The elements of a space-based integrity approach are to monitor the signals on-board the satellite, such that signal performance can be maintained well within desired integrity limits. These elements include 1) a system for monitoring multiple atomic frequency standards (AFS) or clocks, detecting anomalies, and automatically transferring the signal source to a reliable clock, 2) derive a clock and ephemeris solution from a data set independent of the ground control segment, for on-board comparison and verification of the broadcast message 3) hardware methods to ensure valid formation of the broadcast signal. Many of the needed elements are already present in GPS architecture. This combination of design elements is capable of supporting stringent levels of signal integrity.
, Shome, P.
and Beard, R.
On-Board Signal Integrity for GPS, Proc. 2010 ION GNSS Meeting, Portland, OR, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=906614
(Accessed June 1, 2023)