Robert Wilson, whose conception of a UV observatory led to the development of the International Ultraviolet Explorer (IUE), died from complications related to cancer on 2 September 2002 in Chelmsford, England. He made major contributions to both laboratory plasma spectroscopy and astrophysical spectroscopy. For those and other contributions, he was knighted in 1989.
Born on 16 April 1927 in South Shields, England, Robert took his BS in physics from Kings College, Durham, in 1948. He received a PhD in astronomy from Edinburgh University in 1952. His doctoral thesis, carried out under W. M. H. Greaves, concerned optical spectroscopy of O stars.
Robert’s first significant paper presented spectroscopic observations of the Sun made on 26 September 1950, when atmospheric conditions made it appear blue in Edinburgh. On that day, while other students displayed a modern sense for public relations by running to answer telephone inquiries, Robert concerned himself with the scientific phenomenon and dashed to the telescope. He concluded that the selective extinction responsible for the blueness resulted due to dielectric particles of a very uniform size. Those particles were probably submicron globules of oil produced three days earlier by a forest fire in Alberta, Canada.
As a member of the staff at the Royal Observatory, Edinburgh, which he joined in 1952, Robert continued his investigations of O stars. He discovered that such stars have winds and that the wind luminosity correlates with the radiative luminosity. In 1957, he submitted the paper on those findings. In that year, he went to the Dominion Astrophysical Observatory in Victoria, British Columbia, Canada, where he worked primarily on the diffuse interstellar bands.
He returned to England the following year after receiving a letter from John Crockcroft, who said that his team in the UK government laboratory Harwell in Oxfordshire was on the verge of attaining controlled fusion with the Zero Energy Toroidal Assembly (ZETA) device. Although he had worked only in optical astronomical spectroscopy, Robert recognized that he would have to develop UV spectroscopic diagnostics to infer the ZETA plasma’s conditions. He measured the UV features of ions of neon, argon, and krypton injected in trace amounts into the plasma to deduce thermal and turbulent contributions to their linewidths. He also developed an analytically tractable model, which included plasma losses, of the time-dependent ionization structure of a rapidly heated plasma. Robert concluded that the ZETA plasma reached temperatures of only roughly 1 million kelvin and escaped in about 100 microseconds. He also realized the diagnostic utility of coherent scattering of laser radiation by plasma fluctuations and established an effort to exploit it.
In 1962, the entire fusion team moved to Culham. There, Robert began using the ZETA device for astrophysical experiments, in which he showed that many extreme UV solar lines that had previously been unidentified were due to iron. Robert turned increasingly to solar plasmas and, during much of the rest of the 1960s, oversaw the development of extreme UV and soft x-ray spectrometers, which he used to employ so-called satellite and forbidden line features of heliumlike ions as diagnostics of solar regions. Robert also became involved in a rocket program to study other stars spectroscopically in the UV. He led the British team in the joint UK-Belgium UV sky survey experiment (S2/68) that was launched on the European Space Research Organization’s satellite TD-1.
Robert’s work that eventually led to the launch of IUE began in 1964. After a frustrating series of dealings with the ESRO, he obtained permission from the UK Science Research Council (SRC) to present to NASA, as an outright gift, the concept that he had developed. NASA’s support prompted a joint program eventually involving NASA, the SRC, and the European Space Agency.
Initially, Robert directed the UK effort on IUE from Culham, but he then joined University College London in 1972 as the Perren Professor of Astronomy. In that year, the group he had led was transferred to the Rutherford Appleton Laboratory to found that establishment’s effort in space research.
IUE was launched on 26 January 1978. Robert made use of it during its lifetime of nearly two decades to make significant contributions on the winds of Wolf-Rayet stars, x-ray binaries, interstellar extinction, and the variability of Seyfert galaxies. He was particularly proud of his work with Prab Gondhalekar on a double quasar produced by the gravitational lensing of a single object. In 1982, in a paper they published on their studies of that quasar, they gave the currently accepted value of Hubble’s constant considerably before groups that had observed Cepheid variables in other galaxies.
In 1980, Robert, together with Allan Willis, started the series of nearly annual international meetings on astronomy sponsored by University College London and held in Cumberland Lodge in Windsor Great Park. That series continues as a testament to the great pleasure he took in serving as the host, being in a beautiful and peaceful environment, enjoying a fine meal and a good wine, and giving younger scientists an opportunity to mix congenially with, and be encouraged by, more senior ones. The atmosphere at any of the meetings he organized reflected his generosity, kindness, and civility.
