| Abstract |
A quantitative approach based on sampling theory and experiment design was used to evaluate configurations of satellite borne altimeters. A simple 2D representation of the experiment design problem, retaining most of the major design issues was implemented. Two different oceanic regions - a large/slow (equatorial Pacific) and a small/fast (Atlantic mid-latitude) region - were selected. The sampling characteristics of configurations of two or three altimeters - all constrained to be of the Topex/Poseidon (T/P) type - vis a vis the two regions were investigated under changes in phase angle between the orbital planes of the altimeters. The preferred arrangement for two T/P altimeters is a separation of 180-degrees. This arrangement simultaneously samples the large/slow region nearly optimally; the small/fast region less so. Under these constrained conditions - and for these two regions - the two orbiter configuration essentially are as good as, or outperform any configuration of three T/P altimeters. This conclusion holds in the two cases of noiseless (perfect measurements) and extreme noise-to-signal levels, and hence would seem likely to hold for all intermediate realistic noise-to-signal regimes as well. With a different representation and fewer constraints however, these conclusions could change. Heterogeneous configurations of two altimeters -one of type T/P, the other, one of the 364 repeating orbits (with an even number of nodal days per repeat) with altitudes between 1 200 and 3 000 km - were also briefly examined. For the limited set of phase angles evaluated, no heterogeneous configurations outperformed two T/P satellite borne altimeters. |
