Solar Array
Silicon solar cells, produce 340 watts of
power for direct use or for storage in bat-
teries (with excess radiated into space as
heat)
Solar Array Drive Motor (SAD)
The drive motor is used to rotate the
solar array so that the array continuously
faces the Sun
Stratospheric Sounding Unit (SSU)
A step-scanned spectrometer which measures temperature in the upper stratosphere. It
senses energy in the 15 micrometer carbon dioxide absorption portion of the infrared
spectrum, allowing for a study of the energy budget at the top of the atmosphere
Sun Sensor Detector (SSD)
A part of the Sun Sensor Assembly (SSA) which provides the Sun’s position with respect
to the spacecraft. The sun sensor is used to reinitialize the spacecraft yaw-attitude cal-
culation once per orbit. (Yaw is the swinging on a vertical axis to the right or left above
nadir, nadir is the point on Earth directly beneath a satellite)
Thermal Control Pinwheel Louvers
T h ree on each of four sides for TIROS-N thru NOAA-D. Four louvers per side for NOAA-E
and newer satellites.
UHF Data Collection System Antenna (UDA)
Antenna used to receive Earth-based platform and balloon System Antenna data, and
to receive search and rescue data
VHF Real-Time Antenna (VRA)
Transmission at 2 kiloHertz per second