Page 221 - Satellite Communications, Fourth Edition

The Space Segment 201

described in Sec. 7.3). Thus the arrays are only partially in sunshine at
any given time, which places a limitation on power.
Higher powers can be achieved with solar panels arranged in the form
of rectangular solar sails. Solar sails must be folded during the launch
phase and extended when in geostationary orbit. Figure 7.2 shows the HS
601 satellite manufactured by Hughes Space and Communications
Company. As shown, the solar sails are folded up on each side, and when
fully extended, they stretch to 67 ft (20.42 m) from tip to tip. The full com-
plement of solar cells is exposed to the sunlight, and the sails are arranged
to rotate to track the sun, so they are capable of greater power output than
cylindrical arrays having a comparable number of cells. The HS 601 can
be designed to provide dc power from 2 to 6 kW. In comparing the power

Figure 7.2 Aussat B1 (renamed Optus B), Hughes first HS 601 commu-
nications satellite is prepared for environmental testing. (Courtesy of
Hughes Aircraft Company Space and Communications Group.)