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Prior to the launch of Alouette 1 (September 29, 1962), the ionosphere was virtually unknown above an altitude of about 400 km. The Alouette-ISIS satellites have provided a wealth of data concerning the morphology of the polar, midlatitude, and equatorial ionosphere to altitudes up to 3500 km. The measurements (which included not only electron density, but also plasma composition and temperatures) included all local times and all seasons, and encompassed a full range of solar activity. New knowledge was also acquired concerning the propagation and generation of electromagnetic waves-in the ionosphere at both radio and VLF frequencies. A large family of plasma wave phenomena was discovered and explained. Valuable data were also obtained concerning the flux of particles at energies ranging from 5 eV to 20 MeV. Last, but not least, spectacular results were achieved with the optical experiments on ISIS 2, which for the first time provided snapshots of the full auroral oval.

The previous paragraph merely hints at some of the scientific areas that have benefited significantly from the Alouette-ISIS data. The importance of the Alouette-ISIS program can also be appreciated from the fact that it represents 50 satellite-years of measurements in the terrestrial ionosphere, which have led to approximately 1000 publications.

Although articles based upon the Alouette-ISIS data continue to appear in the published literature, the majority of them have been written, and one is now able to assess the accomplishments of the program. Alouette 1 won recognition mainly through the success of the topside sounder, which alone led to 220 publications. Some additional interesting statistical data pertaining to the Alouette-ISIS literature will be discussed later. Much of the enormous volume of data obtained has been deposited in the World Data Centers where it has been made available to the scientific community for further studies and analysis. All of these factors have contributed to the major role which the Alouette-ISIS data have played in furthering our understanding of the near-earth environment.

The Alouette-ISIS program was a joint undertaking between Canada and the United States. Canada provided the Alouette and ISIS spacecraft, data acquisition, and satellite control. The USA provided the launch capability, tracking, and data acquisition. Satellite instruments and data processing support were provided by both countries. The USA also provided the Explorer 20 and Explorer 31 spacecraft that are considered part of the Alouette-ISIS program and are included in this summary. During the course of the program these countries contributed telemetry support and collaborative data analysis: Australia, Finland, France, India, Japan, New Zealand, Norway, and the United Kingdom.

The design of the Alouette 1 spacecraft was begun in 1959 at a very early stage of space technology, when satellite equipment and components were prone to failure, and most spacecraft had a lifetime of only a few months. Alouette was at least as complex as any spacecraft previously launched, and it incorporated large structures that had never been used in space before. The performance of Alouette 1 exceeded by far the most optimistic expectancies and its 10-year life established a longevity record. The other Canadian spacecraft of the program--Alouette 2, ISIS 1 and ISIS 2--have matched and surpassed this record. At least 90 percent of the Alouette-ISIS experiments have operated for at least 1 year and many of them considerably longer. The next section of this document provides a discussion of the objectives, history, spacecraft characteristics, mission profiles, technological accomplishments, and unique aspects of the Alouette-ISIS program.

Excerpted from document NSSDC/WDC-A-R&S 86-09

Reprinted courtesy of the National Space Science Data Center

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