The ISIS Satellite Program

Model of ISIS-1

Photo CRC 64-9110

Artist's concept of ISIS 2 in space with earth in the background.

Photo CRC 71-22754

Dr. R. Uffen, left, Chairman of the Defence Research Board, and Dr. J. Chapman with the ISIS spacecraft.

Photo CRC 68-16577

ISIS 1 on the rocket.

CRC Photo 69-18707

DRTE satellite tracking station with Kennedy dish antenna (right), Yagi (left) and 230-foot tower. The Yagi received telemetry from the Alouette satellites and the Kennedy dish was installed for the ISIS satellites.

CRC Photo 68-16895

The resounding success of the Alouette satellites led to an agreement between Canada and the United States to collaborate on a series of International Satellites for Ionospheric Studies (ISIS). The United States agreed to launch up to four satellites from the NASA Western Test Range; Canada designed, developed and constructed the satellites. Originally built as a back-up model for Alouette 1, Alouette 2 was quickly modified and reconstructed to conduct five types of ionospheric measurements. The primary objective of Alouette 2 (originally known as the ISIS-X mission) was to extend the scope of the Alouette 1 mission, both in altitude coverage and in the number of ionospheric parameters to be investigated. ISIS 1 was far more complex than Alouette 2. ISIS 1 had ten experiments, which came from American and Canadian university and government laboratories. ISIS 2 was very similar in design to ISIS 1. A third ISIS satellite was scheduled for construction, but it was cancelled in 1969 when the federal government changed its policy and began to focus on communications technology.

Alouette 2 held five experiments. Its swept frequency sounder was extended and included a VLF receiver and an energetic particle experiment supplied by NRC. It also included a Langmuir probe experiment to measure the large ion sheath about the satellite caused by the long antennas. Modifications were made to the antenna system to correct the excessive spin rate decay by adding highly reflective plates on the ends of the longer antennas.

ISIS 1 was far more complex than Alouette 2. It became clear that knowledge of electron distribution was insufficient for an understanding of the ionosphere, and that such additional information as ion mass, and electron and ion temperatures would be required to interpret the ionospheric behaviour revealed by the sounder. The ISIS satellites, with their complements of carefully selected experiments, provided much of the necessary supporting data. ISIS 1 was the first of the series to incorporate swept and fixed frequency sounders, combined with a complete set of direct measurement experiments; active spin maintenance and spin axis orientation control and an onboard tape recorder for data storage. Thus, when the satellite was not in sight of a telemetry station, an onboard porgrammer could switch on the required experiments and tape record at pre-selected times. The clock also acted as the master spacecraft oscillator which was used to synchronize the various experiments as required.

Due to budgetary constraints, the design changes to ISIS 2 were kept to a minimum. The design of as many systems and units as possible from ISIS 1 were used. A few changes were made in the sounder design to increase frequency marker accuracy and the output power of both sounder transmitters. A new feature termed Automatic Ionogram Transmission (AIT) was added to allow automatic operation of the sounder once every three minutes. This gave an opportunity for small institutions to acquire ionograms with very low cost ground stations. The scope of the VLF experiment was increased to include antenna impedence measurements on the sounder's short dipoles. The most significant addition to the ISIS 2 was two optical experiments which were designed and built in Canada. One was called the Red Line Photometer and the second an Auroral Scanning Photometer. These new experiments were designed to study atmospheric optical emissions. The optical experiments required a circular orbit and attitude control.

DRTE involvement in the design and construction of the satellites was gradually reduced throughout the program, until industry accepted complete responsibility for meeting the performance specifications for ISIS 2. One of the conditions made by the Canadian government when approving the ISIS plan was that industry should be brought into the program to the fullest extent with the aim that by the end of the program a skilled industry should exist in Canada for spacecraft development.

RCA Victor Company of Montreal was the prime contractor for Alouette 2, with de Havilland Aircraft of Canada in Toronto as associate contractor. This was also the case for ISIS 1. Subsequently, the Special Products and Applied Research Division separated from de Havilland as SPAR Aerospace. Its first large contract was as a subcontractor for ISIS 2 to provide the mechanical structure and sounder antennas. Thus, Canadian industry became a major participant in the Canadian space program. The overall management of the mission remained at DRTE.

C. David Florida was program manager of the ISIS project. He died suddenly just prior to the launch of ISIS 2 and a plaque was mounted on the spacecraft to commemorate his contributions to the program. In addition, the satellite-testing facility at CRC was named the David Florida Laboratory. A number of individuals from industry and government worked together on this project.

Alouette 2 and Explorer 31 were launched together on a Thor Agena rocket from the Western Test Range in California on November 29, 1965. Alouette 2 lasted for almost ten years. It was terminated on August 1, 1975. ISIS 1 was launched on January 30, 1969 and ISIS 2 was launched on March 31, 1971, both from the Western Test Range in California. Canada ceased to use ISIS 1 and 2 on March 13, 1984, but Japan was authorized to continue using them. ISIS 1 and 2 remained in use until 1990.

The ISIS program spawned numerous scientific papers. Scientists learned about the physical processes of the upper atmosphere and ionosphere - densities, temperatures, magnetic field strengths, ionospheric structures, as well as charge, density and energy of energetic particles. Canadians became leaders in sounding (waves), imaging from space and particle measurements (plasmas). ISIS 2's optical sensors made it possible for the first time to produce images of the entire aurora borealis as seen from above. The ISIS series of satellites achieved near-perfect spacecraft performance for all missions, including near-perfect orbits and a very high percentage of successful experiments.

Sources

Chapman, J. The Alouette-ISIS Program. Ottawa; DRTE, 1966.
Hartz, T.R. and I. Paghis. Spacebound. Ottawa; Supply and Services, 1982.
Jelly, D. Satellite, Engineering Model ISIS. Ottawa; Museum of Science and Technology, 1993.
McNally, J.L. Alouette to Mobilesat - A Review of Canadian Space Programs. Ottawa; Department of Communications, 19--.