1. Preface *

2. Introduction *

3. Archive Volume Generation *

4. Archive Volume Contents *

5. Archive Volume Format *

6. Support Staff and Cognizant Persons *

Table 1 – Standard Data Products in MAG and ER Archive Collections *

Figure 1 – Generation of MAG/ER Archive Volumes During Mapping. *

1. Preface

This document describes the format and content of the MAG MAG and ER Standard Products Archive Collection on CD-R and CD-ROM media.

1. Distribution List

C. Acton

M. Acuna

R. Arvidson

J.E.P. Connerney

V. Henderson

S. Joy

M. Martin

D. Mitchell

R. Springer

T. Thorpe

R. Walker

2. Document Change Log

Change	Date	Affected Portions
Original outline	7/31/92	All
Update for MGS mission	5/17/99	all

3. TBD Items

The MAG-MAP Standard Product format is TBD. This product will not be defined until very late in the mission. This product is part of a separate archive collection

4. Acronyms and Abbreviations

ASCII	American Standard Code for Information Interchange
CD-R	Compact Disk - Recordable media
CD-ROM	Compact Disk - Read-Only Memory
DVD	Digital Video Disk
ER	Electron Reflectometer
GSFC	Goddard Space Flight Center
ISO	International Standards Organization
JPL	Jet Propulsion Laboratory
MAG	Magnetometer
MAG/ER	Magnetometer / Electron Reflectometer
MB	Megabytes
MGS	Mars Global Surveyor
MOI	Mars Orbital Insertion
NSSDC	National Space Science Data Center
PDB	Project Database
PDS	Planetary Data System
PPI	Planetary Data System, Planetary Plasma Interactions Node
RDR	Reduced Data Record
PSG	Project Science Group
SDVT	Science Data Validation Team
SFDU	Standard Formatted Data Unit
SIS	Software Interface Specification
SPO	Science Phasing Orbits
STS	Standard Time Series
TBD	To Be Determined
UCLA	University of California, Los Angeles

5. Glossary

Archive – An archive consists of one or more data sets along with all the documentation and ancillary information needed to understand and use the data. An archive is a logical construct independent of the medium on which it is stored.

Archive Volume, Archive Volume Set – A volume is a unit of media on which data products are stored; for example, one CD-ROM. An archive volume is a volume containing all or part of an archive; that is, data products plus documentation and ancillary files. When an archive spans multiple volumes, they are called an archive volume set. Usually the documentation and some ancillary files are repeated on each volume of the set, so that a single volume can be used alone.

Catalog Information – High-level descriptive information about a data set (e.g. mission description, spacecraft description, instrument description), expressed in Object Description Language (ODL) which is suitable for loading into a PDS catalog.

Data Product – A labeled grouping of data resulting from a scientific observation, usually stored in one file. A product label identifies, describes, and defines the structure of the data. An example of a data product is a planetary image, a spectral table, or a time series table.

Data Set – A data set is an accumulation of data products together with supporting documentation and ancillary files.

Standard Data Product – A data product generated in a predefined way using well-understood procedures, processed in "pipeline" fashion. Data products that are generated in a nonstandard way are sometimes called special data products.

 

2. Introduction

1. Content Overview

The Magnetometer and Electron Reflectometer (MAG/ER) are two instruments on the Mars Global Surveyor (MGS) orbiter that acquire data towards a common scientific objective. There is a single instrument team for both instruments. The data products are highly complementary and are archived together. The Standard Data Products generated by the MAG/ER instruments are listed in Table 1.

 

Table 1 – Standard Data Products in MAGER Archive Collection

Acronym	Standard Data Product
ER-STS	Electron Reflectometer Standard Time Series
MAG-STS	Magnetometer Standard Time Series
MAG-MAP	Martian Near-Surface Magnetic Field Map(s)

 

Each MAG-STS product is an ASCII file containing a time series of magnetic field vectors in geophysical units (nanotesla, nT) that have been corrected for instrumental and spacecraft effects (calibrated). In addition, these data have been transformed into geophysically meaningful coordinate systems. Each ER-STS product is also an ASCII file containing omni-directional electron fluxes from each of the nineteen (19) ER energy channels. The two STS data products are generated for all mission phases. The MAG-MAP product is a high-level data product that can only be produced at the end of the mapping phase of the mission. A single map product will delivered to the Planetary Data System (PDS) and included on the final archive volume of the prime mission.

