the data table. ^TABLE Pointer to the external data file which contains the table object. OBJECT = TABLE Specifies that the EDR is a PDS TABLE object. This object contains its own elements which are defined below. NOTE: the end of the object definition is always marked with an END_OBJECT line. COLUMNS Identifies the number of columns (fields) in the table. INTERCHANGE_FORMAT Specifies the format of the table. ROWS Number of rows in the table. ROW_BYTES Number of bytes for each row in the table. ^STRUCTURE This is a pointer to the external file which provides the structure definition for the table object. 6.3.1 Table Object Keyword Definitions The following describes the keywords used to define the PDS table object: OBJECT = COLUMN Identifies this as a column in the table object. COLUMN_NUMBER Identifies the location of the column within the larger data object (such as a table). For tables consisting of rows (I= 1, N) and columns (j = 1, M) the column_number is the j-th index of any row. NAME Indicates a literal value representing the common term used to identify the column object. BYTES Specifies the number of bytes allocated for this particular column element. DATA_TYPE Specifies the internal representation and/or mathematical properties of the value being stored in this column. START_BYTE Identifies the location of the first byte of the particular column, counting from 1. ITEMS Defines the number of multiple, identical occurrences of a single object. Ex. For the HPGe_Raw EDR it is used to describe that the Gamma-Ray spectra contains 16384 bins. ITEM_BYTES Represents the size in bytes of an individual item. 6.4 File Naming Conventions The file names developed for PDS data volumes are restricted to a maximum 36 character file name and a 3 character extension name with a period separating the file and extension names. The GRS data products use a 17.3 file naming convention - 17 character base name and 3 character extension. The general form of the file name is "GRS_ZZZYYYYDDDWWW.XXX", where: GRS instrument identifier: represents the GRS instrument ZZZ The data product name: RAW - HPGe Raw spectrum ANC - HPGE Anti-coincident spectrum SHI - SHIELD spectrum SCR - SHIELD count rate MID - Microphonics spectrum SWC - Software rate counter STA - Status telemetry ADC - FPGA ADC CMD - Command Echo YYYY The four digit year corresponding to the start time of the first record in the EDR data file. DDD The three digit day of year corresponding to the start time of the first record in the EDR data file. WWW Reserved 3 character string to use during the course of the mission as necessary to identify "special" data products. Nominal data products will be identified with 'ZZZ'. .XXX The file extension. The detached PDS label file has the extension 'LBL', the binary table file has the extension 'DAT', and the ASCII table file has the extension 'TAB'. 6.5 Archive Volume and File Size The final GRS EDR archive volume has a size of approximately 62 GB. 6.6 Directory Structure and Contents The following illustration shows the directory structure overview for the GRS EDR Data Archive Volume. This volume contains the GRS EDR data products, supporting documentation, and any additional files required for the volume to be compliant with PDS standards. The content of the volume is expected to be updated with each periodic EDR release. Revised EDRs will have an incremented version number in the PDS label. Directory Structure Overview | _____________________|_____________________ | | | | | | | | | |