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/H Description
Launch Date: 1972-09-23 at 13:20:00 UTC
On-orbit dry mass: 390.00 kg
IMP-H (Explorer 47, IMP 7) 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/J Description
Launch Date: 1973-10-26
On-orbit dry mass: 371.00 kg
Nominal Power Output: 150.00 W
IMP 8 (Explorer 50, IMP J), 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 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 (IMP 7) 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 (IMP 8) 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.
IMP H/7 &
IMP J/8
LEPEDEA Distribution Function data as well as plasma moments are now available from NASA's SPDF OMNIWeb site.
IMP Related Bibliography
- Publications (Last updated Sunday, 22-Sep-2024 15:28:43 CDT)
IMP LEPEDEA Research Contacts
The LEPEDEA instrument team was lead by Dr. Louis A. Frank.
Related IMP Web Sources
Last Modified: Wednesday, 25-Sep-2024 00:49:32 CDT
IMP LEPEDEA Survey Spectrogram