1 Abstract — This paper discusses the innovative concept and technology development of a Ka-band (35 GHz) radar for mapping the surface topography of glaciers and ice sheets. Dubbed the “Glacier and Land Ice Surface Topography Interferometer” (GLISTIN) the system is a single-pass, single platform interferometric synthetic aperture radar (InSAR) with an 8mm wavelength, which minimizes snow penetration yet remains relatively impervious to atmospheric attenuation. Such a system has the potential for delivering topographic maps at high spatial resolution, high vertical accuracy, independent of cloud cover, with a subseasonal update and would greatly enhance current observational and modeling capabilities of ice mass-balance and glacial retreat. To enable such measurements, a digitally beamformed antenna array is utilized to provide a wide measurement swath at a technologically feasible transmit power. To prove this concept and advance the technology readiness of this design we are currently funded by the NASA ESTO Instrument Incubator Program to build and test a 1m x 1m digitally-beamformed Ka- band waveguide slot antenna with integrated digital receivers. This antenna provides 16 simultaneous receive beams, effectively broadening the swath without reducing receive antenna gain. The design and fabrication of such a large aperture at Ka-band presents many challenges, particularly achieving the phase stability required for digital beamforming and interferometric measurements. In this paper we will overview the system concept, requirements, status of the technology development and the experimental scenario by which the beamforming and interferometric performance will be demonstrated. I. INTRODUCTION This paper describes continuing the technology development effort of a novel Ka-band (35 GHz) radar that utilizes digital beamforming (DBF) over an elevation array in order to achieve significant savings in transmit power when compared with system requirements for a non-beamformed or scanned array that has the same swath illumination [1, 2]. The proposed application for this technology is focused toward interferometric mapping of glaciers and land-ice sheets with high precision and subseasonal complete coverage independent of cloud cover. The choice of Ka-band for these measurements is key, both in terms of the phenomenology and also the technology. The “Glacier and Land Ice Surface Topography Interferometer” (GLISTIN) as we have called the system is depicted in Figure 1. The single-pass, single platform interferometric synthetic aperture radar (InSAR) has an 8mm wavelength, which minimizes snow penetration while incurring minimal attenuation due to the atmosphere. In contrast to lidars, the instrument will be insensitive to clouds, provide significant swath-widths, cover the poles sub- monthly, and provide inherently variable spatial resolution: high spatial resolution for sub-meter-scale vertical precision on glaciers and coastal regions; coarse spatial resolution for decimeter accuracy on featureless ice sheet interiors. Consequently this concept holds the potential for critical synoptic data not available from any equivalent system for observations, modeling and forecasting mass changes of the Earth’s ice cover, as outlined in the Climate Variability and Change roadmap. To date, no civilian spaceborne InSAR system has utilized Ka-band. Also, to our knowledge no digital beam forming radar has flown in space. This technology has no alternatives when high resolution and swath is required other than the use of extremely high power transmitters that are impractical from both a technological and power consumption standpoint (we achieve greater than an order of magnitude savings in power through the use of DBF). GLISTIN also results in a substantial mass savings when compared with a lower frequency system. For example, for equivalent accuracy at 13GHz (WSOA frequency) requires a boom of nearly 24m as opposed to the 8m of our design. Technology Development of a Novel Ka-band Digitally-Beamformed Interferometric Radar With Application to Ice Topography Mapping Delwyn Moller, Yonggyu Gim, Brandon Heavey, Richard Hodges, Sembiam Rengarajan, Eric Rignot, Francois Rogez, Gregory Sadowy, Marc Simard, Mark Zawadzki Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109 Figure 1: GLISTIN mission concept.