INSTRUMENTATION

The PEM System

On the UARS spacecraft, the four PEM instruments, AXIS, HEPS, MEPS, and VMAG, are configured into four subsystems determined principally by field-of-view requirements. The subsystems are shown schematically in the PEM functional block diagram of Figure 1. The Zenith Energetic Particle Subsystem (ZEPS) is located atop a 5.77-meter boom and contains the upward-viewing particle analyzers of HEPS and MEPS, their associated high-voltage power supply units, the vector magnetometer sensor, a remote power unit, and the zenith interface electronics. The Nadir Energetic Particle Subsystem (NEPS) is mounted on a pedestal on the nadir side of the spacecraft and contains the downward-looking particle detectors of MEPS and HEPS, their associated high voltage power supplies, a remote power unit, and the nadir interface electronics. AXIS is a separate PEM subsystem. It is mounted near the forward end of the spacecraft and contains two eight-pixel cameras, an electronics package, and a cone radiator for passive cooling of the solid-state sensors. The fourth subsystem, which is a body-mounted, contains the vector magnetometer electronics, a Central Electronics Package (CEP) for processing data from the ZEPS and NEPS subsystems, and a power control unit. PEM interfaces to the spacecraft via a power switching unit and a remote interface unit.

PEM hardware subsystems were fabricated at three institutions. Lockheed Palo Alto Research Laboratory supplied the AXIS, HEPS, power control unit, and remote power units. The Vector Magnetometer sensor and electronics were furnished by Johns Hopkins University Applied Physics Laboratory. Southwest Research Institute provided the MEPS, CEP, and zenith and nadir interface electronics. Integration of the PEM system was performed by Southwest Research Institute with support from Lockheed Palo Alto Research Laboratory and Johns Hopkins University Applied Physics Laboratory.

Instrument Descriptions

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