Thor 1 retired.
This is a Telenor Press Release.
Oslo/Chilworth:
Last week Telenor’s first TV and communication satellite, Thor 1, was removed from
its fixed position of 1 degrees west and retired far out in space. After 12 years of
continuous operation, the first chapter of Telenor’s role as a major TV distributor
was concluded with success.
The
”de-orbit”, as it’s known in technical jargon, took place from BskyB’s
control centre in Chilworth, England, under the supervision of Bjørn Ottar Elseth,
Manager of Satellite Operations in Telenor Satellite Broadcast. With the final remains of
rocket fuel, Thor 1 was sent 300 km from its fixed path, 36,000 km above the equator. Thor
1 was taken out of active service in autumn 2001, but has functioned as a reserve for its
successors Thor II and Thor III.
In service since
1990
Thor 1, which is a spinner-stabilised satellite, has the type designation Boeing 376
and was launched using a Delta 2 rocket from Cape Canaveral on 17 August 1990. It was
constructed for the British company BskyB but was purchased by Telenor in July 1992 (*)
and moved from 31 degrees west to 1 degrees west, where it has since been in operation 24
hours a day. The Thor 1 satellite was equipped with five transponders, which enabled it to
distribute five analogue TV channels. Its estimated lifetime was 10 years, and now that it
is being retired after 12 and a half years, it has exceeded expectations.
High-tech in
outer space
The Thor satellites are controlled 24 hours a day from the control centre of Space
Systems in zone M3B at Fornebu. The satellites at 1 degrees west are situated
approximately 70 km apart and cover the Nordic region, plus Central and Eastern Europe.
The satellites hang seemingly motionless in outer space, but in reality speed over the sky
at an unbelievable rate of more than 3 km per second, which gives an orbit time of 24
hours around the earth. The control centre is responsible for keeping the satellites on
the correct path. The four rocket engines in the satellites are therefore launched about 5
days apart in order to adjust the 600 kg heavy and 7.7 m high satellite’s axis and
positioning. Its position can vary by up to 70 km, but this has no practical significance
for the satellite receivers on the earth.
A
communication satellite costs around NOK 1 billion to buy, including launching and
positioning in a geostationary path. As repairs are impossible once a satellite has been
launched, the satellite components therefore have double or quadruple redundancy in case
of failure. It is the amount of fuel on board that determines the satellite’s
lifetime. When new, Thor 1 had 220 litres of hydrazine of fuel on board. The satellite
obtains electricity itself via large solar panels fixed to the main body of the satellite.
Thor
1 was Telenor’s first TV and communication satellite and was bought in 1992.
(*) This is badly worded as it seems to indicate that Telenor bought the satellite from BSB new. In fact it had been in service with BSB for about a year. It was purchased in orbit from the wreckage of the BSB operation after Sky closed the BSB service down after their merger.
© Nordic Satellite
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