HEO

From ViRBO

Highly Elliptical Orbiting Satellites (HEO)

Summary
SPASE
Research
Data
1. HEO-1
2. HEO-3

1. Summary

The HEO acronym indicates satellites in a Highly Elliptical Orbit, also known as Molniya orbits. These orbits have period of roughly 12 hours, with a perigee of no more than a few hundred kilometers, apogee of roughly 7 Re, and an inclination of about 63 degrees. The three HEO spacecraft are referred to as HEO-1, HEO-2, and HEO-3 or F1, F2, and F3, meaning flights 1-3. Because science is not the primary mission of the host vehicle, many of the details on the HEO spacecraft cannot be released at this time.

The F1 and F3 dosimeters have Dose channels (D1, D2, D3, D4) and corresponding Electron (E3, E4, E5, E6) and Proton (P4, P5, P6, P7) channels. F1, F2 and F3 also carry an electron-proton telescope to measure lower energies. The telescopes provide two electron channels (E1, E2) and three proton channels (P1, P2, P3, and, on HEO 3 only, P4). Care should be taken with the telescope data. There is evidence of a temperature dependent response in the data, especially in the P1 on F1, F2 and F3 and in P2 on F3. As the instruments and satellites continue to age, the temperature will rise and other telescope channels may show the temperature related "noise" response. Also, P4 on HEO 3 suffers from electron contamination. Both the dosimeters and telescopes are summarized in http://virbo.org/ftp/users/obrien/heo/ascii/Dosimeters.htm.

2. SPASE

Satellite: HEO-1 | HEO-2 | HEO-3
RB-related instruments: EXP

3. Research

Fennell et al., 2004 (html | cached pdf) used HEO data to study the electron response to magnetic storms for L-shells between 2.5 and 6.
Fennell et al., 2007 (html | cached pdf): "... show the results of spacecraft frame and differential potentials that have been measured over several years on a highly elliptical orbit, HEO2, satellite. The measurements are of charging levels."

4. Data

Data from two HEO missions is available in this archive: HEO-1 and HEO-3. These data consist of energetic particle measurements, given as proton counts, electron counts, and dose/dose rate. The spacecraft are equipped with a combination of dome and telescope dosimeters. Data from these instruments is available in 15-second averages and binned by magnetic L-shell in IGRF and Olson-Pfitzer (Quiet) field models. (Data from HEO-2 have not been processed to the level required for release).

Original data files are available at: http://virbo.org/ftp/users/obrien/heo/ascii. Some of the text files contain space and tab delimiters on the same line, time may not be monotonic across files, and there are locations where two rows have the same time stamp but different column values (a very small fraction). If you are interested in the MATLAB file readers for the text file, send email to virbo@virbo.org.

The v0 merged files have monotonically increasing time; any rows with duplicate time stamps were dropped (< 0.1%). A future release may include these dropped time stamps.

A group at Aerospace (contact: O'Brien) is working on (2009.12.02) energy-dependent response functions for converting count rates to flux, but the process is complicated by the lack of preflight data available to validate against.

Version Notes

A revised version of the F3 EXP data files (named *v04b.exp and located in the subdirectories of http://virbo.org/ftp/users/obrien/heo/ascii/f3/exp/) were made available in August, 2009. The only merged file that will require updating is http://virbo.org/ftp/HEO3/EXP/VIRBO/merged. When the new merge file is created, it will be labeled "v1". See Notes#Versioning for information on version labels.