Space Test Program-H4-Miniature Array of Radiation Sensors (STP-H4-MARS) - 07.15.14
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Space Test Program-Houston 4-Miniature Array of Radiation Sensors (STP-H4-MARS) monitors the total dose radiation on a host spacecraft (in this case the host spacecraft is Space Test Program - Houston 4 - Global Awareness Data-Exfiltration International Satellite (STP-H4-GLADIS)) for 3-D radiation modeling with an array of persistent, ubiquitous micro dosimeter sensors. An STP-H4- MARS sensor node consists of a hybrid microcircuit which directly measures accumulated total ionizing dose in a silicon test mass, starting at power-up.
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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 experiment provides data to help improve correlations of on orbit observations with predictions of models such as AE8/AP8 and the follow-on AE9/AP9. The ability to fly an array of radiation “state-of-health” sensors allows one to provide a 3-D radiation depth profile oh the host payload. This is important as it can directly feed into on-orbit anomaly resolution, verification of space vehicle design models, and determination of the amount of shielding needed for different application (internal vs. external) .
A good understanding of the Erath’s radiation environment and how it relates to space flight hardware is important to assess the vulnerability and shielding of electrical components used in other fields that are also exposed to harsh environments such as high altitude aircraft, UAVs and balloons as well as 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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