Voyager's view

It’s finally official: Voyager 1 has become the first human-made object to enter interstellar space, mission scientists report September 12 in Science. On August 25, 2012, the scientists say, Voyager 1 exited a giant invisible bubble called the heliosphere that is inflated by a torrent of subatomic particles spewing from the sun. Now the probe is surrounded almost exclusively by particles produced by other stars. But whether it’s correct to say that the probe has left the solar system depends on how you define the solar system. “From my perspective, Voyager is nowhere near the edge of the solar system,” says planetary scientist Hal Levison of the Southwest Research Institute in Boulder, Colo. The sun continues to exert gravitational dominance out to hundreds of times the distance of Voyager 1 from the sun, where trillions of icy pebbles, boulders and comets orbit. In the last 36 years, Voyager has traveled an impressive 25.4 billion kilometers, but it still has a long way to go to unambiguously depart the solar system.

Source: www.sciencenews.org

Moon's radiation damaging for humans, electronics

Washington: The radiation environment near the Moon could be damaging to humans and electronics on future missions, it has been revealed. To characterize this potentially hazardous environment, the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on board the Lunar Reconnaissance Orbiter mission, which orbits at 50 kilometers (31 miles) above the Moon's surface, measures the radiation that would be absorbed by either electronic parts or human tissue behind the shielding of a spacecraft. 

CRaTER has measured the lunar radiation environment since 2009, during the recent solar minimum. The solar wind is less turbulent during solar minima and thus presents less of a barrier to incoming galactic cosmic rays, so cosmic rays were at a high during that time period. Cosmic rays include various high energy particles, and they create a shower of secondary radiation upon impact with the Moon or a spacecraft's shielding. Looper et al. ran simulations that model the response of the CRaTER sensor to various energetic particles.

The simulations enabled the researchers to extract observations about the radiation environment from observations specific to the sensor. Looking at contributions from galactic cosmic rays, secondary particles, and sensor background, they were able to derive energy spectra for the radiation dose that humans or instruments would absorb in the lunar environment.