NROSS (Navy Remote Ocean Sensing System) Tracking Network Analysis

One of the main objectives of the NROSS mission is the daily production of mesoscale feature maps of selected ocean areas. The NROSS payload will include a SEASAT-class altimeter for the production of these maps and a scatterometer to measure wind speed and direction over the oceans. These wind measurements will be used in conjunction with the precision altimetry from TOPEX to examine the relationship between ocean circulation and winds. The authors conclude that the applicability of a particular tracking network would appear to depend strongly on orbit accuracy requirements. One- to two-meter radial orbit accuracies are fairly easily obtained with current gravity models and almost any tracking scenario if the arcs are long enough. However, if more accurate orbits are required, either the arcs must be shortened to reduce dynamical model error effects, the gravity models must be improved significantly, or some postlaunch gravity 'tuning' is necessary. The latter technique can be successfully employed only if the tracking is fairly global, or geographically correlated errors will occur in the resulting geopotential field. In this case, all the permanent sites and possibly many of the portable sites may be required. The same is true if the arcs are merely shortened, since there must be enough well distributed data to average out measurement model errors. Thus only the denser tracking networks are likely to provide radial orbit accuracies significantly below the 1 meter level.