PROJECT: Mapping ice elevation changes with differential SAR interferometry–a feasibility study based on examples from Alaska and Patagonia
PI: Matthias Braun, Associate Professor, UAF
Alaskan and Patagonian glaciers are two of the largest contributors to sea level rise outside of the large ice sheets of Greenland and Antarctica. In fact, Alaskan glaciers contribute in the same magnitude as the Greenland ice sheet in the period 2002-2008 (Wu et al. 2010). Estimates based on GRACE satellite data provide integrative values for entire regions and mountain ranges combining a variety satellite, ground-based and modeling data sets. However, they do not allow for a more local scale analysis resolving individual glaciers. In this project we systematically evaluate the potential of Synthetic Aperture Radar (SAR) interferometry to measure both the spatial extent and the surface elevation changes at glacier edges. Glacier edges we define here as areas that have been glaciated at tie of DEM acquisition but have become ice free until the time of InSAR image acquisition. Given sufficient signal correlation, interferometric analysis of repeat acquisitions of SAR imagery allow for the determination of surface elevation and movement. While during summer conditions the interferometric phase over glacier surfaces usually decorrelates due to surface changes and movement between the image acquisitions, the ice free, rocky areas reveal stable backscatter signals. In this study we will first show that signal coherence is generally preserved around the margins of outlet and mountain glaciers. In a second step we will show that the phase information at the glacier margins can be used together with existing elevation models from different time stamps to determine elevation changes at the glacier edges. The existing elevation models from different time steps are used to compensate for topographic phase components and the residual phase is directly related to the extent of surface lowering since the acquisition of the reference DEM. As this technique provides topographic change measurements at the glacier borders, it provides complementary information to data from other sources such laser altimetry, which are usually flown along profile lines near the glacier center. In this project we analyze data from different satellite configurations (baselines) as well as different frequencies (L-band, X-band) in regard to their suitability for this purpose.
PROJECT: Board-Level Dynamic Characterization of Stacked Chip Scale Packaging
PI: Cheng-fu Chen, Associate Professor, UAF
Electronic miniaturization plays a key role in bridging new concepts to exploration-mission use for the NASA Electronic Parts and Packaging (NEPP) Program, which requires smaller but more functional electronic systems consuming lower power under extremely hazardous environments. On one end, the advance in semiconductor technology enables fabrication of bare silicon dies with functionally integrated circuits with a gate size as small as a fraction of one thousandth of the diameter of a human hair. Bare-die integrated circuits, on the other end, cannot be directly used without mechanical encapsulation of the fragile silicon as well as electrical fanning-out of very fine circuits in the die. In this regard, electronic packaging deals with design and assembly of various materials to mechanically encapsulate bare dies and electrically fan out the fine-line circuits such as to interface with field applications. Electronic packaging is key to determining the device size and reliability. As electronic devices with a higher packaging density and faster operation speed are on demand, the shift in electronic miniaturization has been to ride packaging components in the z-direction. While the so-called stacking or three dimensional packaging technology allows for a faster operation speed by offering designs for shorter signal/power transmission distances, the sandwich-like packages also exhibit poorer thermal management and weaker structural stability than the planar counterparts. The mechanical reliability of stacked electronic packages is particularly a major concern. In this research we consider the drop impact reliability of stacked chip scale packages. Chip scale packaging, among other advanced electronic packaging technologies, is best known for its packaging size, which can be nearly as small as the bare die. In stacked chip scale packaging, soft solder balls interconnect one level to another and serve as the only mechanical support. Although it enables the shortest electrical passages, the level-by-level stacking configuration also corresponds to the mechanically weakest design, by which the electronic devices are more vulnerable to structural failure under shock and vibrations. The objective of this research is to characterize the dynamic response of stacked chip scale packages under drop impact loading and vibrations. By working with JPL the results will facilitate assessment of new packaging design for NASA spaceflight applications. This research will also be a platform of integrating undergraduate research into the study of electronic packaging.
PROJECT: Multiple-Spacecraft Investigation of Interplanetary Shock Interaction with the Bow Shock
PI: Hui Zhang, Assistant Professor, UAF
Interplanetary shocks play a key role in particle acceleration in the solar wind and in the magnetosphere. One of the objectives of NASA’s Radiation Belt Storm Probes (RBSP) mission is to study shock-associated creation and decay of radiation belts. In preparation for the RBSP mission, this proposed research will provide fundamental information such as shock orientation and strength which control the overall interaction with the magnetosphere including the radiation belts. The objective of the proposed research is to understand the interaction of interplanetary shocks with the Earth’s bow shock and their modification through the magnetosheath and magnetopause. The specific objectives are to use observations from NASA’s THEMIS, Cluster, and Geotail mission to (1) define the propagation and evolution of the transmitted interplanetary shock through the magnetosheath; (2) determine the reaction of the magnetopause to the passage of the interplanetary shock.