SPACE EXPLORATION — SEAMANS 267 



Discovery that sunlight exerts appreciable physical pressure on 

 objects in space. This pressure is shifting the orbit of the Vanguard 

 I satellite about a mile per year and has affected the orbit of the 100- 

 foot-diameter Echo I satellite at a rate 300 times greater. 



Among our most successful experiments to date has been the Pioneer 

 series of space probes. Pioneer V, for example — lamiched into solar 

 orbit on March 11, 1960 — was tracked into space to a distance of 22.5 

 million miles, still the greatest distance any manmade object has been 

 tracked. Pioneer V sent back scientific data on conditions in space 

 until communication contact was lost on June 26, 1960. This space 

 probe gave us new and valuable information about cosmic rays, the 

 earth's magnetic field, and solar "storms" and evidence of the existence 

 of a large "ring current" circulating around the earth at altitudes of 

 about 30,000 to 60,000 miles. 



Advanced launch vehicles are becoming available for both scientific 

 missions and operational systems. They will have greatly improved 

 load-carrying capability for unmanned space experiments. For ex- 

 ample, detailed plans have been made and work has begun on an 

 Orbiting Geophysical Observatory, based on the use of the Agena. 

 This observatory will be one of our first standardized satellites, with 

 a stock-model structure, basic power supply, attitude control, teleme- 

 try, and a command system. Its modular compartments are capable 

 of carrying 50 different geophysical experiments on a single mission. 

 The observatory itself will be about 6 feet long by 3 feet square. The 

 two solar "paddles" which collect energy from the sun will be about 

 6 feet square. The satellite will weigh 1,000 pounds and will include 

 150 pounds of scientific equipment. 



NASA's plans for extending unmanned space exploration to the 

 moon and beyond are maturing. Eanger spacecraft — successors to 

 the one flown in a test on August 23, 1961 — will land instruments on 

 the moon. These instruments will determine the nature and extent of 

 tremors and measure the force of gravity on the lunar surface. 



Following Ranger will come Surveyor, a spacecraft that will be 

 able to make a so-called "soft landing" on the moon. More delicate 

 scientific instruments than those in Ranger can thus be employed. 

 Surveyor will have aboard scientific instruments, including drills and 

 tapes, to analyze the lunar surface and to determine its makeup. At 

 the same time, high-resolution television cameras will transmit to 

 earth pictures of the lunar terrain. 



Also underway is a spacecraft that will fly close to Venus and Mars, 

 land later perhaps other, more distant planets. This spacecraft, 

 called Mariner, will carry instruments to measure planetary atmos- 

 phere, surface temperatures, rotation rates, magnetic fields, and sur- 

 rounding radiation regions. 



