Mars Global Surveyor MAG/ER Pre-Mapping Level 1 CD_ROM Series
Volume 16 (MGSM_1016)
Planetary Data System
|
Links to sections of this document: |
Links to data and documentation: |
|
|
|
|
|
|
|
|
This disk contains a subset of the Transition to Mapping data from the Mars Global Surveyor (MGS) Magnetometer and Electron Reflectometer (MAG/ER) instruments, submitted to the Planetary Data System (PDS).
Users are encouraged to provide comments back to the PPI Node of the PDS if errors or omissions are found either in data or in documentation. Please send comments by e-mail or U.S. mail to PDS Operator as defined at the end of this document.
Questions regarding data content, processing, or quality should be sent to
Dr. J.E.P. Connerney (jec@lepjec.gsfc.nasa.gov)
NASA Goddard Space Flight Center
Code 695
Greenbelt, MD 20771
This volume contains MGS MAG/ER data from the Transition to Mapping subphase of the orbit insertion mission phase (1999-02-04 to 1999-03-09). The data included on this volume are Mars data from days 1999-02-09 through 1999-02-19. Processed data in physical units from the Magnetometer are provided at full word downlink sampling resolution, while data from the Electron Reflectometer are provided at full downlink sampling resolution.
All data files are stored in the DATA branch of the directory tree. Each instrument is given a subdirectory, and each data set is located in that subdirectory or in a subdirectory beneath it. All data are stored in ASCII tables with attached MAG/ER team headers. Time values are expressed in Spacecraft Event Time (SCET).
The documentation for this volume is located in the CATALOG directory. Each data set is documented as part of the archive (MAG_DS.CAT, ER_DS.CAT); so are the MAG/ER instruments (MAG_INST.CAT, ER_INST.CAT), the MGS mission (MISSION.CAT) and spacecraft (MGS_HOST.CAT), the MAG/ER team and other relevant personnel (PERSON.CAT), and useful literature references (REF.CAT).
All data files on this CD-ROM are described by detached PDS labels (.LBL) and format files (.FMT). Metadata are stored as text files with the data. Information on the particular form of metadata used in the PDS catalog can be found in the CATALOG directory.
This CD-ROM is the sixteenth volume of the MGSM_1xxx sequence. These volumes contain MAG/ER data from the part of the mission before the mapping phase. The MGSM_1xxx volume sequence will have approximately 1 volume for every month during the premapping period.
The MGS MAG/ER Level 1 archive volume set contains two distinct sequences of disks, each with a different naming convention for its members. The sequence MGSM_1xxx (starting with MGSM_1001) contains premapping data, while the sequence MGSM_2xxx (starting with MGSM_2001) contains mapping phase data. This difference in volume names reflects the significant differences between mapping and premapping phases (for example, the orbits during the mapping phase are nearly circular while orbits in the premapping period can be strongly elliptical).
The disk is organized into a hierarchical directory structure. The disk is formatted according to both ISO 9660 and POSIX (UNIX) standards in order to accommodate users on a wide variety of platforms. This volume does not contain any Extended Attribute Records (XAR). Thus, VAX/VMS users may have some problems accessing files on this volume.
The data files on this volume are ASCII files. Data files are described by detached PDS labels, while text files have attached labels. A detached label file has the same name as the data file that it describes, but with the extension .LBL. For example, the file ORBFACTS.TAB is accompanied by the detached label file ORBFACTS.LBL in the same directory. File names within this archive comply with the "8.3" convention to conform with the ISO-9660 standard.
All document files, detached PDS labels, and HTML files are stream format files, with a carriage return (ASCII 13) and a line feed character (ASCII 10) at the end of the record. This allows the files to be read by MacOS, DOS, Windows, UNIX, and VMS operating systems. UNIX system and Macintosh users will see the unnecessary carriage return character (^M) at the end of each line. Mac users will see an unnecessary line feed (^J) character at the start of each line. ASCII tabular data files (*.TAB) are formatted so that they may be read directly into many database management systems (DBMS) or spreadsheet programs on various computers. All fields are of fixed length and are separated by white space (blank characters or commas). Character fields are left justified, and numeric fields are right justified. The "start byte" and "bytes" values listed in a PDS label do not include the white space 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 normal text file on other computers.
The document, PDS label, and ASCII table files on this volume can be viewed with a Web browser. Note that to view these files, the browser may need to be configured to recognize files with extensions of .LBL and .TAB as text files. Also, this disk contains HTML files whose links can be used for navigation of the data. Links to these HTML files can be found in the present document, at the top and elsewhere.
PDS labels are object-oriented. The object to which the label refers (e.g., SERIES, TABLE, etc.) is denoted by a statement of the form:
^object = location
in which the caret character (^, also called a pointer in this context) indicates that the object starts at the given location. For an object in the same file as the label, the location is an integer representing the starting record number or byte of the object (the first record/byte in the file is 1). If this value is omitted, then the data begin at record one (1). For an object located outside the label file, the location denotes the name of the file containing the object, along with the starting record or byte number.
Examples:
^TABLE = "EL980601.DAT"
^TABLE = ("19980601.DAT", 3)
The first example points would tell the user that file EL980601.DAT is described by a TABLE object and the data begin at record 1 of the file. The other TABLE object begins at record 3 of the file 19980601.DAT. In both cases, the data files exist in the same directory as the detached label file. Below is a list of the possible formats that use the ^object keyword.
