Autonomous orbit propagation system and method

Abstract

A method of predicting a location of a satellite is provided wherein the GPS device, based on previously received information about the position of a satellite, such as an ephemeris, generates a correction acceleration of the satellite that can be used to predict the position of the satellite outside of the time frame in which the previously received information was valid. The calculations can be performed entirely on the GPS device, and do not require assistance from a server. However, if assistance from a server is available to the GPS device, the assistance information can be used to increase the accuracy of the predicted position.

1 .- 20 . (canceled) 
     
     
         21 . A method of determining an orbit of a non-GPS GNSS satellite, comprising:
 receiving, at an RF antenna of a GNSS device, position data and a velocity associated with the non-GPS GNSS satellite, the position data and velocity valid for an effective time period;   the GNSS device calculating transformed GNSS position data and a velocity for a plurality of time intervals over the effective time period by mapping the position data and velocity associated with a non-GPS GNSS satellite reference coordinate system to the WGS84 reference coordinate system;   the GNSS device calculating, at a time during the effective time period, a correction for reducing error between predicted transformed GNSS position data and velocity of the non-GPS GNSS satellite and transformed GNSS position data and velocity of the non-GPS GNSS satellite at the plurality of time intervals over the effective time period, the predicted transformed GNSS position data and velocity being determined using a plurality of previously calculated orbit state vectors stored in memory of the GNSS device, the correction, predicted transformed GNSS position data and velocity and previously calculated orbit state vectors being based on the WGS84 reference coordinate system; and   the GNSS device calculating a current orbit state vector using force model coefficients adjusted based on the correction and storing the current orbit state vector in the memory, the current orbit state vector being used as initial state for propagating the orbit of the non-GPS GNSS satellite within a predicted time period, at least a portion of the predicted time period occurring after the effective time period;   wherein the current orbit state vector and the orbit are based on the WGS84 coordinate system reference.   
     
     
         22 . The method of  claim 21 , wherein the GNSS device determines a position of the non-GPS GNSS satellite by calculating a WGS84 reference coordinate system-based position of the non-GPS GNSS satellite using the orbit and mapping the WGS84 reference coordinate system-based position from the WGS84 reference coordinate system to the non-GPS GNSS satellite reference coordinate system. 
     
     
         23 . The method of  claim 21 , wherein the GNSS device determines a velocity of the non-GPS GNSS satellite by calculating a WGS84 reference coordinate system-based velocity of the non-GPS GNSS satellite using the orbit and mapping the WGS84 reference coordinate system-based velocity from the WGS84 reference coordinate system to the non-GPS GNSS satellite reference coordinate system. 
     
     
         24 . The method of  claim 21 , wherein the position data and velocity associated with the non-GPS GNSS satellite is received in a navigation message. 
     
     
         25 . The method of  claim 21 , wherein the correction comprises a plurality of correction acceleration terms. 
     
     
         26 . The method of  claim 21 , wherein the non-GPS GNSS satellite is a GLONASS satellite and the position data and velocity associated with the non-GPS GNSS satellite are mapped from the PZ90 coordinate system to the WGS84 reference coordinate system. 
     
     
         27 . The method of  claim 21 , wherein the position data and velocity of the non-GPS GNSS satellite are mapped to the WGS84 coordinate system reference using a Helmert transformation. 
     
     
         28 . The method of  claim 21 , wherein the effective time period is less than a valid time period of a GPS ephemeris. 
     
     
         29 . The method of  claim 28 , wherein the valid time period of a GPS ephemeris is four hours. 
     
     
         30 . The method of  claim 22 , wherein the position of the non-GPS GNSS is reverse mapped from the WGS84 reference coordinate system to the PZ90 coordinate system. 
     
     
         31 . The method of  claim 23 , wherein the velocity of the non-GPS GNSS is reverse mapped from the WGS84 reference coordinate system to the PZ90 coordinate system. 
     
     
         32 . The method of  claim 24 , wherein the navigation message is a GLONASS navigation message. 
     
     
         33 . A GNSS device comprising:
 an RF receiver for receiving position data and a velocity associated with a non-GPS GNSS satellite, the position data and velocity valid for an effective time period;   a memory for storing a plurality of previously calculated orbit state vectors; and   a processor for calculating:   transformed GNSS position data and a velocity for a plurality of time intervals over the effective time period by mapping the position data and velocity associated with a non-GPS GNSS satellite reference coordinate system to the WGS84 reference coordinate system;
 a correction, at a time during the effective time period, for reducing error between predicted transformed GNSS position data and velocity of the non-GPS GNSS satellite and transformed GNSS position data and velocity of the non-GPS GNSS satellite at the plurality of time intervals over the effective time period, the predicted transformed GNSS position data and velocity being determined using the plurality of previously calculated orbit state vectors, the correction, predicted transformed GNSS position data and velocity and previously calculated orbit state vectors being based on the WGS84 reference coordinate system; 
 a current orbit state vector using force model coefficients adjusted based on the correction and storing the current orbit state vector in the memory, the current orbit state vector being used as initial state for propagating the orbit of the non-GPS GNSS satellite within a predicted time period, at least a portion of the predicted time period occurring after the effective time period; 
 wherein the current orbit state vector and the orbit are based on the WGS84 coordinate system reference. 
   
     
     
         34 . The GNSS device of  claim 33 , wherein a position of the non-GPS GNSS satellite is determined by calculating a WGS84 reference coordinate system-based position of the non-GPS GNSS satellite using the orbit and mapping the WGS84 reference coordinate system-based position from the WGS84 reference coordinate system to the non-GPS GNSS satellite reference coordinate system. 
     
     
         35 . The GNSS device of  claim 33 , wherein a velocity of the non-GPS GNSS satellite is determined by calculating a WGS84 reference coordinate system-based velocity of the non-GPS GNSS satellite using the orbit and mapping the WGS84 reference coordinate system-based velocity from the WGS84 reference coordinate system to the non-GPS GNSS satellite reference coordinate system. 
     
     
         36 . The GNSS device of  claim 33 , wherein the correction comprises a plurality of correction acceleration terms. 
     
     
         37 . The GNSS device of  claim 33 , wherein the non-GPS GNSS satellite is a GLONASS satellite and the position data and velocity associated with the non-GPS GNSS satellite are mapped from the PZ90 coordinate system to the WGS84 reference coordinate system. 
     
     
         38 . The GNSS device of  claim 33 , wherein the effective time period is less than a valid time period of a GPS ephemeris. 
     
     
         39 . The GNSS device of  claim 34 , wherein the position of the non-GPS GNSS is reverse mapped from the WGS84 reference coordinate system to the PZ90 coordinate system. 
     
     
         40 . The GNSS device of  claim 35 , wherein the velocity of the non-GPS GNSS is reverse mapped from the WGS84 reference coordinate system to the PZ90 coordinate system.