PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 2017-05-12 INTERCHANGE_FORMAT = ASCII NOTE = "N/A" END_OBJECT = TEXT END MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) Mercury Dual Imaging System (MDIS) Derived Data Record (DDR) Archive 1. Introduction This archive contains data acquired by the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) Mercury Dual Imaging System (MDIS) instrument. 2. File Formats This section describes the format of the files contained in the MDIS Archive Volumes. Data that comprise the archive is formatted in accordance with Planetary Data System standards. 2.1. Document File Formats Document files with the .TXT suffix exist in the ROOT, INDEX, CATALOG, and DOCUMENT directories, and in the BROWSE and EXTRAS directories if they are present. They are ASCII files which may have embedded PDS labels. Lines in a .TXT file end with a carriage return character (ASCII 13) and a line feed character (ASCII 10). This allows the files to be readable under various operating systems. Some documents in the DOCUMENT directory contain formatting and figures that cannot easily be rendered as ASCII text. Therefore each document is given in PDF format. PDF (Portable Document Format) is a proprietary format of Adobe Systems Incorporated that is frequently used for distributing documents. Adobe offers free software, Acrobat Reader, for viewing PDF files. Some type of ASCII text versions of these documents are also included, using HTML or XML, in order to meet the PDS requirement that documents must be archived as ASCII text. 2.2. Tabular File Format Tabular files (.TAB suffix) exist in the INDEX directory and EXTRAS directory if it is present. Tabular files are ASCII files formatted for direct reading into many database management systems on various computers. All fields are separated by commas. (Character fields are padded with spaces to keep quotation marks in the same columns of successive records.) Character fields are left justified, and numeric fields are right justified. The 'start byte' listed in the labels indicate the starting position in bytes of each field in a record; the field length 'bytes' does not include the commas between fields, or quotation marks for ASCII strings. The records are of fixed length, and the last two bytes of each record contain the ASCII carriage return and line feed characters. This allows a table to be treated as a fixed length record file on computers that support this file type and as a text file with embedded line delimiters on those that don't. Every MDIS tabular file is described by a detached PDS label with the same name as the data file it describes, and the extension .LBL. For example, the file INDEX.TAB is accompanied by the detached label file INDEX.LBL in the same directory. 2.3. PDS Label Format All data files in the MDIS DDR archive have attached PDS labels. For examples of PDS labels, see the Data Product SIS in the DOCUMENT directory. A PDS label provides descriptive information about the associated file. The PDS label is an object-oriented structure consisting of sets of 'keyword=value' declarations. The object to which the label refers (e.g. IMAGE, TABLE, etc.) is denoted by a statement of the form: ^object = location in which the carat character (^, also called a pointer in this context) indicates where to find the object. In an embedded label, the location is an integer representing the starting record number of the object (the first record in the file is record 1). In a detached label, the location denotes the name of the file containing the object, along with the starting record or byte number, if there is more than one object in the file. For example: ^HEADER = ("F01.IMG",1) ^IMAGE = ("F01.IMG",1025 ) indicates that the IMAGE object begins at byte 1025 of the file F01.IMG, in the same directory as the detached label file. Below is a list of the possible formats for the ^object definition. ^object = n ^object = n ^object = "filename.ext" ^object = ("filename.ext",n) ^object = ("filename.ext",n) where n is the starting record or byte number of the object, counting from the beginning of the file (record 1, byte 1), indicates that the number given is in units of bytes, filename is the up to 28 character, alphanumeric upper-case file name, ext is the 3 character upper-case file extension Lines of text in detached labels end with a carriage return character (ASCII 13) and a line feed character (ASCII 10). This allows the files to be readable under various operating systems. 2.4. Catalog File Format Catalog files (suffix .CAT) exist in the ROOT and CATALOG directories. They are text files formatted in an object-oriented structure consisting of sets of 'keyword=value' declarations, so that they are readable by humans and by software. 2.5. Science Data File Formats For more information about the format and content of the data products, see the discussions in the MDIS Data Product SIS located in the DOCUMENT directory. 