Title of Presentation: The Design and Characterization of a Ku- and Ka-band Downcoverter for Spaceborne Interferometric Radar

Primary (Corresponding) Author: Paul Siqueira

Organization of Primary Author: University of Massachusetts

Co-Authors: Michael Tope, Harish Vedantham, Edin Insanic, Karthik Srinivasan

Abstract: Radar Interferometry is a remote sensing technique for determining topography and target velocity that relies on the differential phase measured from a common signal received by two different antennas separated by a baseline. Generally speaking, higher frequencies lead to smaller baselines and therefore smaller deployment structures. Maintaining phase stability and measuring phase to a high degree of accuracy however becomes more difficult with increasing frequency. As such, in 2005, NASA awarded (through the Earth Science Technology Office's Advanced Technology Program; ESTO-ACT) a joint effort by the University of Massachusetts and the Jet Propulsion Laboratory to develop and characterize two interferometric downconverters, one that worked at Ku-band and the other Ka-band.
In this, the project's third year, the development effort has been completed and the two downconverters have been tested from an electromagnetic/microwave engineering point of view, and through detailed testing meant to explore the devices response to a changing thermal environment. Phase measurements accurate to within 3 millidegrees have been performed on the downconverters with results showing that the two constructed devices meet the needs of maintaining phase stability to within 50 millidegrees in a thermally stabilized environment. Current work continues on modeling the response of the system to thermal changes and for removing the effects of those changes from the device output. Further, for improving the overall instrument's Technology Readiness Level, a simple interferometric system has been constructed suitable for rooftop and airborne deployment. In this way, observables such as differential penetration and topographic measurements at the two frequencies can be made that are relevant to the spaceborne equivalent of the millimeterwave interferometric devices.