Robot Explorers: US Unmanned Space Missions: page 2 |
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The U.S. space age began on January 31, 1958 with the launch of Explorer 1, the nation's first satellite. Its objective was to study the conditions in space outside of Earth's atmosphere. This small 30 pound satellite discovered the largest feature of planet Earth -- the Van Allen Radiation Belts. The Van Allen Radiation belts are a pair of doughnut-shaped rings composed of ionized gas. |
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On December 3, 1958 after eighteen years of work for the U.S. Army and other defense agencies, JPL was transferred to the recently formed civilian agency called NASA -- the National Aeronautics and Space Administration. It was then that NASA assigned JPL the lead responsibility for robotic space exploration. 1958 also saw the development of the Deep Space Network, or DSN -- a worldwide system of large sensitive antennas. The DSN is capable of sophisticated tracking and data acquisition, making it possible to maintain communication with long-term space missions. |
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JPL's first NASA project was Pioneer IV. Launched on March 3, 1959, its objectives were to measure cosmic radiation, to test the design of the tracking and communication system, and to help determine a more accurate estimate of the Moon's mass. Pioneer IV, weighing in at only thirteen pounds, was the first U.S. spacecraft to escape Earth's velocity. The batteries which powered the transmitters on board lasted for eighty-two hours after launch, when the craft was 407,000 miles from Earth - setting a new tracking record. Later PIONEER missions V, VI, VII, VIII, and IX, launched between 1960 - 1968 were aimed at gathering data on the Sun and interplanetary space. These craft all entered solar orbit immediately after leaving the Earth. |
| In August of 1961, Ranger 1 was launched. Its main purpose was to develop and test basic elements of spacecraft technology required for future lunar and interplanetary missions. Five months later, Ranger 3 headed out en route to the Moon. It was NASA's first attempt to take close-up pictures of the moon and make measurements on the lunar surface. Unfortunately, due to excess launch vehicle velocity, Ranger 3 arrived at intercept with the Moon's orbit too early and flew right by it at a distance of nearly 23,000 miles. |  |
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Mariner 2, the world's first successful interplanetary space craft set sail on August 27, 1962. Three and one half months later it reached its destination, Venus, where it passed within 22,000 miles of the planet. Mariner's onboard instruments performed close-range infrared and microwave measurements of Venus for 42 minutes as it flew by. |
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In July of 1964 Ranger 7 was able to achieve what Ranger 3
could not -- three days after its launch from the Earth it impacted the Moon at the Sea of
Clouds. Ranger 7 was the first U.S. spacecraft to obtain close-up photographs of the Moon
-- at a resolution 1,000 times better than that of any Earth-based image. Before impact it
transmitted over 4,000 pictures back to Earth. Both Rangers 8 and 9 were launched in 1965.
Their mission was the same as Ranger 7's -to acquire and transmit pictures of the Moon
before impact. This shot of the Alphonsus crater was taken by Ranger 9 at a distance of 300 miles, about 3 minutes before impact in the upper right portion of the crater. The best of the photographs had a resolution as fine as 10 inches. |
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Copyright ©2004 Colleen Gino |
Images courtesy JPL and NASA. |
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