Fact sheet number: FS-2001-02-40-MSFC
Radiation constitutes one of the most important hazards for humans during long-term space missions. Leaving Earth’s surface exposes human beings to a wide spectrum of radiation particles and energies. The International Space Station provides shielding, but some radiation gets through.
Dosimetric Mapping, or Dosmap, attempts to record and map the different types of radiation that get inside Space Station and ultimately could cause harm to humans — including cataracts and cancer.
Dosmap’s radiation detection devices are called dosimeters. Because of the variety of particles and energies that make up radiation, no single type of dosimeter is capable of providing sufficient information to study radiation, so several different types of dosimeters are used in this experiment.
Radiation gathered by the dosimeters will provide scientists information on the nature and distribution of radiation inside the Space Station t.
Dosimeters, placed throughout the Station, will absorb radiation during a three-month period. Some of the dosimeters will be collected every two weeks, their data recorded, and saved on a Station computer. Other dosimeters will record all the radiation absorbed and be returned to Earth for analysis.
Nuclear Tracking Detector Packages (NTDP) measure how much radiation is absorbed, the level of neutrons present and the angle of entry for the radiation into a variety of different radiation-shielding materials. These small packages will be placed in different locations on the Station to monitor incoming radiation.
Each package contains three strips of a plastic film on which high energy particles passing through this film will leave a track. One strip will be used for each of three perpendicular axes. The film will be returned to the Earth for analysis.
The Dosimetry Telescopes, called DOSTELs, containing two thin silicon detectors, will be used to measure the flow or stream of ions, which are atomic particles carrying a positive or negative electric charge. Two of these will be placed near each other in empty rack space in the U.S. Laboratory.
Several mobile dosimetry units will be used by crew members as personal dosimeters or placed throughout the Station.
Twelve thermoluminescence dosimeters (TLDs) will measure the neutron dose of the incoming radiation and the average absorbed dose on board the Station during the mission. Neutrons are uncharged atomic particles that have the ability to penetrate living tissues. The TLDs are encased in Lexan plastic which responds to radiation by exciting long-lived electronic states in various lithium compounds. After exposure, the amount of this radiation can be revealed by applying heat and measuring the amount of visible light released as these excited states decay.
Station crew members will set up and activate the Dosmap during the 5A.1 stage of Expedition Two, which is the time between Shuttle mission STS-102 in March and Shuttle mission STS-100 in April. DOSTEL data will be transferred and downlinked to Earth every 10 days using the computer in the Human Research Facility rack. The mobile dosimetry units will be recharged every five days, and the readout of the TLDs will be checked every 10 days.
The Station crew will deactivate and stow the Dosmap at the end of Expedition Two, to prepare it for return to Earth on Space Shuttle mission STS 105, scheduled in July 2001.
Since balloon launches in the 1940s, scientists have been measuring radiation in Earth’s upper atmosphere and beyond. Radiation experiments have been part of many human space missions, including space station Mir, measuring radiation exposure to spacecraft and space travelers. Specific missions during which some type of Dosmetric Mapping equipment was used include:
STS-9/SL-1: Nov. 1983
The Dosimetric Mapping system research will help scientists more accurately predict the radiation exposure Space Station crew members will experience in space. The result will be the development of countermeasures to safely prolong human exposure to radiation during space travel.
The Dosmap is one of three radiation measuring experiments which will fly on board the Space Station during Expedition Two.
For more information and photos on these radiation experiments and other Expedition Two science experiments, visit: