Aircraft Avoidance Systems

TBAD Antenna TBAD Discriminator and Decoder

AAS is a company started in 2014 by Tom Murphy to build systems to help observatories avoid accidental illumination of aircraft from lasers.

The principal product is TBAD, the Transponder-Based Aircraft Detector. TBAD—conceived by Murphy and Bill Coles at UCSD, and developed in conjunction with the UCSD Physics Electronics Shop—passively listens to transmissions from aircraft transponders to determine if an aircraft is close to the direction of laser propagation, or is too close to the telescope to operate safely.

Joining TBAD is TSIM, the transponder simulator. TSIM is used to verify and calibrate TBAD operation via controlled signals emulating those transmitted by aircraft.


TBAD is installed (or is being installed) on the following telescopes, in order of appearance:

The two Keck telescopes, Gemini North, and the Apache Point telescope are operating under FAA approval using TBAD alone and no spotters. The other observatories are pursuing validation and approvals for their sites as well.


The W. M. Keck Observatory has characterized performance of TBAD over a combined 34-month period. See this summary of their report.

Key Resources


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