Space Test Program-H4-Miniature Array of Radiation Sensors (STP-H4-MARS) - 08.12.14
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Space Test Program-Houston 4-Miniature Array of Radiation Sensors (STP-H4-MARS) uses a network of 8 small radiation dosimeters to monitor the radiation experienced by a host spacecraft. The host is the STP-H4-GLADIS satellite. An STP-H4-MARS sensor includes a small circuit, which directly measures ionizing radiation from the sun and other cosmic sources.
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Naval Research Laboratory, Washington, DC, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
National Laboratory - Department of Defense (NL-DoD)
ISS Expedition Duration
March 2013 - March 2015
Previous ISS Missions
Space Test Program-Houston 4-Miniature Array of Radiation Sensors (STP-H4-MARS) providse the radiation depth-dose profile in the vehicle, which can be directly compared with calculations using environmental models and radiation transfer computer codes.
STP-H4-MARS allows for verification of space vehicle radiation design models.
STP-H4-MARS tests and characterizes on-orbit performance of a new radiation shielding material (Demron®).
The Space Test Program-Houston 4-Miniature Array of Radiation Sensors (STP-H4-MARS) experiment flies an array of eight microdosimeters, seven external nodes and one internal node. Three nodes are placed on mutually orthogonal surfaces on the outside of the host experiment (STP-H4 GLADIS). One node is located inside the GLADIS experiment near the FPGA to allow for radiation dose monitoring near a critical electrical component. An array of four nodes is externally co-located on STP-H4. This four-node array has differing shielding thickness to provide a radiation dose energy spectrum.
A new radiation shielding material, Demron®, is being space flight tested at three different thickness levels (1, 3, and 8). Demron® Fabric is a relatively high TRL material that has demonstrated energetic electron (beta emitting radionuclides) and X-ray/gamma-ray shielding performance and is already in use in protective garments used in the nuclear industry and in DoD/Homeland Security products. Demron® consists largely of tungsten and bismuth particles in a proprietary fabric composite. Given the demonstrated electron shielding properties of Demron® Fabric as demonstrated in ground based accelerator and radionuclide testing, it is a natural candidate for flexible shielding against trapped electrons at geosynchronous orbit (GEO).
The next step in evaluating Demron® for space applications is a flight demonstration and STP-H4-MARS offers an opportunity for such testing. Even though the ISS trapped electron environment is much more benign than the GEO environment, measurements of trapped electron/proton dose to the STP-H4-MARS sensors on ISS, as a function of Demron® thickness, can provide such a flight demonstration because the ISS trapped electron/proton environment is well characterized and the measurements can be interpreted using existing high energy particle transport codes, e.g., FLUKA (a particle physics Monte Carlo simulation package). Reasonably accurate estimates of GEO performance can then follow using energetic particle transport codes in combination the standard GEO environment models.
The STP-H4-MARS investigation provides data to inform a new 3-dimensional model of radiation impact on an example payload. This verifies design parameters for spacecraft, and help researchers determine how much shielding is necessary for internal instruments and external instruments. The investigation also tests the effectiveness of a new type of radiation shield, which could be used for geosynchronous satellites.
An improved understanding of the radiation environment surrounding Earth helps determine the radiation risks for high-altitude aircraft, unmanned aerial vehicles and balloons. Understanding the ability of space flight hardware to shield against radiation helps researchers studying forms of shielding on Earth, including medical imaging electronics.
The intent is to collect a full year’s worth of data and correlate it with solar and geophysical activity. Data is routinely telemetered down for analysis by the PI institution.
The STP-H4-MARS experiment is a "state-of-health" type array of sensors. As such there is minimal need for operations aside from telemetering the data to the ground. There is an initial on-orbit checkout period to assure that the sensors and communications systems are working properly. After that has been completed it is expected to enter a nominal mode and continue to collect in that mode for the duration of the mission.
Computer generated image of STP-H4.
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