Experiment Data Record Software Interface Specification for the MESSENGER Mercury Atmospheric and Surface Composition Spectrometer/ Visible and Infrared Spectrograph (MASCS/VIRS) SIE-06-045 D Prepared by: Raymond Espiritu Erick Malaret Applied Coherent Technology Corporation Document Review This document and the archive it describes have been through PDS Peer Review and have been accepted into the PDS archive. William McClintock, MESSENGER Cognizant Co-Investigator/MASCS, has reviewed and approved this document. Noam Izenberg, MESSENGER MASCS Instrument Scientist, has reviewed and approved this document. Lyle Huber, PDS Atmospheres Node Representative, has reviewed and approved this document. Susan Ensor, MESSENGER Science Operations Center Lead, has reviewed and approved this document. Document Change History Revision Number Revision Date Author Section Remarks 1 6/23/06 Start of revision history. Version submitted to PDS for Release 4. 1.1 1/7/10 J. Ward, GEO TOC, 5.3.4 1. Added page numbers to Table of Contents. 2. Replaced sample PDS labels with new versions containing PRODUCT_VERSION_ID. 1.2 1/12/10 J. Ward, GEO 6.3.2, Appendix Updated column 64 of MASCS_HK.FMT to match delivered file in LABEL directory. 1.3 1/14/10 J. Ward, GEO Title Page Added “Experiment Data Record” to document title. 1.4 9/15/10 J. Ward, GEO 6.1.3, 6.1.4 Added EXTRAS directory tables. 1.5 12/09/10 J. Ward, GEO 7 Updated archive release schedule. 1.6 5/5/11 J. Ward, GEO 6.1.3, 6.1.4 Updated to reflect new data directory structure. 1.7 6/10/11 J. Ward, GEO 6.1.4 Updated EXTRAS directory contents. 1.8 6/14/11 S. Ensor, SOC Document Review Replaced signature page with Document Review information. 1.9 6/17/11 J. Ward, GEO 6.1.4 Renamed SUPERTABLE.XLS TO MASTER_CRUISE_TABLE.XLS. 2.0 12/21/11 J. Ward, GEO 6.1.4 Updated EXTRAS directory contents. 2.1 5/25/12 S. Ensor, SOC 2, 7, 6.1.2 1. Change document name from Data Management and Science Analysis Plan to Data Management and Archiving Plan. Update references. 2. Reference Data Management and Archiving Plan for release schedule and remove release schedule, table B-1, from this document. 3. Add mission phase for second year of orbital operations. 2.2 11/12/12 J. Ward, GEO 6.1.4 Updated EXTRAS directory contents. 2.3 7/7/2015 S.Ensor Various, 5.4.2, 6.1.2 Change “Experimental Data Record” to “Experiment Data Record” in text. 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). Table of Contents 1. Purpose and Scope of Document 5 1.1 Purpose 5 1.2 Scope 5 2. Applicable Documents 6 3. Relationships with other Interfaces 6 4. Roles and Responsibilities 6 5. Data Product Characteristics and Environment 6 5.1 Overview 6 5.2 Data Product Overview 7 5.3 Data Processing 8 5.3.1 Data Processing Level 8 5.3.2 Data Product Generation 8 5.3.3 Data Flow 9 5.3.4 Labeling and Identification 11 5.4 Standards Used in Generating Data Products 13 5.4.1 PDS Standards 13 5.4.2 Time Standards 13 5.4.3 Coordinate Systems 13 5.4.4 Data Storage Conventions 14 5.5 Data Validation 14 6. Detailed Data Product Specifications 14 6.1 Data Archive Structure and Organization 14 6.1.1 Handling Errors 15 6.1.2 File Naming Conventions 15 6.1.3 Directory Structure and Contents for MASCS EDR Archive Volume 16 6.1.4 Directory Contents 16 6.2 Data Format Description 19 6.3 Label and Header Descriptions 19 6.3.1 VIRS EDR Table Columns 20 6.3.2 MASCS_HK EDR Table Columns 23 7. Archive Release Schedule to PDS 33 8. Appendices 34 APPENDIX - VIRS.FMT FILE 34 APPENDIX - MASCS_HK.FMT FILE 37 APPENDIX - SPICE Kernel Files Used In Messenger Data Products 53 APPENDIX - CODMAC 54 APPENDIX - ACRONYMS 55 APPENDIX - MASCS Instrument Overview 57 1. Purpose and Scope of Document 1.1 Purpose This document will provide users of the MESSENGER Visible and Infrared Spectrograph (VIRS) data products with a detailed description of the Spectrograph instrument (Figure 1: VIRS subsystem) and EDR data product generation, data validation and storage. The VIRS data products are a deliverable to the Planetary Data System (PDS) and the scientific community that it supports. All data formats are based on the PDS standard. Figure 1: MASCS Instrument, VIRS subsystem. In addition this SIS provides documentation on the format and content of the MESSENGER MASCS EDR PDS Volume Archive. The document is both an EDR data product SIS and an EDR archive volume SIS. 1.2 Scope This specification is useful to those who wish to understand the format and content of the VIRS EDR data products. Typically, these individuals include software engineers, data analysts, and planetary scientists. The SIS applies to the EDR data products produced during the course of Messenger Mission operations. Calibrated and Reduced Data Records (CDRs and RDRs) are outside the scope of this SIS and are described in a separate SIS document. RDRs and CDRs are also archived in their own, separate PDS archive volume. 