This Software Interface Specification (SIS) describes the format, content, and generation of the MAG/ER Standard Product Archive Volumes. Section 3, Archive Volume Generation, describes the procedure for transferring data products to archive media. Section 4, Archive Volume Contents, describes the structure of the archive volumes and the contents of each file. Section 5, Archive Volume Format, describes the file formats used on the archive volumes. Finally, Section 6, Support Staff and Cognizant Persons, lists the individuals responsible for generating the archive volumes.

2. Scope

The specifications in this document apply to all MAG/ER standard product archive volumes that are produced on compact disk media during the Orbit Insertion, Science Phasing, and Aerobraking Phases of the Mars Global Surveyor mission. Most of the specifications in this document also apply to MAG/ER archive volumes containing data acquired during the Mapping Phase of the mission. The chief difference between the pre-Mapping Phases and Mapping Phase volumes is that there are no encounters with the moon Phobos during the Mapping Phase.

3. Applicable Documents

ISO 9660-1988, Information Processing - Volume and File Structure of CD-ROM for Information Exchange, April 15, 1988.

Arvidson, R., E. Guinness, and S. Slavney, Mars Global Surveyor Project Archive Generation, Validation, and Transfer Plan, MGS Document #542-312, 1998.

Connerney, J. E. P., and S. Joy, Mars Global Surveyor Magnetometer / Electron Reflectometer Standard Data Product Software Interface Specification Document (MGS-MAGER-SIS), MGS Document #??????, 1999

Planetary Science Data Dictionary Document, July 15, 1996, Planetary Data System, JPL D-7116, Rev. D.

Planetary Data System Data Preparation Workbook, February 1995, Version 3.1, JPL D-7669, Part 1.

Planetary Data System Standards Reference, July, 1995, Version 3.2. JPL D-7669, Part 2.

4. Audience

 

This specification is useful to those who wish to understand the format and content of the MAG/ER Standard Product Archive Collection. Typically, these individuals would be software engineers, data analysts, or planetary scientists.

 

 

3. Archive Volume Generation

1. Data Transfer and Validation Methods

The MAG/ER Standard Product Archive Collection is produced by the PDS Planetary Plasma Interactions (PPI) Node at the University of California, Los Angeles (UCLA), in cooperation with the MAG/ER Instrument Team. The PPI activities are funded by the Planetary Data System.

The Archive Collection includes data acquired during the Mars Orbit Insertion (MOI), Science Phasing Orbits (SPO-1, SPO-2), Aerobraking (AB-1, AB-2), and Mapping Phases of the MGS mission. The archive validation procedure described in this section applies to volumes generated during all phases of the mission. The first data volume for each of the mission phases is validated by using the PDS peer review procedures. Data processing presents new challenges in each of the mission phases and independent validation of these products is prudent. Subsequent volumes within mapping phases are validated by the Science Data Validation Team (SDVT).

A single archive volume set of MAG/ER data is produced for the entire MGS mission (see Figure 1, Generation of MAG/ER Standard Product Archive Volumes). When sufficient data for a new archive volume are ready for validation, the MAG/ER team will deliver a CD-R volume with the data to the PPI Node of the PDS. The PPI Node will create PDS documentation (label) files and ancillary products (index tables, html access files, etc). Each volume of standard products, documentation and ancillary products is stored on a recordable compact disk (CD-R) generated by PPI. All data formats are based on the Planetary Data System standards as documented in the PDS Standards Reference [section 2.3, Applicable Documents].

Six (6) CD-R copies of each volume are produced. Two copies are sent back to the MAG/ER team (GSFC and Berkeley) and one copy is sent to the SDVT for review. Included is a Manifest that lists the contents of the volume in detail, and an Error Report Log that describes any known deviations from the Manifest or other anomalies. The remaining two copies remain at UCLA for online access and backup. Upon approval of a volume from the SDVT, the volume is considered officially released to the PDS as defined by the Mars Global Surveyor data release policy [Arvidson et al., 1998]. The PPI Node then sends the fourth copy of the volume to the PDS Central Node to be forwarded to a CD-ROM vendor for replication.

