Ice thickness and bed topography of fast-flowing outlet glaciers are large sources of uncertainty for the current ice sheet models used to predict future contributions to sea-level rise. Due to a lack of coverage and difficulty in sounding and imaging with ice-penetrating radars, these regions remain poorly constrained in models. Increases in off-nadir scattering due to the highly crevassed surfaces, volumetric scattering (due to debris and/or pockets of liquid water), and signal attenuation (due to warmer ice near the bottom) are all impediments in detecting bed-echoes. A set of high-frequency (HF)/very high-frequency (VHF) radars operating at 14 MHz and 30-35 MHz were developed at the University of Kansas to sound temperate ice and outlet glaciers. We have deployed these radars on a small unmanned aircraft system (UAS) and a DHC-6 Twin Otter. For both installations, the system utilized a dipole antenna oriented in the cross-track direction, providing some performance advantages over other temperate ice sounders operating at lower frequencies. In this paper, we describe the platform-sensor systems, field operations, data-processing techniques, and preliminary results. We also compare our results with data from other ice-sounding radars that operate at frequencies both above (Center for Remote Sensing of Ice Sheets (CReSIS) Multichannel Coherent Depth Sounder (MCoRDS)) and below (Jet Propulsion Laboratory (JPL) Warm Ice Sounding Explorer (WISE)) our HF/VHF system. During field campaigns, both unmanned and manned platforms flew closely spaced parallel and repeat flight lines. We examine these data sets to determine image coherency between flight lines and discuss the feasibility of forming 2D synthetic apertures by using such a mission approach.

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The purpose of this work is to investigate the effect of adding winglets of various dihedral angles to a small unmanned aerial system. Although significant research has been completed on the effects of winglets on large aircraft, there has been little focus on winglet effects for small unmanned systems. This work attempts to better understand the effects of winglets on small unmanned systems with modeling, analysis, and flight tests. The results of this research are promising and may help increase the capabilities of current and future unmanned aerial systems. The Advanced Aircraft Analysis modeling software is used to create a physics based models of the 40% scale YAK-54 unmanned aerial system. Five models are created to analyze the aircraft with no winglets, a wing extension, and winglets at angles of thirty, fourty-five, and sixty degrees. Aircraft stability and control derivatives for each model are developed to analyze the effects of winglets on the small aircraft's dynamic modes. Winglets are found to increase the damping ratio and natural frequency of Short Period mode. The lateral-directional stability of the small aircraft with winglets is also increased. For validation and verification purposes, winglets are manufactured at a dihedral angle of fourty-five degrees and attached to the 40% scale YAK-54 aircraft. Flight system identification tests are performed to verify the physics based models. Nomenclature AAA = Advanced Aircraft Aerodynamics AR = Aspect Ratio b = Span (ft) c = Chord C = Coefficient of L,M,N = Rolling, Pitch, and Yaw Moments (lbf•ft) L/D = Lift to Drag Ratio p,q,r = Roll, Pitch, and Yaw Rates (ft/s) S = Area (ft 2 ) SM = Static Margin T2S = Time to Double Amplitude α = Angle of attack (deg) β = Sideslip Angle (deg) δ = Deflection (deg) ε = Downwash Angle (deg) ζ = Damping Ratio λ = Taper ratio τ = Time Constant (s) ωd = Damping Frequency (Hz) ωn = Natural Frequency (Hz)

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