Summary
The New Millennium Program's Earth Observing-1 (EO-1)
mission provides for the on-orbit demonstration of a high
data rate, low mass X-Band Phased Array Antenna (XPAA)
for down-linking imaged data from the EO-1 solid state
recorder. The XPAA offers significant benefits over current
mechanically pointed parabolic antennas, including the
elimination of deployable structures, moving parts, and
the torque disturbances that moving antennas impart to
the spacecraft.
The XPAA is composed of a flat grid of 64 radiating
elements whose transmitted signals are combined spatially
to produce the desired antenna directivity. The phases
of each of the radiating elements are varied by computer
to point the beam in the desired direction. For the
EO-1 mission, the radiating elements are combined with
low power, high efficiency solid-state amplifiers to
achieve the required radio frequency power level. The
antenna is mounted on the Earth-facing side of the spacecraft
to allow communications with ground stations. The antenna's
mass is 5.5 kilograms and is contained in a single 12
x 13 x 2.9 inch enclosure. It has a minimum Effective
Isotropic Radiated Power (EIRP) of 22 dBW and transmits
data at 105 megabits per second.
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