Risk and Performance Assessment of Generic Mission Architectures: Showcasing the Artemis Mission

A has initiated a strong push to return face. In this work, we astronaut assess performance and risk for proposed mission architectures using a new Mission Architecture Risk Assessment (MARA) tool. The MARA tool can produce statistics about the availability of components and overall performance of the mission considering potential failures of any of its components. In a Monte Carlo approach, the tool repeats the mission simulation multiple times while a random generator lets modules fail according to their failure rates. The results provide statistically meaningful insights into the overall performance of the chosen architecture. A given mission architecture can be freely replicated in the tool, with the mission timeline and basic characteristics of employed mission modules (habitats, rovers, power generation units, etc.) specified in a configuration file. Crucially, failure rates for each module need to be known or estimated. The tool performs an event-driven simulation of the mission and accounts for random failure events. Failed modules can be repaired, which takes crew time but restores operations. In addition to tracking individual modules, MARA can assess the availability of predefined functions throughout the mission. For instance, the function of resource collection would require a rover to collect the resources, a power generation unit to charge the rover, and a resource processing module. Together, the modules that are required for a given function are called a functional group. Similarly, we can assess how much crew time is available to achieve a mission benefit (e.g. research, building a base, etc) as opposed to spending crew time on repairs. Here we employ the method on the proposed NASA Artemis mission. Artemis aims to return United States astronauts to the lunar surface by 2024. Results provide insights into mission failure probabilities, up- and downtime for individual modules and crew-time resources spent on the repair of failed modules. The tool also allows us to tweak the mission architecture in order to find setups that produce more favorable mission performance. As such, the tool can be an aid in improving the mission architect abling cost-benefit analysis for mission improvement

Asteroid impact effects and their immediate hazards for human populations

A set of 50,000 artificial Earth impacting asteroids was used to obtain, for the first time, information about the dominance of individual impact effects such as wind blast, overpressure shock, thermal radiation, cratering, seismic shaking, ejecta deposition, and tsunami for the loss of human life during an impact event for impactor sizes between 15 and 400 m and how the dominance of impact effects changes over size. Information about the dominance of each impact effect can enable disaster managers to plan for the most relevant effects in the event of an asteroid impact. Furthermore, the analysis of average casualty numbers per impactor shows that there is a significant difference in expected loss for airburst and surface impacts and that the average impact over land is an order of magnitude more dangerous than one over water

Apophis planetary defense campaign

We describe results of a planetary defense exercise conducted during the close approach to Earth by the near-Earth asteroid (99942) Apophis during 2020 December–2021 March. The planetary defense community has been conducting observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. These community-led global exercises were carried out with the support of NASA's Planetary Defense Coordination Office and the International Asteroid Warning Network. The Apophis campaign is the third in our series of planetary defense exercises. The goal of this campaign was to recover, track, and characterize Apophis as a potential impactor to exercise the planetary defense system including observations, hypothetical risk assessment and risk prediction, and hazard communication. Based on the campaign results, we present lessons learned about our ability to observe and model a potential impactor. Data products derived from astrometric observations were available for inclusion in our risk assessment model almost immediately, allowing real-time updates to the impact probability calculation and possible impact locations. An early NEOWISE diameter measurement provided a significant improvement in the uncertainty on the range of hypothetical impact outcomes. The availability of different characterization methods such as photometry, spectroscopy, and radar provided robustness to our ability to assess the potential impact risk

Asteroid impact risk

Asteroid impacts are a hazard to human populations. A method to assess the impact risk of hazardous asteroids was developed in this work, making use of the universal concept of risk culminating in the Asteroid Risk Mitigation Optimization and Research (ARMOR) tool. Using this tool, the global spatial risk distribution of a threatening asteroid can be calculated and expressed in the units of expected casualties (= fatalities). Risk distribution knowledge enables disaster managers to plan for a potential asteroid impact through identification of high risk regions and estimation of total risk as a scalar value. Expressing the risk in terms of expected casualties would allow the placement of the asteroid threat on the same scale as other human hazards. Thus, this unit provides an accessible way of defining thresholds for asteroid threat response protocols, of communicating the threat utilizing a new hazard scale, and of allocating adequate resources to address the hazard by comparison with other natural disasters. To accomplish risk estimation, vulnerability models were needed that relate the severity of impact effects (wind blast, overpressure shock, thermal radiation, cratering, seismic shaking, ejecta out-throw, and tsunami) on the human population and a novel comprehensive suite of such models were derived and presented. The need for high fidelity impact effect and vulnerability modelling, as opposed to a simplified, impact location based approach, for risk estimation of a specific asteroid threat was analysed and confirmed. Subsequently, the method of ARMOR was applied to asteroid 2015 RN35 to produce an example risk distribution output. Additional analysis shows that the general impact location distribution of asteroids is approximately uniform, confirming, for the first time, a common assumption made in planetary defense. Extensive global simulations were performed utilizing an artificial sample of 50,000 impactors with sizes up to 400m to identify which impact effects are most hazardous to the human population. Aerothermal effects are most hazardous while tsunamis only contribute moderately to the overall hazard. The average land impactor is an order of magnitude more dangerous than a similar water impactor and asteroids smaller than 50-60m (density ≈ 3100 kg/m3) are expected to airburst rather than reach the surface. Furthermore, the average loss estimate for asteroid impactors enables fast threat analysis of newly discovered asteroids and helps determine the asteroid size that contributes most to the residual asteroid impact risk. These results provide new insights to inform efficient preparation for a future asteroid threat. In the future, ARMOR can be used to perform on-ground risk driven asteroid detection mission design which would reduce risk of an incoming asteroid progressively and this is not accomplished with current methods

