Title: The Airborne Glacier and Land Ice Surface Topography Interferometer (GLISTIN-A)
Author: Delwyn Moller
Organization: Remote Sensing Solutions
Co-Authors: Scott Hensley, Greg Sadowy, James Carswell, Charles Fisher, Yunling Lou

In May 2009 a new radar technique for mapping ice surface topography was demonstrated in a Greenland campaign as part of the NASA International Polar Year (IPY) activities. This was achieved with the airborne Glacier and Ice Surface Topography Interferometer (GLISTIN-A): a 35.6 GHz single-pass interferometer. Although the technique of using radar interferometry for mapping terrain has been demonstrated before, this is the first such application at millimeter-wave frequencies.

The proof-of-concept demonstration was achieved by interfacing Ka-band RF and antenna hardware with the Uninhabited Airborne Vehicle Synthetic Aperture Radar (UAVSAR). The GLISTIN-A was implemented as a custom installation of the NASA Dryden Flight Research Center Gulfstream III. Instrument performance indicates swath widths over the ice between 5-7km, with height precisions ranging from 30cm-3m at a posting of 3m x 3m. Following the success of the GLISTIN-A demonstration and the IPY campaign, we have been funded under the ESTO Airborne Innovative Technology Transition (AITT) program to transition this capability to a permanently-available pod-only Ka-band UAVSAR configuration compatible with unpressurized operation. As part of this effort, the interferometric antenna panel and modified pod from the IPY will be populated with new Ka-band up and down-converter chains and a state-of-the-art solid-state-power-amplifier that will result in:
1) more peak transmit power and
2) the ability to alternate transmission between two antennas (ìping-pongî).
These fundamental upgrades will greatly enhance the performance beyond that achieved during IPY and make wider-swath and higher altitude operation possible. Ultimately, as UAVSAR is transitioned to flight on the GlobalHawk, GLISTIN-A will have the capability of providing detailed maps of scientifically significant Antarctic regions that have previously proved too remote for dedicated observations.

We will present results from the IPY data collections including system performance evaluation and an intercomparison with the NASA Wallops Airborne Topographic Mapper (ATM) to quantify the interferometric penetration bias of the Ka-band returns into the snow cover. We will also summarize the on-going AITT upgrades and present the impact that these activities will have in terms of GLISTIN-Aís performance and operational capabilities.