File: VY1MAG_1H_FMT.txt                 Version: NSSDC 11/15/2001 JFC
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Voyager 1 Hourly Average Interplanetary Magnetic Field Data, ASCII

Date Coverage: 1977-09-05 to 1989-12-31

Version Date: 1995-02-09

NSSDC Data Set ID: 77-084A-05O 

Spacecraft Source: Voyager 1

Experiment Source: Voyager 1 Triaxial Fluxgate Magnetometer

Principal Investigator: 

   Dr. Norman F. Ness
   Bartol Research Institute
   University of Delaware
   Newark, DE 19716-4793
   Ph: 302-831-8116
   Fx: 302-831-1843
   E-mail: bartol::nfness

Data Set Contact: 

   Sandy Kramer 
   Laboratory for Extraterrestrial Physics
   Code 692, NASA Goddard Space Flight Center
   Greenbelt, MD 20771
   Ph: 301-286-4957
   E-mail: z1sbk@lepvgr.gsfc.nasa.gov

Data Set Description:

This data set contains hour averages of the interplanetary magnetic field 
(IMF) measurements obtained by the triaxial fluxgate magnetometer (MAG)
experiment on Voyager 1. Identical instruments on Voyager 1 and 2 were 
designed to measure the IMF between  Earth and Saturn (10 AU) during the 
primary Voyager mission. The  design and performance yielded absolute 
accuracies to better than < 0.1 nT. In general, each component of the IMF 
hourly average has an uncertainty of up  to (+/- 0.05 nT) in the region 
beyond 10 AU. More accurate measurements can be  obtained by special 
processing of the data, but it was not feasible to do this for the entire 
data set included here. The magnetic field magnitude in nT is provided 
along with angles of the field vector in the spacecraft-centered 
Heliographic (HG) coordinate system, also known as RTN. The X-HG axis is 
directed from the Sun to the spacecraft, Y-HG is the cross product of the 
solar rotation axis and X-HG, and Z-HG completes the orthogonal axis system. 
The accompanying format description file defines the transformation of the 
HG angles to vector components. Cartesian coordinates are given for the 
spacecraft in the sun-centered Inertial Heliographic (IHG) system, where 
the Z-IHG axis is parallel to the solar rotation axis, X-IHG points towards 
the ascending node direction of the solar equator's intersection with the
Ecliptic, and Y-IHG is parallel to the solar equator and completes the
orthogonal system. The MAG instruments are described by K. W. Behannon et 
al., Space Science Reviews, 21, 235, 1977. The data and coordinates are 
described by L. F. Burlaga, Space Science Reviews, 39, 255, 1984.

Data Set Files:

   VY1MAG_1H_FMT.txt - format description file (ASCII), volume = 6 MB 

   VY1MAG_1H.asc - hourly average data file (ASCII)

Data File Parameter Format: VY1MAG_1H.asc

   s/c id (1 = Voyager-1, 2 = Voyager-2)
   year (0-99)
   day  (1 = Jan. 1)
   hour (0-23)
   x position component (A.U. - IHG coordinates)
   y "                "
   z "                "
   r = sqrt(x*x+y*y+z*z)
   F1 - field magnitude (nT)  ( avg(F2(48sec)) )
   F2 - field modulus (nT)  ( norm (B1,B2,B3) )
   delta - latitudinal angle (degrees - HG coordinates)
   lambda - longitudinal angle (degrees - HG coordinates)

   Fill data = 0.0

   Data is provided in ASCII format with each field separated by a space 
   to allow a Fortran list directed read.

   MAG field components may be recovered using F2, delta and lambda.

      BR = F2*COS(lambda)*COS(delta)      * Fortran users need to convert
      BT = F2*SIN(lambda)*COS(delta)        degrees to radians before 
      BN = F2*SIN(delta)                    using trig fcns.


Related Information and Data:

Further details on the spacecraft, experiment, data sets at NSSDC, and 
related WWW sites can be found on the Voyager 1/2 flight project page under

http://nssdc.gsfc.nasa.gov/space/

Hour averages of the interplanetary solar wind data from, and hourly 
heliocentric coordinates of, Voyager 1/2 and other interplanetary spacecraft 
may be also be accessed and plotted on-line through the COHOWeb service 
based at the same WWW site as above.

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.