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Introduction ASM VFM STR EFI GPSR LRR ACC

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
CAP, Carrier Phase data record
CAA, Carrier Amplitude data record
COP, Code Phase data record
GNA, GPS Nav Almanac data record
GNU, GPS Nav UTC and Ionosphere data record
MNS, Minimum Navigation Solution data record
IGC, IMT/GPST Correlation data record
GNE, GPS Nav Ephemeris data record
CS, Constellation Status record
AUX, Swarm Auxiliary data record

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:

  • L0 processing, which comprises reading and checking of the raw binary level 0 instrument data.
  • L1a processing, which comprises reformatting as well as interpretation and unit conversions of the L0 ISPs. The result is stored as L1a products.
  • L1b processing, which comprises correction of the L1a data corresponding to the characterized distortions comprised in the Instrument Characterization Data Base (ICDB) which will be a part of the CCDB. The result is stored as RINEX 3.00 formatted ASCII data.

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].

Figure 7: Level 0 to Level 1b processing flow for GPSR

Level 0 to Level 1b processing flow for GPSR

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