The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011, and for most of the 253-day, 560-million-kilometer cruise to Mars, the Radiation ...Assessment Detector made detailed measurements of the energetic particle radiation environment inside the spacecraft. These data provide insights into the radiation hazards that would be associated with a human mission to Mars. We report measurements of the radiation dose, dose equivalent, and linear energy transfer spectra. The dose equivalent for even the shortest round-trip with current propulsion systems and comparable shielding is found to be 0.66 ± 0.12 sievert.
The Kuiper Belt hosts a swarm of distant, icy objects ranging in size from small, primordial planetesimals to much larger, highly evolved objects, representing a whole new class of previously ...unexplored cryogenic worlds. Pluto, the largest among them, along with its system of five satellites, has been revealed by NASAs New Horizons spacecraft flight through the system in July 2015, nearly a decade after its launch.
The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) is an energetic particle detector designed to measure a broad spectrum of energetic particle radiation. It will make the ...first-ever direct radiation measurements on the surface of Mars, detecting galactic cosmic rays, solar energetic particles, secondary neutrons, and other secondary particles created both in the atmosphere and in the Martian regolith. The radiation environment on Mars, both past and present, may have implications for habitability and the ability to sustain life. Radiation exposure is also a major concern for future human missions. The RAD instrument combines charged- and neutral-particle detection capability over a wide dynamic range in a compact, low-mass, low-power instrument. These capabilities are required in order to measure all the important components of the radiation environment.
RAD consists of the RAD Sensor Head (RSH) and the RAD Electronics Box (REB) integrated together in a small, compact volume. The RSH contains a solid-state detector telescope with three silicon PIN diodes for charged particle detection, a thallium doped Cesium Iodide scintillator, plastic scintillators for neutron detection and anti-coincidence shielding, and the front-end electronics. The REB contains three circuit boards, one with a novel mixed-signal ASIC for processing analog signals and an associated control FPGA, another with a second FPGA to communicate with the rover and perform onboard analysis of science data, and a third board with power supplies and power cycling or “sleep”-control electronics. The latter enables autonomous operation, independent of commands from the rover. RAD is a highly capable and highly configurable instrument that paves the way for future compact energetic particle detectors in space.
The Radiation Assessment Detector, RAD, is one of the ten instruments that make up the science payload of the Mars Science Laboratory Curiosity rover. RAD is an energetic particle detector, capable ...of measuring the charged and neutral particles that make significant contributions to the radiation dose that will be received by future human explorers when they visit Mars. Prior to the launch of MSL in November 2011, RAD and its near-identical twin flight spare unit were calibrated using laboratory sources, charged particle beams, and neutron fields. The initial calibration parameters obtained in these tests were used for real-time data analysis by the instrument’s onboard software. These parameters have subsequently been refined using data obtained during the cruise to Mars and during Curiosity’s mission on the surface of Mars. The most critical use of calibration is in the dosimetry analysis performed onboard. Calibration is also used in onboard analysis to determine which events should be stored for telemetry to Earth. Accelerator data obtained with the flight spare unit after Curiosity was launched provide detailed information about the response of the organic and inorganic scintillators to ion beams over a wide range of charge and energy. Here we report on the methods used to determine calibration parameters, the results obtained, as well as providing an overview of the modifications to the instrument’s software and configuration that have been made over the course of the mission.
The Radiation Assessment Detector (RAD), onboard the Mars Science Laboratory (MSL) rover Curiosity, measures the energetic charged and neutral particles and the radiation dose rate on the surface of ...Mars. An important factor for determining the biological impact of the Martian surface radiation is the specific contribution of neutrons, with their deeper penetration depth and ensuing high biological effectiveness. This is very difficult to measure quantitatively, resulting in considerable uncertainties in the total radiation dose. In contrast to charged particles, neutral particles (neutrons and gamma rays) are generally only measured indirectly. Measured spectra are a complex convolution of the incident particle spectrum with the detector response function and must be unfolded. We apply an inversion method (based on a maximum likelihood estimation) to calculate the neutron and gamma spectra from the RAD neutral particle measurements. Here we show the first spectra on the surface of Mars and compare them to theoretical predictions. The measured neutron spectrum (ranging from 8 to 740 MeV) translates into a radiation dose rate of 14±4μGy/d and a dose equivalent rate of 61±15μSv/d. This corresponds to 7% of the measured total surface dose rate and 10% of the biologically relevant surface dose equivalent rate on Mars. Measuring the Martian neutron and gamma spectra is an essential step for determining the mutagenic influences to past or present life at or beneath the Martian surface as well as the radiation hazard for future human exploration, including the shielding design of a potential habitat.
