Documentation for ISEE 3 Data Set 78-079A-02D:  One-Minute, Hourly and
Daily Averaged Vector Helium Magnetometer Data 

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This digital document is from an e-mail message sent September 28,
1992 by Sumant Krishnaswamy of the NSSDC staff. 
Entered into NSSDC's Technical Reference File as #B44997. 
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		NSSDC DATA SET	78-079A-02D
		===========================

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


Each file contains an integral number of days of data. There are 50
blocks (physical records) per day. The first block is a header record
240 bytes long. Each of the remaining 49 blocks is 7200 bytes long,
and consists of 30 logical records of 240 bytes each. The 1440 logical
records of blocks 2-49 contain averages for the 1440 minutes of the
day. In block 50, the first 24 logical records contain hour averages;
the 25th contains day averages, and the last 5 contain blanks. 

Each logical 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). Thus 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>


The structure of the header record is:

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  

----------------------------------------------------------------------


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). 


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[NSSDC TRF #B40840 is assigned to the 3-page memo to distribution from
Joyce Wolf, dated January 16, 1979, from which the material above was
taken (with a few editorial changes by Sumant Krishnaswamy, mainly in
making a text description of the IS coordinate system shown in a
figure).]