Lunar Prospector, NASA Probe, Discovery of Polar Water Ice
Like Clementine 1, Lunar Prospector was built quickly and cheaply. Mission cost was just $63 million. The entire process of development to completion and testing was accomplished in less than 2 years. When full of fuel, the spacecraft weighed only 295 kg (650 lb). That's much less than your car -- an average size car weighs about four times that much. Lunar Prospector carried five instruments to study the moon, and the spacecraft was largely made from off-the-shelf, flight-proven hardware -- used whenever feasible. Lunar Prospector launched in January, 1998, almost exactly 4 years after the launch of Clementine.
Lunar Prospector's five sensors included a Gamma Ray Spectrometer (GRS) and a Neutron Spectrometer (NS) to provide global maps of elemental abundances on the lunar surface (in addition to water). The NS sensor can detect traces of water down to 10 parts per million (PPM), though it found vastly higher concentrations than that. The data also reports on the mapping of the global distribution of major rock types, key resources and trace elements in all other places on the Moon.
The data from Clementine 1 and Lunar Prospector made obsolete much of the data from previous lunar orbiters, but does not make obsolete the data from the Apollo samples and other imaging and geophysical data from other landers in the 1960s and 1970s.
Data from all the lunar probes, including the massive amounts of detailed data from Clementine 1 and Lunar Prospector, are open to the public and can be acquired by internet at the NASA National Space Science Data Center (NSSDC) at http://nssdc.gsfc.nasa.gov/planetary/planets/moonpage.html or ordered on CD-ROMs.
This very important page is set for an update in April 2012.
There is an excellent book by the Lunar Prospector Probe's initial creator, manager, mission director, and Principal Investigator, Dr. Alan Binder, which gives an 1181 page personal story and diary of the entire process, from the time he developed the idea in the late 1980s, to the various fundraising efforts, which were unsuccessful for years, the politics of space advocacy organizations, government, and the chosen government contractor (much of it dirty politics in all three realms), various personalities involved, the eventual funding, and the good, the bad, and the ugly of the entire program, which was eventually successful in large part due to the many battles Dr. Binder fought tirelessly. Dr. Binder also shows how we can dramatically reduce the cost of these probes, as the Lunar Prospector probe cost only $ 63 million. (I've read about a third of this book, and my friend Sam Fraser here in Thailand borrowed my copy and read all 1183 pages.) If you want to learn a lot about the realities of what's required for success in this industry, this is highly recommended reading. You can order it at Amazon.