PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
OBJECT = TEXT
PUBLICATION_DATE = 2001-07-16
NOTE = "INFO.TXT describes the Magnetometer (MAG)
data available on this volume."
END_OBJECT = TEXT
END
The DATA/MAG directory contains the Magnetometer (MAG) vector magnetic
field data. These data were acquired by the Magnetometer instrument
aboard the Mars Global Surveyor (MGS) spacecraft. The MAG data on this
disk cover the period 7/9/99 - 7/17/99.
The MAG data are calibrated and are provided in physical units (nT). In
addition, instrumental and spacecraft effects have been removed from the
data during processing.
Each MAG data file consists of an attached ASCII text header, followed
by an ASCII table containing the time series data. The table in each
file has fixed-length records of length 232 bytes. Each row of data
contains 24 columns, and is terminated by the ASCII record delimiter
characters carriage return and line feed.
MAG data are represented in the planetocentric (PC) and Sun-State (SS)
coordinate systems. In the SS coordinate system, the X-axis lies along
the instantaneous Mars-Sun vector and is positive toward the Sun. The
negative of Mars' velocity vector is a second (Y) reference vector, so
the vector cross product of X and Y yields a Z vector parallel to the
northward (upward) normal of the orbit plane of Mars. The PC coordinate
system is body-fixed and rotates with the body as it spins on its axis.
In the PC system, the Z-axis lies along the body rotation axis and is
positive in the direction of angular momentum. The X-axis lies in the
equatorial plane of the body, perpendicular to Z and in the direction
of the prime meridian as defined by the IAU. The Y axis completes the
right-handed set.
Each file in SS coordinates contains either one day of data or the data
near a single periapsis of the spacecraft. Each file in PC coordinates
contains data near a single periapsis.
The MAG data files reside in the following subdirectories of DATA/MAG:
SUNSTATE MAG data expressed in Sun-State coordinates.
PCENTRIC MAG data expressed in planetocentric coordinates.
The file naming convention for files in these subdirectories is
as follows:
99067.STS is interpreted as
99 = year 1999
067 = day of year 067 (where Jan. 1 = day of year 001)
STS = 'standard time series' format
The detached PDS label file describing the file 99067.STS is named
99067.LBL.
In addition to the data files, this disk contains documentation files
which describe the datasets on the disk, the instruments from which the
data came, and the Mars Global Surveyor spacecraft and mission. These
files are found in the CATALOG and DOCUMENT directories, and are
described in the files CATALOG/CATINFO.TXT and DOCUMENT/DOCINFO.TXT.
This disk also contains browse plots (PostScript files) summarizing the
MAG and Electron Reflectometer (ER) data on the disk. These plots are
contained in subdirectories of the BROWSE directory.
In addition to accessing MAG data files directly, users with Web
browsers can access them via links in the HTML file MAGDATA.HTM in
the EXTRAS directory. Such users also can navigate the entire disk
using the file AAREADME.HTM in the disk root directory.