Deep Space Network

NASA's Deep Space Network location at Tidbinbilla, Australia, connected by microwave to Australia's CSIRO Parkes Radio Telescope 200 miles away, is being used to observe the recently discovered supernova SN 1987A.

The two antennas connected in real time form theoretical receiver the size of the distance between them in an operation called interferometry.

The Network dish is 34 meters (110 feet) in diameter and the Parkes dish is 64 meters (210 feet).

Dr. Robert Preston of Jet Propulsion Laboratory, which operates the Network for NASA, said an even wider network, using technique called very long baseline interferometry (VLBI) has been set up using four antennas: Tidbinbilla, Parkes, Landsat ground station at Alice Springs in central Australia and 26-meter (85 feet) dish (donated 2 years ago by NASA) at University of Tasmania at Hobart on Tasmania, an island southeast of Australia.

VLBI is non-real time. The set of observatories record on tape and the data is combined later. Some VLBI observations also have been made between the Tidbinbilla site and the Hartbeesthoek Observatory at Johannesburg, South Africa.

Preston said weak radio burst was detected during the first two weeks after the supernova's discovery, but it died away, unlike any previously studied supernova.

Supernovas generally turn into strong radio sources typically many weeks after the explosion when the radio emission can first penetrate the thinning cloud of material ionized by the explosion.

He said the Network is awaiting that emission, thought to come from the expanding shell of gases from the exploded star colliding with materials near it.

The supernova, an exploding star, was first detected by the reception of atomic particles called neutrinos Feb. 23, and optically by astronomers Feb. 24. It is in the neighboring galaxy, the Large Magellanic Cloud, about 163,000 light years from Earth. The star exploded that long ago and its emissions are just arriving at Earth.

It is the first such detectable star explosion in the neighborhood of our own galaxy, the Milky Way, since 1604.

The supernova is at 69 degrees south of the equator and is observable only in the Southern Hemisphere.

The Tidbinbila-Parkes interferometer began observations Feb. 26. Parkes is operated by Australia's Commonwealth Scientific and Industrial Research Organization.

Radio astronomy, which detects microwave emissions rather than visible light, using interferometry can see details in celestial objects with tens to hundreds of times finer resolution than can optical telescopes.

The microwave link between the Tidbinbilla facility and Parkes was established for the Voyager 2 Uranus encounter in January 1986 and was critical to Voyager imaging and science data acquisition. Similar antenna arraying will be used to support the Voyager Neptune encounter in August 1989.

The Deep Space Network also has stations near Madrid, Spain and at Goldstone, Calif.

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