Title of Paper: The New Generation of Radar Altimeters: Proof of Concept

Principal Author: Dr. R. Keith Raney

Abstract: Through airborne flight tests, we have successfully demonstrated the technical viability and waveform characteristics of an innovative radar altimeter concept (D2P), the first of its kind. The D2P altimeter is built around two techniques. The delay-Doppler technique enhances along-track resolution and measurement precision, reduces transmitter power requirements, improves near-shore performance, and allows robust height measurements of surfaces with along-track slope. The phase-monopulse technique measures the across-track angle-of-arrival of the height waveform, which mitigates cross-track slope errors. In future satellite versions, a flight-proven D2P radar altimeter will offer unprecedented measurement accuracy over continental ice sheets, better height precision from a smaller instrument over the open ocean, and closer near-shore utility. Variations on the D2P approach embrace remote depth sounding of ice, applicable to the Earth's polar ice sheets or Europa's mantel. The D2P concept is the first of a new generation of radar altimeters that simultaneously satisfies high signal-to-noise ratio, high signal-to-speckle ratio, and high signal-to-clutter ratio. These characteristics represent a substantial and innovative breakthrough. This paper highlights the design of the altimeter, and summarizes the results of airborne operations over the open ocean and the ice sheets of Greenland. The radar's performance met or exceeded expectations. Results already have had substantial impact on the design of the CryoSat mission, have inspired several new proposals for airborne and spaceborne projects, and are enabling new concepts for ocean altimetry.