This directory includes hourly heliocentric coordinate data for the
Helios 1 spacecraft as extracted into the ASCII files HE1TRJyy.asc (yy
is the two-digit year) from the merged solar wind magnetic and plasma
data set in HELIOS_1/MGD_FREEMAN. All trajectory parameters except solar
ecliptic and heliographic inertial coordinates were taken from the
original merged dataset. The other parameters were computed and added
using the code HELTRJCON in the MGD_FREEMAN directory. Source routines
for coordinate conversions in this code were provided by R. Parthasarathy
of the Satellite Situation Center at NSSDC. The code READHEL in
MGD_FREEMAN was used to read the archived datasets into an intermediate
format for input to HELTRJCON. Code HELTRJCN1 was used to correct the
solar ecliptic angles as of 6/14/94 (see Note 2 above). HELTRJCON was
also corrected as of this date.

Data Parameter Description:

NY - YEAR OF THE DATA INTERVAL (LAST TWO DIGITS ONLY).
ND - DAY OF THE DATA INTERVAL FROM THE FIRST DAY OF THE ABOVE YEAR,
JAN. 1= DAY 1.
NH - HOUR OF THE DAY OF THE DATA INTERVAL.
NCARROT - CARRINGTON ROTATION NUMBER AS SEEN BY AN EARTH BASED OBSERVER
AT THE START OF THE DATA INTERVAL.
SPAU - SPACECRAFT HELIOCENTRIC DISTANCE IN ASTRONOMICAL UNITS.
SECLAT - SOLAR ECLIPTIC LATITUDE IN DEGREES
SECLON - SOLAR ECLIPTIC LONGITUDE IN DEGREES
HELLAT - SOLAR HELIOGRAPHIC LATITUDE IN DEGREES
HELLON - SOLAR HELIOGRAPHIC (CARRINGTON) LONGITUDE IN DEGREES
HILLON - SOLAR HELIOGRAPHIC INERTIAL LONGITUDE IN DEGREES WITH RESPECT TO
ASCENDING NODE OF SOLAR EQUATOR ON THE ECLIPTIC
ESSCSANG - EARTH-SUN-SPACECRAFT SEPARATION ANGLE (IN DEGREES, 0-360).
ICODE - DATA CODE: 1 MEANS PLASMA DATA ONLY ARE PRESENT FOR THAT HOURLY
INTERVAL; 2 MEANS MAGNETOMETER DATA ONLY; 3 MEANS BOTH PLASMA
AND MAGNETOMETER DATA PRESENT.

Note 1: The solar ecliptic coordinates are given with respect to true
equinox and ecliptic of date. The solar ascending node was located at
ecliptic longitude +74.367 degrees as of 1 Jan. 1900 at 1200 UT; this
longitude increases by 1.4 degrees/century.

Note 2: The solar ecliptic cordinates in this directory before 6/14/94 were
calculated incorrectly and have been corrected as of this date. The
heliographic angles are from the original source dataset and had no problems.