Documentation for ISEE 3 Data Set 78-079A-02K:  Hourly & Daily
Averages of Magnetic Field Data (from 78-079A-02D) 

______________________________________________________________________
This material was modified from the documentation prepared by Sumant
Krishnaswamy for the original higher-resolution data set 78-079A-02D,
from which this data set was derived.  H. K. Hills, October 5, 1995.
Entered into NSSDC's Technical Reference File as #B44998.
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		NSSDC DATA SET	78-079A-02K
		===========================

ISEE-3/ICE HOURLY AND DAILY AVERAGED MAGNETIC FIELD DATA   
------------------------------------------------------------------

This data set was derived at NSSDC from the ISEE 3 data set
78-079A-02D, which contained magnetic field data with averages over
each minute, hour, and day.  From the 50 blocks per day in that
original data set, the present data set was created by simply copying
only the first (the header) block and the 50th block, which contains
24 hourly averages and the daily averages, and blank fill.  These two
copied blocks were concatenated into one, so that the present record
is 7440 bytes long (240 from the original header record, followed by
7200 from the data). 

Thus the present data record contains 31 logical records (240 bytes 
each) as follows: 
    1. Header 
 2-25. Data: Hourly averages for each hour of the day.
   26. Data: Averages for the day.
27-31. Blank


Header Record Structure:
========================

Variable          Format                  Meaning
-------           ------                  -------
IYR               3X,I2             Last 2 digits of year
IDAY              2X,I3             Day of year (Jan. 1 = Day 1)
ISC               4X,A1             Spacecraft identifier (3 = ISEE-3)
TRAJ(I), I=1,6   15X,6E15.6         Trajectory parameters 
TEXT(I), I=1,30    30A4             Identifying Text  

For ISEE-3, the trajectory parameters are as follows: 
TRAJ(1) = Geocentric Solar Ecliptic (GSE) x-coordinate of the 
          spacecraft position at start of day's data, in meters.
TRAJ(2) = GSE y-coordinate of spacecraft position, in meters.
TRAJ(3) = GSE z-coordinate of spacecraft position, in meters.
TRAJ(4)=TRAJ(5)=TRAJ(6)=0  



Data Record Structure:
======================

Each logical data record contains 15 quantities in the format (8E15.6,
15X, 7E15.6). The first quantity is the number of milliseconds for
which data exists in the period over which the average was taken; the
next 14 are data averages (in I,S coordinates which are essentially
spacecraft-centered Solar-Ecliptic coordinates). The quantities are: 

 1.  number of milliseconds of data
 2.  <Bx>
 3.  <By>
 4.  <Bz>
 5.  <Bx^2>
 6.  <BxBy>
 7.  <BxBz>
 8.  <By^2> 
 9.  <ByBz>
10.  <Bz^2>
11.  <cos alpha> = <Bx/|B|>
12.  <cos beta>  = <By/|B|>
13.  <cos gamma> = <Bz/|B|>
14.  <|B|>
15.  <|B|^2>

Values of <Bx>, <By>, <Bz>, and <|B|> are given in nanoteslas. 

The coordinate system for the B-field components is the JPL-defined
I,S coordinate system (origin at the spacecraft): I is the unit vector
in the direction of the ISEE-3 spin axis (positive in the northward
direction), and S is the unit vector from the spacecraft to the sun.
The z-axis is parallel to to I, the y-axis to the cross-product I x S,
and the x-axis to Y x Z. The I,S coordinate system is approximately
the same as the Solar Ecliptic (SE) system since the spacecraft z-axis
(the spin axis) is maintained within 0.5 degree of perpendicular to
the ecliptic plane. (SE is defined the same way as GSE, but with the
spacecraft [point of observation] substituted for Earth).