At Millstone Hill, we employ a strategy first introduced by P. Erickson for Arecibo data analysis. The algorithm encourages piecewise smooth temperature profiles. These techniques use higher resolution data from the lag product matrix to extract additional information about the measured ACFs which is averaged out under normal circumstances. This can then be used to assist the nonlinear least-squares fitting process in finding the optimum fit solution. The transition level remains above 1000 km until 2100 LT and the descent of the layer after sunset is readily apparent.
Helium ions are more difficult to image, and more sophistication in fit algorithms is needed.
All we can reasonably say at this point is that remains less than 20 percent of the total ion composition at all times. It aims to coordinate as many instruments as possible to simultaneously measure the topside ionosphere and atmosphere. These multi-point observations stand to advance our understanding of such topics as light ion dynamics, chemical equilibrium critical height morphology, neutral hydrogen solar cycle variation, and longitudinal and latitudinal ion variability.