MSSL CRRES LEPA - Low Energy Plasma Analyser

LEPA - Low Energy Plasma Analyser

Air Force Geophysics Lab / Mullard Space Science Lab's contribution to the USAF CRRES Mission.

Description of LEPA Instrument

Particles in the energy range from 10 eV to 30 KeV account for a large fraction of the total plasma energy density in the inner magnetosphere and as such play a major role in controlling the dynamics of this region. For this reason, a detailed specification of these particles and the determination of their spatial and temporal evolution are critical to the development of dynamic models of the Earth's radiation belts. The Low Energy Plasma Analyser (LEPA) for CRRES was designed to provide this specification.

LEPA was composed of two component instruments, two 270 degree Johnstone Plasma Analysers (one ions, one electrons). High resolution imaging anodes gave high energy resolution and angular resolution with an energy range from eV to 43 KeV, and an angular resolution of 8 degrees in the coarse zone plus 1 degree in the fine zones. The total field of view of the instrument is 5.6 degrees in the spin plane and 120 degrees along the axis, this fan shaped field of view rotated with the spacecraft every 30 seconds.

LEPA has a second part, built by the University of Sussex and called SPACE (the Sussex Particle Correlator experiment). Further details may be sought from Nick Watkins at Warwick or Paul Gough at Sussex and the experiment's first results are detailed in the Advances in Space Research preprint 'Suspected Wave-Particle Interactions Conincident with a Pancake Distribution Seen by the CRRES Spacecraft ' (Postscript file). Further details of the particle correlation technique may be found in the reprints from IWWPP 1994 (On the Effectiveness of the 1 Bit Cross-Correlation Technique as Implemented on the CRRES Satellite) and the ESA Cluster workshop in Toulouse, 1994 (Fourier Techniques in Space Plasma Measurements), respectively. (Sussex's homepage and Warwick's homepage)

LEPA Dataset Description

LEPA Summary Dataset files exist that contain frames and sectors for each 15 second half spin. Telemetered data included the spin frames that were 90 degrees to the magnetic field and spin frames that were aligned with the magnetic field. Each data element comprised 20 to 30 energy channels. Excepting data drop-outs due to power shortages, the dataset is available from July 1990 to October 1991.


Low Energy Plasma Analyzer, Hardy, Walton, Johnstone et al, IEEE Trans. on Nuclear Sci., Vol 40, No 2, April 1993

Story of L, Hardy, Walton, Johnstone et al, AFGL, USAF.

LEPA Plots

Some SURVEY.exe (a program by AFGL's Kevin Kerns) summary plots for various orbits ...

Each file is approx. 50 kb, 16 colours, 640x480 res.

* orbit 077 * orbit 317 * orbit 319

* orbit 320 * orbit 322 * orbit 323 Includes a charging event.

* orbit 330 * orbit 417 * orbit 491 * orbit 531

Equatorial projections of flux over local time for the entire mission

Each file is approx. 200 kb, 256 colours, 1024x768 res. (It's your bandwidth)

*Mag Field Detected

*Mag Field Expected

*Background (covered sensor) detected (90 deg to B) - shows belts & March event

*Background (covered sensor) detected (parallel to B)

* Electron Energy Channel 01 * Electron Energy Channel 03 * Electron Energy Channel 05

* Electron Energy Channel 07 * Electron Energy Channel 13 * Electron Energy Channel 15

* Electron Energy Channel 17 * Electron Energy Channel 19 * Electron Energy Channel 21

* Electron Energy Channel 23 * Electron Energy Channel 29 (low energy - min response)

*Background (covered sensor) detected (90 deg to B)

*Background (covered sensor) detected (parallel to B)

* Ion Energy Channel 01 * Ion Energy Channel 03 * Ion Energy Channel 05

* Ion Energy Channel 07 * Ion Energy Channel 09 * Ion Energy Channel 15

* Ion Energy Channel 17 * Ion Energy Channel 19 * Ion Energy Channel 21

* Ion Energy Channel 23

* Back to CRRES Page
* SWRI CRRES Page (US - a good few kb)

* Mullard Space Science Lab. * Space Plasma Physics Group.

This page is maintained by :-
Nick Flowers (, +44 1483 274111
Space Plasma Physics Group, Mullard Space Science Laboratory,
Holmbury St. Mary, Dorking, Surrey, RH5 6NT, United Kingdom

Version 2.3: Updated March 9th, 1995, 1042 GMT, NJF.