Near-Earth asteroid 2014 AA entered the Earth's atmosphere on 2014 January 2, only 21 hours after being discovered by the Catalina Sky Survey. In this paper we compute the trajectory of 2014 AA by combining the available optical astrometry, seven ground-based observations over 69 minutes, and the International Monitoring system detection of the atmospheric impact infrasonic airwaves in a least-squares orbit estimation filter. The combination of these two sources of observations result in a tremendous improvement in the orbit uncertainties. The impact time is 3:05 UT with a 1σ uncertainty of 6 min, while the impact location corresponds to a west longitude of 44.7 • and a latitude of 13.1 • with a 1σ uncertainty of 140 km. The minimum impact energy estimated from the infrasound data and the impact velocity result in an estimated minimum mass of 22.6 t. By propagating the trajectory of 2014 AA backwards we find that the only window for finding precovery observations is for the three days before its discovery.

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The Saric ßic ßek howardite meteorite shower consisting of 343 documented stones occurred on September 2, 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Saric ßic ßek experienced a complex cosmic-ray exposure history, exposed during~12-14 Ma in a regolith near the surface of a parent asteroid, and that añ 1 m sized meteoroid was launched by an impact 22 AE 2 Ma ago to Earth (as did one-third of all HED meteorites). SIMS dating of zircon and baddeleyite yielded 4550.4 AE 2.5 Ma and 4553 AE 8.8 Ma crystallization ages for the basaltic magma clasts. The apatite U-Pb age of 4525 AE 17 Ma, K-Ar age of~3.9 Ga, and the U,Th-He ages of 1.8 AE 0.7 and 2.6 AE 0.3 Ga are interpreted to represent thermal metamorphic and impact-related resetting ages, respectively. Petrographic; geochemical; and O-, Cr-, and Ti-isotopic studies confirm that Saric ßic ßek belongs to the normal clan of HED meteorites. Petrographic observations and analysis of organic material indicate a small portion of carbonaceous chondrite material in the Saric ßic ßek regolith and organic contamination of the meteorite after a few days on soil. Video observations of the fall show an atmospheric entry at 17.3 AE 0.8 km s À1 from NW; fragmentations at 37, 33, 31, and 27 km altitude; and provide a pre-atmospheric orbit that is the first dynamical link between the normal HED meteorite clan and the inner Main Belt. Spectral data indicate the similarity of Saric ßic ßek with the Vesta asteroid family (V-class) spectra, a group of asteroids stretching to delivery resonances, which includes (4) Vesta. Dynamical modeling of meteoroid delivery to Earth shows that the complete disruption of ã 1 km sized Vesta family asteroid or a~10 km sized impact crater on Vesta is required to provide sufficient meteoroids ≤4 m in size to account for the influx of meteorites from this HED clan. The 16.7 km diameter Antionia impact crater on Vesta was formed on terrain of the same age as given by the 4 He retention age of Saric ßic ßek. Lunar scaling for crater production to crater counts of its ejecta blanket show it was formed~22 Ma ago.A field expedition to the area was conducted by the

Simulations of asteroid airburst are being conducted to obtain best estimates of damage areas and assess sensitivity to variables for asteroid characterization and mitigation efforts. The simulations presented here employed the ALE3D hydrocode to examine the breakup and energy deposition of asteroids entering the Earth's atmosphere, using the Chelyabinsk meteor as a test case. This paper examines the effect of increasingly complex material models on the energy deposition profile. Modeling the meteor as a rock having a single strength can reproduce airburst altitude and energy deposition reasonably well but is not representative of real rock masses (large bodies of material). Accounting for a yield curve that includes different tensile, shear, and compressive strengths shows that shear strength determines the burst altitude. Including yield curves and compaction of porous spaces in the material changes the detailed mechanics of the breakup but only has a limited effect on the burst altitude and energy deposition. Strong asteroids fail and create peak energy deposition close to the altitude at which ram dynamic pressure equals the material strength. Weak asteroids, even though they structurally fail at high altitude, require the increased pressure at lower altitude to disrupt and disperse the rubble. As a result, a wide range of weaker asteroid strengths produce peak energy deposition at a similar altitude.