All volumes created by the vendor for the PDS are delivered to the PPI Node for further distribution. The PPI maintains a mailing list of scientists interested in received fields and particles (F&P) data from the inner planets. Users can add or remove themselves from the MGS mailing list through a web page maintained at PPI. The PDS requests enough copies to serve its anticipated user needs, and funds the production of those copies. The NSSDC may choose to order (and pay for) additional copies at the time of the PDS order. If the NSSDC chooses to purchase these CD-ROMS, the vendor will ship them directly to the NSSDC. The NSSDC and the PDS are each separately responsible for making additional future copies to meet the needs of their user communities.

Figure 1 – Generation of MAG/ER Archive Volumes During Mapping. The MAG/ER Team generates MAG/ER standard data products and delivers them on CD-R media to the Planetary Plasma Interactions Node of the PDS. PPI generates archive volumes on recordable CD-R media. Six (6) copies of each archive volume are made. Two (2) copies are sent back to the MAG/ER Team (GSFC and Berkeley) and another to the MGS Science Data Validation Team (SDVT) for validation. Two (2) copies are kept as backups at the PPI Node one of which is placed online in the PPI web pages under an "in review, use caution" banner. The SDVT sends validation reports to the MGS Project Science Group, which recommends either that the volume be released or, in case of errors, that it be regenerated. When a volume passes validation and is approved by the MGS Project for release, the sixth CD-R copy is delivered to a CD-ROM vendor for replication. The vendor mails the CD-ROM archive volumes to the PPI Node and the NSSDC. The PPI Node then distributes the CD-ROMs to scientists on its distribution list and to any other users who request copies. The distribution disk then replaces the CD-R volume on the PPI web pages and the under review warning is removed.

---

 

 

In the event that a volume is found to contain errors, the reviewers can recommend one of two courses of action: fix the disk or publish as is with a note in the ERRATA.TXT file. If the errors are minor, typically minor errors in the documentation, the volume can be published if the appropriate notes added to the volume's errata file and the error(s) are corrected on subsequent volumes. If the errors are major, typically involving errors in the data themselves, then the volume must be corrected, re-generated, and sent back out for review.

2. Data Product Sizes and Delivery Rates

Table 2 summarizes sizes and delivery rates for the MAG/ER Standard Product that contains MAG-STS, ER-STS, and Ancillary data products.

 

Table 2 – MAG/ER Standard Product Sizes and Delivery Rates

Product	Product Size	Production Rate (approximate)	Days to Fill One 650-Mbyte Volume	Volumes for 687-Day Primary Mission
MAG-STS	6-12 MB	1 product per day ~10 MB per day	30-40	25
ER-STS	2-4 MB	1product per day ~3 MB per day
Ancillary Data	<10 MB	1 set / volume
*Since the MAG-MAP product is only produced at the end of the mission, it is not included in this table. The MAG-MAP product volume is small.

 

The current plan is for each MAG/ER Standard Product Archive Volume to contain at most 650 Mbytes of data, including documentation and ancillary files, based on the storage capacity of CD-ROMs readable by most CD-ROM drives. Some CD-ROMs may be under-filled when doing so prevents volumes from crossing logical data units (mission phases, etc.). If DVD technology becomes a widely adopted standard during the mission, the instrument team and PDS reserve the right to adopt this media with its substantially larger storage capacity.

The Archive Volumes are produced when enough data are accumulated, processed, and validated to fill a disk. The MAG/ER data are accumulated at the rate of about 70-90 MB per week, so CD-WO volumes containing these data are produced about every 7-8 weeks during the Mapping Phase. The time required to process the data and validate the products is one (1) year. The MAG-MAP is a single product generated after the primary mission is completed. This product is small and will be included on the final volume containing data from the prime mission.

3. Interface Media Characteristics

All volumes in the MAG/ER Standard Product Archive Collection conform to ISO 9660 standards [ISO 9660, 1988] with level-1 compliance. If the archive media changes from CD-ROM to DVD, there will be no changes to the file naming or other conventions associated with the ISO 9660 (level 1) standard.

4. Backup and Duplicates

UCLA keeps two copies of each CD-R volume. One volume is placed in the jukebox at UCLA in order to make the data web accessible. The other copy is a backup that can be used if the CD-R sent to the vendor becomes lost or damaged. The three CD-R volumes sent to the MAG/ER Team and the SDVT for review do not need to be returned to UCLA.

