Bob Benson (Goddard Space Flight Center, Code 692) is heading an effort to convert Alouette and ISIS topside sounder data from the original analog telemetry tapes into digital ionograms. A sample ISIS 2 digital ionogram is shown at the top of this page. These sounders have produced the only global mapping of the topside ionosphere over more than an entire solar cycle. The National Space Science Data Center (NSSDC) has more than 12,000 rolls of 35 mm microfilm containing Alouette 1, Alouette 2, ISIS 1 and ISIS 2 topside ionograms. These data extend from the launch of Alouette 1 in September, 1962 to March, 1983 and have resulted in nearly 1,000 scientific publications. Not all of the data during this time period were processed into ionograms. In addition, most of the data extending from March, 1983 up to the turn-off of ISIS 1 and 2 in January, 1990 exist only on the original analog telemetry tapes stored in Canada. Most of these tapes have now been destroyed because of problems with media deterioration and the cost of tape storage.
The NASA Space Physics Data System (SPDS)-related Ionosphere, Thermosphere, Mesosphere (ITM) Data Evaluation Panel has rated the rescue and transformation of this data set as its highest priority project. The full ITM report is available here.
Some 13,800 Alouette and ISIS analog telemetry tapes were selected from 100,000 tapes available (as of March, 1996) in Canada and were shipped to Goddard for analog-to-digital (A/D) transformation and archival in the NSSDC. Since that time all but approximately 4000 selected ISIS 1 and 2 tapes have been destroyed. These tapes will be saved in Canada for a period of 5 years in anticipation of possible processing. The tapes shipped to Goddard were selected in order to obtain global coverage and to accommodate requests to address subjects and time periods of special interest. For more details about the data selection process and the A/D conversion system please see the April 1996 Status Report. This information was also presented in a talk at the Ionospheric Effects Symposium (IES-96) held in Alexandria, Virginia, 7-9 May 1996 and will be published in the Symposium Proceedings.
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