TECHNOLOGY AREAS: Sensors, Electronics

ACQUISITION PROGRAM: Navy Unmanned Combat Air System (N-UCAS)/ACAT 1

OBJECTIVE: Develop and demonstrate architecture innovations for precision relative GPS/INS navigation systems that satisfy the stringent accuracy, integrity and continuity performance required to support autonomous, networked, low-observable (LO) unmanned air systems.

DESCRIPTION: Precision GPS/INS techniques have been developed to support operations including automated aerial refueling (AAR) and autonomous shipboard launch and recovery. The basic architecture of a relative GPS/INS navigation sensor system sends GPS and INS sensor measurements from the host platform (tanker or ship) to the unmanned aircraft platform via the airborne data network. Supporting communications and situational awareness functions are exchanged on the same network. Autonomous UAS bring additional challenges to the performance of these systems including the impact of low observability, networking interface, scalability, redundancy, and autonomy. Specific technology innovations are needed to advance the state of the art of precision GPS/INS techniques for autonomous UAS systems, including the following:

• Impact of Low Observability. Low observability may attenuate GPS antenna performance significantly from non-LO designs. Degradation in tracking thresholds reduces system performance and availability. Methods of addressing this degradation can include the use of external augmentations (to compensate for satellites unable to track) such as two-way ranging via the data network and precision time transfer; techniques to increase the available gain to each satellite such as active antenna multi-beamforming; and techniques to lower the carrier-to-noise ratio, which provides quality GPS carrier tracking, such as GPS/INS deep integration. Preferred techniques minimize cost and integration impact to the platform while maximizing availability of system performance.
• Autonomy and Airborne Redundancy. Autonomous UAS require very high continuity in the GPS/INS system, since there is no piloted backup to the navigation operation. Operation of redundant GPS/INS processors requires that errors can be detected between the navigation outputs at the submeter-level with high integrity (high assurance of fault detection) and high continuity (low false alarm rate). Architecture innovations are desired to improve performance of redundant systems including fault detection and isolation algorithms.
• Networking and Service Oriented Architecture (SOA). Autonomous UAS achieve interoperability, scalability, and re-usability through implementing communications, navigation, command and control and other mission functions over a SOA implemented via the Internet-Protocol based airborne network. Innovative concepts are needed to select SOA frameworks for GPS/INS data exchanges that provide open architecture, re-usability and scalability across large, networked "swarms" of UAS while still supporting the performance needed for aviation operations. Specific challenges include security, efficiency, latency, certification and robustness of performance.

In all cases the architecture innovations must satisfy the stringent accuracy, integrity and continuity performance of precision UAS operations such as AAR and carrier-based autonomous launch and recovery.

PHASE I: Design and demonstrate a cost-effective approach to using differential GPS/INS augmentations to provide a significant improvement in performance on LO UAVs.

PHASE II: Develop a prototype of the relative GPS/INS innovation including the necessary hardware, software, and associated simulations. Using the prototype with simulation and field/flight test data, demonstrate the performance under representative conditions via real-time or post- processing.

PHASE III: Integrate the innovation approach into an existing precision relative GPS/INS system applicable to autonomous UAS operations in precision relative navigation. Demonstrate performance in flight test conditions in a relevant environment.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Precision relative navigation can be used for a host of vehicle-to-vehicle navigation applications in the private sector. Precision relative navigation is related to the general class of differential GPS systems and augmentations used in civilian transportation, farming, mining, and other sectors. In particular, the required navigation performance for unmanned air platforms is on the same order as performance requirements for Cat III Local Area Augmentation System (LAAS).

REFERENCES:
1. NA-4115-UCAS-1000, Unmanned Combat air System CV Demonstration (UCAS-D) Performance Specification, Version 1.0, January 22, 2007.

2. NA-4150-UCAS-1003, UCAS Ship Interface Reference Document (USIRD).

3. NA-4580-PGPS-5000, PGPS System Requirements Document.

KEYWORDS: Navigation; Unmanned Air System (UAS); Global Positioning System (GPS); Inertial Navigation System (INS); Low Observable (LO); Service Oriented Architecture (SOA).

** TOPIC AUTHOR (TPOC) **

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