5. Labeling and Identification

Each MAG/ER CD-ROM bears a volume ID using the last two components of the volume set ID [PDS Standards Reference, 1995]. The MAG/ER volume set ID is USA_NASA_JPL_MGSM_1nnn where nnn is the sequence number of the individual volume. Hence the first MAG/ER volume has the volume ID MGSM_1001.

 

 

4. Archive Volume Contents

This section describes the contents of the MAG/ER Standard Product Archive Collection volumes, including the file names, file contents, file types, and organization responsible for providing the files. The complete directory structure is shown in Appendix A. All the ancillary files described herein appear on each MAG/ER volume, except where noted. See the MAG/ER Data Product SIS documents [MAG/ER SIS, 1999] for examples of PDS labels for each type of product.

1. Root Directory Contents

The following files are contained in the Root Directory, and are produced by the PPI Node at UCLA:

File Name	File Contents	File Provided By
AAREADME.TXT	This file completely describes the volume organization and contents (PDS label attached).	PPI Node
AAREADME.HTM	Hypertext version of AAREADME.TXT	PPI Node
AAREADME.LBL	A PDS detached label that describes AAREADME.HTM.	PPI Node
ERRATA.TXT	A cumulative listing of comments and updates concerning all MAG/ER Standard Data Products on all MAG/ER compact disk volumes published so far	PPI Node
VOLDESC.CAT	A description of the contents of this volume in a PDS format readable by both humans and computers	PPI Node

2. INDEX Directory Contents

The following files are contained in the Index Directory and are produced by the PPI Node.

File Name	File Contents	File Provided By
INDXINFO.TXT	A description of the contents of this directory	PPI Node
CUMINDEX.TAB	A table listing all MAG/ER products published so far in this volume set, including the data on this volume	PPI Node
CUMINDEX.LBL	A PDS detached label that describes CUMINDEX.TAB	PPI Node
INDEX.TAB	A table listing all MAG/ER products on this volume	PPI Node
INDEX.LBL	A PDS detached label that describes INDEX.TAB	PPI Node

4. DOCUMENT Directory Contents

The following files are contained in the Document Directory and are produced or collected by the MAG/ER team.

File Name	File Contents	File Provided By
DOCINFO.TXT	A description of the contents of this directory	PPI Node
MAGERSIS.HTM	The MAG/ER standard data product SIS as hypertext.	MAG/ER Team
MAGERSIS.PDF	The MAG/ER standard data product SIS as a PDF file readable with Adobe Acrobat Reader software	MAG/ER Team
MAGERSIS.LBL	A PDS detached label that describes both MAGERSIS.HTM and MAGERSIS.PDF.	PPI Node
VOLSIS.HTM	The Archive Volume SIS (this document) as hypertext	PPI Node
VOLSIS.PDF	The Archive Volume SIS (this document) as a PDF file.	PPI Node
VOLSIS.LBL	A PDS detached label that describes both VOLSIS.HTM and VOLSIS.PDF.	PPI Node

5. CATALOG Directory Contents

The files in the Catalog directory provide a top-level understanding of the Mars Global Surveyor Mission, spacecraft, instruments, and data sets in the form of completed PDS templates. The files are produced or collected by the MAG/ER team. The files in this directory are coordinated with the PDS data engineer.

File Name	File Contents	File Provided By
CATINFO.TXT	A description of the contents of this directory	PPI Node
MAG_DS.CAT	PDS data set catalog description of the MAG-STS data	MAG/ER Team
ER_DS.CAT	PDS data set catalog description of the ER-STS data	MAG/ER Team
MGS_HOST.CAT	PDS instrument host (spacecraft) catalog description of the MGS spacecraft	Geosciences Node
MAG_INST.CAT	PDS instrument catalog description of the MAG instrument	MAG/ER Team
ER_INST.CAT	PDS instrument catalog description of the ER instrument	MAG/ER Team
MISSION.CAT	PDS mission catalog description of the MGS mission	Geosciences Node
PERSON.CAT	PDS personnel catalog description of the MAG/ER Team members and other persons responsible for generating data products	MAG/ER Team
MAG_REF.CAT	References mentioned in other *.CAT files	PPI Node

 

 

6. GEOMETRY Directory Contents

Some basic orbit information is tabulated for the user and included with the archive in the GEOMETRY directory. The orbit summary data that are relevant to the orbits contained on each volume are included in the ASCII file ORBFACTS.TAB. The parameters included in the orbit facts file include: orbit number, periapsis UTC, periapsis sclk, apoapsis UTC, Solar Latitude, Longitude and Range at periapsis, and the Planetocentric Latitude, Longitude, and Altitude at periapsis.

