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. ------------------------------------------- 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/ -------------------------------------------- --------------------------------------------------