Technolology
Spacecraft
ACTS weighed 3250 pounds at launch. It measures 47.1 feet
from tip to tip of the solar arrays and 29.9 feet across the
main receiving and transmitting antenna reflectors, with a
height of 15.2 feet from the spacecraft separation plane to
the tip of the highest antenna. Approximately 1.4 kilowatts
are provided by the solar arrays. The main receiving antenna
is 7.2 feet in diameter; the main transmit antenna is 10.8
feet in diameter. ACTS also incorporates beacons at 20.2 and
27.5 GHz.
ACTS communications payload encompassed several key technologies
through which supported a full range of on-demand voice, video
and data communications services. Key ACTS technologies include:
- Ka-band Spectrum: Operation
in the Ka-band radio spectrum (30/20 GHz) where there is
2.5 GHz of spectrum available for use — five times
that available in lower frequency bands.
- Multiple Hopping Beam Antennas:
Multiple, high gain, hopping-beam antenna systems which
permit the use of smaller dish earth terminals.
- On-Board Digital Processing and Switching:
On-board baseband processing and switching (BBP), which
interconnects users at different earth stations locations
at an individual circuit level.
- Microwave Switch Matrix: A microwave
switch matrix (MSM) which enables high-speed (gigabits per
second) communications and data transfer between users.
- Adaptive Rainfade Compensation:
The effects of rain on the satellite signal (rain fades)
are automatically compensated for on uplink and downlink
transfers of information. The effects of rain remain transparent
to the end-user.
Overview of ACTS Communications Payload
These technologies are typical of what is being incorporated
into the next generation of commercial communication satellites
that will seamlessly operate with terrestrial networks to
provide wideband global communications.
| 
