Very Large Array radio telescope

Perhaps the most interesting and surprising discovery about Mercury s surface is the possible presence of ice caps at the planet s north and south poles. The first evidence for this discovery came as the result of studies conducted by researchers at NASA s Jet Propulsion Laboratory in Pasadena, California. The researchers bounced radar signals off the planet s north polar region and analyzed the reflected beams at the Very Large Array radio telescope system in New Mexico. They found that the spectra of the reflected beams were very similar to those for water ice. Since they first reported this result in 1991, further studies have been conducted to determine whether the poles really do contain water ice, although final confirmation has not yet been obtained. 

Many point-spread functions, however, are far less well-behaved. For example. Fig. 1 shows an Airy disk and the point-spread functions of particular observations of the Hubble Space Telescope and the Very Large Array (a radio telescope) are shown in Figs. 3 and 4. 

Napier, P. J., Thompson, R. T, and Ekers, R. D. (1983). The very large array Design and performance of a modem synthesis radio telescope, Pmc. lEEEll, 1295-1320. 

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