Spatial scanning PNT

A position, navigation, and/or time (PNT} system comprising:

• a plurality of satellites;
• a plurality of receiver units;
• a bidirectional link between each receiver unit of the plurality of receiver units and at least one satellite of the plurality of satellites, wherein each bidirectional link is configured to use two-way time transfer,
• a satellite active electronically steerable antenna (AESA) coupled to each satellite of the plurality of satellites and a receiver AESA coupled to each receiver unit of the plurality of receiver units, wherein each satellite AESA is configured to scan a beam over a volume of interest during an update period, wherein each update period occurs after a fixed interval of time, and wherein each receiver unit is configured to receive and transmit for the two-way time transfer during a dwell time of the scanned beam that is less than the fixed interval;
• and
• an inertial navigation system coupled to each receiver unit of the plurality of receiver units,
• wherein at each update period, a receiver unit of the plurality of receiver units is configured to establish the bidirectional link to at least one satellite of the plurality of satellites to determine PNT;
• and
• wherein the inertial navigation system is configured to provide PNT between successive update periods by utilizing an extended Kalman filter to fuse inertial navigation system data with time and range updates obtained via the two-way time transfer.

A method for determining position, navigation, and/or time (PNT) using a receiving unit, the method comprising the steps of:

• performing a first update by bidirectionally linking the receiving unit to a first satellite using two-way time transfer between the receiving unit and the first satellite to acquire a time and range update at a first location of the receiving unit;
• performing a second update, a fixed amount of time after the first update, by bidirectionally linking the receiving unit to a second satellite using the two-way time transfer between the receiving unit and the second satellite to acquire a time and range update at a second location of the receiving unit;
• performing a third update, the fixed amount of time after the second update, by bidirectionally linking the receiving unit to a third satellite using the two-way time transfer between the receiving unit and the third satellite to acquire a time and range update at a third location of the receiving unit;
• determining inertial navigation system (INS) data, using an inertial navigation system, the INS data including the relative motion of the receiving unit between the first, second, and third time and range updates;
• and
• determining the PNT of the receiving unit utilizing an extended Kalman filter, the INS data, and the first, second, and third time and range updates,
• wherein the first, second, and third updates are discrete and sequential, not simultaneous, and the receiving unit receives and transmits for the two-way time transfer only during respective dwell times of beams scanned over a volume of interest by active electronically steerable antennas (AESAs) of the receiving unit and the respective satellites, wherein the respective dwell times are less than the fixed amount of time.