Minoru Oda

Minoru Oda, the founder of space astronomy in Japan and a key participant in the exploratory work in the US that initiated the field of x-ray astronomy, died in Tokyo on 1 March 2001 from complications following surgery.

Oda was born on 24 February 1923 in Sapporo, Japan, the elder son of a distinguished physician. After earning a BS degree in physics at Osaka Imperial University (now Osaka University) in 1944, he was recruited to the Japan Naval Research Laboratory’s Shimada branch, established by Prince Takamatsu in a remote location to shield scientists from the war. Many years later, Oda recounted that microwave research at Shimada achieved a beam strong enough to cook rice or even kill a dog at some distance. More important, many of the Shimada scientists became leaders in the postwar development of science in Japan and around the world.

As a graduate student in 1947, Oda’s interest was drawn to the possibilities of radio astronomy by his supervisor, Yuzuru Watase. Oda and Tatsuo Takakura built a 3.3-GHz radio telescope with which they observed solar radio emissions, the first radio astronomy observations in Japan. In 1950, Oda was appointed assistant professor of physics at Osaka City University. Three years later, he came to MIT as a visitor to the cosmic-ray group of Bruno Rossi. Oda helped set up the first of the large extensive cosmic-ray air shower experiments carried out by the Rossi group with their new methods of density sampling and fast timing. Thus began a lifelong friendship between Oda and Rossi, two of the most influential scientists in the development of cosmic-ray and space physics.

On his return to Japan in 1956, Oda received his doctorate in physics from Osaka Imperial University. That same year, he was appointed an associate professor of physics at Tokyo University’s Institute for Nuclear Studies (INS). At INS, Oda initiated cosmic-ray studies, among which was the Bolivian Air Shower Joint Experiment (BASJE). Inspired by the theoretical work of Satio Hayakawa, the BASJE was designed to detect extensive air showers of low muon content initiated by primary gamma rays produced in interactions of cosmic-ray nuclei with interstellar matter. Koichi Suga came to MIT from INS to build the equipment that was set up at 17‥000 feet on Mount Chacaltaya in Bolivia under the direction of Ismael Escobar. The experiment detected showers with the expected low proportions of muons at an occurrence rate consistent with predictions, but did not yield certain evidence of a predominantly gamma-ray origin.

Oda returned to MIT in 1962, intending to work on BASJE data. His interest was diverted by the discovery of the first extrasolar x-ray source, Sco X-1, in a rocket experiment initiated at the urging of Rossi and carried out by Riccardo Giacconi and his associates at American Science & Engineering Inc (AS&E). Recognizing the importance of higher angular resolutions in x-ray observations than could be obtained with conventional collimators, in 1965 Oda invented the modulation collimator, a device of two or more layers of parallel wires and the forerunner of the various transform collimators that have since been used in x-ray and gamma-ray observations where imaging by reflection is not feasible.

In 1966, a joint AS&E-MIT rocket experiment with modulation collimators determined the position of Sco X-1 within a few arc minutes, which enabled scientists to identify the optical counterpart as a rapidly fluctuating 13th-magnitude blue star in observations at the Tokyo and Palomar observatories. The discovery and optical identification of Sco X-1 were the sparks that ignited the field of x-ray astronomy.

That same year, Oda was appointed a professor of physics at the newly formed Institute of Space and Aeronautical Science (ISAS) at Tokyo University. Under his leadership, ISAS launched a series of increasingly sophisticated satellite observatories, several with instruments developed in collaborations with US and European laboratories. In 1984, Oda became ISAS’s director general. Among the projects he promoted was VSOP, the VLBI (Very Long Baseline Interferometry) space observatory program. The acronym VSOP (also a type of cognac) suggests the many well-lubricated occasions enjoyed by Oda and his colleagues as one after another of their satellites was launched, on schedule and within budget.

On retirement from ISAS in 1988, Oda was appointed president of the Institute of Physical and Chemical Research (RIKEN), an organization in Wako, Japan, with more than 2000 people in more than 50 research areas, from particle physics to genome science. Oda widened international collaborations, stimulated new programs in high-energy astronomy and brain research and established the RIKEN advisory council, similar to the visiting committees of many US and European institutions but rarely used in Japan. Following a five-year term at RIKEN, Oda became director of the International Institute for Advanced Studies for two years, and president of the Tokyo University of Information Sciences until his death.

As scientist, administrator, and adviser to the Japanese government, Oda was esteemed for his wisdom and fairness, his sure sense of scientific strategy, his ability to marshal the resources for large projects, and his generosity in promoting the careers of his students and associates.

Among Oda’s many honors are the Nishina Memorial Prize (1967), the most prestigious physics prize in Japan, given by the Nishina Memorial Foundation; the Japan Academy Award (1975); and Japan’s Order of Cultural Merit (1993). He also was awarded the First Class Order of the Sacred Treasure, presented by the Japanese emperor, and the 1996 COSPAR Space Science Award from the Committee on Space Research (COSPAR) of the International Council for Science.

Away from his duties he was a member of the Mozart Society of Tokyo and the Japan Alpine Club. He and his wife Tomoe often stopped on their travels at a favorite chalet in the Swiss Alps where they would hike, enjoy fine wines, and eat well. She would gather wildflowers of which he would make exquisite drawings and watercolor paintings.