Meteoroid Impact Detection for Exploration of Asteroids (MIDEA)

Asteroids contain a wealth of resources including water and precious metals that can be extracted. These resources could be applied to in-space manufacture of products that depend less on material launched from Earth's surface. The Meteoroid Impact Detection for Exploration of Asteroids (MIDEA) concept addresses the challenge of characterizing an asteroid surface using a small satellite with a constellation of free-flying plasma sensors to assess the asteroids viability for in situ resource utilization (ISRU). The plasma sensors detect ions ejected from the surface of an asteroid by meteoroid impacts, enabling the surface composition to be inferred. The objective of this NIAC Phase I study was to demonstrate feasibility of the MIDEA architecture in the context of proximity operations around an asteroid target and to develop the design of an orbital geometry and attitude control strategy for the ultralight plasma sensors. This was undertaken through a simulation framework to identify and characterize a favorable orbit for the MIDEA sensor constellation, and developing a sensor geometry that is consistent with maintaining the pointing requirements necessary to operate with sufficient power generation. Our study showed that a polar orbit aligned along the asteroid terminator provided sufficient stability for the sensors in the low gravitational environment under the influence of substantial solar radiation pressure. Reflector vanes using controlled reflectivity devices implemented with liquid crystal technology are capable of maintaining the sensor attitude so that it consistently points its solar panels in the sun direction and the sensor electrode at the asteroid surface. Finally, the reduction in meteoroid impact detection due to visibility constraints from the proposed orbit does not substantially extend the expected mission duration. These results indicate that the MIDEA concept can be achievable using a 1020 kg spacecraft, which would be able to characterize the surface composition of an asteroid within 3050 days of proximity operations. This architecture, implemented in parallel to multiple asteroid targets, would enable widespread exploration of near-Earth asteroids at low cost

Genetic Algorithm-Based Optimization to Match Asteroid Energy Deposition Curves

An asteroid entering Earth's atmosphere deposits energy along its path due to thermal ablation and dissipative forces that can be measured by ground-based and spaceborne instruments. Inference of pre-entry asteroid properties and characterization of the atmospheric breakup is facilitated by using an analytic fragment-cloud model (FCM) in conjunction with a Genetic Algorithm (GA). This optimization technique is used to inversely solve for the asteroid's entry properties, such as diameter, density, strength, velocity, entry angle, and strength scaling, from simulations using FCM. The previous parameters' fitness evaluation involves minimizing error to ascertain the best match between the physics-based calculated energy deposition and the observed meteors. This steady-state GA provided sets of solutions agreeing with literature, such as the meteor from Chelyabinsk, Russia in 2013 and Tagish Lake, Canada in 2000, which were used as case studies in order to validate the optimization routine. The assisted exploration and exploitation of this multi-dimensional search space enables inference and uncertainty analysis that can inform studies of near-Earth asteroids and consequently improve risk assessment

Modeling the Meteoroid Input Function at Mid-Latitude Using Meteor Observations by the MU Radar

The Meteoroid Input Function (MIF) model has been developed with the purpose of understanding the temporal and spatial variability of the meteoroid impact in the atmosphere. This model includes the assessment of potential observational biases, namely through the use of empirical measurements to characterize the minimum detectable radar cross-section (RCS) for the particular High Power Large Aperture (HPLA) radar utilized. This RCS sensitivity threshold allows for the characterization of the radar system s ability to detect particles at a given mass and velocity. The MIF has been shown to accurately predict the meteor detection rate of several HPLA radar systems, including the Arecibo Observatory (AO) and the Poker Flat Incoherent Scatter Radar (PFISR), as well as the seasonal and diurnal variations of the meteor flux at various geographic locations. In this paper, the MIF model is used to predict several properties of the meteors observed by the Middle and Upper atmosphere (MU) radar, including the distributions of meteor areal density, speed, and radiant location. This study offers new insight into the accuracy of the MIF, as it addresses the ability of the model to predict meteor observations at middle geographic latitudes and for a radar operating frequency in the low VHF band. Furthermore, the interferometry capability of the MU radar allows for the assessment of the model s ability to capture information about the fundamental input parameters of meteoroid source and speed. This paper demonstrates that the MIF is applicable to a wide range of HPLA radar instruments and increases the confidence of using the MIF as a global model, and it shows that the model accurately considers the speed and sporadic source distributions for the portion of the meteoroid population observable by MU

