Dosimetric Mapping (DOSMAP) allowed mapping of radiation levels throughout the internal environment of the International Space Station (ISS) and in the immediate vicinity of each crewmember. The resulting data helped determine the best radiation shielding locations on board the ISS, thereby providing the crew with the best possible protection during unusually high levels of radiation due to solar flares and other cosmic phenomena.Principal Investigator(s)
Johnson Space Center, Human Research Program, Houston, TX, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)Research Benefits
Information PendingISS Expedition Duration
March 2001 - August 2001Expeditions Assigned
2Previous ISS Missions
The DOSMAP investigation was performed on the following Space Shuttle flights: STS-9, STS-61, STS-42, STS-55, STS-65, STS-76, STS-79, STS-81, STS-84, STS-86; three Russian research satellites and EuroMir.
Interactions of ionizing radiations with the ISS structure and its contents creates a somewhat different radiation field at each location inside the ISS modules. This is in part due to a large contribution from secondary radiation created by particles colliding with the spacecraft materials. Dosimetric Mapping (DOSMAP) was designed to map the total absorbed dose in the US Laboratory module of the ISS. DOSMAP was deployed from March through August of 2001. This time frame included results from the solar particle event (SPE) that occurred on April 15, 2001.
To fully characterize the doses observed on the ISS, four detector types were used: thermo-luminescence dosimeter (TLD) chips, CR39 nuclear track detectors with and without converters (NTDPs), a silicon dosimetry telescope (DOSTEL), and four mobile silicon detector units (MDUs). Crewmembers used the MDUs as personal dosimeters. They provided the ability to measure spectral composition with respect to nuclear charge, energy, and rate of energy deposition (linear energy transfer (LET)), as well as to estimate absorbed dose from galactic radiation, radiation belt particles, and the April solar particle event (SPE).
DOSMAP will produce a clearer image of the radiation environment aboard the ISS, revealing what segments provide better radiation shielding and examining the radiation levels immediately surrounding crewmembers.
DOSMAP research will help scientists more accurately predict radiation exposure in long-duration space flight, both in low Earth orbit and outside Earth's magnetic field. With this information, it will be possible to develop countermeasures that will protect crews in space on longer missions to Mars and the Moon, and it may also help lead to technologies to protect people working in potentially radioactive areas on Earth, such as nuclear power plants and nuclear submarines.
This experiment is teaching scientists more about the use of devices for data collection and how to monitor real-time data. This could prove beneficial to radiation monitoring of commercial airline crews and military flight crews.
DOSMAP required the use of the computer in the Human Research Facility - 1 (HRF-1), which was used to transmit DOSTEL information to Earth every 10 days. MDUs were recharged every 5-days. Crew members deactivated and stowed all dosimeters for return on STS-105.Operational Protocols
Dosimeters placed around the ISS absorbed radiation during a three-month period. Crewmembers collected select dosimeters every 10 days and recorded the data. Crewmembers also charged their MDUs every 5 days. TLDs required maintenance every 10 days. Other dosimeters recorded information for the entire three-month mission for postflight analysis on Earth.
In general, radiation damage to the human body is indicated by the amount of energy deposited in living tissue, modified by the type of radiation causing the damage; this is measured in units of Sieverts (Sv). The background radiation dose received by an average person in the United States is approximately 3.5 milliSv/year. An exposure of 1 Sv/hour can result in radiation poisoning and a dose of 5 Sv/hour will result in death in 50% of exposed individuals. An average dose due to all detectors during Expedition 2 was found to be 532 microSv/day. This is significantly lower than measurements taken on previous space shuttle and Mir missions. All dosimeters showed agreement to within 10% of one another and over 95% of the projected measurements were able to be collected (Reitz 2001, 2005).
Three important conclusions were drawn from this experiment that will help with future monitoring activities:
Beaujean R, Dachev TP, Deme S, Reitz G, Heinrich W, Luszik-Bhadra M, Olko P. Dosimetric Mapping. Conference and Exhibit on International Space Station Utilization, Cape Canaveral, FL; 2001
Beaujean R, Benton E, Dachev TP, Reitz G, Burmeister S, Deme S, Luszik-Bhadra M, Olko P. Space radiation measurements on-board ISS - the DOSMAP experiment. Radiation Protection Dosimetry. 2005; 116(1-4): 374-379. DOI: 10.1093/rpd/nci262.