Key Points
We calculated the Martian neutron and gamma spectra
We compare the results to Planetocosmics simulations
We calculate dose and dose equivalent rate for the neutron spectrum
The Mars Science Laboratory rover Curiosity, operating on the surface of Mars, is exposed to radiation fluxes from above and below. Galactic Cosmic Rays travel through the Martian atmosphere, ...producing a modified spectrum consisting of both primary and secondary particles at ground level. These particles produce an upward directed secondary particle spectrum as they interact with the Martian soil. Here we develop a method to distinguish the upward and downward directed particle fluxes in the Radiation Assessment Detector (RAD) instrument, verify it using data taken during the cruise to Mars, and apply it to data taken on the Martian surface. We use a combination of Geant4 and Planetocosmics modeling to find discrimination criteria for the flux directions. After developing models of the cruise phase and surface shielding conditions, we compare model‐predicted values for the ratio of upward to downward flux with those found in RAD observation data. Given the quality of available information on Mars Science Laboratory spacecraft and rover composition, we find generally reasonable agreement between our models and RAD observation data. This demonstrates the feasibility of the method developed and tested here. We additionally note that the method can also be used to extend the measurement range and capabilities of the RAD instrument to higher energies.
Plain Language Summary
The MSL rover Curiosity is exposed to energetic particles from above and below on the Martian surface. Particles enter the Martian atmosphere from above and travel through it until they reach the ground. Particles lose energy and can produce secondary particles while passing through the atmosphere, resulting in an energy distribution on ground level that is different from that on the top of the atmosphere. The resulting particles produce an upward directed particle distribution in the soil. We develop a method to distinguish the upward and downward particle fluxes in the RAD instrument, verify it using data taken during the cruise to Mars, and apply it to data taken on the Martian surface. We use a combination of models to find criteria for discriminating the flux directions. After developing models of the cruise phase and surface shielding conditions, we compare simulated values for the ratio of upward to downward flux with those found in observation data. We find generally reasonable agreement between our models and RAD observation data. This demonstrates the feasibility of the method developed and tested here. The method can also be used to extend the measurement range and capabilities of the RAD instrument to higher energies.
Key Points
We model the radiation environment during the MSL cruise phase and on the Martian surface
We obtain the particle energy spectra at the RAD instrument for both scenarios
After developing a method to distinguish between upward and downward fluxes, we apply the method both to simulation data and to data taken by the RAD instrument during the cruise phase and on the surface
We prospectively compared the occurrence of morbidity during high-risk interhospital transport in two types of transport systems: specialized tertiary center-based vs. nonspecialized, referring ...hospital-based.
Concurrent, prospective comparison of morbidity at two pediatric centers that use different types of transport team.
Two tertiary care pediatric intensive care units (ICU). The specialized team consisted of a pediatric resident, pediatric intensive care nurse, and a pediatric respiratory therapist. Comparison was made with referring institution transports by nonspecialized personnel to a second center. The two centers were similar in size and patient mix, with referral areas of similar population and rural/urban ratio.
One hundred forty-one patients transported to two tertiary pediatric ICUs.
None.
Two types of events were assessed: vital signs and other observable clinical events were described as "physiologic deteriorations." Events such as loss of intravenous access, endotracheal tube mishaps, and exhaustion of oxygen supply were described as "intensive care-related adverse events." Pretransport severity of illness and therapy were described by Pediatric Risk of Mortality (PRISM) and Therapeutic Intervention Scoring System (TISS) scores. Only high-risk patients with PRISM scores of > or = 10 were analyzed. Intensive care-related adverse events occurred in one (2%) of 49 transports by the specialized team and 18 (20%) of 92 transports by nonspecialized personnel. The difference is statistically significant (p < .05). Physiologic deterioration was similar in the two groups occurring in five (11%) of 47 specialized team transports and 11 (12%) of 92 transports by the nonspecialized team.
We conclude that specialized pediatric teams can reduce transport morbidity. This is the first published study to compare two models of pediatric transport using identical definitions of severity and morbidity.
•Haze settles rapidly onto Pluto's surface, yet there is color diversity.•Interaction of haze is explored for three distinct surface units.•Haze particles could evolve differently in different ...regions or haze particles with different characteristics arrive in different regions.
Pluto's atmospheric haze settles out rapidly compared with geological timescales. It needs to be accounted for as a surface material, distinct from Pluto's icy bedrock and from the volatile ices that migrate via sublimation and condensation on seasonal timescales. This paper explores how a steady supply of atmospheric haze might affect three distinct provinces on Pluto. We pose the question of why they each look so different from one another if the same haze material is settling out onto all of them. Cthulhu is a more ancient region with comparatively little present-day geological activity, where the haze appears to simply accumulate over time. Sputnik Planitia is a very active region where glacial convection, as well as sublimation and condensation rapidly refresh the surface, hiding recently deposited haze from view. Lowell Regio is a region of intermediate age featuring very distinct coloration from the rest of Pluto. Using a simple model haze particle as a colorant, we are not able to match the colors in both Lowell Regio and Cthulhu. To account for their distinct colors, we propose that after arrival at Pluto's surface, haze particles may be less inert than might be supposed from the low surface temperatures. They must either interact with local materials and environments to produce distinct products in different regions, or else the supply of haze must be non-uniform in time and/or location, such that different products are delivered to different places.
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