2. Applicable Documents The MESSENGER VIRS SIS is responsive to the following Documents: * 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 * Planetary Data System Standards Reference, Aug 1, 2003, Version 3.6. JPL D-7669, Part-2. * MESSENGER Data Management and Archiving Plan. The Johns Hopkins University, APL. Document ID number 7384-9019 * [PLR] Appendix 7 to the discovery program Plan; Program Level Requirement for the MESSENGER Discovery project; June 20, 2001. * MASCS Users Guide. Laboratory for Atmospheric and Space Physics, University of Colorado. Document ID number 20580-T5-5103 * Instrument Calibration Report Mercury Atmospheric and Surface Composition Spectrometer 3. Relationships with other Interfaces The VIRS data products are stored on Hard Disk and in an SQL (Structured Query Language) relational database for rapid mission access during mission operations. The data products will be electronically transferred to the PDS Geosciences and Atmospheres Nodes according to the delivery schedule in the MESSENGER Data Management and Archiving Plan. The VIRS and UVVS EDRs (detailed in the UVVS EDR SIS) have some data that would be useful in cross-comparison, therefore both the UVVS and VIRS EDR data will be grouped together in the MASCS EDR volume archive stored at both PDS nodes. The data in the EDR files themselves will be stored in a PDS TABLE object as binary tables. 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 Overview Visible and Infrared Spectrograph measures the visible and infrared surface reflectance. It is a concave grating spectrograph equipped with Si and InGaAs photodiode arrays. Visible and infrared Spectrograph Focal length 210 mm Grating 120 g/mm blazed at 600 nm Spectral resolution 4 nm Wavelength range VIS channel 300-1050 nm IR channel 850-1450 nm Detector VIS channel Hamamatsu S3902-512 Si Diode Array IR channel Hamamatsu G8052-256 InGaAs Diode Array Field of view 0.023  x 0.023  An overview of the whole MASCS instrument is provided in the APPENDIX – MASCS Instrument Overview. 5.2 Data Product Overview There are two EDR data products produced by the VIRS instrument, one for each detector (VIS and NIR). These are identified in the PDS label as “VIRSVIS” and “VIRSNIR” standard data products, respectively. There is also a MASCS housekeeping EDR data product generated by the MASCS instrument. This is identified in the PDS label as the “MASCSHK” standard data product. The housekeeping EDR is defined both in this SIS and in the UVVS SIS for completeness but is the same data product. For the VIRS EDR data product, one EDR will contain all the data from one observation. However, one observation will generate a variable number of spectra and a variable number of CCSDS packets. Thus there is not a one- to-one correspondence between CCSDS packets and VIRS EDRs. Identification of which CCSDS packet belongs to a given observation will be done by correlating the packet MET with the planned start MET and planned duration of the observation set by the MASCS science team. The MASCS Housekeeping EDR will contain all housekeeping packets generated in a given day. The day is defined as a 24-hour period from 00:00:00 to 23:59:59.999. A variable number of housekeeping packets will be generated each day; the data from each packet will be inserted as 1 row in the EDR binary table. Each EDR data product consists of two files. One file contains the data itself, and is arranged in a PDS binary table format. The other file is a detached PDS label file, which describes the content of the data file. The label file defines the start time and end of the observation, product creation time, etc. The