LRO's current projected cost is $396 million, which puts it in the borderline between Discovery and New Frontiers. The piggyback LCROSS is projected at $73 million -- with what accuracy, God knows, since it strikes me as a fairly intricate mission, much more so than JPL's Lunar Impactor. (I've heard an unconfirmed rumor that Griffin picked it because of a desire to make Ames Research Center into a major player in the deep-space program.)

Science Payload:
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Framing Camera : German Aerospace Center, DLR, Institute of Space Sensor Technology and Planetary Exploration, Berlin.

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Mapping Spectrometer : The Institute for Astrophysics in Space (IAFS), Rome

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Gamma Ray and Neutron Spectrometer : Los Alamos National Laboratory, Los Alamos NM

In the period leading up to the stand down, worries also spread concerning several key spacecraft issues. Relying on a solar electric ion propulsion system, Dawn was to have carried a tank for the xenon gas propellant required by the three cutting edge engines. The xenon tank - composed of a titanium liner covered with composite wrapping - is located deep inside the spacecraft bus, and other pieces were added around it during the manufacturing process.

The flight tank inside Dawn passed pre-flight tests that included taking it to pressures far above those necessary for ground or space operations. Yet when similar tanks were put through more stringent tests, they ruptured at pressures lower than the expected design limits. By finding that the tank was not as strong as first thought, engineers were forced to compensate the weakness by forming a new strategy that included not filling the tank to its full capacity.