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Robert McCracken, a retired optical-electronics engineer and nuclear researcher with the former National Bureau of Standards (NBS) and the U.S. Army Harry Diamond Laboratories (HDL), trustee and past president of the National Capital Astronomers, Inc. (NCA), founder and past president of the Hopewell Corporation and Observatory, and past president of the Washington Academy of Sciences (WAS), died on 1996 May 28 after a long battle with cancer.
Bob was born on 9 May 1921 in Greensboro, North Carolina. He attended North Carolina State University and started working at the NBS in 1945, where he joined the atomic clock team. Bob was responsible for devising the electronics system of the first (cesium-beam) atomic clock, and made the first direct measurement of the high-frequency (microwave) hyperfine structure spectrum of cesium, which led to its adaptation today as the primary standard definition of the second.
From NBS, Bob transferred to the HDL where he worked on the Redstone missile program. He also developed astro- and television-guidance systems, proximity fuses, and radar countermeasures. Bob retired from HDL, and government service, in 1978 with numerous papers and patents to his name.
In the mid-1950s, as NCA President, Bob was a key member of Project Moonwatch during both the International Geophysical Year (IGY) and beyond (Moonwatch officially ended in 1975). He was always proud of his Moonwatch role, and always stressed how it showed that citizens could directly participate effectively in the grand adventure of what he called "Cosmic Discovery." For Moonwatch and his other IGY contributions, Bob received awards from both the Smithsonian Institution and the National Academy of Sciences.
Bob sparked interest in astronomy among all generations, particularly the young. He did so by emphasizing the truly seamless nature of all scientific endeavors and technological innovations. "Phenomenology transfer" he called it. As testament to Bob's positive influence, one NCA junior member he mentored — Walter Gilbert — eventually shared the 1980 Nobel Prize for Chemistry.
Bob helped establish the Washington Area Astronomers meetings, bringing together astronomers throughout the Washington-Baltimore region. He also urged the National Park Service (NPS) to build a planetarium at their Rock Creek Park Nature Center. It remains the only one in the entire NPS system. He started NCA's "astro-consumer" clinics, which continue today, and the NCA Science Fair Awards program. For many years he also taught NCA's telescope-making classes at The American University and elsewhere. But these local level achievements only scratch the surface of Bob's long public service to science and society. For these many contributions, he received the Superintendent's Award from the Naval Observatory, and the Outstanding Contributions to Astronomy award from the WAS.
Bob remained forever young by his dreams, and inspired us all. Even as the cancer began to relentlessly pursue him, Bob dreamed of — and formally proposed — establishing an interscience center for the District of Columbia as a public hands-on experimental and display facility providing phenomenology transfer among the various sciences underlying today's and tomorrow's technology. That dream, and so many others, kept him alive and vigilant well beyond the time the doctors gave him. Or as Bob put it in his own unique way: sometimes you have to aim for the Moon just to get over the fence.
Bob was best described by the title of his obituary in The Washington Post (June 4, p. B7): "U.S. Astronomer." While he will be remembered for helping create the atomic clock, Bob should be remembered equally as one who cared deeply for astronomy and related sciences, and passionately forged support for them throughout society. We who knew him will not forget his selfless dedication.
Photo (available in PDF version): RHM at the NBS, c. 1952
Obituary written by: Daniel J. Costanzo (National Capital Astronomers, Inc.)
BAAS Citation: BAAS, 1996, 28, 1456
SAO/NASA ADS Bibcode: 1996BAAS...28.1456C