label file also defines the fields of the binary table contained within the data file. 5.3 Data Processing 5.3.1 Data Processing Level For MESSENGER there is one archive for the VIRS instrument. The archive includes level 2 (or above) data as defined by the Committee on Data Management and Computation (CODMAC). The archive will also contain SPICE files, standard data products, relevant software, and documentation describing the generation of the products, Each product will have a unique file name across all MASCS data products, see section 6.1.2. All data level products will be stored at the Science Operations Center (SOC) located at Johns-Hopkins University Applied Physics Laboratory (APL). Level 1 CODMAC data will be received at the SOC where it will be ingested via an automatic data processing system and stored in a database reserved for the VIRS instrument. Bundled with the sensor spectral data products will be scientific and engineering housekeeping data sampled by the VIRS instrument at the same time as the integral spectra onboard the spacecraft. 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 will consist of telemetry in the form of CCSDS packets. The data will be available via a real-time TCP stream service and post pass FTP file service. Level-0 VIRS raw spectral and engineering data is then broken out of the data stream and stored online at the SOC. The SOC will produce early versions of the data products by utilizing SPICE kernels to enable a “quick look” functionality that lets users view the coverage areas recorded by the sensor. The early versions will be of the same type, content, and format as the final science products with default values for unknown data. Unknown data refers to the PDS keywords corresponding to spacecraft position, sun position, target latitude and target longitude. The values for these keywords will be calculated via the use of SPICE kernels and will be filled in prior to delivery to PDS. 5.3.2 Data Product Generation The VIRS EDR files will be produced by the MESSENGER SOC; operated jointly by APL and ACT. The ‘PIPE-MASCS2EDR’ software converts the data to the proper PDS labeled format. This software is not part of the deliverable to the PDS archive. The EDR data products are made available to the MESSENGER Science Team during the mission 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 6.1.3 for transmittal to the Geosciences and Atmospheres Nodes. The transmittal process is described in the following section, Data Flow. PDS will then provide public access to the data products through its online data distribution system. These products will be used for engineering support, direct science analysis, and construction of other science products. Although there is enough information in the header to perform some processing, for more sophisticated processing, ancillary data will be required. Examples of ancillary data include calibration files and viewing geometry files (SPICE kernels). Calibration files and their use will be described in the UVVS RDR SIS and VIRS RDR SIS as well as in the MASCS Instrument Calibration Report. The GEOMETRY.TXT file mentioned in section 6.1.4 will contain the SPICE kernel types that will be needed by a user to generate viewing geometry. The SPICE kernel files will be archived with the PDS NAIF Node. 5.3.3 Data Flow The MESSENGER SOC operates under the auspices of the MESSENGER Project Scientist to plan data acquisition and 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 will be located at the Johns-Hopkins University Applied Physics Lab (JHU/APL). During the mission operations phase the SOC will produce early versions of products that can be used by the science and instrument teams. The MESSENGER SOC will deliver data to both the PDS Geosciences and Atmospheres Nodes in standard product packages according to the schedule outlined in the MESSENGER Data Management and Archiving Plan. The VIRS and UVVS archive volumes (detailed in a separate UVVS SIS) will be archived at both Nodes. Each package will comprise both data and ancillary data files, organized into directory structures consistent with the volume design described in Section 6.1.3. In the week prior to the delivery date the directory structure will be compressed into a single “zip archive” file for transmittal to both PDS Nodes. 