[meteorite-list] Deep-Space Radiation Hazards Documented and Quantified

[Ron Baalke]

http://www.sciencedaily.com/releases/2013/11/131118133044.htm

Deep-Space Radiation Hazards Documented and Quantified
Science Daily
November 18, 2013

Scientists from the University of New Hampshire and colleagues have published 
comprehensive findings on space-based radiation as measured by a UNH-led 
detector aboard NASA's Lunar Reconnaissance Orbiter (LRO). The data provide 
critical information on the radiation hazards that will be faced by astronauts 
on extended missions to deep space such as those to Mars.

The papers in a special issue of the journal Space Weather document and 
quantify measurements made since 2009 by the Cosmic Ray Telescope for 
the Effects of Radiation (CRaTER) radiation detector.

"These data are a fundamental reference for the radiation hazards in near 
Earth 'geospace' out to Mars and other regions of our sun's vast heliosphere," 
says CRaTER principal investigator Nathan Schwadron of the UNH Institute 
for the Study of Earth, Oceans, and Space (EOS).

The space environment poses significant risks to both humans and satellites 
due to harmful radiation from galactic cosmic rays and solar energetic 
particles that can easily penetrate typical shielding and damage electronics. 
When this radiation impacts biological cells, it can cause an increased 
risk of cancer.

Before CRaTER's long-term radiation measurements were derived using a 
material called "tissue-equivalent plastic" -- a stand-in for human muscle 
capable of gauging radiation dosage -- those hazards were not sufficiently 
well characterized to determine if long missions outside low-Earth orbit 
can be accomplished with acceptable risk.

CRaTER's seminal measurements now provide quantified, radiation hazard 
data from lunar orbit and can be used to calculate radiation dosage from 
deep space down to airline altitudes. The data will be crucial in developing 
techniques for shielding against space-based radiation dosage. The measurements 
have also played a vital role in UNH space scientists' efforts to develop 
both the first Web-based tool for predicting and forecasting the radiation 
environment in near-Earth, lunar, and Martian space environments and a 
space radiation detector that possesses unprecedented performance capabilities.

The near real-time prediction/forecasting tool known as PREDICCS integrates 
for the first time numerical models of space radiation and a host of real-time 
measurements being made by satellites currently in space. It provides 
updates of the radiation environment on an hourly basis and archives the 
data weekly, monthly, and yearly -- an historical record that provides 
a clear picture of when a safe radiation dose limit is reached for skin 
or blood-forming organs, for example.

CRaTER offers an opportunity to test the capability of PREDICCS to accurately 
describe the lunar radiation environment. The Space Weather special issue 
provides comparisons between dose rates produced by PREDICCS with those 
measured by CRaTER during three major solar energetic particle events 
that occurred in 2012.

The detector developed at UNH, known as DoSEN, short for Dose Spectra 
from Energetic Particles and Neutrons, measures and calculates the absorbed 
dose in matter and tissue resulting from the exposure to indirect and 
direct ionizing radiation, which can change cells at the atomic level 
and lead to irreparable damage. Schwadron is lead scientist for both the 
PREDICCS and the DoSEN project.

"DoSEN is an innovative concept that will lead to a new generation of 
radiation detectors, or dosimeters, to aid in understanding the hazards 
posed by the radiation environment of space," says Schwadron. "The ability 
to accurately understand these hazards will be critical to protect astronauts 
sent beyond low-Earth orbit on extended space missions."

DoSEN combines two advanced, complementary radiation detection concepts 
that present fundamental advantages over traditional dosimetry. The dosimeter 
measures both the energy and the charge distribution of energetic particles 
that affect human and robotic health in a way not presently possible with 
current technology. Protons, heavy ions, and neutrons all contribute significantly 
to the radiation hazard.

"Understanding how different particles such as neutrons and heavy ions 
pose hazards will be extremely important in completely characterizing 
the types of environments we will operate in," Schwadron says. "For example, 
on the moon, there are additional hazards from neutrons that are created 
by high-energy radiation interacting in the lunar soil and radiating outward 
from the surface."

That "backsplash" of protons, which was discovered by CRaTER and is known 
as the moon's radiation "albedo," is caused by the partial reflection 
of galactic cosmic rays off the moon's surface. This creates a surprising 
one-two punch of deadly radiation and can also be used to peer below the 
lunar surface like a geological probe.

Says Harlan Spence, CRaTER deputy lead scientist and director of EOS, 
"Until now, people have not had the 'eyes' necessary to see this particular 
population of particles. With CRaTER, we just happen to have the right 
focus to make these discoveries."