Signals of Opportunity Positioning (SOOP)

Signals of Opportunity Positioning (SOOP) is a passive navigation technique that extracts positioning information from radio-frequency signals that were not originally designed for navigation purposes.

Instead of relying on dedicated GPS satellites, SOOP receivers measure the phase-curvature φ̈(t) and Doppler frequency shifts of signals broadcast by commercial satellite constellations - primarily Starlink (~6,000+ satellites in LEO), OneWeb (~600 satellites), and Iridium (~66 satellites). These constellations transmit at significantly higher power levels than GPS and orbit at much lower altitudes (340-1,200 km vs 20,200 km), resulting in signal strengths 100-1000x stronger than GPS at the receiver.

The critical innovation in Kepler Nav's SOOP implementation is keyless signal processing: the system does not need to decrypt or decode the satellite's data payload. Instead, it tracks the raw physical properties of the electromagnetic wave - specifically the second derivative of carrier phase (phase-curvature) and the rate-of-change of Doppler shift. These physical observables are invariant to encryption and provide sufficient geometric information for trilateration when combined with known satellite ephemeris data.

Kepler Nav's SOOP architecture processes signals from 15-40 simultaneous satellites across multiple constellations, achieving horizontal positioning accuracy comparable to GPS L1 C/A code in benign environments and significantly outperforming GPS in contested RF environments where jamming is present.