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 will be 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 several days of transmittal the PDS Node will acknowledge receipt of the archive and checksum file. If acknowledgement is not received, or if problems are reported, the MESSENGER SOC will immediately take corrective action to effect successful transmittal. After transmittal the PDS Node will uncompress the zip archive file and check for data integrity using the checksum file. The Node will then perform any additional verification and validation of the data provided and will report any discrepancies or problems to the MESSENGER SOC. It is expected that the Node will perform these checks in about two weeks. After inspection has been completed to the satisfaction of the PDS Node, the Node will issue to the MESSENGER SOC acknowledgement of successful receipt of the data. Following receipt of a data delivery each Node will organize the data into PDS volume archive structure within its online data system. The Node will generate all of the required files associated with a PDS archive volume (index file, readme files, etc) as part of its routine processing of incoming MASCS data. Newly delivered data will be made available publicly from PDS once accompanying labels and other documentation have been validated. 5.3.4 Labeling and Identification The label area of the data file conforms to the PDS version 3 standards. For more information on this standard consult the PDS Standards Reference JPL D-7669 Document. The purpose of the PDS label is to describe the data product and provide ancillary information about the data product. For every EDR data file there exists a PDS label file. The following is an example of a PDS label. There are three standard data products, “VIRSNIR”, “VIRSVIS”, and “MASCSHK” (section 5.2). The data files are linked to the standard data product via the STANDARD_DATA_PRODUCT_ID. Details about the label format are specified later in section 6.3. 5.3.4.1 EXAMPLE PDS LABEL FOR THE VIRS EDR DATA PRODUCTS PDS_VERSION_ID = "PDS3" /*** FILE FORMAT ***/ RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 1102 FILE_RECORDS = 20 /*** GENERAL DATA DESCRIPTION PARAMETERS ***/ PRODUCT_ID = "VIRSNE_MF3_09285_004616_DAT" PRODUCT_VERSION_ID = "V1 " PRODUCT_CREATION_TIME = 2009-12-02T21:05:30 PRODUCT_TYPE = "EDR" SOFTWARE_NAME = "PIPE-MASCS2EDR" SOFTWARE_VERSION_ID = "1.0" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = " MERCURY ATMOSPHERIC AND SURFACE COMPOSITION SPECTROMETER" INSTRUMENT_ID = "MASCS" DETECTOR_ID = "VIRS" DATA_SET_ID = "MESS-E/V/H-MASCS-2-VIRS-EDR-V1.0" STANDARD_DATA_PRODUCT_ID = "VIRSNIR" MISSION_PHASE_NAME = "MERCURY 3 FLYBY" TARGET_NAME = "MERCURY" START_TIME = 2009-10-12T00:46:16 STOP_TIME = 2009-10-12T00:46:52 SPACECRAFT_CLOCK_START_COUNT = "163795842" SPACECRAFT_CLOCK_STOP_COUNT = "163795878" ^TABLE = "VIRSNE_MF3_09285_004616.DAT" OBJECT = TABLE COLUMNS = 24 INTERCHANGE_FORMAT = BINARY ROW_BYTES = 1102 ROWS = 20 DESCRIPTION = " This table contains MESSENGER VIRS spectra collected in the near infrared wavelength as well as instrument engineering data. Detailed descriptions for the parameters defined below are contained in the EDR SIS. The complete column definitions are contained in an external file found in the DATA directory of the archive volume. " ^STRUCTURE = "VIRS.FMT" END_OBJECT = TABLE END The following is an example of the contents of the MASCS housekeeping EDR PDS label. The housekeeping EDR contains instrument parameters that may be useful in analyzing the UVVS data. Details about the label format are specified in section 6.3. The large amount of table fields in the housekeeping EDR necessitate the use of an external format (.FMT) file which contains all the fields for the housekeeping EDR. This format file will be placed at the top-level of the MASCS data folder to optimize archive space. The complete layout of the format file can be found in APPENDIX – MASCS_HK.FMT. 5.3.4.2 EXAMPLE PDS LABEL FOR THE MASCS HOUSEKEEPING EDR PDS_VERSION_ID = "PDS3" RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 254 FILE_RECORDS = 1177 PRODUCT_ID = "MASCS_HK_09285_DAT" PRODUCT_VERSION_ID = "V1 " PRODUCT_CREATION_TIME = 