On January 30, 1969, the Canadian-built ISIS I satellite soared into space on a Delta E rocket from the Vandenberg Air Force Base in California. Launched under the International Satellites for Ionospheric Studies (ISIS) program, a joint Canada-U.S endeavour, it was second of three, in the program after Alouette II and followed by ISIS II in March 1971.
Like its predecessor, Alouette II, the ISIS satellites were designed to study the ionosphere and the aurora borealis, also known as the Northern Lights. Before the advent of communications satellites, radio signals were transmitted across Canada by bouncing them off the ionosphere, an electrically charged layer of the upper atmosphere. But the transmissions were often disrupted by aurora, a phenomenon that scientists have long been trying to better understand.
The ISIS satellites carried experiments from Canadian and American universities and government laboratories to understand the physical processes in the ionosphere. Measurements were taken over an entire 11-year solar cycle to determine how the ionosphere reacts to changes in the Sun's radiation.
Both ISIS satellites were designed and developed in Canada. The Defense and Research Telecommunications Establishment managed the project, while the private sector handled most of the hardware development. RCA Ltd. of Montréal largely built both satellites, with some of the work subcontracted to De Havilland and SPAR. Through this project, Canadian companies became significant participants in the Canadian Space Program.
The ISIS satellites were more technically advanced than their predecessors, with more complex navigational systems and larger data collection capabilities. The most significant additions to ISIS II were two optical sensors, including an Auroral Scanning Photometer from the University of Calgary. These sensors made it possible to produce the first images of the entire aurora borealis oval from above.
ISIS I was the first of the series to incorporate fixed- and swept-frequency sounders like those used on the ground. It also had a complete set of direct measurement experiments and a tape recorder for data storage. An onboard system could turn the experiments and tape recorder on when the satellite was not in sight of a telemetry station. The clock was also used to synchronize the experiments.
All of the ISIS series of satellites achieved near-perfect performance and orbits, with a very high percentage of successful experiments. The data collected spawned more than 1,200 scientific papers, as scientists learned about the physical processes of the upper atmosphere and ionosphere, including densities, temperatures, magnetic field strengths, and structure. As a result of this research, Canadians became experts in imaging from space, and solar particle or plasma measurement.