Abstract: Methods and systems are disclosed for determining a spatial position of an aircraft, without replying on measurements from the Global Positioning System. Various embodiments are described using a single Secondary Surveillance Radar (SSR), and multiple SSRs.

Abstract: A detect-and-avoid system for an ownship aircraft is disclosed. The system has a control station in communication with an ownship aircraft, and a Passive Secondary Surveillance Radar (PSSR) system at the ownship aircraft. The PSSR is equipped to receive a reply from a target object, in response to an interrogation signal of staggered P1 and P3 pulses sent by a narrow-beam antenna of a Secondary Surveillance Radar (SSR) to the target object, and also to receive P2 pulses transmitted by a wide-beam antenna of the SSR. A pulse repetition frequency (PRF) pattern for the staggered interrogation signal is determined, followed by estimating a transmit time of the interrogation signal, and determining a position of the target object. A corresponding detect-and-avoid method is also disclosed.

Abstract: Methods are described for generating encrypted messages and unicast/multicast transmitting the encrypted messages to one or more aircraft using Automatic Dependent Surveillance-Broadcast (ADS-B) transmission. Corresponding system for communicating messages to an aircraft using ADS-B link is also provided.

Abstract: The present invention provides a low-cost and low-volume mode A/C/S transponder positioning system to detect the position of a target aircraft, or intruder, outside the range of a secondary surveillance radar system. The system uses a signal of the intruder to pinpoint the location of the intruder. The system can be used on both the ground and on an aircraft in a full 360 degree range around the system.

Abstract: A method and system for determining a position of a non-cooperative object using a reflected signal from Secondary Surveillance Radar (SSR) system is disclosed. The method enables the ownship to detect a non-cooperative intruder, an aircraft which does not have a functioning transponder. The position and altitude of the non-cooperative intruder are determined from reflected signals by a phased array antenna or mechanically scanned directional antenna (MSDA) to perform tracking and avoidance of the non-cooperative object. In the case that a phased array antenna or MSDA is not available, a co-altitude assumption is applied to conservatively determine an avoidance area around the non-cooperative object, which defines coordinates to be tracked and avoided by the ownship.

Abstract: Method for determining a staggered pattern and interrogation mode pattern of an Secondary Surveillance Radar (SSR) is disclosed. The method enables a Passive SSR (PSSR) to work not only inside but also outside the SSR beam. When PSSR is in the wider beam of the SSR, multiple P2-pulses are detected as time-ordered sequence of P2-pulse intervals, from which a repeating sequence and further a stagger pattern is determined. The interrogation mode pattern is determined by comparing the staggered pattern with the interrogation signals. A transmit time of the P3-pulse is predicted based on the staggered pattern and the interrogation mode pattern. Corresponding system is also provided.

Abstract: Methods are described for generating encrypted messages and unicast/multicast transmitting the encrypted messages to one or more aircraft using Automatic Dependent Surveillance-Broadcast (ADS-B) transmission. Corresponding system for communicating messages to an aircraft using ADS-B link is also provided.