The Next Generation Integrity Monitor Testbed (IMT) for Ground System Development and Validation Testing

Abstract

The Stanford University Integrity Monitor Testbed (IMT)is a prototype of the Local Area Augmentation System (LAAS) Ground Facility (LGF). It is used to evaluate whether the LGF can meet the integrity and continuity requirements that apply to Category I precision approach. With support from the U.S. Federal Aviation Administration (FAA), Stanford University has developed IMT algorithms and has implemented them in real-time with special emphasis on automated fault diagnosis and recovery. The first generation IMT hardware was designed in the mid-1990s, and since then computer power and receiver technology has evolved significantly. Therefore, a transition has been made to a new and improved system to further development and testing for Category I precision approach and to use as a starting point for Category II/III LGF development. This paper describes the hardware and motivation behind the second-generation IMT system. One key element of the upgrade has been the development of new software to communicate with the receivers. This function, known as Signal-in-Space Receive and Decode (SISRAD), is now a modular means of integrating different receiver types, providing synchronization of receiver measurement packets, and extracting receiver measurement packets into a specified IMT data format. With these modifications, the new IMT is able to support more extensive and efficient nominal and failure testing. The upgrade has been completed, and in this paper present nominal data fault free data is presented along with how the IMT responds to a satellite clock ramp failure.