We are deeply saddened by the passing of Dr. Terry Mast on June 5, 2016. Terry made many fundamental contributions to the design and construction of the Keck 10-meter Telescopes and made equally important contributions to initiation of the Thirty-Meter Telescope project. He was a valued colleague and good friend to many in the UC astronomy community and beyond.
Terry completed his undergraduate degree at Caltech in 1964 and his PhD in high-energy physics at UC Berkeley in 1971. As a graduate student he published six papers in the Physical Review, including two for which he was the first author. His early work was primarily in the area of characterizing the interesting new particles that were being discovered in accelerators, but he was lead author, with Jerry Nelson a coauthor, on papers describing techniques and early limits in searching for evidence of gravitational waves from pulsars and probing the origins of high-energy cosmic rays.
He worked as a research physicist at Lawrence Berkeley Lab and UC Berkeley's Space Science Lab in areas as diverse as developing new particle detector technologies to measuring cosmic ray elemental abundances. In 1993 he moved from Berkeley to UC Santa Cruz as a research physicist at the University of California Observatories.
Among Terry's many papers in physics and astrophysics journals between 1968 and 1981 was a 1979 LBL Report and conference proceedings entitled “Figure Control for a Segmented Telescope Mirror” (Mast and Nelson). This foreshadowed the next 35 years of Terry’s career. A series of papers over the next 15 years investigated in great detail all aspects of building and controlling a 10-meter segmented-mirror primary mirror, including calculations of the effects of primary mirror segmentation on image quality, the design of edge sensors that could reliably work to a precision of a few nanometers in the conditions present in a telescope dome, solutions to challenges in fabricating off-axis segments, algorithms for aligning and phasing segments, and many other topics that had to be addressed in order for the Keck Observatory to be the world-changing success that it has been. His primary collaborators in these efforts were Jerry Nelson and Gary Chanan (UC Irvine).
Terry made a large number of other contributions to the instrumentation program at UC Santa Cruz and UC Observatories, and, when the opportunity was presented to consider the next step in giant telescopes, he worked on a number of fundamental concepts for the California Extremely Large Telescope that subsequently became the Thirty-Meter Telescope.
Terry’s great strengths were a very sophisticated command of the relevant mathematics and physics and a particularly clear and logical approach to defining and solving complex problems. He was well known for his imperturbable, even-tempered, and exceedingly pleasant manner.
In recent years, Terry had been slowed by multiple sclerosis. For those of us who have had the privilege to continue working with him, his approach to this challenge was inspiring. In the face of increasing difficulties, he continued his always careful and correct calculations and maintained his steady, optimistic approach. He will be greatly missed professionally and personally. He leaves a truly giant scientific legacy.