ABOUT the middle of this month Australian astronomers will bring back from Cape Canaveral in Florida the most significant payload Australia has launched into space for almost three decades. The payload is the Australian Space Telescope called Endeavour which was built to obtain images of violent explosive events in nearby galaxies. It flew in the cargo bay of an American space shuttle 鈥� by coincidence also called Endeavour 鈥� for just over two weeks last month.
No other space hardware designed and built in Australia has flown in the cargo bay of a shuttle. It is also the first time since Wresat 鈥� Australia鈥檚 first satellite 鈥� was launched in 1967 that a payload completely designed and built in Australia has been taken into space.
The Australian telescope was one of several payloads carried into space by the shuttle Endeavour to observe ultraviolet radiation from stars and galaxies. This is best done in space because the Earth鈥檚 atmosphere absorbs UV light. 鈥淭he American payloads 鈥� from universities and the Goddard Space Flight Center 鈥� were disassembled first,鈥� said Ted Stapinski, managing director of Auspace in Canberra. Auspace built the Endeavour telescope with funds from the Australian Space Office. The total cost was A$10 million. 快猫短视频s from Auspace and the Mount Stromlo Observatory, which designed the experiments carried out by the telescope, will bring back from Florida the magnetic tapes containing the data collected by the telescope.
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Although Endeavour has flown in a shuttle before in January 1992, it was not used because the temperature of the cargo bay exceeded the safety limit, causing the telescope to shut down automatically.
鈥淭his time we believe everything went well,鈥� said Stapinski. 鈥淔our successful observations were made of Andromeda and the Large Magellanic Cloud. We were looking for supernovae, or exploding stars, and galaxies in collision.鈥� These galactic events generate extreme heat and emit large amounts of UV radiation. Background radiation or 鈥渘oise鈥�, in the form of bright light emitted by the galaxies, was removed from the signal received by the telescope, leaving a narrow band of UV radiation.
Endeavour was housed in two canisters on the side of the shuttle鈥檚 cargo bay. One canister consisted of a binocular reflecting telescope 100 mm in diameter, a detector to count the individual particles of light called photons, and the computer control system. The other canister was made up of a battery to power the payload, and the tapes to record the images for processing.
More than 100 Australian companies and research laboratories contributed to the design and construction of Endeavour. These included the CSIRO Division of Applied Physics which manufactured UV filters for the detector and British Aerospace Australia which built the detector鈥檚 control system.
Just as Endeavour returns to Australia, the country鈥檚 other major contribution to space payloads 鈥� the Along Track Scanning Radiometer II (ATSR II) 鈥� is due to be launched late this month by the European Space Agency as one of the instruments on board the agency鈥檚 remote sensing satellites ERS-2. The satellite will be launched to an altitude of 780 kilometres from the spaceport at Kourou in French Guiana.
The radiometer, which measures infrared radiation from the Earth鈥檚 surface, is the second in a series of three. Australia is progressively contributing more money and instrumentation to the project. The first ATSR instrument, ATSR 1, was launched in 1991 and the third, the Advanced ATSR is due for launch in 1999. Australia wil contribute about A$10 million to develop the advanced telescope, about a third of the cost.
Together the three radiometers will provide more than 10 years鈥� data on temperature of the world鈥檚 oceans at the surface. This is being collected over such a long period to provide evidence to support theories of global warming. Small changes in the temperature of the sea surface, where the oceans interact with the atmosphere, can have large scale effects on climate.
The radiometer was designed at Oxford University and at the Rutherford Appleton Laboratory. Ian Barton from the CSIRO Division of Atmospheric Research in Melbourne helped with the work. Their design made the instrument more accurate than earlier orbiting radiometers because it measures the same spot on the Earth twice 鈥� once at an angle of 47掳 before it flies over a particular location and then directly above about two minutes later. By having two measurements, it is possible to adjust for the effect that particles in the Earth鈥檚 atmosphere have on temperature readings. Researchers expect to measure sea surface temperature within an accuracy of 0.1 掳C.
For ATSR II, the instrument being launched this month, Auspace manufactured the Infrared Focal Plane Array. The company says this is the most sophisticated and complex part of the radiometer. The array separates the incoming light into different wavelength bands and focuses the light onto detectors.