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L In the past few years, scientists have learned more about the other planets in our solar system than had been discovered in almost 370 years of observation through earthbound telescopes. This newly-acquired knowledge, to a large extent, comes from a number of highly successful unmanned space probes, launched by the United States and the Soviet Union. These tiny craft have flown past five of the nine planets in our solar system, in some cases orbiting and even landing upon the planets themselves. In December of 1973, the probe, Pioneer 10, became the first man-made object to reach the planet Jupiter. It sent back thousands of instrument readings and several excellent color photographs 0.f the giant planet. It is currently on its way out-of the solar system altogether, thus becoming the first interstellar spacecraft.
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1974 ias -even more eventful, In February of that year, the Makiner 10 spacecraft sent back the first closerup photographs of the planet Venus, taken in ultraviolet light through a temporary gap in that planet’s almost continuous cloud cover. One month later, Mariner 10 became the first probe ever to visit the planet Mercury. It sent back numerous .pictures of the heavily-qratered surface, and returned to that planet twice during the following year. In December of T974, Pioneer 11 (twin of Pioneer 10) flewpast Jupiter, providing additional information about that world. But its mission did not stop there. By using Jupiter’s enormous gravity, Pioneer 11 was able to change its trajectory and continue on into the outer solar sy’stem, passing Saturn just this month and giving us our ‘first detailed look at the ringed world. In early 1976, two Viking spacecraft arrived at Mars. This was not our first look at the Red Planet; a number of earlier American and Soviet probes had flown past the planet, and several had actually gone into orbit. However, this spacecraft was a little different.
After‘ orbiting the planet for a while, scouting out suitable landing sites, the first of the two spacecraft separated into two parts. The larger of the two, known as the Orbiter, remained where it was. Its task wasto circle the planet and take readings from above. The smaller vehicle, known as the Lander, fired it.s engines and descended from orbit, coming to rest on the surface a short time later. Although earlier Russian probes had attempted to land, all but one failed to survive down to the surfade; the one that did make it transmitted for a scant 20 seconds before dying. The laboratories analyzed the atmosphere, determining its density and composition. They took photographs of the surface through all the seasons of the Martian year. They looked for life, and found no conclusive evidence of its presence or its absence. Above all, they told us things about that world that could never have been learned from Earth. By contrast, 1977 was a relatively dull year. Though the Vikings were still in full operation, the main excitement was over. The first of a trio of sophisticated mini-telescopes was put into orbit around the earth, scanning the skies using x-rays and gamma rays instead of ordinary light. They also looked for black holes by searching for the powerful energy emmissions -given off when matter falls inwards towards them. Nothing, however, was new on the planetary front. In this respect, 1978 was somewhat better. A virtual armada of sophisticated probes, both American and Soviet, were arriving at the planet Venus. The American fleet consisted of an orbiter, designed to circle the planet for a full Venusian year while monitoring it from the van,tage point of a planetary orbit, and a cluster of five atmospheric probes. Upon arrival at the planet, the probecluster separated into its component elements. One large probe with a heat shield to protect it during passage through the atmosphere of Venus was released. Three smaller probes, also equipped with heat shields, were similar,ly sent off. Finally, the drum-
drawing shaped platform which held the cluster together (and which was also equipped with instrument ation) plunge-d into the planet’s atmosphere. The probes descended down to the surface, floating down on parachutes to give them as much useful time as possible. They produced a detailed “map” of the planet’s atmosphere, determining its pressure, temperature, and composition. They studied the winds of Venus, and the variation in brightness on the way down, One hardy probe even survived the landing and sent back considerable information about conditions at ground level. All in all, the mission was a success. The Soviets fared equally well. T*heir two orbiters, though apparently not as heavily loaded with instruments as the American orbiter, went into orbit and released their landers. The landers descended to the surface and collected data for some time. before finally succumbing to the heat and pressure of the Venusian surface. This year has been an eventful one as well. The arrival of Pioneer 11 at Saturn just three weeks ago has given scientists a new wealth of data about that world. In addition the Voyager 1 and Voyager 2 probes that provided so much information about Jupiter and its moons
by Ludek
Pesek/OMNI
earlier this year are already on their way to visit Saturn during the next two years. The future, however, seems bleak. The only space probe currently planned is Project Galileo, designed to orbit Jupiter and send a probe into its atmosphere. Other missions are possible, but funding cutbacks make major new starts unlikely, at least for the time being. Most observers attribute space program cutbacks to the apparent high cost of such missions. Compared to other government programs, however, the cost of space exploration is not high. The entire Pioneer lo-11 mission, which gave us our first glimpses of the two largest planets in our solar system, cost each American only a few dollars, which were spread out over a period of’ years. To put this in perspective, the total cost of Project Voyager to each adult American is about the same as a six-pack of beer, again spread out over a period of years. It remains to be seen whether these statistics influence the decision-makers who determine how resources are allocated. But there can be little doubt that the return on the investment will, in the long term, be enormous.
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