2009-10-22T07:45:44 PRODUCT_TYPE = "EDR" SOFTWARE_NAME = "PIPE-MASCS2EDR" SOFTWARE_VERSION_ID = "1.1" INSTRUMENT_HOST_NAME = "MESSENGER" INSTRUMENT_NAME = " MERCURY ATMOSPHERIC AND SURFACE COMPOSITION SPECTROMETER" INSTRUMENT_ID = "MASCS" DATA_SET_ID = {"MESS-E/V/H-MASCS-2-UVVS-EDR-V1.0","MESS-E/V/H-MASCS-2-VIRS-EDR-V1.0"} STANDARD_DATA_PRODUCT_ID = "MASCSHK" MISSION_PHASE_NAME = "MERCURY 3 FLYBY" TARGET_NAME = "MERCURY" START_TIME = 2009-10-12T00:00:08 STOP_TIME = 2009-10-12T19:32:24 SPACECRAFT_CLOCK_START_COUNT = "163793074" SPACECRAFT_CLOCK_STOP_COUNT = "163863410" ^TABLE = "MASCS_HK_09285.DAT" OBJECT = TABLE COLUMNS = 95 INTERCHANGE_FORMAT = BINARY ROW_BYTES = 254 ROWS = 1177 DESCRIPTION = " This table contains MASCS Housekeeping data. Voltage, current, and temperature parameters are converted from raw DN counts into engineering data values. Detailed descriptions for the parameters defined below are contained in the EDR SIS. The complete column definitions are contained in an external file found in the DATA directory of the archive volume. " ^STRUCTURE = "MASCS_HK.FMT" END_OBJECT = TABLE END 5.4 Standards Used in Generating Data Products 5.4.1 PDS Standards The VIRS 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 VIRS data is grouped into pairs, with one file containing the binary table data and a detached PDS label describing the data. The detached label file will contain a pointer to the binary table file which stores the housekeeping data, derived pointing data, and the spectra. 5.4.2 Time Standards The SC_TIME field matches the spacecraft time in integer seconds that is transmitted to MESSENGER subsystems by the Integrated Electronics Module (IEM). It is intended to be the Mission Elapsed Time (MET). MET = 0 is August 3, 2004, at 05:59:16UTC, 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 reset1 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 SPICE spacecraft clock coefficients file is included as part of the archive in order to calculate the conversion between MET and UTC. 5.4.3 Coordinate Systems Table 1 lists the computational assumptions for the geometric and viewing data provided in the PDS label. There are two coordinate systems in use: 1) the celestial reference system used for target and spacecraft position and velocity vectors; and 2) the planetary coordinate system for geometry vectors and target location. The celestial coordinate system is J2000 (Mean of Earth equator and equinox of J2000). The planetary coordinate system is planetocentric. TABLE 1. - COMPUTATIONAL ASSUMPTIONS <> The start time of observation (MET) is used for the geometric element computations. <> Label parameters reflect observed, not true, geometry. Therefore, light-time and stellar aberration corrections are used as appropriate. <> The inertial reference frame is J2000 (also called EME2000). <> Latitudes and longitudes are planetocentric. <> The "sub-point" of a body on a target is defined by the surface intercept of the body-to-target-center vector. This is not the closest point on the body to the observer. <> Distances are in km, speeds in km/sec, angles, in degrees, angular rates in degrees/sec, unless otherwise noted. <> Angle ranges are 0 to 360 degrees for azimuths and local hour angle. Longitudes range from 0 to 360 degrees (positive to the East). Latitudes range from -90 to 90 degrees. <> SPICE kernel files used in the geometric parameters is outlined in APPENDIX – SPICE Kernel Files Used in MESSENGER Data Products. 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 will transfer data to PDS via electronic transfer and delivery methods as detailed in section 5.3.3. After verification of the data transfer PDS will provide public access to MESSENGER science data products through its online data distribution system. Data will be stored under a unique file name as defined in section 6.1.2. 