Inertial Measurement Unit (IMU)
Contains gyros and accelerometers to
provide information for determining
spacecraft attitude and position
Instrument Mounting Platform (IMP)
Highly stable structure used to hold some
instruments and level with Earth to accu-
racy of 0.2 degrees
Instrument Mounting Platform Sunshade
Shading to protect instruments from the Sun
Medium Energy Proton and Electron Detector (MEPED)
Senses protons, electrons, and ions with energies from 30 keV (thousand electron volts)
to several tens of MeV (million electron volts)
Microwave Sounding Unit (MSU)
A passive scanning microwave spectrometer with four frequency channels that mea-
sures the energy from the troposphere to construct a vertical temperature profile to an
altitude of 20 km, and measures precipitation
Nitrogen Tank
Used for thrusting and to provide ullage (fills the tank the amount that the hydrazine
propellant lacks being full to ensure proper flow) pressurant for the hydrazine propel-
lant tanks. The spacecraft has two tanks containing nitrogen
Reaction System Support Structure
Second-stage motor, batteries, and fuel
Rocket Engine Assembly (REA)
Used for thrusting, the spacecraft has four hydrazine engines
S-Band Real-time Antenna
Transmission at 665.4 kilobits per second
S-Band Omni Antenna (SOA)
B roadcasts relatively low-frequency microwave bands for transmitting instrument and
spacecraft data to ground stations during boost phase and during on-orbit emerg e n c i e s