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Monthly Archives: April 2014

There is a typographical error on p. 363, column 1, second line from the bottom, when referring to the event horizon: ‘1/3’ should be ‘2/3’ in the sentence:
“Its radius is exactly 2/3 times that of the photon sphere, or 3 km for each solar mass.”

From a NASA press release, April 18, 2014:

Ground controllers at NASA’s Ames Research Center in Moffett Field, California, have confirmed that NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft impacted the surface of the Moon, as planned, on Thursday, April 17. LADEE lacked fuel to maintain a long-term lunar orbit or continue science operations and was intentionally sent into the lunar surface. The spacecraft’s orbit naturally decayed following the mission’s final low-altitude science phase. (See p. 135.)

Credit: NASA

During impact, engineers believe the LADEE spacecraft, the size of a vending machine, broke apart, with most of the spacecraft’s material heating up several hundred degrees – or even vaporizing – at the surface. Any material that remained is likely buried in shallow craters. At the time of impact, LADEE was traveling at a speed of 3,600 miles per hour.

In early April, the spacecraft was commanded to carry out maneuvers that would lower its closest approach to the lunar surface. The new orbit brought LADEE to altitudes below one mile (two kilometers) above the lunar surface. This is lower than most commercial airliners fly above Earth, enabling scientists to gather unprecedented science measurements.

In the coming months, mission controllers will determine the exact time and location of LADEE’s impact and work with the agency’s Lunar Reconnaissance Orbiter (LRO) team to possibly capture an image of the impact site. A thorough understanding of the characteristics of our nearest celestial neighbor will help researchers understand other bodies in the solar system, such as large asteroids, Mercury and the moons of outer planets.

Links: full NASA press release; NY Times article; LADEE mission homepage.