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.