NEAR Landing Recalls Early Moon Probes By Andrew Chaikin Executive Editor, Space and Science posted: 01:39 pm ET 14 February 2001 ET
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When the NEAR Shoemaker spacecraft made its landing on the Asteroid 433 Eros earlier this week, NASA rightly hailed it as a historic first. But some space watchers who viewed
NEAR's stream of close-up images may have had a touch of déjà vu about the event: Those pictures hearken back to another mission from the early days of space exploration more than 35 years ago.
Back in the early 1960s,
NASA launched a series of robotic probes, called Ranger, that were designed to crash-land on the Moon. By transmitting pictures during their approach, the Rangers would give scientists their first close-up look at the mysterious lunar surface -- a goal that was also crucial for engineers designing the piloted Moon lander for Project Apollo.
The first six Rangers failed, some of them missing the Moon entirely. Finally, on July 31, 1964, Ranger 7 sent back more than 4,000 images before crashing into the Moon's Mare Cognitum (Known Sea). The closest images, taken only seconds before impact, showed features as small as a few feet across. Ranger 8 repeated the feat in February 1965, while Ranger 9 brought a successful end to the program in March 1965. Altogether, these three Rangers gave scientists a new understanding of the lunar surface and helped pave the way for the Apollo astronauts.
Similarly,
NEAR Shoemaker's final images, radioed during its descent to Eros, have given scientists their most intimate look at an asteroid. Unlike the Rangers, NEAR survived its landing because Eros' extremely weak gravity allowed the craft to descend so slowly that it practically floated onto the asteroid's surface.
After the successful landing, scientists debated whether to "re-launch" NEAR on a 0.6-mile (1-kilometer) high arc, triggering another memory for space history buffs. On November 9, 1966 the
Surveyor 6 probe soft landed on the Moon's Sinus Medii (Central Bay). Eight days later, controllers on Earth ordered the spacecraft to re-ignite its vernier rocket engines for 2.5 seconds, causing Surveyor 6 to ascend briefly and then come to rest 8 feet (2.4 meters) from where it started. This "hop," which reached an altitude of 12 feet (3.7 meters), constituted the first liftoff from an extraterrestrial body. It also gave Apollo planners data on such important matters as how rocket firings would affect the lunar surface.