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Magnetometer Data

in the Mars Global Surveyor MAG/ER Level 1 Archive

 

Overview

The Magnetometer (MAG) vector magnetic field data reside in the directory DATA/MAG. These data were acquired by the Magnetometer instrument aboard the Mars Global Surveyor (MGS) spacecraft. The MAG data on this disk cover the period Oct. 18 - Nov. 14, 2000. The data files are in two subdirectories: one for data in planetocentric coordinates (PCENTRIC) and one for data in Sun-State coordinates (SUNSTATE). The files contain ASCII tables of time series data and are referred to as standard time series (STS) files.

The 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 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. Data are housed in the subdirectories PCENTRIC or SUNSTATE according to which system they embody. 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 (Mars) 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 or PC coordinates contains one day of data.

This disk also contains browse plots which summarize the MAG and other data.

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Documents

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.

The following files in CATALOG are of particular interest to MAG data users.

The DOCUMENT directory contains the Software Interface Specification document for the data, in HTML and Microsoft Word document formats. (An ASCII text version is included for the sake of completeness, but is not fully formatted.)

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File Formats

The files on this disk are in level 1 compliance with the ISO 9660 standard. The MAG data are provided as ASCII tables of time series data.

Each MAG data file has an attached header that contains text describing the file processing and structure. The content of the headers is described in MAG_DS.CAT.

What follows is a very brief summary of the format of the data in the MAG files. All of the data fields indicated here, including the calibration columns, are explained more fully in the PDS format file MAG_DATA.FMT found in the subdirectories; that file is both human-readable and machine-readable. Note that the data file headers do not conform to this format.

sample UT

Time (UT) as year, day of year, hour, minute, second, and millisecond.

decimal day 

Time as decimal day of year. (0000 hours on Jan. 1 = decimal day 1.000)

mag_vector 

Array[3] giving B-field components in the order Bx, By, Bz.

range

Gain range of MAG instrument.

sc_pos_vector 

Array[3] giving location of spacecraft (x, y, z).

calibration columns 

15 more columns, relevant to understanding the Magnetometer calibration.

Here are three lines of data with headings added, as an example of this format. Due to space limitations, only the first nine columns are displayed; the rest of each line is indicated by three dots. (Note: these data may be displayed with spacing different from that of the actual data. Each data line ends with two ASCII record delimiter characters, carriage return and line feed.)

sample UT

decimal day

Bx

By

Bz

range

sc_pos x

sc_pos y

sc_pos z

...

1998 87 0 26 51 371

87.018650127

-1.119

-1.059

4.960

11.

-9018.001

2299.323

-10512.695

...

1998 87 0 26 54 371

87.018684850

0.083

-1.377

2.719

11.

-9018.060

2300.060

-10507.870

...

1998 87 0 26 57 371

87.018719572

1.146

1.021

-2.139

11.

-9018.118

2300.797

-10503.042

...

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Browse Files

In addition to the data files, this disk contains PostScript browse plots summarizing the magnetic field data on the disk. These plots are contained in the BROWSE directory. They are housed in two subdirectories, corresponding to two different kinds of plots: RMS and MAG Calibration. The RMS plots are 3-panel plots of magnetic field magnitude and of RMS values of components Bx and By (in sensor coordinates). The MAG Calibration plots pertain to the calibration of the Magnetometer instrument.

Return to link in Overview section

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Links to Data and Browse Files

The links in the table below can be used to navigate the MAG data files and browse files on this disk.

The file naming convention for these data files is illustrated by the following example. (The file mentioned here, from PCENTRIC, is only an example; there are many more such files on the disk.)

00292.STS is interpreted as

00 = year 2000
292 = day of year 292 (where Jan. 1 = day of year 001)
STS = "standard time series" format

00292.LBL is the name of the PDS label file which describes the data file 00292.STS. Such label files provide descriptive information in a format which is both human-readable and machine-readable.

The naming convention for RMS browse files is similar to that for the data files:

00292.PS is interpreted as

00 = year 2000
292 = day of year 292 (where Jan. 1 = day of year 001)
PS = PostScript file.

