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Flight 161
May 7: Spotlight on the mission's Optus and Defence C1 satellite
payload

One of the two satellites to be launched by the next Ariane 5 mission
is the product of a close cooperation between Australia's civil and
defense sectors.

With a liftoff mass of approximately 4,700 kg., the Optus and Defence
C1 satellite carries a mixed payload that will serve the needs of
Singtel Optus Pty. Limited - a large Australian integrated
telecommunications provider, and the Australian Department of
Defence.

The Optus and Defence C1 relay platform will operate in four
different frequency bands: commercial services in Ku-band for Singtel
Optus; and military communications at UHF, X and Ka-bands for the
Australian Department of Defence.

This cooperative effort began in 1997 as the result of an unsolicited
invitation from Optus to the Australian Department of Defence for a
sharing arrangement on Australia's next generation commercial
communications satellite.

Contracts were signed by the Australian Department of Defence and
Optus in October 1999, with participants agreeing to share the costs,
benefits and risks of acquiring, launching and operating the
spacecraft.

Optus and Defence C1 is one of the most advanced communications
satellites ever built, carrying a total of 16 antennas that will
provide 18 beams across Australia, New Zealand and the Asia-Pacific
region, as well as global beams covering from India to Hawaii. It is
to operate from an orbital slot of 156 degrees East Longitude.

Singtel Optus has the prime contractor role to the Australian
Department of Defence for the military communications payload, and
the satellite was built under the responsibility of Japan's
Mitsubishi Electric. The spacecraft uses a FS 1300 satellite bus from
California's Space Systems/Loral, which handled its assembly,
integration and testing, as well as the supply of the commercial
Ku-band payload subsystem. Raytheon from the U.S. was the military
UHF payload subsystem contractor. 

Australian military officials said the benefits of this shared
program are substantial - providing a large satellite communications
capability, delivered years ahead and at a fraction of the cost than
if the Australian Department of Defence had acquired a telecom
satellite alone. 

In addition, lessons learned from the program will assist the
country's defense forces in its acquisition of satellite
communications capabilities in the future.

The military Ka-band payload has four 33-MHz active transponders and
one spare. It will provide medium to high data rate defense theatre
coverage and duplex video, along with voice and data communications.
This Ka-band communications service is a new capability for the
Australian Department of Defence.

X-band telecommunications links provided via the satellite will be
used by the military for medium to high data rate one- and two-way
video, as well as voice and data communications. Service will be
provided by four 60-MHz active transponders, with an additional
transponder serving as a spare. The X-band communications links also
are new for the country's defense network. 

UHF links via the relay satellite will enhance UHF capabilities
already employed by the Australian Department of Defence, and will be
used for low data rate two-way voice and data communications. There
are five 5-kHz channels and one 25-kHz channel provided via the
satellite. 

Optus and Defence C1 will share the Ariane 5 ride on Flight 161 with
BSAT-2c, which will be orbited for the Broadcasting Satellite System
Corporation (B-SAT) of Japan. Liftoff of Flight 161 is set for early
June from the ELA-3 launch complex at the Spaceport in French Guiana.

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