| Ka-Band Radar Terminal Descent Sensor |
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| NASA’s Jet Propulsion Laboratory, Pasadena, California | |
| Sep 30 2007 | |
Radar altimeter/velocimeter improves velocity sensing by an order of magnitude and eliminates angle-of-descent errors.
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The terminal descent sensor (TDS) is a radar altimeter/velocimeter that improves the accuracy of velocity sensing by more than an order of magnitude when compared to existing sensors. The TDS is designed for the safe planetary landing of payloads, and may be used in helicopters and fixed-wing aircraft requiring highaccuracy velocity sensing. The TDS uses 35.75-GHz frequency to optimize accuracy without requiring new technology, and incorporates a millimeter- wave center frequency to eliminate angle-of-arrival errors that can result in large velocity errors over non-homogeneous terrain. A memory-less approach to altimetry reacquires the target on each beam for each unique measurement, overcoming problems of ambiguous measurements or high dynamics that have plagued previous altimeter designs. The independent beam-to-beam and repeatbeam performance avoids “loss of lock” problems, as well as any issue where the heat shield, or an anomaly of some sort, might put the radar in a false state.  The TDS RF Design consists of a receiver rackdrawer, a frequency synthesizer rack drawer, andan upconverter/downconverter. At the time of this reporting, the TDS was in breadboard form, and was a single-channel, Ka-band model created with a commercial- off-the shelf (COTS) antenna, connectorized RF components, miniature Ka-band RF hybrids in small, connectorized packages for the T/R module, and a LabVIEW/laptop interface. The RF design is shown in the figure. The equipment has been verified with bench testing that included shortpulse generation, Doppler/velocity product generation, FPGA (field-programmable-gate-array) timing, RF power levels, and RF passband response. This work was done by Brian Pollard, Andrew Berkun, Michael Tope, Constantine Andricos, Joseph Okonek, and Yunling Lou of Caltech for NASA’s Jet Propulsion Laboratory. NPO-44462. This Brief includes a Technical Support Package (TSP).
Ka-Band Radar Terminal Descent Sensor (reference NPO-44462) is currently available for download from the TSP library. Login first to download.
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