The role of distributed, real-time Ada amp; C++ on the Airborne Surveillance Testbed (AST) program

摘要

The Airborne Surveillance Testbed (AST) program, managed by SMDC for BMDO, is a technology demonstration program that supports development, test, and evaluation of defensive systems to counter intercontinental and theater ballistic missiles (ICBMs and TBMs) and their warheads. The heart of the AST program is a Boeing 767 aircraft equipped with a Raytheon-built, large-aperture, multiband, high data rate infrared sensor and a wide variety of processing equipment designed to detect, track, and discriminate ballistic missiles at long ranges. A Raytheon interceptor seeker (part of a Navy risk reduction effort) has recently been integrated onto the aircraft; a staring medium wave infrared (MWIR) camera is currently being added as well. Onboard processing capabilities include a Concurrent TurboHawk (multi-CPU PowerPC flight computer) along with a variety of custom and off-the-shelf signal processing equipment, SGI workstations, DEC Alphas, and PCs, largely programmed in Ada and C++. These systems are linked via SCRAMNet, Ethernet, 1553B, RS422 and RS232, and communicate externally via various radio systems. Since the start of the program in 1984, AST has been making use of Ada83, Ada95, and C++ for both simulations and embedded flight software. During that time, we have gathered a lot of experience in the use of Ada for real-time distributed systems, especially concerning:• The pitfalls of task scheduling algorithms and priorities• The benefits of the (careful) use of generics• The importance of some changes between Ada83 and Ada95• Interfacing Ada software to hardware (and standardized interrupt handling)• The importance of proper use of exception handling to ensure fault tolerance