Monitoring the global asteroid impact risk

ESA’s asteroid risk list contains all known asteroids that have a non-zero chance of colliding with the Earth in the future. The possible impact locations of the asteroids in the list with a minimum diameter of 30 m were calculated. To this end, the freely available software OrbFit was utilized to find orbit solutions for each asteroid that result in a future collision with the Earth. These orbit solutions are called virtual impactors (VIs). Subsequently, the Asteroid Risk Mitigation Optimization and Research (ARMOR) tool was used to determine the impact locations for each VI taking into account orbit solution uncertainty and global impact probability. The resulting 261 impact corridors were visualized on a global map. Furthermore, the impact data were combined with Earth population data to determine the risk of direct asteroid impacts that each nation faces until 2100. These data are the global asteroid risk distribution based on observed asteroids as is known today. A ranking of the countries that exhibit highest risk was produced showing their relative risk with respect to the global risk. It becomes clear that population size is a good proxy for relative risk. Each nation should raise public awareness about the asteroid hazard and should include the asteroid threat in their natural disaster response planning. Physical impact effects are introduced into the analysis. This expands the validity of the results beyond the previously considered relative risk and allows the estimation of the future absolute risk (expected casualties) that the currently known asteroids pose to the populations of the Earth. The alteration of the results based on the introduction of physical impact effects is discussed

Sensitivity to Uncertainty in Asteroid Risk Assessment (Global Effects)

No abstract availabl

An Algorithmic Approach for Detecting Bolides with the Geostationary Lightning Mapper

The Geostationary Lightning Mapper (GLM) instrument onboard the GOES 16 and 17 satellites can be used to detect bolides in the atmosphere. This capacity is unique because GLM provides semi-global, continuous coverage and releases its measurements publicly. Here, six filters are developed that are aggregated into an automatic algorithm to extract bolide signatures from the GLM level 2 data product. The filters exploit unique bolide characteristics to distinguish bolide signatures from lightning and other noise. Typical lightning and bolide signatures are introduced and the filter functions are presented. The filter performance is assessed on 144845 GLM L2 files (equivalent to 34 days-worth of data) and the algorithm selected 2252 filtered files (corresponding to a pass rate of 1.44%) with bolide-similar signatures. The challenge of identifying frequent but small, decimeter-sized bolide signatures is discussed as GLM reaches its resolution limit for these meteors. The effectiveness of the algorithm is demonstrated by its ability to extract confirmed and new bolide discoveries. We provide discovery numbers for November 2018 when seven likely bolides were discovered of which four are confirmed by secondary observations. The Cuban meteor on Feb 1st 2019 serves as an additional example to demonstrate the algorithms capability and the first light curve as well as correct ground track was available within 8.5 hours based on GLM data for this event. The combination of the automatic bolide extraction algorithm with GLM can provide a wealth of new measurements of bolides in Earth’s atmosphere to enhance the study of asteroids and meteors

The influence of spin-misalignment scattering on the SANS data evaluation of martensitic age-hardening steels

Small-angle neutron scattering has proved to be a valuable technique for probing precipitates in steels. The investigated sample is thereby exposed to a large magnetic field and is assumed to consist of a single domain with all the magnetic moments perfectly aligned with the external field. In this situation the dominating magnetic scattering contrast is expected to stem from the differences between the magnetization values of matrix and particles. However, the present work shows that strong additional scattering can be present which is due to spin misalignment. The effects of this spin-misalignment scattering are discussed as being exemplary for differently heat-treated martensitic steel samples. It is revealed that the amount of spin-misalignment scattering is very sensitive to the applied heat treatment and is most pronounced in the as-quenched condition. In particular, when considering nuclear scattering curves the influence of spin-misalignment scattering may be very large and must not be neglected