Herbert S. Bridge, Professor Emeritus of Physics at MIT, died on August 30, 1995, after a long illness. He was one of the pioneers in the exploration of the solar system from unmanned spacecraft.
Born in 1919, in Berkeley, California, Herb Bridge obtained his Bachelor's degree from the University of Maryland in 1941. During the war, he was a member of the staff of the National Defense Research Committee Separation Project at Princeton and later joined the staff of the Los Alamos Laboratories. In 1946 he came to the Massachusetts Institute of Technology to join the cosmic ray and elementary particle group headed by Bruno Rossi, under whose supervision he received his Ph.D. in physics in 1950. From 1950 until 1966, he was a member of the research staff of the Laboratory for Nuclear Science of MIT. During the year 1957, he took a leave of absence from MIT to work at the CERN Laboratory at Geneva, Switzerland. He did work on high-energy particles at CERN and Brookhaven National Laboratory. In 1966, he was appointed Professor of Physics at MIT.
His early work in cosmic rays was mainly directed toward the study of nuclear interactions produced by cosmic ray particles and of the new unstable particles resulting from these interactions. The remarkable success achieved by Herb Bridge in these studies was due in part to his exceptional experimental skill and in part to his sharp and sound judgment in the evaluation of experimental data. The results achieved by Herb and his collaborators include, among others, the discovery of the positive K-meson and the cloud chamber observation of a cosmic ray event interpreted tentatively as the annihilation of a heavy anti-particle (prior to discovery of the anti- proton).
Beginning in 1958, Professor Bridge worked in space plasma physics. He was the leader of a group of physicists at MIT who designed and constructed a novel instrument for the study of interplanetary plasma, the modulated-grid Faraday cup. This instrument was successfully flown aboard the Explorer X spacecraft in the spring of 1961. For the first time, it provided direct measurements of the density and velocity of the solar wind (the supersonically expanding outer atmosphere of the sun), and on the interaction of the solar wind with the magnetic field of the Earth.
After that initial discovery, Herb was Principal Investigator on space plasma experiments aboard numerous unmanned scientific missions. His plasma probes have been successfully flown on seven NASA earth satellites, two deep space probes and four planetary missions. Herb Bridge holds the unique distinction of having been Principal Investigator on missions to every planet in the solar system except Pluto. The pioneering work of Herb Bridge and his collaborators in this field received worldwide recognition and the MIT group acquired a leading position in the field of plasma measurements in outer space.
These experiments have provided a wealth of accurate data on the properties of the interplanetary plasma, on the Earth's magnetosphere, and on the interaction of the solar wind with the Moon, Venus and Mercury, Mars, Jupiter, Saturn, Uranus, and Neptune. Herb's plasma experiment on board the Voyager spacecraft directly measured the properties of plasmas in the magnetospheres of the large planets, including plasmas originating from the volcanoes on Io (the innermost Galilean satellite of Jupiter), from the dense atmosphere of Titan (the large satellite of Saturn), from the upper atmosphere of Uranus, and from Triton (the large satellite of Neptune). The Voyager spacecraft are currently at about 50 Astronomical Units from the Sun, and continue to measure the properties of the distant solar wind.
Herb Bridge was Associate Director of the MIT Center for Space Research from its inception in 1965 until 1978, and Director from 1978 until his retirement in 1984. He also contributed effectively to MIT's educational program through formal teaching and, more importantly, the training that graduate students and young Ph.D.'s have received under his leadership.
Uncompromisingly honest and frank in evaluating scientific matters, Herb was at the same time extraordinarily fair and humane in personal relations and always treated his collaborators, whether students, professors, or scientists from other institutions, as human beings above all.
In addition to his professional accomplishments, Herb had a number of outside interests, including cars, photography, mountaineering and the out-of-doors. His combined interests in high-energy particles and mountaineering took him to high-altitude laboratories throughout the world.
His colleagues have lost a dear friend. His wisdom, humanity, and farsighted guidance will be sorely missed.
Bridge, H. S. and B. B. Rossi, Burst production by penetrating cosmic-ray particles, Phys. Rev., 72, 257, 1947.
Bridge, H. S. and B. B. Rossi, Cosmic-ray bursts in an unshielded chamber and under one inch of lead at different altitudes, Phys. Rev., 71, 379, 1947.