File Name	File Contents	File Provided By
GEOMINFO.TXT	A description of the contents of this directory	PPI Node
ORBFACTS.TAB	ASCII table with orbit summary data	MAG/ER Team
ORBFACTS.LBL	Detached PDS label describing the ORBFACTS table	PPI Node

7. DATA (Standard Products) Directory Contents and Naming Conventions

The Data directory contains the actual data products and ancillary information files produced by the MAG/ER team. The MGS-STS, ER-STS, and ancillary data files are stored in separate subdirectories of the main data directory.

Required Files

In every directory beneath the DATA directory there is a file named INFO.TXT that is an ASCII text description of the directory contents. Every file in the DATA path of an archive volume must be described by a PDS label. Text documentation files will have internal (attached) PDS labels and data files will have external (detached) labels. Detached PDS label files have the same root name as the file they describe but have the suffix ".LBL". In directories where there are multiple data files with the same internal table structure, the table column description is included in a single format file (.FMT) that is referenced by a pointer within the PDS label files. This prevents the needless repetition of information that is not changing within the PDS label files. DATA / MAG Directory Contents

The MAG-STS data product is a variable length, ASCII data file with an attached header followed by a time series (table) of magnetic field vectors. The header internally documents the file contents and is used by the MAG/ER team to facilitate its automated use in graphics and analysis software (not provided). Each file is also described by a detached PDS label file (*.LBL). The columns of the data tables do not change from file to file within a directory. To reduce redundancy, the MAG data table columns are described by a single PDS format file (MAG_DATA.FMT) that is referenced in each PDS label file.

As stated previously, the MAG-STS data product consists of data files containing data in two (2) primary Mars centered-coordinate systems: Sun-State (SS) and Planetocentric (PC). Data acquired in the vicinity of Phobos on a few of the pre-Mapping Phase orbits are archived in similar Phobos-centered coordinate systems.

The Sun-State coordinate system is defined such that its principal direction vector (x) is the instantaneous vector from the Mars center of mass to the Sun center of mass. The secondary vector used to define this coordinate system is the Martian ecliptic normal (z), which is taken to be positive "upward". Since this coordinate system can be generated by using vector cross products of the state vector of Mars as viewed from the Sun (after changing the sign of the velocity vector), this coordinate system is called a Sun-State coordinate system. This coordinate system is analogous to the GSE (Geocentric Solar Ecliptic) coordinate system that is widely used at Earth. The Sun-State coordinate system is useful for analyzing the solar wind and IMF interactions with the Martian system.

The planetocentric coordinate system is fixed to Mars and is useful for analyzing phenomenon of Martian origin. The z-axis is taken along the Martian spin axis, positive in the direction of angular momentum. The x-axis is defined to lie in the equatorial plane, perpendicular to z, and in the direction of the Martian prime meridian as define by the International Astronomical Union (IAU) 1994 report (Pole Right Ascension: 317.681^o, Pole Declination: +52.886^o, Prime Meridian: 176.901^o, Rotation Rate: +350.8919830^o/24 hours).

Phobos encounters occur occasionally in some of, but not all, pre-Mapping phases of the mission. When Phobos encounter data are available, they are included in the archive in Phobos-centered coordinates. The Sun-State coordinate system at Phobos does not change its principal directions as described previously, however, distances are measured from the center of Phobos rather than Mars. Planetocentric coordinates are fixed to Phobos with the z-axis along the Phobos rotation axis, positive in the direction of angular momentum. The x-axis is defined to lie in the equatorial plane, perpendicular to z, and in the direction of the Phobos prime meridian as defined by the International Astronomical Union (IAU) 1994 report (Pole Right Ascension: 317.68^o, Pole Declination: +52.90^o, Prime Meridian: 35.06^o, Rotation Rate: +1128.8445850^o/24 hours). Since Phobos is phase locked, the x-axis always points in the direction of Mars. Again, the Sun-State coordinate system is useful in the analysis of the solar wind and IMF interactions with Phobos and the planetocentric coordinate system is useful for studying Phobos itself.