3. Archive Contents Files in this archive are organized into a series of subdirectories below the top-level directory. The archive organization and the contents of each directory are described below. Top-level Directory ------------------- AAREADME.TXT The file you are currently reading. ERRATA.TXT This text file content describes known anomalies and errors along with additional comments and updates concerning the archive volume. VOLDESC.CAT This text file contains a description of the volume contents as a PDS catalog object. It is a required file on PDS archive volumes. INDEX Directory --------------- The INDEX directory contains PDS index files for this archive. An index file is an ASCII table with each record (or line) in the table containing information about a single data product in archive. Files in the Index directory are provided to help the user locate products on the archive volume. INDXINFO.TXT Identifies and describes the function of each file in the index subdirectory. This includes a description of the structure and contents of the index table and usage notes. INDEX.TAB The image index file is organized as a table: there is a row for each map tile image on the volume; the columns contain the image and mapping parameters. Information includes map projection type, resolution, and map extents in latitude and longitude. INDEX.LBL Detached PDS label for INDEX.TAB that describes its organization and contents. MD5.TAB The checksum table. The checksum table is a listing of all files in the archive (with the exception of the checksum table itself) that gives the MD5 checksum (message digest) for the file and the full path including file name. It is generated by the commonly available "MD5Deep" utility. This file is useful as a manifest for the archive and for data integrity assurance. MD5.LBL Detached PDS label for MD5.TAB that describes its organization and contents. DDR Directory -------------- The DDR directory contains the Derived Data Record (DDR) data set. It consists of single images that have 5 bands of data as 32-bit PC_REAL or IEEE_REAL: (a) latitude, (b) longitude, and (c) incidence angle, (d) emission angle, and (e) phase angle at the equipotential surface. In version 0 DDRs, latitude and longitude are calculated using the best-determined spacecraft and instrument pointing values, spacecraft position, and camera model recorded in SPICE kernels, and an ellipsoidal model of the planet surface. For version 1 DDRs delivered one year after the end of orbital operations, "smithed" c-kernels that record the time history of pivot pointing and a global digital elevation model (DEM) are used. In the smithed c-kernels used for version 1, pointing history is adjusted to control map projection, to provide improved agreement in the location of geographic features in overlapping NAC and WAC G-filter images. Version 2 DDRs, delivered two years after the end of orbital operations, were constructed for only WAC G-filter images used in multispectral data products (MDRs, MD3s, MP5s). In the smithed c-kernels used for version 2, the usage of only WAC G-filter images optimizes the control of multispectral images, resulting in less "blur" from the averaging procedures described for the newest version of MDRs, MD3s, and MP5s. See the CDR/RDR data product SIS in the DOCUMENT directory for a more detailed description of the DDRs. DOCUMENT Directory ------------------ The DOCUMENT directory contains documentation to help the user understand and use the archive data. DOCINFO.TXT Identifies and describes the function of each file in the document directory. MDIS_CDR_RDRSIS.DOC Software Interface Specification for the CDR/RDR data products as a Microsoft Word document. MDIS_CDR_RDRSIS.PDF Software Interface Specification for the CDR/RDR data products as an Adobe PDF document. MDIS_CDR_RDRSIS.HTM Software Interface Specification for the CDR/RDR data products as an HTML document. MDIS_CDR_RDRSIS.LBL PDS label for MDIS_CDR_RDRSIS.PDF and MDIS_CDR_RDRSIS.HTM. PDSDD.FUL The PDS Data Dictionary that includes definitions of all keywords used in MESSENGER data labels, including MESSENGER-specific keywords (i.e. the MESSENGER Local Data Dictionary). This is a text file that is human-readable and also usable as input to PDS label validation software. CATALOG Directory ----------------- The files in the Catalog directory provide a top-level understanding of the mission, spacecraft, instrument, and data set. The files in this directory become part of the PDS Catalog to provide background information for the user searching for data. Their format and contents are further specified in the PDS Standards Reference. CATINFO.TXT Identifies and describes the function of each file in the catalog directory. MDIS_DDR_DS.CAT DDR Data set description. INSTHOST.CAT Description of the MESSENGER spacecraft for the PDS catalog. MDIS_NAC_INST.CAT, MDIS_WAC_INST.CAT Description of the MDIS NAC and WAC instruments for the PDS catalog. MISSION.CAT Description of the MESSENGER mission for the PDS catalog. PERSON.CAT List of personnel associated with the MESSENGER mission. REF.CAT Catalog objects' citation list for the PDS catalog. TARGET.CAT Contains the definition for all MDIS targets (objects of interest that the instrument observed). 4. Whom to Contact for Information For questions concerning this volume set, contact: PDS - Flagstaff Imaging Node United states Geological Survey 2255 North Gemini Drive Flagstaff, AZ 86001 Electronic mail address: pdsmgr@usgs.gov For general information related to the PDS, contact: Planetary Data System, PDS Operator M/S 202-101 Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109-8099 (818) 354-4321 WWW Site: http://pds.jpl.nasa.gov/ E-mail: pds_operator@jpl.nasa.gov 5. Cognizant Persons This archive volume designed and produced at Applied Coherent Technology, Inc. in Herndon, VA by Christopher Hash, Raymond Espiritu, and Erick Malaret, and at the Applied Physics Laboratory, Laurel, MD by Scott Murchie.