Word: spacecrafts
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Ranger was preparing itself for its long voyage. Its computer brain came to life and began issuing orders. It spread its purple wings so their silicon cells could make electricity out of sunlight. Its dish antenna unfolded; its tiny eyes (sensors) commanded tiny gas jets to turn the spacecraft so that they could bear on the sun and the earth. Its radios chattered furiously, sending reports that all was going well...
...spot that cannot be seen from the earth. Any pictures it might take would be not much use for future astronauts, who will want to land on the visible side. A radio command was sent from J.P.L.'s Goldstone station in the Mojave Desert telling the spacecraft how to correct its course...
...showed a section of the Sea of Clouds about 78 miles square. It was taken when Ranger was still 470 miles away, and Kuiper said that it showed just about as much detail as the best photographs obtainable with the biggest telescopes on earth. Picture by picture, as the spacecraft sped toward the moon, the scene expanded. Craters seemed to blossom on lunar plains that had looked perfectly smooth; in the next pictures even smaller craters appeared...
Three-Foot Craters. The last pictures snapped as the spacecraft sped toward the surface showed smaller and smaller craters, some of them sharp-edged pits blasted by the explosive effect of high-velocity meteors, some of them soft-edged secondary craters dug by low-speed debris from bigger impacts. The very last shot was taken when Ranger was about 1,000 ft. above the surface, and before impact the scanning beam had time to transmit only a part of it-an area 60 ft. by 100 ft. There, sharp and clear, were tiny craters no more than 3 ft. across...
...important Ranger observation was the great number of small secondary craters that litter some parts of the moon. They seem to have fairly steep slopes that might topple any spacecraft that attempts to land on them. Dr. Kuiper thinks that regions splashed with rocks tossed out of big craters should be studiously avoided, but other parts of the lunar plains are probably smooth enough for landing. An encouraging sign is the comparative scarcity of small primary craters blasted by meteor impacts...