The MAG-STS data product is divided into subdirectories by coordinate system. Data in Sun-State coordinates are stored in the SUNSTATE subdirectory and those in planetocentric coordinates are stored in the PCENTRIC subdirectory. In order to avoid confusion, data in the vicinity of Phobos will be archived on separate volumes rather than with the rest of the "Mars" data. This organization will also facilitate the distribution of Phobos only or Mars only volumes to researchers not interested in the other target. The DATA/MAG directory on the Phobos volumes will have the same two subdirectories as the Mars volumes.

1. DATA / ER Directory Contents

The ER-STS Standard Product data files are stored in the DATA/ER subdirectory. The ER data do not require further subdivision to separate data by target or coordinate system. All data are archived in ASCII files that contain MAG/ER team attached headers, similar to the MAG file headers. Each file is also described by a detached PDS label file (*.LBL)

The ER-STS data product is a variable length, ASCII data file with an attached header followed by a time series (table) of omni-directional electron fluxes for 19 energy channels. The header internally documents the file contents and is used by the MAG/ER team to facilitate its automated use in graphics and analysis software (not provided). In addition, each file is described by a detached PDS label file (*.LBL). The columns of the data tables do not change from file to file within a directory. To reduce redundancy, the ER data table columns are described by a single PDS format file (MAG_DATA.FMT) that is referenced in each PDS label file.

2. DATA / ANCIL Directory Contents

In addition to the standard data products, the MAG/ER team has provided some ancillary information files in the form of SPICE kernels. Although these files are not strictly data, they may provide users of the data products with some additional insight into the spacecraft and instrument operations during data acquisition.

File Name	Description	Source
MAG_ER.TI	NAIF instrument kernel that describes the mounting geometry of the MAG/ER instrument sensors	MAG/ER Team
MO_OBJ.KER	A definitions file that describes the objects that might be present in the MAG or ER STS headers.	MAG/ER Team
PCK00005.TPC	A NAIF planetary constants kernel that gives the values of the various parameters (Mars radii, Mars pole right ascension, etc.) that have been used in the processing of the data.	NAIF

3. Browse Data

In addition to digital magnetometer data, quick-look or "browse" plots of the data in planetocentric coordinates are included on the archive volumes. These data are stored in the BROWSE directory off of the root of the archive volume. There are four (4) types of plot files for each periapsis pass: RMS values, and XY-Plane, XZ-Plane, and YZ-Plane projections of the magnetic field along the trajectory. Each type of plot file is stored in a separate subdirectory of the BROWSE directory (RMS, XYPLANE, XZPLANE, YZPLANE). Browse files are created by the MAG/ER team in Adobe Postscript (PS-Adobe-3.0) format. All of the browse files in a single directory are described by a single detached PDS label file (dirname.LBL).

4. File Naming Conventions

All Standard Time Series (STS) Products conform to the file naming convention

yyddd[Px].STS

where:

yy is the last 2 digits of the year in which the data were acquired,

ddd is the 3 digit (zero padded) day of year in which the data were acquired

The Px portion of the file name is optional. If present, this pair of characters is used to define the periapsis of day (daily orbit number). If present,

P is literal, and
x is the daily orbit periapsis number.

The MAG Postscript (PS) browse plot files conform to the naming convention

yydddPx.PS
where:

yy is the last 2 digits of the year in which the data were acquired,

ddd is the 3 digit (zero padded) day of year in which the data were acquired

P is literal, and

x is the daily orbit periapsis number.

All additional information about the data file content (instrument, target, coordinate system, etc.) is derived from the file location in the directory tree.

5. Archive Volume Format

This section describes the format of MAG/ER Standard Product Archive Volumes. Data that comprise the MAG/ER Standard Product Archives will be formatted in accordance with Planetary Data System specifications [Planetary Science Data Dictionary, 1996; PDS Data Preparation Workbook, 1995; PDS Standards Reference, 1995].

