Jun 23 1982
From The Space Library
Three astronomers at the University of Hawaii, using NASA's Infrared Telescope Facility on Mauna Kea and data from Voyager 2, announced the first measurement of the sizes of four of the five known moons of Uranus. Voyager 2 was heading for Uranus after a successful flyby of Saturn 10 months ago, and the new calculations would be useful in planning the scientific studies to be done after arrival. Uranus was so far from Earth, about 3 billion kilometers (2 billion miles), that it was visible only through telescopes. Sizes of the moons were figured from their infrared (heat) radiation. NASA had built the Mauna Kea telescope, most sensitive in the world for measuring faint infrared sources, to provide support for spacecraft exploring the planets; Dr. David Morrison of the University of Hawaii team, also a member of the Voyager project, said that the Moon data were exactly the sort of support NASA had in mind.
The moons of Uranus, smaller than Earth's, were all as large as any of Saturn's except Titan, the giant moon that was the only planetary satellite found to have an atmosphere. Oberon, largest of the Uranus moons, had a diameter of about 1,690 kilometers (1,100 miles). Besides measuring the Uranus moons, the astronomers reported that Triton, largest moon of Neptune, and the planet Pluto were both too small and too cold for any heat radiation to be detected; the weakness of the sources led them to decide that Triton must be smaller than Earth's Moon. Triton and Pluto, "based on our current knowledge," might be very similar; past speculation suggested that Pluto might have been a escaped moon of Neptune. (NASA Release 82-104)
WFC announced the launch of a Nike Orion sounding rocket at 11:40 a.m. to measure magnetosphere instabilities induced by very low-frequency (VLF) waves produced in the troposphere. Its measurements would coincide with a satellite overpass to detect particle precipitation triggered by VLF waves from a high-intensity transmitter. (WFC Release 82-3)
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