GPS Receiver (GPSR)
Through the GPS antenna, the GPS receiver (GPSR) receives the signals from all of the antenna visible GPS satellites. The L1b processing corrects for known effects related to the Swarm instruments and satellite. The external errors e.g. due to the GPS segment are corrected in the orbit determination processing.
Eleven different input packet definitions from the ISP exists, these are
MDH, Measurement Data Header format
However, for the GPS algorithms processing only seven of them are used. The collection of the data record from the CAP, CAA, COP, and GNE has to be repeated N times for the N viewed satellites with a 0.1 Hz update frequency.
GPSR Algorithm Overview
The processing flow of algorithms is separated into three major steps:
The overall data flow from L0 to L1b is shown in the figure below. An overview of the sequential walk-through of the data flow can be found in [AD-7].
Level 0 to Level 1b processing flow for GPSR