Kristi Kay Klatt, age 11, of Canton, Kansas, for her question:
What is an orbiting astronomical observatory?
An astronomical observatory, of course, is a special building for studying the heavens. We cannot send the huge structure and its teams of experts into orbit. But we can send up a small satellite to do some of its observing and there are many good reasons why we should.
Our cosmic information is gathered at ground stations that house telescopes, radio telescopes and a lot of other astronomical instruments. These major observatories are high on mountains around the world. We depend upon them for such practical information as the correct time of day. Their teams of experts report positions of the moons and planets of our Solar System. They also gather information about our starry neighbors near and far in the Milky Way. And they probe much farther to piece together a picture of the infinite universe beyond our Galaxy.
This is a large order and an important one. In the present century the advances in astronomy have been astounding, but the work could go even faster. Observatories on the ground are limited, even on high mountains, by the earth's atmosphere. Telescopes, spectrographs and even radio telescopes scan the heavens through a thick veil of airy gases. It is this veil that causes the stars to twinkle. It also limits all cosmic surveys to the visible light of the spectrum and to somewhat distorted radio signals. If only an observatory could rise above the atmosphere, its range would be wider and more accurate.
This could be done by packing a small scale observatory into an unmanned satellite and sending it up to orbit the earth. And our Space Program has plans for one, two and three of these orbiting astronomical observatories. A typical O.A.O. satellite is designed to weigh 3,600 pounds, almost two tons. It is an 8 sided tube, 10 feet long and 80 inches wide. Its delicate instruments are encased in a tube 48 inches wide and set inside the main body. Auxiliary electronics equipment is packed neatly on selves in the space between the outer shell and the instrument tube.
The power to operate the instruments and relay their reports to the ground is to be provided by solar cells. When the O.A.O. orbit is set, these batteries will open like wind mills and start converting the sun's energy into electrical power. The O.A.O. orbit is to be about 500 miles above the earth. This is below the Van Allen radiation belts, far above the weathery level of the troposphere an above most of the interfering gases of the atmosphere. The panels of solar cells could work indefinitely and the O.A.O. is expected to perform its duties for years.
Astronomers on the ground depend a lot on the spectroscope. The O.A.O. will carry miniature equipment for gathering and relaying spectra information on celestial objects. Unhampered by the atmosphere, it will not be limited to the rainbow spectrum. It is expected to report on invisible infrared and ultraviolet radiation. All this and other cosmic data will be relayed to ground stations.
The major O.A.O. instrument is the photometer telescope system. It has a telescope equipped with photometer and filter for taking and relaying celestial pictures. The system also has a 16 inch telescope. There are diffraction gratings to gather and relay star spectra. One instrument will search for low energy gamma rays. One will probe to find the sources of high energy gamma rays. Another O.A.O. instrument will survey the sky to find the sources of cosmic Xray radiation.