Asteroid 2008 TC 3 impacted the Earth's atmosphere with a known shape and orientation. Over 600 meteorites were recovered at recorded locations, including meteorites of nonureilite type. From where in the asteroid did these stones originate? Here, we reconstruct the meteor lightcurve and study the breakup dynamics of asteroid 2008 TC 3 in 3-D hydrodynamic modeling. Two fragmentation regimes are found that explain the lightcurve and strewn field. As long as the asteroid created a wake vacuum, the fragments tended to move into that shadow, where they mixed with small relative velocities and surviving meteorites fell along a narrow strip on the ground. But when the surviving part of the backside and bottom of the asteroid finally collapsed at 33 km altitude, it created an end flare and dust cloud, while fragments were dispersed radially with much higher relative speed due to shock-shock interactions with a distorted shock front. Stones that originated in this final collapse tended to survive in a larger size and fell over a wider area at locations on the ground. Those locations to some extent still trace back to the fragment's original position in the asteroid. We classified the stones from this "large mass" area and used this information to glean some insight into the relative location of recovered ureilites and ordinary and enstatite chondrites in 2008 TC 3 .

The June 2, 2018 impact of asteroid 2018 LA over Botswana is only the second asteroid detected in space prior to impacting over land. Here, we report on the successful recovery of meteorites. Additional astrometric data refine the approach orbit and define the spin period and shape of the asteroid. Video observations of the fireball constrain the asteroid's position in its orbit and were used to triangulate the location of the fireball's main flare over the Central Kalahari Game Reserve. Twenty‐three meteorites were recovered. A consortium study of eight of these classifies Motopi Pan as an HED polymict breccia derived from howardite, cumulate and basaltic eucrite, and diogenite lithologies. Before impact, 2018 LA was a solid rock of ~156 cm diameter with high bulk density ~2.85 g cm−3, a relatively low albedo pV ~ 0.25, no significant opposition effect on the asteroid brightness, and an impact kinetic energy of ~0.2 kt. The orbit of 2018 LA is consistent with an origin at Vesta (or its Vestoids) and delivery into an Earth‐impacting orbit via the ν6 resonance. The impact that ejected 2018 LA in an orbit toward Earth occurred 22.8 ± 3.8 Ma ago. Zircons record a concordant U‐Pb age of 4563 ± 11 Ma and a consistent 207Pb/206Pb age of 4563 ± 6 Ma. A much younger Pb‐Pb phosphate resetting age of 4234 ± 41 Ma was found. From this impact chronology, we discuss what is the possible source crater of Motopi Pan and the age of Vesta's Veneneia impact basin.

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This paper describes the design of bio-mimetic remote controlled airplanes and experiments in perching them. The goal of this research is the development of a biomimetic robotic bird that can alight and rest on a perch. Design starts with the overall architecture including airfoil selection and mass determination given performance requirements. Particular attention is given to the stability analysis since with a bird-like planform with the tail so close to the body and without a vertical tail surface many designs are unstable. The stability matrices are also the basis of the PID controller design. Several foamie planes were built to test different designs and control strategies. Most of the perching experiments used the Dreamflight® Alula glider because it was one of the most bird-like planforms that is available commercially. A catapult launcher and a perch were set up in the AFRL Aviari indoor flight facility which uses motion capture cameras to determine to vehicle state. This allows control algorithms to be developed off-board the plane saving on weight of sensors and on-board computers. Various control strategies were tested from mostly open loop flights, relatively simple PID controllers, to fuzzy logic and dynamic inversion. This paper is limited to the development and testing of the PID controllers. NomenclatureAoA = angle of attack AR = aspect ratio c = chord C D , C L , C M = drag, lift, pitch moment coefficients CG = centre of gravity CP = centre of pressure h = altitude M = pitch moment MAV = micro air vehicle PID = proportional-integral-derivative RC = remote control Re = Reynolds Number U = velocity X,Y,Z = downrange position, cross-range position, altitude α = angle of attack  = deflection angle  = flight path angle  = bank angle  = heading angle 1 Senior Research Engineer, 300 College Park, Dayton OH 45469, AIAA Member 2 Senior Research Engineer, AFRL/RQSE, 21300 8 th St., WPAFB OH 45433, AIAA Associate Fellow Downloaded by ROKETSAN MISSLES INC. on February 8, 2015 | http://arc.aiaa.org |