Cellular Ocean Altimetry/Scatterometry Technology (COAST)

Lead PI: Thomas Yunck, GeoOptics Inc
Start Year: 2018 | Duration: 2 years
Partners: University of Colorado

GeoOptics is pursuing an integrated cubesat constellation called COAST for, among other applications, high-resolution observation of littoral sea surface heights and surface vector winds. The approach features concurrent radar altimetry and scatterometry from arrays of cubesats, or cells, augmented with InSAR-based wide-swath topographic mapping. In the final execution, a single low-cost cell can perform any of the radar functions. Many of the major elements – processor, avionics, structures – are already available.

The initial concept employs three types of radar cubesats with largely common components. The core cell (Type 0) is designed for high-precision altimetry and (primarily) bistatic scatterometry, as well as basic SAR. The full chassis bottom is a radar antenna. Type 0 units alone can form a powerful ocean observing system. Type 1 is a simple extension in which a larger foldout surface becomes a radar antenna with electronically steerable beam for 2D altimetry and scatterometry and coastal SAR/InSAR.

These can be augmented with Type 2 cells in which the two panels extend lengthwise to form a longer 180 x 20 cm SAR antenna. Two SARs along with an ALT cell can perform InSAR-based wide-swath altimetry, exemplified by NASA’s SWOT mission. Two SAR images are merged to form InSAR interferograms, revealing centimeter-level topographic variations over a wide area. The ALT cell provides absolute height. All functions can be performed, at a somewhat reduced level, with Type 0 cells alone.

A distinguishing feature of cubesat systems is their low cost. Whereas a Jason-class mission can cost $500M or more, a 12U cubesat altimeter offering the same measurement precision may be a few M$ each, including launch, if many are built at once. This can offer large benefits to littoral ocean observation. Daily track separation for the Jason altimeter is ~3,100 km at the equator. An array of 16 cells can improve that, not by 16x, but by more than 80x, to 34 km daily, while yielding copious additional wind and sea state information from multi-cell bistatic scatterometry. We can improve that by another 10x or more for coastal observations by flying in tighter formation. The wide-swath option improves on that far more for topography and provides centimeter-level vertical topographic mapping.

Under this proposal we will develop the basic design and functionality for monostatic and bistatic altimetry, monostatic and bistatic scatterometry, and SAR/InSAR for a Type 0 COAST cell.