VLS CHEBYSHEV INTERPOLATION

The variable lag smoother (VLS) performs optimal sequential orbit determination from spacecraft sensor measurements, where smoothing at fixed epochs is performed simultaneously with forward filtering. For low earth orbit (LEO), smoothed VLS spacecraft orbit estimates are created at fixed epochs with uniform one-minute granularity to enable sufficiently accurate Lagrange interpolation. But for Lagrange interpolation, computer execution is unacceptably slow due to computation of many smoothed VLS orbit estimates at fixed epochs. This problem is solved using Chebyshev interpolation. We quantify the relative reduction in computer wall time throughput due to reduced number of VLS smoothed estimates required for Chebyshev interpolation as compared to Lagrange interpolation. Chebyshev interpolation works on a non-uniform time grid with far fewer interpolation points than is required for Lagrange interpolation.