In Memoriam:I join the entire SETI community in mourning the recent passing of our colleague Jack Welch. Jack's history and legacy have been well covered by my colleagues. Jack's pioneering work in millimeter-wave interferometry, his long tenure as director of the UC Berkeley radio astronomy lab, his leadership in the design of the Allen Telescope Array, and his co-discovery of interstellar ammonia and water are all stories that bear retelling. But I would prefer to share here a personal recollection of a gift that Jack bestowed upon me decades back, when I was one of his grad students at Berkeley.
Shortly after I began my doctoral studies, I was introduced to Jack Welch by my longtime friend Malcolm Raff (known to many of you for his steadfast support of our SETI League). Mal, Jack, and I shared many interests, including radio astronomy, general aviation (all three of us were pilots and aircraft owners), and of course SETI. Since my proposed PhD research dealt with both aviation safety and microwave systems, I asked Jack to serve on my advisory committee, and he readily agreed.
When the time approached for my qualifying exams, I sought out Jack's advice, by scheduling a meeting with him in his office, during an open hour he had between classes. When I arrived at the appointed time, I asked Jack what I should expect on my orals, and how I could best prepare. "We'll talk about that later," Jack responded. "I have a question for you. Do you know anything about GPS?"
It was a fair question. The first Global Positioning Satellites were just then being launched, and they had profound implications for the future of air navigation (and hence aviation safety). Coincidentally, more than a decade earlier (when GPS development was in its infancy), I had been a Senior Engineering Instructor at Lockheed Missiles and Space Company. One of my tasks was to write curriculum and teach courses for Lockheed's customer (the US Military) on this emerging technology.
I had those old lesson plans well memorized. Without hesitation, I launched into Teacher Mode. I started with the orbital mechanics: how 24 satellites would share six orbital planes 20,000 km above the Earth, at an inclination of 55 degrees. I explained how this geometry would ensure that any point on the Earth would thus be within visual line of sight of at least four satellites at all times, and why lines of position from four satellites would permit precise 3D position determination. I then talked about the necessary Doppler measurements requiring a precise common time source, and how atomic clocks aboard the satellites would provide this. Next I introduced the concept of ionospheric sounding, that two separate time-synched and phase-locked microwave transmitters on each satellite would enable correction for propagational delays. By the time I finished with a discussion of the techniques to be used to correct for relativistic errors, Jack glanced at his watch, said "oops, I have a class -- gotta go," and headed for the door.
"But -- but, what about my orals?" I blurted out. "Don't worry," said Jack. "You've got this."
A week later, it was time for the dreaded oral exam. I was ushered into a classroom filled with other grad students. My dissertation committee filled the front row. I proceeded to the blackboard (yes, it really was black back then, with white chalk), and launched into a one-hour summary of my PhD research: hypothesis, experimental design, hardware, software, data analysis, conclusions, recommendations, the works. After this, we had another hour scheduled for my advisory committee to pelt me with questions.
Jack jumped in first. "So Mr. Shuch," he asked, "do you know anything about GPS?"
I didn't skip a beat. Immediately I erased the equations with which I had covered the blackboard, and segued onto familiar ground. By the time I finished with relativistic corrections and emerged from out of Teacher Mode, our time was up, no other member of my Committee had gotten a chance to ask a question -- and, thanks to Jack's gift, I had passed my PhD Orals!
Jack Welch, Paul Shuch, and Jill Tarter at UC Berkeley, December 2017
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