HELIOS-1 HOURLY AND DAILY INTERPLANETARY DATA
The HELIOS-1 spacecraft was one of the pair of deep space probes developed
by the Federal Republic of Germany (FRG) in a cooperative program with
NASA. The purpose of the mission was to make pioneering measurements of
the interplanetary medium from the vicinity of the Earth's orbit to 0.3
AU. (The planet Mercury is at 0.4 AU.)
For the hourly resolution records,
this directory contains hourly and daily averages of selected parameters for
the interplanetary magnetic field (1974-12-14 - 1981-06-14),
solar wind plasma (1974-12-12 - 1980-12-31), and spacecraft trajectory
coordinates (1974-12-10 - 1981-06-14).
Magnetic field data were provided by Prof. F. Mariani, Istituto di
Fisica G. Marconi, Rome, Italy;
Plasma data - by Dr. R. Schwenn, Max-Planck-Institut fur Aeronomie,
Lindau, Germany.
Helios 1&2 E6 fluxes, Principal Investigator: Horst Kunow, U. Kiel.
Helios 1&2 E7 fluxes, Principal Investigator: James Trainor, NASA/GSFC
Time Coverage of merged files: December 10, 1974 - June 14, 1981.
Helios-1 data have been reprocessed to ensure a uniformity of
content and coordinate systems relative to data from other deep-
space missions:
- All spacecraft trajectory data were transformed to a Heliographic
Inertial (HGI) coordinate system.
- Magnetic field components and flow direction angles
were transformed to RTN system (the angles in 2008);
- Trajectory data, interplanetary magnetic field data, and plasma data
were merged into individual hourly records grouped into annual files
with naming convention he1_YR.asc, where YR is a given year;
- E6 hourly fluxes were made by averaging of ~hourly data from E6 instrument,
for more detaills see: http://omniweb.sci.gsfc.nasa.gov/ftpbrowser/helios_e6_flux_descr.txt.
E7 hourly fluxes were made by averaging of 30-min data from E7 instrument,
for more detaills see: http://omniweb.sci.gsfc.nasa.gov/ftpbrowser/helios_e7_flux_descr.txt
- Data gaps were filled with dummy numbers for the missing hours or entire
days to make all files of equal length. The character '9' is used to
fill all fields for missing data according to their format, e.g.
' 9999.9' for a field with the FORTRAN format F7.1. Note that format F7.1
below really means (1X,F6.1),etc.
- For the daily resolution data (one file), simple averages were taken over
the hourly values. The format is identical to that for the hour averages
However, the "hour" field has 0 as a value.and the "Magnitude of Average
Vector" field is the simple average of the 24 hourly values of this parameter.
FORMAT DESCRIPTION
WORD ASCII MEANING UNITS/COMMENTS
1 I4 Year 1976, 1977, etc.
2 I4 Decimal Day January 1 = Day 1
3 I3 Hour 0, 1, ... 23
4 I5 Carrington Rotation Number Seen by an Earth based
observer at the start
of the data interval
5 F7.2 Spacecraft Heliocentric astronomical units
Distance
6 F7.1 Heliographic Inertial Latitude degrees, +/- 90
of the spacecraft position
at the start of data interval
7 F7.1 Heliographic Inertial Longitude degrees, 0-360
of the spacecraft position
at the start of data interval
8 F7.1 Earth - Sun - Spacecraft degrees, 0-360
separation angle
9 F9.2 BX in SSE coordinate system nanoteslas
10 F9.2 BY in SSE coordinate system nanoteslas
11 F9.2 BZ in SSE coordinate system nanoteslas
12 F9.2 BR in RTN coordinate system nanoteslas
13 F9.2 BT in RTN coordinate system nanoteslas
14 F9.2 BN in RTN coordinate system nanoteslas
15 F9.2 Scalar B (avg of fine scale nanoteslas
magnitudes)
16 F7.1 Solar wind bulk flow speed km/s
17 F7.1 Flow elevation angle (RTN) degrees +/- 90
18 F7.1 Flow azimuth angle (RTN) degrees, +/-180
19 F6.1 Solar wind proton density protons/cm3
20 F9.0 Radial component of the proton degrees, K
temperature
21 E11.4 4-13 MeV H flux,E6 1/(sec-cm**2-ster-MeV)
22 E11.4 13-27 MeV H flux,E6 1/(sec-cm**2-ster-MeV)
23 E11.4 27-37 MeV H flux,E6 1/(sec-cm**2-ster-MeV)
24 E11.4 37-51 MeV H flux,E6 1/(sec-cm**2-ster-MeV)
25 E10.3 3.4-6.05 MeV H flux,E7 1/(sec-cm**2-ster-MeV)
26 E10.3 6.05-11.1 MeV H flux,E7 1/(sec-cm**2-ster-MeV)
27 E10.3 11.1-21.6 MeV H flux,E7 1/(sec-cm**2-ster-MeV)
28 E10.3 24.52-28.82 MeV H flux,E7 1/(sec-cm**2-ster-MeV)
29 E10.3 32.0-46.3 MeV H flux,E7 1/(sec-cm**2-ster-MeV)
30 E10.3 46.3-57.22 MeV H flux,E7 1/(sec-cm**2-ster-MeV)
31 E10.3 135.2-206.5 MeV H flux,E7 1/(sec-cm**2-ster-MeV)
REFERENCES
1. H. Rosenbauer, R. Schwenn, E. Marsch, B. Meyer, H. Miggenrieder,
M. D. Montgomery, K. H. Muhlhauser, W. Pilipp, W. Voges, and S.M. Zink,
A survey on initial results of the helios plasma experiment,
J. Geophys.,42, 561-580, 1977.
DESCRIPTION OF COORDINATE SYSTEMS
The Heliographic Inertial (HGI) coordinates are Sun-centered and inertially
fixed with respect to an X-axis directed along the intersection line of
the ecliptic and solar equatorial planes. The solar equator plane is
inclined at 7.25 degrees from the ecliptic. This direction was towards
ecliptic longitude of 74.36 degrees on 1 January 1900 at 1200 UT;
because of precession of the celestial equator, this longitude increases
by 1.4 degrees/century. The Z axis is directed perpendicular and northward
from the solar equator, and the Y-axis completes the right-handed set. This
system differs from the usual heliographic coordinates (e.g. Carrington
longitudes) which are fixed in the frame of the rotating Sun.
The RTN system is fixed at a spacecraft (or the planet). The R
axis is directed radially away from the Sun, the T axis is the cross
product of the solar rotation axis and the R axis, and the N axis is the
cross product of R and T. At zero Heliographic Latitude when the
spacecraft is in the solar equatorial plane the N and solar rotation axes
are parallel.
In the SSE system for Helios 1 and 2 the X axis points from the spacecraft
towards the Sun, the Y axis lies within the spacecraft orbital plane and
in the direction opposite to planetary motion around the Sun, and the Z
axis completes the right-handed set.
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Hour averages of the interplanetary solar wind data from, and hourly
heliocentric coordinates of, Helios1/2 and other interplanetary spacecraft
may be also be accessed and plotted on-line through the COHOWeb service
http://omniweb.sci.gsfc.nasa.gov/coho/
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