The Lunar Prospector Electron Reflectometer (ER) is designed to collect information on the lunar remnant paleomagnetic fields. The ER measures the energy spectrum and direction of electrons. This information is used to determine the location and strength of magnetic fields. The Moon has no global magnetic field, but does have weak localized magnetic fields at its surface. This experiment will help to map these fields and provide information on their origins, allow possible examination of distribution of minerals on the lunar surface, and aid in a determination of the size and composition of the lunar core.

The Electron Reflectometer and the electronics package are located at the end of one of the three radial science booms on Lunar Prospector. (The magnetometer is in turn extended further on a 0.8 m boom which extends from the ER.) The electron reflectometer works by measuring the pitch angles of solar wind electrons reflected from the Moon by lunar magnetic fields. Stronger local magnetic fields can reflect electrons with larger pitch angles. The electron reflectometer and magnetometer instruments have a combined mass of 5 kg and use 4.5 watts of power. The ER will measure field strengths as small as 0.01 nT with a spatial accuracy of about 3 km at the lunar surface.

To find out more about the Lunar Prospector:

• NASA Ames Research Center
• NASA Goddard Space Flight Center
• Berkeley High School Summer Students

• MAG/ER Internal Communications