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

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 18 Nov 2013 22:13:53 -0800 (PST)
Message-ID: <201311190613.rAJ6DrNa020417_at_zagami.jpl.nasa.gov>

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."
Received on Tue 19 Nov 2013 01:13:53 AM PST


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