Satellite navigation receivers with self-provided future ephemeris and clock predictions

An improved extended ephemeris navigation receiver, comprising:

• a fully autonomous satellite navigation receiver for receiving microwave transmissions from orbiting navigation system satellites, and able to demodulate navigation messages that include the ephemerides for those navigation system satellites;
• a limited-capability microcomputer disposed in the fully autonomous satellite navigation receiver;
• the improvement characterized by:
• a force model of accelerations acting on a particular satellite vehicle (SV), and disposed only in the receiver, wherein a single observation of the ephemeris for each SV is input and propagated days into the future by integrating each SV's orbital position with its corresponding force model;
• an orbit integration algorithm program code for execution on the limited-capability microcomputer, and that reduces the computational loads that would otherwise result by using a Bulirsch-Stoer type algorithm which combines Richardson extrapolation, the use of rational function extrapolation in Richardson-type applications, and a modified midpoint method, to obtain high accuracy numerical solutions to ordinary differential equations (ODEs) with comparatively little computational effort;
• a Keplerian solver program code for execution on the limited-capability microcomputer, and that computes estimates for as many as fifteen Keplerian parameters in, {right arrow over (X)}=[a,e,i0,M0,Δn,di/dt,ω,Ω0,{dot over (Ω)},Crs,Crc,Cus,Cuc,Cis,Cic], that are equivalent to the ephemeris parameters that would best fit a series of X-Y-Z type SV position samples in an earth-centered, earth-fixed (ECEF) coordinate system;
• a coordinate transformation program code for execution by the limited-capability microcomputer;
• a scheduler for managing when the orbit integration algorithm program code will be scheduled for execution on the limited-capability microcomputer, and for running said execution in foreground or background, and for controlling operating power supplied to various parts of the hardware of the receiver to conserve power;
• and
• a device to acquire and use an up-to-date EOP sinusoidal polynomial for said polar motion rotation quaternion;
• wherein, the fully autonomous satellite navigation receiver thereafter has available to it extended ephemeris predictions that can be used as substitutes when said navigation messages from the respective SV cannot otherwise be immediately obtained and demodulated;
• wherein, the Bulirsch-Stoer type algorithm is such that only two steps are required for each integration sampling period, and the force model accelerations need only be computed twice in each sampling period, and wherein the inclusion of an extrapolation stage of a conventional Bulirsch-Stoer method is rendered unnecessary;
• wherein said ephemeris parameters enable compact storage in local memory as long-term compact satellite models (LTCSM's) and are simplified for assimilation by the limited-capability microcomputer in the future when computing position fixes;
• and
• wherein, two coordinate systems are used in orbit integration calculations, and coordinate transformations of ECEF to ICRF, and ECEF to ICRF, comprise four quaternion rotations, and a polar motion rotation quaternion based on Earth Orientation Parameters (EOP).