Bridge, H. S., C. Peyrou, B. B. Rossi and R. Safford, Cloud chamber observations of the heavy charged unstable particles in cosmic rays, Phys. Rev., 90, 921, 1953.
Bridge, H. S., Experimental results on charged K-mesons and hyperons, Chapter II in Progress in Cosmic Ray Physics, Vol. III, North Holland Publishing Company, Amsterdam, Holland, 1956.
Bridge, H. S., An instrument for the investigation of interplanetary plasma, J. Geophys. Res., 65, 1960.
Bridge, H. S., A. J. Lazarus, E. F. Lyon, B. Rossi and F. Scherb, Plasma probe instrumentation on Explorer X, J. Phys. Soc. Japan, 17, Supplement A-III 1113-1121, 1962.
Bonetti, A., H. S. Bridge, A. J. Lazarus, E. F. Lyon, B. Rossi and F. Scherb, Explorer X plasma measurements, Proceedings of the Third International Space Science Symposium, Space Research III, W. Priester, ed., 540-552, North-Holland Publ. Co., Amsterdam, the Netherlands, 1963.
Bridge, H. S., Plasmas in space, Physics Today, 16, 31, 1963.
Bridge, H. S., A. J. Lazarus, C. W. Snyder, E. J. Smith, L. Davis, Jr., P. J. Coleman, Jr. and D. E. Jones, Mariner V: Plasma and magnetic fields observed near Venus, Science, 158, 1669-1673, 1967.
Bridge, H. S., A. J. Lazarus, J. D. Scudder, K. W. Ogilvie, R. E. Hartle, J. R. Asbridge, S. J. Bame, W. C. Feldman and G. L. Siscoe, Observations at Venus encounter by the plasma science experiment on Mariner 10, Science, 183, 1974.
Ogilvie, K. W., J. D. Scudder, R. E. Hartle, G. L. Siscoe, H. S. Bridge, A. J. Lazarus, J. S. Asbridge, S. J. Bame and C. M. Yeates, Observations at Mercury encounter by the plasma science experiment on Mariner 10, Science, 185, 145-151, 1974.
Bridge, H. S., J. W. Belcher, R. J. Butler, A. J. Lazarus, A. M. Mavretic, J. D. Sulivan, G. L. Siscoe and V. M. Vasyliunas, The plasma experiment on the 1977 Voyager mission, Space Sci. Rev., 21, 259-287, 1977.
Bridge, H. S., J. W. Belcher, A. J. Lazarus, J. D. Sullivan, R. L. McNutt, Jr., F. Bagenal, J. D. Scudder, E. C. Sittler, G. L. Siscoe, V. M. Vasyliunas, C. K. Goertz and C. M. Yeates, Plasma observations near Jupiter: Initial results from Voyager 1, Science, 204, 987-991, 1979.
Bridge, H. S., F. Bagenal, J. W. Belcher, A. J. Lazarus, R. L. McNutt, Jr., J. D. Sullivan, P. R. Gazis, R. E. Hartle, K. W. Ogilvie, J. D. Scudder, E. C. Sittler, Jr., A. Eviatar, G. L. Siscoe, C. K. Goertz and V. M. Vasyliunas, Plasma observations near Saturn: Initial results from Voyager 2, Science, 215, 563-570, 1982.
Bridge, H. S., J. W. Belcher, B. Coppi, A. J. Lazarus, R. L. McNutt, Jr., S. Olbert, J. D. Richardson, M. R. Sands, R. S. Selesnick, J. D. Sullivan, R. E. Hartle, K. W. Ogilvie, E. C. Sittler, Jr., F. Bagenal, R. S. Wolff, V. M. Vasyliunas, G. L. Siscoe, C. K. Goertz and A. Eviatar, Plasma Observations Near Uranus: Initial Results from Voyager 2, Science, 233, 89-93, 1986.
Belcher, J. W., H. S. Bridge, F. Bagenal, B. Coppi, O. Divers, A. Eviatar, G. S. Gordon, Jr., A. J. Lazarus, R. L. McNutt, Jr., K. W. Ogilvie, J. D. Richardson, G. L. Siscoe, E. C. Sittler, Jr., J. T. Steinberg, J. D. Sullivan, A. Szabo, L. Villanueva, V. M. Vasyliunas and M. Zhang, Plasma observations near Neptune: Initial results from Voyager 2, Science, 246, 1478-1483, 1989.