1. Disk Format

Archive Volumes have a compact disk format that is compatible with the computer operating systems MS-DOS, Macintosh, and SunOS. The MAG/ER CD-ROM format is in accordance with ISO 9660 level 1 Interchange Standard [ISO 9660, 1988].

2. File Formats

The following section describes file formats for the kinds of files contained on Archive Volumes. For more information, see the PDS Data Preparation Workbook [1995] and Appendix B.

1. Document File Format

Document files with the .TXT suffix exist in all directories. They are ASCII files with embedded PDS labels. All document files contain 80-byte fixed-length records, with a carriage return character (ASCII 13) in the 79th byte and a line feed character (ASCII 10) in the 80th byte. This allows the files to be read by the MacOS, DOS, UNIX, OS2, and VMS operating systems.

In general, documents are provided in ASCII text format. However, some of the documents in the Document directory contain formatting and figures that cannot be rendered as ASCII text. Each of these documents is given in two formats, hypertext and PDF. The hypertext file contains ASCII text plus hypertext markup language (HTML) commands that enable it to be viewed in a Web browser such as Netscape Navigator or Microsoft Internet Explorer. Hypertext documents may reference ancillary files such as images that are incorporated into the document by the Web browser. The second 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.

2. Tabular File Format

Tabular files (.TAB suffix) exist in the INDEX and GEOMETRY directories. Tabular files are ASCII files formatted for direct reading into many database management systems on various computers. All fields are separated by commas, and character fields are enclosed in double quotation marks ("). 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" and "bytes" values listed in the labels do not include the commas between fields or the quotation marks surrounding character 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.

All tabular files are described by detached PDS label files. A detached PDS label file has the same name as the data file it describes, with the extension .LBL; for example, the file INDEX.TAB is accompanied by the detached label file INDEX.LBL in the same directory.

3. PDS Label Format

All data files in the MAG/ER Standard Product Archive Collection have PDS labels [Planetary Science Data Dictionary, 1996; PDS Standards Reference, 1995]. These labels are all detached from the data files (same file name prefix, .LBL suffix). For examples of PDS labels for each type of data product, see the Data Product SIS [MAGERSIS, 1999].

A PDS label, whether embedded or detached from its associated file, 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 a PDS 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 = ("98118P1.STS",1)

^TABLE = ("98118P1.STS",1025 <BYTES>)

indicates that the HEADER object begins at record 1 and that the TABLE object begins at byte 1025 of the file 98D118P1.STS. The file 98118P1.STS must be located 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 <BYTES>

^object = "filename.ext"

^object = ("filename.ext", n)

^object = ("filename.ext", n <BYTES>)

 

where

n is the starting record or byte number of the object, counting from the beginning of the file (record 1, byte 1),

<BYTES> indicates that the number given is in units of bytes,

filename is the up to 8 character, alphanumeric upper-case file name,

ext is the 3 character upper-case file extension,

All detached labels contain 80-byte fixed-length records, with a carriage return character (ASCII 13) in the 79th byte and a line feed character (ASCII 10) in the 80th byte. This allows the files to be read by the MacOS, DOS, UNIX, OS2, and VMS operating systems.

4. Catalog File Format

Catalog files (suffix .CAT) exist in the Root and Catalog directories. They are formatted in an object-oriented structure consisting of sets of 'keyword = value' declarations.

5. Science Data File Formats

1. MAG-STS Data Product Format

A MAG-STS product is organized as a table of ASCII data for a single day or fraction of day from a single orbit. Preceding the tabular data is a text header that describes the file contents and processing parameters. Each data record contains two (2) UTC time stamps using different date/time representations, a magnetic field vector, the instrument gain (range), and the spacecraft position vector at the sample time. For information about the format and contents of a MAG-STS product, see the MAGER SIS [1999].

2. ER-STS Data Product Format

An ER-STS product is organized as a table of ASCII data for a single day. Preceding the tabular data is a text header that describes the file contents and processing parameters. Each data record contains a time stamp (UTC) and nineteen omni-directional electron flux values spanning the various energy ranges of the detector. For more information about the format and contents of a ER-STS product, see the MAGER SIS [1999].

3. MAG-MAP Data Product Format

TBD

7. Support Staff and Cognizant Persons