Is any of the scientific equipment left on the Moon by the Apollo astronauts still in use?

Perhaps surprisingly, the answer is yes. Scientific experiments from Apollo continue.

Although the Apollo astronauts left the Moon for the final time in 1972, they left behind an array of equipment, including the bases of the Lunar Landers, the Lunar Rovers, a variety of scientific equipment, and at least one golf ball. From Apollo 12 to Apollo 17, a scientific package called Apollo Lunar Surface Experiment Package (ALSEP) was deployed and left by each mission (Apollo 13 obviously an exception). The ALSEPs were powered by Radioisotopic Thermoelectric Generators (RTGs) and had arrays of scientific experiments. By the Fall of 1977, the power from the RTGs was beginning to dwindle, and so was funding for collecting the data from the ALSEP experiments, so the ALSEPs were turned off. Although there has been some talk about trying to re-activate them, no action has been taken.

Not all the scientific experiments on the Apollo missions required power, however. Apollo 11, 14, and 15 each carried an experiment called the Laser Ranging RetroReflector (LRRR), consisting of an array of corner cube reflectors. Lasers from telescopes on Earth reflect light back from these arrays, providing information about the time it takes light to make the round trip. These measurements pinned down the distance to the Moon with accuracy of about 3 centimeters and measured the rate at which the Moon is receding from the Earth (about 3.8 cm per year, or over 4 feet since the time of the Apollo missions).

More recently, these LRRRs have been used to show that the gravitational binding energy of the Earth generates its own gravity and to provide evidence that the Moon may have a molten core. An ongoing program, called APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation), hopes to reduce the measurement of the lunar distance to 1 mm, along with carrying out more experiments on the properties of gravity.

Some links of interest:

http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/ApolloLaser.html

http://www.myspacemuseum.com/alseph1.htm

http://www.space.com/scienceastronomy/moon_impact_020916.html

http://www.lpi.usra.edu/expmoon/Apollo15/A15_Experiments_LRRR.html

http://www.washington.edu/newsroom/news/2002archive/01-02archive/k011402.html

This week's question is provided by Dr. Dave Thompson. Dr. Thompson is an astrophysicist who studies gamma rays in the Laboratory for High Energy Astrophysics. He helped build, test, and analyze data from EGRET on the Compton Gamma Ray Observatory, and he is now helping build part of the Gamma Ray Large Area Space Telescope (GLAST), scheduled for launch in 2006. His particular scientific interest is gamma-ray pulsars.