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Fact sheet number: FS-2001-11-191-MSFC
Release date: 10/01
Extravehicular Activity Radiation Monitoring (EVARM)
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Missions: Up on Expedition Four, ISS Flight UF-1, Space Shuttle mission STS-108. Down on Expedition Six, ISS Flight ULF-1, Space Shuttle mission STS-114.
Experiment Location on ISS: U.S. EMU space suits during EVA; stored in Human Research Facility rack in Destiny module
Principal Investigator: Ian Thomson, Thomson & Nielsen Electronics, Ltd., Ottawa, Canada
NASA Project Manager: Michelle Kamman, Johnson Space Center, Houston, Tex
CSA Project Manager: Ron Wilkinson, Canadian Space Agency, Ottawa, Canada
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The blueprint of life, DNA's double helix, left, is found in the cells of everything from bacteria to astronauts. Exposure to radiation, right, such as X-rays or heavy ion particles, can damage DNA and cause dire consequences both to the organism itself and to future generations. One of NASA's main goals is to develop better radiation shielding materials to protect astronauts from destructive radiation in space. (Frank Cucinotta, NASA/Johnson Space Cente, Prem Saganti, Lockheed Martin)
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Overview
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Shown is the storage/badge reader unit for the Extravehicular Activity Radiation Monitoring (EVARM) experiment. It contains sets of three radiation detector badges for up to four spacewalkers, designated EV-1, EV-2, EV-3 and EV-4. The EV-1 badges are shown plugged into the badge reader, while others are stored in the lid. (NASA/JSC)
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Space travel can be dangerous for humans because of the large amounts of radiation - particularly Extra Vehicular Activity, or EVA, when an astronaut is spacewalking outside the shielded walls of his or her spacecraft and protected only by a spacesuit. Construction and maintenance of the Space Station will require hundreds of hours of spacewalk time over the life of the program. Very high doses of radiation can kill cells and damage tissue, leading to cancer, cataracts, and even cause injury to the central nervous system.
Monitoring devices have flown on several Space Shuttle missions, and Russia's space station Mir to learn more about how to protect crews from the effects of radiation. But these devices were not specifically designed to study radiation dosages obtained during spacewalks.
The Extravehicular Activity Radiation Monitoring (EVARM) will be the first to measure radiation dosage encountered by the eyes, internal organs and skin during specific spacewalks, and relate it to the type of activity, location and other factors. An analysis of this information may be useful in mitigating potential exposure to space walkers in the future.
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Experiment Operations
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Shown are the Extravehicular Activity Radiation Monitoring (EVARM) experiment badges for the EV-1 crew member. Measuring less than 3 inches (7.62) long and less than an inch (2.54 cm) thick, each badge contains a silicon chip called a Metal Oxide Silicon Field Effect Transistor (MOSFET) that continuously measures total radiation. (NASA/JSC)
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EVARM is designed for use with the NASA Extravehicular Mobility Unit, or spacesuit, worn by both Space Station and Space Shuttle crewmembers during Station operations. The experiment consists of a storage/badge reader unit and 12 badges - a set of three each for up to four spacewalkers. The sets are designated EV-1, EV-2, EV-3 and EV-4, corresponding to the designation of each potential spacewalker. When not in use, the badges are placed in the storage/reader box, which is stored in the Human Research Facility payload rack.
The badge contains a silicon chip specially designed by Thomson-Nielsen - called a Metal Oxide Silicon Field Effect Transistor (MOSFET) - that continuously measures total radiation dosage and a connector that plugs into the badge reader. The reader can download radiation data from three badges simultaneously. Extravehicular Activity Radiation Monitoring (EVARM) experiment badge is shown placed in a pocket in the lower left leg of an astronaut liquid cooling garment. Badges also are placed in the front torso and fabric communications cap of the spacesuit undergarment. (NASA/JSC)
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Extravehicular Activity Radiation Monitoring (EVARM) experiment badge is shown placed in a pocket in the lower left leg of an astronaut liquid cooling garment. Badges also are placed in the front torso and fabric communications cap of the spacesuit undergarment. (NASA/JSC)
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During normal operations, the Station crew will record the background radiation dosage on each badge and transmit it to the ground every week. Shortly before a spacewalk by Station or Shuttle crew members, the crew will measure the radiation dosage of each badge to be used in the spacewalk. A set of three badges will be inserted into pockets sewn into the front torso and front leg areas of the liquid cooling undergarment and the top of the fabric communications cap of each spacesuit. Those locations were selected because of the radiation hazard to sensitive soft tissues such as eyes and internal organs, as well as the hazard to the skin on the arms and legs, which are not as well shielded as the torso.
Shortly after the spacewalk, the crew will plug each badge set into the badge reader. They will later transfer the data to the Human Research Facility laptop computer for transmission to the payload team on the ground.
EVARM will be ferried to the Station on the STS-108 Space Shuttle mission scheduled for Nov. 29, 2001. It will be used during Expeditions Four through Six before being returned to Earth.
Flight History/Background
Scientists have been measuring radiation in Earth's upper atmosphere and beyond since balloon launches in the 1940s. Radiation experiments have been part of many human space missions, measuring radiation exposure to spacecraft and space travelers. The Canadian Space Agency and the principal investigator for the experiment flew a similar radiation monitoring experiment on three missions aboard the Russia's space station Mir in the mid-1990s. That experiment used passive dosimeters that were read after they were returned to Earth. The dosimeters were placed in the cosmonauts' sleeping quarters but were not carried on spacewalks. The purpose of the experiment, in partnership with the Institute for Biomedical Problems in Moscow, was to correlate an electronic dosimeter with the passive dosimeters commonly worn by the cosmonauts.
Benefits
EVARM will help scientists better understand and predict radiation exposure encountered by astronauts during spacewalks and compare that to specific activities. For instance, scientists believe that spacewalkers who work close to the massive structure of the Station will receive a lower radiation dosage than spacewalkers working at the end of the Shuttle or Station robot arms. The results of the investigation may offer ways to mitigate exposure to radiation during spacewalks. Thomson-Nielsen also manufactures radiation sensors for use during cancer therapy. This space experiment will help further the technology used for radiation sensors on Earth.
More Information
More information on the EVARM experiment and other experiments are available at:
http://www.scipoc.msfc.nasa.gov/
http://www.spaceflight.nasa.gov/
http://spaceresearch.nasa.gov/
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