5.5 Data Validation The VIRS EDR data products will be validated by the VIRS Instrument scientist for science content and for compliance with PDS archive standards and the MESSENGER Data Management and Archiving Plan. 6. Detailed Data Product Specifications 6.1 Data Archive Structure and Organization The VIRS EDR data set is a static dataset. Static data sets, once produced and validated, are not subject to update or modification. The VIRS Calibrated and Reduced Data Set, which is contained in a separate volume archive, is a dynamic dataset. Dynamic data sets have the inherent property that they continue to evolve and improve as the knowledge of the mission parameters improve. These data sets are periodically updated or replaced with new versions, and are likely to be updated by post-mission data analysis programs. As an example, the calibration files continue to evolve as knowledge of the MASCS sensor, as well as of the pointing accuracy of the MESSENGER spacecraft improves. Calibration has not been performed on the data products stored in the EDR data archive volume. The EDR data archive volume is meant to contain the data in a format as close to that received from the MESSENGER spacecraft. The VIRS RDR data archive volume, which is separate from the EDR data archive volume, will contain calibrated data records and reduced data records created via calibration performed on the EDR data set. This calibration process is documented in the MASCS Instrument Calibration Report as well as in the VIRS RDR SIS. 6.1.1 Handling Errors It is inevitable that errors will be introduced into the archive even with data validation procedures applied to the volumes. As errors are discovered, they are reported to the MESSENGER SOC. An ERRATA report file is maintained to track and document all discovered errors during the mission, including any EDRs that are revised during the course of the mission. Revised EDRs or EDRs that were missing from a previous PDS delivery will be provided at the next scheduled PDS delivery or at the final PDS delivery as needed. PDS will then replace the outdated files with the revised files in the data directories of the archive volume. The ERRATA report file is archived in the ROOT directory of the PDS archive volume. 6.1.2 File Naming Conventions The file names developed for PDS data volumes are restricted to a 36 character file name and a 3 character extension name with a period separating the file and extension names. The general form of the base file name for the EDR product is “VIRSdL_mmm_YYDDD_HHMMSS” where: VIRS: instrument name d: detector identifier. N = NIR, V=VIS L: data level. E=EDR, C=CDR, R=RDR mmm: Mission Phase EAC = Earth cruise to Earth flyby EAF = Earth flyby VC1 = cruise, post Earth flyby to pre-Venus 1 flyby VF1 = Venus 1 flyby VC2 = cruise, post Venus 1 to pre-Venus 2 flyby VF2 = Venus 2 flyby MC1 = cruise, post Venus 2 to pre-Mercury 1 flyby MF1 = Mercury 1 flyby MC2 = cruise, post Mercury 1 to pre-Mercury 2 flyby MF2 = Mercury 2 flyby MC3 = cruise, post Mercury 2 to pre-Mercury 3 flyby MF3 = Mercury 3 flyby MC4 = cruise, post Mercury 3 to pre-orbit insertion ORB = orbit insertion until end of nominal orbit Mission OB2 = second year of orbital operations OB3 = third year of orbital operations OB4 = fourth year of orbital operations OB5 = fifth year of orbital operations YY: the last two digits of the year in which the data was acquired DDD: The three digit day of year in which the data was acquired. HHMMSS: Is the 6 digit hour, minute, second of the start of the observation. The general form of the MASCS housekeeping EDR will be “MASCS_HK_YYDDD”, where: YY: Is the last two digits of the year in which the data were acquired. DDD: Is the three digit (zero padded) day of the year in which the data where acquired. This identifies that the housekeeping EDR is common to both the UVVS and VIRS subsystems. For the VIRS EDR and housekeeping EDR the binary table file will end with a “.DAT” extension and the detached PDS label file will end with a “.LBL” extension. 6.1.3 Directory Structure and Contents for MASCS EDR Archive Volume The following illustration shows the directory structure overview for the MASCS EDR Archive Volume. Note that the volume contains UVVS, VIRS, and HK EDRs. Details for the UVVS EDRs are contained in a separate UVVS SIS document. This archive volume is stored at both the Atmospheres and Geosciences PDS Nodes for reasons stated in section 3. A detailed description of the directory tree is provided following Table 2. Empty directories are not included on the volume. TABLE 2 Directory Structure Overview __________________________________|__________________________________ | | | | | | |