Mr. McDonald's career in space physics spanned more than a half-century, starting with experimental research in the mid-1950s to measure the radiation above the Earth's atmosphere. His mentor in this effort was James A. Van Allen, a University of Iowa physicist who became a leader in space research and for whom the radiation belts encircling the Earth were later named.
From 1970 to 1982, Mr. McDonald was chief of Goddard's lab of high energy astrophysics and helped design a satellite program with instruments that could study X-rays, gamma rays, and cosmic rays.
As chief NASA scientist from 1982 to 1987, Mr. McDonald was a principal adviser to the NASA administrator and other senior officials. In that role, he helped start a NASA partnership with historically black colleges to fund research projects by faculty members and graduate students.
In recent years, Voyager 1 has been at the edge of what scientists believe is the end of our solar system and the start of interstellar space. Mr. McDonald continued to monitor information from the probe until shortly before his death, curious whether expectations would prove true of a "termination shock," or shock wave, where the two regions collide. - Washington Post