^object = n
^object = n<BYTES>
^object = ("filename.ext",n)
^object = ("[dirlist]filename.ext",n)
^object = ("filename.ext",n<BYTES>)
^object = ("[dirlist]filename.ext",n<BYTES>)
where n is the starting record or byte number of the object, counting from beginning of the file (record 1, byte 1); default is record number.
<BYTES> indicates that number given is in units of bytes.
filename is upper-case file name.
ext is upper-case file extension.
dirlist is a period-delimited path-list of parent directories, in upper case, that specifies the object file directory (used only when the object is not in the same directory as the label file).*
* All PDS labels on this volume are located in the same directory as the file they describe, so this construct is not used here.
In cases where many files of the same format or structure are present, the structure description component from the label is detached from the primary label and placed in a separate file. This minimizes repetition of information which does not vary from file to file. In these cases, a format file (.FMT) contains the file structure information and the base label (.LBL) describes the parameters which vary from file to file (number of records, file name, start/stop time, etc.). When a format file is used within the PDS label the syntax is:
^STRUCTURE = filename
Example:
^STRUCTURE = ''ER_DATA.FMT''
(where the '' represents one double-quotation mark). Syntactically, the contents of the format file can be inserted directly into the base label in such a way that the entire file contents replace the single line ^STRUCTURE = filename.
There is a file called ERRATA.TXT found at the root level of this volume which contains a list of known deficiencies or caveats associated with data on this volume at the time this CD was published. Any changes or errors that are found on this or any MGSM_1xxx CD-ROM after the production of this volume can be obtained via the Web.
If you find an error on this disk, please report the error to the PDS Operator at the PPI Node of the PDS.
Internet: pds_operator@igpp.ucla.edu
Telephone: (310) 206-6073
U.S. Mail:
PDS Operator
c/o Dr. Raymond Walker
UCLA - IGPP
Los Angeles, CA 90095-1567
Only through the support and feedback of the users of these data can an effective errata list be maintained.
No software is provided with these data.
This section describes the volume structure and naming conventions for this disk. Below is a tree diagram of the CD-ROM, followed by a description of the directory function and key files in each directory.
MGSM_1xxx (root directory) | |- AAREADME.HTM The file you are reading now. Describes volume | contents, organization, and CD-ROM use. | |- AAREADME.TXT Describes volume contents, organization and CD-ROM | use. (The file you are reading now is an HTML | version of this file.) | |- ERRATA.TXT Describes known deficiencies or caveats in the data | or on this CD-ROM. (A Web version of this file, | which may be more up-to-date, can be obtained | via this link.) | |- VOLDESC.CAT High-level description of CD-ROM contents. | |- [BROWSE] PostScript files containing plots of trajectory and | | magnetic field data. | | | |-[RMS] 3-panel plots showing magnitude of B field along | | with RMS values of components BX and BY. | | | |-[MAG_CAL] Plots pertaining to Magnetometer calibration. | | | |- [CATALOG] Information on data sets and how they are processed | and produced. Also contains information regarding | Mars Global Surveyor, the instruments covered by | this volume, personnel involved, and references from | various documents including those contained in the | /CATALOG directory. | |- [DATA] Contains all data in a branching tree structure of | | subdirectories. | | | |- [ER] Data from the Electron Reflectometer (ER). | | | |- [MAG] Data from the Magnetometer (MAG). | | | | | |- [PCENTRIC] MAG data expressed in a planetocentric (PC) | | | coordinate system. | | | | | |- [SUNSTATE] MAG data expressed in a Sun-State (SS) | | coordinate system. | | | |- [ANCIL] Ancillary data pertaining to the spacecraft and | | its trajectory, in the form of kernel files. | |- [DOCUMENT] Documents describing the data on the volume. | |- [GEOMETRY] Table of spacecraft trajectory data, comprised | of data describing individual orbits, and kernel | files. | |- [INDEX] Contains a table of contents for all files located | on the CD-ROM and the volume sequence to date. |
Driver and Hardware Information
This disk has been formatted according to the ISO standard for CD-ROM production (9660) with level 1 compliance. Any system which complies with this standard (all of them should) should be able to access this disk.
The person most directly responsible for the construction and release of this CD-ROM is Dr. Mark Sharlow. He was the data engineer at the time this disk was created and understands as much about the disk structure and data organization as anyone. Other PPI personnel who may be aware of issues related to this CD-ROM include Mr. Steven Joy, the PPI Node Data Administrator, and Dr. Raymond Walker, the PDS/PPI Node manager. For questions or problems regarding this CD-ROM, please contact the PDS/PPI PDS operator:
Internet: pds_operator@igpp.ucla.edu
Telephone: (310) 206-6073
U.S. Mail:
PDS Operator
c/o Dr. Raymond Walker
3845 Slichter Hall
UCLA - IGPP
Los Angeles, CA 90095-1567
For questions regarding PDS Standards or other CD-ROM's available from the PDS, please contact the PDS Operator at the PDS Central Node (at JPL):
Internet: pds_operator@jpl.nasa.gov
Telephone: (818) 354-4321
U.S. Mail:
Planetary Data System, PDS Operator
Jet Propulsion Laboratory
Mail Stop 202-101
4800 Oak Grove Dr.
Pasadena, CA 91109-8099
The PDS, and the Planetary Plasma Interactions (PPI) Node in particular, assume no legal liability for errors on this disk. All users are encouraged to verify the "correctness" of the data prior to submitting any publications or other work based on these data. Errors on this disk should be reported back to the PPI Node of the PDS through the ERRATA reporting procedures described above.