• Data Set Overview
• =================

This Data Set contains Voyager 1 Magnetometer Data from the Interplanetary Cruise averaged to 48 s 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 differing Telemetry Modes of the Mission. In the Case of the Magnetometer Experiment, the Records contain both 1.92 s, 9.6 s and 48 s Averages. 1.92 s Averages are created from the detail Detail Data, 9.6 s Averages are created from 1.92 s Averages and 48 s Averages are created from the 9.6 s 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 s 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 used to define the Position of the Spacecraft. 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 Spin Axis of the Sun. The XY Plane of the IHG System 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.

The Magnetic Field Orientation is defined in relation to the Spacecraft. Drawing a Line from the Center of the Sun, which is the Origin of the IHG System, 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 as well. 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), 255-316, MHD Processes in the Outer Heliosphere, L. F. Burlaga.

• Data Format
• ===========

+-------------------------------------------------------------------+
| Num | Field | Description |

| 1 | Spacecraft ID | FLT1=Voyager 1, FLT2=Voyager 2 |
| 2 | Coordinate System | Heliographic, HG |
| 3 | Time (UTC) | Format: YY DDD HH MM SS MSS |
| 4 | Field Magnitude | in nT |
| 5 | Field Component 1 | in nT, HG Coordinates |
| 6 | Field Component 2 | in nT, HG Coordinates |
| 7 | Field Component 3 | in nT, HG Coordinates |
| 8 | Spacecraft Radial Distance | in AU |
| 9 | Spacecraft X Position | in AU, IHG Coordinates |
| 10 | Spacecraft Y Position | in AU, IHG Coordinates |
| 11 | Spacecraft Z Position | in AU, IHG Coordinates |
+-------------------------------------------------------------------+

Time Format Definitions: YY=Year, DDD=Day of Year, HH=Hour, MM=Minute, SS=Second, MSS=Millisecond

• 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
• ===============