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Interview with Steve Bussolari - 11/3/00

  • In 1984, the group began conducting experiments at oil platforms off the coast of the Gulf of Mexico. They had gone down to Baton Rouge to one of the Helicopter Safety Air Controllers (HSAC) quarterly meetings and "briefed them on the technology." HSAC agreed to help conduct a helicopter-to-helicopter test and provided one of their helicopters, while the LL researchers leased another helicopter to use.

  • Bussolari noted that the principal challenge in air traffic control design is "to work in the existing system." In the case of the GPS Squitter, the challenge was to share the channel with the ATCRBS system. The "principal strength is that you don't use spectrum", since it uses the same frequency band for transmitting and receiving signals. Since TCAS already has a 1090 MHz receiver, the design for GPS Squitter is intended to be "seamless."

  • "Cost for delay is high (5%), so if you can save a little bit of delay, that's enormous savings." "Where the info will be useful is for aircraft to be able to see each other, [so] you can preserve your operations even in bad weather." Right now pilots have to rely on visually self-separate.

  • "1090 [MHz] is the most loaded channel." "ATCRBS does 15-20 planes in a beam's the replies...these are called fruit (false replies uncorrelated in time)'s that high fruit environment" which causes such heavy traffic. "Frankfurt has a lot of military aircraft...before the Berlin Wall came down, all the Allied and Russia aircraft were [constantly] interrogating their borders."

  • Many years ago, the FAA did try to mandate that Mode S transponders be installed in brand new transponders. "What they failed to do was deploy Mode S radar they were on very weak ground to be forcing the general aviation community" to along with their plan. "It polarized the community" and many people said "we don't want Mode S" and became very afraid of Mode S.

  • Currently, Mode S transponders are still more expensive than ATCRBS transponders. "The waveforms of Mode S transponders require much tighter control," and the cavity oscillators in ATCRBS "tend to droop" so they cannot be used for Mode S. Mode S, in addition, is a "solid-state front end" which has both processing and software. The development costs for the processor and software are quite high, so Bussolari believes the FAA "needs to adopt a common chipset with the same processor and a common chipset and the same software" to help lower the cost. "It's a perfect function of government, [but] not welcome by manufacturers [such as Honeywell and Allied Signal] because [they] don't want to be undercut."

  • "We're doing air traffic control in a very manual process. San Francisco is an example where PRM will help. You have to look at where what am I trying to accomplish here? What paradigm do I need to shift to? What technology do I need to get there?" To think in terms of the technology is a "dangerous trap that we as technologists fall in...."

  • "At the end of the war, the focus was Soviet bombers coming over the pole...what was needed was a system of radars on the system and radar order to do that, it was the digital computer. Lincoln built an air defense system...and was asked by the Department of Defense as an outgrowth. Lincoln Laboratory focus in 1951 sole job was Project Lincoln called the SAGE system." The notion that "radars [are] linked by a digital computer" is "no different than ATC." Lincoln's strength was "building and showing that it worked." A company was spunoff MITRE to do "contract monitoring" because MIT did not want to be responsible for maintaining the air traffic control system.

  • The Story of Mode S: An Air Traffic Control Data Link Technology last modified: 12.06.2000