To use a simple analogy. If you were filling a bucket from 3 tanks of different concentrations then the lowest concentration you could get is to fill the bucket from the lowest concentrated tank. In this example that wold be cislunar space. The lowest exposure possible would be that obtained without contribution from lunar or VAB sources. That is why all lunar missions have to be at least as high as cislunar space.
Someone correct me if I am wrong, I'm just a high school drop out, but the .6 millirads per hour of the lunar surface is measure separately from the 1 milirads per hour figure for cis-lunar, yes? So you have two separate buckets. Jay and I both already went over why the lunar and cis-lunar GCR doses are different, you got a whole moon between you and the GCR. Plus, we're measuring GCR here, not the bremsstrahlung from their interaction with the lunar surface.
Raven, I will keep posting this until it is fully understood:
Measurements taken by NASA's Lunar Reconnaissance Orbiter show that the number of high energy particles streaming in from space did not tail off closer to the moon's surface, as would be expected with the body of the moon blocking half the sky.
Rather, the cosmic rays created a secondary — and potentially more dangerous -- shower by blasting particles in the lunar soil which then become radioactive.
"The moon is a source of radiation," said Boston University researcher Harlan Spence, the lead scientist for LRO's cosmic ray telescope. "This was a bit unexpected."
While the moon blocks galactic cosmic rays to some extent, the hazards posed by the secondary radiation showers counter the shielding effects, Spence said at a press conference at the American Geophysical Union meeting in San Francisco this week.
Overall, future lunar travelers face a radiation dose 30 percent to 40 percent higher than originally expected, Spence said.
