Postprocessing of L1 GPS radio occultation signals recorded in open-loop mode

Obtaining high-quality observations near the surface requires recording of RO signals in model-aided open loop (OL) mode by the GPS receiver. Postprocessing of the OL RO signals is different from that of the signals recorded in traditional phase-locked loop (PLL) mode.

It requires modeling of the signal frequency for connection of the phase between samples and removal of the GPS navigation data modulation (NDM). It is important that the postprocessing does not introduce errors (biases) in the connected phase. This paper describes the postprocessing of the OL RO signals which does not depend on the receiver model.