IMP

Interplanetary Monitoring Platform
IMP H & J (7 & 8)

Low-Energy Proton and Electron Differential Energy Analyzer (LEPEDEA)
Instrument Descriptions

NSSDC ID: 72-073A-04/73-078A-04
Mission Name: IMP-H/IMP-J
Principal Investigator: Frank


These experiments were designed to measure the energy spectra of low-energy electrons and protons in the geocentric range of 30 to 40 earth radii to give further data on geomagnetic storms, aurora, tail and neutral sheet, and other magnetospheric phenomena. The detectors were a dual-channel, curved-plate electrostatic analyzer (LEPEDEA - low energy proton and electron differential energy analyzer) with 16 energy intervals between 5 eV and 50 keV. They had an angular field of view of 9° x 25°. The detectors could be operated in one of two modes: (1) one providing good angular resolution (16 directions for each particle energy band) once each 272 s, and (2) the other providing good temporal resolution in which the entire energy range in four directions was measured every 68 s.

For further details on IMP-H, see Frank, L. A. et al., J. Geophys. Res., 82, p. 129, 1977.

For further details on IMP-J, see Frank, L. A. et al., J. Geophys. Res., 81, p. 5859, 1976.


Spacecraft Descriptions

IMP 7 Description


Launch Date: 1972-09-23 at 13:20:00 UTC
On-orbit dry mass: 390.00 kg

IMP-H continued the study begun by earlier IMP spacecraft of the interplanetary and magnetotail regions from a nearly circular orbit, near 37 earth radii. This 16-sided drum-shaped spacecraft was 157 cm high and 135 cm in diameter. It was designed to measure energetic particles, plasma, and electric and magnetic fields. The spin axis was normal to the ecliptic plane, and the spin period was 1.3 s. The spacecraft was powered by solar cells and a chemical battery. Scientific data were telemetered at 1600 bps (with a secondary 400-bps rate available). The spacecraft was turned off on October 31, 1978.

IMP 8 Description


Launch Date: 1973-10-26
On-orbit dry mass: 371.00 kg
Nominal Power Output: 150.00 W

IMP 8 (Explorer 50), the last satellite of the IMP series, was a drum-shaped spacecraft, 135.6 cm across and 157.4 cm high, instrumented for interplanetary and magnetotail studies of cosmic rays, energetic solar particles, plasma, and electric and magnetic fields. Its initial orbit was more elliptical than intended, with apogee and perigee distances of about 45 and 25 RE. Its eccentricity decreased after launch. Its orbital inclination varied between 0° and about 55° with a periodicity of several years. The spacecraft spin axis was normal to the ecliptic plane, and the spin rate was 23 rpm. The data telemetry rate was 1600 bps. The spacecraft was in the solar wind for 7 to 8 days of every 12.5 day orbit. Telemetry coverage was 90% in the early years, but only 60-70% through most of the 1980's and early 1990's. The objectives of the extended IMP-8 operations were to provide solar wind parameters as input for magnetospheric studies and as a 1-AU baseline for deep space studies, and to continue solar cycle variation studies with a single set of well-calibrated and understood instruments.

IMP SpectrogramIMP LEPEDEA Survey Spectrogram

This is a sample of spectrogram data from one of the LEPEDEA Instruments on board an IMP spacecraft.

Data Availability

NOTE: Both the IMP-H and IMP-J have an extended period of time of overlap and the survey images are stored together in the same directories. The filenames will start with IMPH or IMPJ appropriately. All the images are 1024 x 768 and ranging in size up to 210 kB each.

IMP-H Survey spectrograms like that above are currently available as GIF images for 24 hour periods ranging from 25 Sep 1972 (72/269) to 31 Oct 1978 (78/304). They are sorted by year and then by quarter-year sub-directories.

IMP-J Survey spectrograms like that above are currently available as GIF images for 24 hour periods ranging from 15 Nov 1973 (73/319) to 13 Aug 1996 (96/226). They are sorted by year and then by quarter-year sub-directories.

[NEW!] LEPEDEA Distribution Function data as well as plasma moments are now available from NSSDC's FTPWeb Helper.

IMP Related Bibliography

IMP LEPEDEA Research Contacts

The LEPEDEA instrument team is lead by Dr. Louis A. Frank.

Related IMP Web Sources


[WWW-PI Home] [Galileo PLS] [Geotail CPI] [Polar VIS] [Dynamics Explorer SAI] [ISEE LEPEDEA]

Last Modified: Wed Feb 12 11:32:39 2014
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