Note: To make full use of the .LBL files in the following table, you must have a MAG_DATA.FMT file, for the correct coordinate system, in the same directory as each .LBL file. Obtain these MAG_DATA.FMT files via these two links:

MAG_DATA.FMT (Planetocentric)        MAG_DATA.FMT (Sun-State)

 

Date

Data Files (Planetocentric)

Data Files (Sun-State)

Browse Files

 

File

Label

File
Bytes

File
Records

File

Label

File
Bytes

File
Records

 

10/18/00

00292.STS

00292.LBL

5460703

23847

00292.STS

00292.LBL

5460703

23847

00292.PS

10/19/00

00293.STS

00293.LBL

6479647

28239

00293.STS

00293.LBL

6479647

28239

00293.PS

10/20/00

00294.STS

00294.LBL

6266207

27319

00294.STS

00294.LBL

6266207

27319

00294.PS

10/21/00

00295.STS

00295.LBL

6580335

28673

00295.STS

00295.LBL

6580335

28673

00295.PS

10/22/00

00296.STS

00296.LBL

5979154

26082

00296.STS

00296.LBL

5979154

26082

00296.PS

10/23/00

00297.STS

00297.LBL

6629983

28887

00297.STS

00297.LBL

6629983

28887

00297.PS

10/24/00

00298.STS

00298.LBL

5913567

25799

00298.STS

00298.LBL

5913567

25799

00298.PS

10/25/00

00299.STS

00299.LBL

6596575

28743

00299.STS

00299.LBL

6596575

28743

00299.PS

10/26/00

00300.STS

00300.LBL

5878767

25649

00300.STS

00300.LBL

5878767

25649

00300.PS

10/27/00

00301.STS

00301.LBL

6357383

27712

00301.STS

00301.LBL

6357383

27712

00301.PS

10/28/00

00302.STS

00302.LBL

5902431

25751

00302.STS

00302.LBL

5902431

25751

00302.PS

10/29/00

00303.STS

00303.LBL

6422111

27991

00303.STS

00303.LBL

6422111

27991

00303.PS

10/30/00

00304.STS

00304.LBL

5872735

25623

00304.STS

00304.LBL

5872735

25623

00304.PS

10/31/00

00305.STS

00305.LBL

6185007

26969

00305.STS

00305.LBL

6185007

26969

00305.PS

11/01/00

00306.STS

00306.LBL

5086418

22234

00306.STS

00306.LBL

5086418

22234

00306.PS

11/02/00

00307.STS

00307.LBL

6574071

28646

00307.STS

00307.LBL

6574071

28646

00307.PS

11/03/00

00308.STS

00308.LBL

6036063

26327

00308.STS

00308.LBL

6036063

26327

00308.PS

11/04/00

00309.STS

00309.LBL

6203103

27047

00309.STS

00309.LBL

6203103

27047

00309.PS

11/05/00

00310.STS

00310.LBL

6199391

27031

00310.STS

00310.LBL

6199391

27031

00310.PS

11/06/00

00311.STS

00311.LBL

6583583

28687

00311.STS

00311.LBL

6583583

28687

00311.PS

11/07/00

00312.STS

00312.LBL

5857887

25559

00312.STS

00312.LBL

5857887

25559

00312.PS

11/08/00

00313.STS

00313.LBL

6533471

28471

00313.STS

00313.LBL

6533471

28471

00313.PS

11/09/00

00314.STS

00314.LBL

5553503

24247

00314.STS

00314.LBL

5553503

24247

00314.PS

11/10/00

00315.STS

00315.LBL

6500063

28327

00315.STS

00315.LBL

6500063

28327

00315.PS

11/11/00

00316.STS

00316.LBL

6177119

26935

00316.STS

00316.LBL

6177119

26935

00316.PS

11/12/00

00317.STS

00317.LBL

6132575

26743

00317.STS

00317.LBL

6132575

26743

00317.PS

11/13/00

00318.STS

00318.LBL

5753719

25110

00318.STS

00318.LBL

5753719

25110

00318.PS

11/14/00

00319.STS

00319.LBL

4228319

18535

00319.STS

00319.LBL

4228319

18535

00319.PS

 

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