DATA_SET_DESCRIPTION |
Data Set Overview
=================
This dataset contains Voyager 1 magnetometer data from the
interplanetary cruise averaged to 48 second samples in Heliographic
coordinates.
Data Processing
===============
The high resolution data submitted to the NSSDC has its origins in the
original MVS 'Summary' data sets formally produced on the NSSC IBM MVS
mainframe system. The original data sets contain a mix of engineering,
electron, magnetic field and plasma data. The Voyager magnetometer
(MAG) experiment now resides on a dedicated workstation where only MAG
data are processed.
All Voyager MAG data submitted to the NSSDC consists wholly of high
resolution LFM averages. These files consist of a set of averages
applied across all of the mission's differing telemetry modes. In the
case of the Magnetometer Experiment, the records contain both
1.92 second, 9.6 second and 48 second averages. 1.92 second averages
are created from the detail detail data, 9.6 second averages are created
from 1.92 second averages and 48 second averages are created from the
9.6 second averages.
All data in this NSSDC data set are interplanetary and in heliographic
coordinates (see below). An ASCII formated data set containing key
components of the 48 second magnetic field data and ephemeris data has
been created allowing more convenient access to high resolution Voyager
magnetometer data.
Coordinate System
=================
Interplanetary magnetic field studies make use of two important
coordinate systems, the Inertial Heliographic (IHG) coordinate system
and the Heliographic (HG) coordinate system.
The IHG coordinate system is use to define the spacecraft's position.
The IHG system is defined with its origin at the Sun. There are three
orthogonal axes, X(IHG), Y(IHG), and Z(IHG). The Z(IHG) axis points
northward along the Sun's spin axis. The X(IHG) - Y(IHG) plane lays in
the solar equatorial plane. The intersection of the solar equatorial
plane with the ecliptic plane defines a line, the longitude of the
ascending node, which is taken to be the X(IHG) axis. The X(IHG) axis
drifts slowly with time, approximately one degree per 72 years.
Magnetic field orientation is defined in relation to the spacecraft.
Drawing a line from the Sun's center (IHG origin) to the spacecraft
defines the X axis of the HG coordinate system. The HG coordinate
system is defined with its origin centered at the spacecraft. Three
orthogonal axes are defined, X(HG), Y(HG), and Z(HG). The X(HG) axis
points radially away from the Sun and the Y(HG) axis is parallel to the
solar equatorial plane and therefore parallel to the X(IHG)-Y(IHG) plane
too. The Z(HG) axis is chosen to complete the orthonormal triad.
An excellent reference guide with diagrams explaining the IHG and HG
systems may be found in Space and Science Reviews, Volume 39 (1984),
pages 255-316, MHD Processes in the Outer Heliosphere, L. F. Burlaga
[BURLAGA1984].
Data Format
===========
field descriptor
----- ----------
1. s/c identification (FLT1=Voyager 1)
(FLT2=Voyager 2)
2. coordinate system
(HG=heliographic)used for this data set
3. Time (UTC) format YY DDD HH MM SS MSS
YY = year
DDD = day of year
HH = hour
MM = minute
SS = second
MSS = millisecond
4. field magnitude (nT)
5. field component 1 (nT) - HG
6. field component 2 (nT) - HG
7. field component 3 (nT) - HG
8. spacecraft radial distance (AU)
9. spacecraft x position (AU) - IHG
10. spacecraft y position (AU) - IHG
11. spacecraft z position (AU) - IHG
Contact Information
===================
Principal Investigator:
Prof. Norman F. Ness
Bartol Research Institute
Univerity of Delaware
Newark, Delaware 19716-4793
Phone: (302) 831-8116
Fax: (302) 831-1843
Email: norman.ness@mus.udel.edu
Acknowledgement
===============
Use of these data in publications should be accompanied at minimum by
acknowledgements of the National Space Science Data Center and the
responsible Principal Investigator defined in the experiment
documentation provided here.
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