Multi-level arc combination with stochastic parameters

The method of square root information filtering and smoothing (SRIF/S) is r eviewed and has been implemented in the combined square root information fi lter and smoother (CSRIFS) program. CSRIFS is a part of the GEOSAT space ge odesy software developed at Forsvarets forskningsinstitutt (FFI, The Norweg ian Defence Research Establishment). The state vectors and complete varianc e-covariance matrices from the analyses of a number of independent arcs of space geodesy data can be combined using CSRIFS. Four parameter levels are available and any parameter can, at each level, be represented as either a constant or a stochastic parameter (white noise, colored noise, or random w alk). The batch length (i.e. the time interval between the addition of nois e to the SRIF array) can be made time and parameter dependent. CSRIFS was a pplied in the combination of 623 very long baseline interferometry (VLBI) o bserving sessions. The purpose of this test was to validate the computer im plementation of the SRIF/S method and to give an example of how this method can be used in the analysis of a large number of space geodetic observatio ns. The results show that the implementation is very satisfactory.