This Canadian satellite was designed and built as a joint industry-university venture with the prime contractor being RCA in Montréal. Spar Aerospace in Toronto did the opto-mechanical design of the photometer, parts of which were machined by Preci-Tool of Montréal, and the flight model was assembled by Space Engineering Division (SED) of the University of Saskatchewan in Saskatoon. Being launched from Vandenberg Air Force Base in the US on April 1, 1971, the ISIS-II spacecraft was the fourth in the Alouette/ISIS series. The instrument, which was the primary focus of the Space Science Group (now the ISR) at the University of Calgary, was an Auroral Scanning Photometer (ASP) which scanned the aurora in visible light ( 557.7 nm (OI ¹S»¹D) oxygen emission {Green} and 391.4 nm N nitrogen emission {Deep Purple}). The imager took 5° image strips as the satellite spun. These strips were then put together by computer to produce one image per orbit which was every 20 minutes. The satellite was in a nearly circular orbit (1358 km perigee, 1428 km apogee) at an inclination of 88.1°.
The ASP on the ISIS-II satellite provided data from launch till the satellite was effectively decommissioned in the early 80's. It was a joint Canada/USA venture and thus the operations and data acquisition were handled through the relevant space agencies of both countries. A science team representing the complement of instruments from both countries was created to provide input into the operations of the satellite much as has been done with subsequent missions which Canada has been involved in. For ISIS-II this input was primarily a specification of the spin axis attitude and choice of ground stations at which telemetry (TM) would take place. This required considerable ability to predict the satellite's position and instrument viewing conditions under a variety of conditions which was developed and utilized mainly at the University of Calgary. The ground station data acquisition was handled through NASA (Goddard). Tracking stations from all over the world received TM from the ISIS-II satellite. The TM was shipped to the Data Distribution Centre of the The Communications Research Centre in Ottawa with the U of C being provided analogue tapes containing the ASP data. Once in Calgary, the data was processed by the imaging team using the state-of-the-art Digital PDP-8i computer.
Below are some typical images taken during the mission. As the images were taken at specific wavelengths of light, they are inherently monochromatic (ie. taken in one colour only). To improve the contrast in each image, they are displayed in false colour with blue being the least intense source regions of light, working up through green to yellow and finally to red for the most intense source regions. One can clearly see the strips from each spin of the satellite. The stips are curved instead of straight for two resons. 1. The Earth is curved. 2. These images have been transformed so that the magnetic north pole has been placed at the center of the image. The bright (red) fringe at the top of each image was caused by the scanner viewing the sunlit side of the Earth which is much brighter than the aurora in the visible part of the spectrum.
