PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 2012-03-15 INTERCHANGE_FORMAT = ASCII NOTE = "N/A" END_OBJECT = TEXT END MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) Mercury Dual Imaging System (MDIS) Uncalibrated Data 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 MDIS Archive Volumes. Data that comprise the Archive will be formatted in accordance with Planetary Data System standards. 2.1. Disk Format Archive Volumes are formatted so that when written to CD or DVD media according to PDS policy, the media are compatible with most commonly used computer operating systems including Windows, Unix, and Macintosh systems. The CD volume format is in accordance with ISO 9660 level 2 InterchangeStandard. The DVD volume format is in accordance with the UDF Standard with ISO 9660 Level 2 compatibility. 2.2. File Formats This section describes file formats for the kinds of files contained on Archive Volumes. 2.2.1. Document File Formats Document files with the .TXT suffix exist in the ROOT, INDEX, CATALOG, DOCUMENT, and CALIB 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 and CALIB directories 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 will also be included, possibly using HTML or XML, in order to meet the PDS requirement that documents must be archived as ASCII text. 2.2.2. Tabular File Format Tabular files (.TAB suffix) exist in the INDEX and CALIB directories, 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. 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. 2.2.3. PDS Label Format All data files in the MDIS EDR 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. 2.2.4. 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. 2.2.5. 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 contains a listing of 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. DATA Directory -------------- The DATA directory contains MDIS WAC and NAC Experiment Data Records (EDRs) and information on data validation. 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. See the file INDXINFO.TXT for additional details. DOCUMENT Directory ------------------ The DOCUMENT directory contains documentation to help the user understand and use the archive data. See DOCINFO.TXT for a description of the files in the DOCUMENT directory. 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. See the file CATINFO.TXT for details. GEOMETRY Directory ----------------- This subdirectory contains the file GEOMINFO.TXT that points to and describes the function of each SPICE kernel relevant to MDIS. LABEL Directory ------------------ The LABEL directory is optional in the MDIS archive. If present, it contains files that describe data format and organization. These format files (*.FMT suffix) are referenced by PDS labels that accompany data products. They are "include" files that are intended to be parsed as if they were part of the PDS labels that point to them. The purposes of keeping this information in a separate file are (a) to keep labels short and (b) to allow the information to be updated without having to update many labels. If the LABEL directory is present, see the file LABINFO.TXT for a description of the files in the LABEL directory. CALIB Directory ------------------ The CALIB directory contains the files needed to convert EDRs to calibrated images in units of radiance or I/F. The file CALINFO.TXT describes the files in the CALIB directory, as well as the calibration algorithm and how to apply conversions described in the files in the CALIB directory. BROWSE Directory ---------------- The BROWSE directory is optional in the MDIS archive. If present, it contains synoptic versions of data products to help identify products of interest. If the BROWSE directory is present, see the file BROWINFO.TXT for more information. EXTRAS Directory ---------------- The EXTRAS directory is optional in the MDIS archive. If present, it contains other materials that the user may find helpful, but that are beyond the scope of the required elements of the archive. If the EXTRAS directory is present, see the file EXTRINFO.TXT for more information. 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 Michele Gannon, Scott Murchie, and Louise Prockter.