Analysis of electromagnetic and electrostatic effects of particle impacts on spacecraft

Abstract Particle impacts on spacecraft can cause considerable damage, even leading to complete failure. A theory for the resulting vehicle potential changes and the electromagnetic radiation from impact-induced plasma has been published b

Experimental Verification of Pulsed Electrostatic Manipulation for Reentry Blackout Alleviation

Spacecraft entering the Earth’s atmosphere from space are enveloped by a plasma layer containing highly mobile electrons that cause attenuation of electromagnetic waves, often leading to a loss of command, communication and telemetry signals, which is commonly referred to as the “blackout period”. The blackout period may last up to several minutes, and is a major contributor to the landing error ellipse. In the context of human spaceflight, this may also present a significant safety hazard. A new method called Pulsed Electrostatic Manipulation (PEM) was recently proposed to circumvent the communications blackout by applying strong electronegative voltage pulses from electrodes placed on the reentering spacecraft. Through two dimensional Particle-In-Cell (PIC) simulations, a reduction in electron density of up to three orders of magnitude in the vicinity of the electrode was demonstrated. These simulations were performed on the electron time scale ( nanoseconds), with emphasis on the interactions of the plasma with the insulation surrounding the electrode. In January 2016, a preliminary experimental campaign was conducted at the DLR L2K archeated facility in Cologne, Germany to verify the efficacy of PEM in reducing the electron density in a hypersonic plasma, in order to allow for the transmission of electromagnetic waves, thereby restoring communications during the blackout. We discuss the experimental setup for these tests - ranging from the design of the model, including the communication system, to the implementation of experimental protocols. Further, we share data for the attenuation caused by the presence of plasma between the receiving and transmitting antenna, and the effect of the applied high voltage pulses (up to 2.5kV) over short periods of time ( 10 microseconds) on the attenuation. Several unexpected effects have been observed in the voltage response of the electrode, including inductive spikes, stray capacitive effects, and Paschen breakdown of the gas inside the test stand. No measurable change in the attenuation profile was observed for pulses with voltage up to 2.5kV. This is consistent with the results obtained from a Hybrid-PIC Boltzmann Electron (HPBE) simulation of the experimental setup, which are presented in this work. These simulations also show an increase in window duration with the use of surface treatments that minimize the absorption of charge on the electrode insulation. We finally present design changes planned for future tests with higher voltage pulses based on the data obtained from simulation results and from the preliminary tests

Modelling high-power large-aperture radar meteor trails

Despite decades of research, many questions remain about the global flux of meteoroids at Earth, their influence on the atmosphere, and their use as upper atmospheric diagnostics. We see high-power large-aperture (HPLA) radar observations of meteor phenomena called head echoes and non-specular trails as a valuable tool for answering these questions. In the past we conducted plasma simulations demonstrating that meteor trails are unstable to growth of Farley-Buneman gradient-drift (FBGD) waves that become turbulent and generate large B-field aligned irregularities (FAI). These FAI result in reflections called non-specular meteor trails. Using these and other results, we have developed a model that follows meteor evolution from ablation and ionization through the creation of radar head echoes and non-specular trail reflections. This paper presents results from this model, showing that we can reproduce many aspects of these large radar observations, such as the general altitude profile of head echoes and non-specular trails. Additionally we show that trail polarization due to E-fields or neutral winds causes a noticeable trail feature as well as may be responsible for trails lasting longer than about 1 s. We also demonstrate how such a model is a valuable tool for deriving meteoroid properties such as flux, mass, and velocity. Finally, such a model could also provide some composition information, and diagnose the atmosphere and ionosphere where meteors produce their trails

• CLOSE, HUNT, MINARDI, AND MCKEEN Meteor Shower Characterization at Kwajalein Missile Range Meteor Shower Characterization at Kwajalein Missile Range

■ Approximately one billion meteors enter the Earth’s atmosphere daily, and their potential impact on spacecraft is not yet well characterized. Kwajalein Missile Range radar systems, because of their high sensitivity and precise calibration, have contributed new information on meteor phenomena, including observations of the Perseid and Leonid meteor showers of 1998. Initially