As Astronauts Walk, NASA Keeps Tabs on Radiation

Feb. 19, 2008 -- For more than 40 years, NASA has kept tabs on astronauts' heart rates, respiration, temperature and dispositions as they ventured outside their ships to work in open space.

But it wasn't until the spacewalks by shuttle Atlantis astronauts last week that the U.S. space agency attempted to track how much solar radiation they might be exposed to during their outings.

"We're testing this model to see if it can be used in an operational situation," said Stephen Guetersloh, a particle physicist with NASA's Space Radiation Analysis Group at the Johnson Space Center in Houston told Discovery News.

Taking data from instruments aboard the now orbiting Solar Heliospheric Observatory, or SOHO, scientists are attempting to correlate solar activity with the approach of highly energetic particles that could pose a health threat to spacewalking astronauts.

The system is intended to give NASA about an hour advance warning of potentially threatening radiation, said Arik Posner, with the Texas-based Southwest Research Institute.

"Although it seems relatively short notice, the warning can be mission-critical," said Posner, pointing to the spacewalks that will be required when NASA returns astronauts to the lunar surface.

Earth's magnetic field provides a protective bubble for people on the ground and most of the time for spaceships, like the International Space Station and space shuttles, in low-Earth orbit.