Canada has the second largest surface area of all countries, yet only 60, or so, meteorites have been found within its borders. Most of those were accidental discoveries. One was found as the result of having recorded the fireball with the MORP camera system, a few were found after visual observation of the fireball (e.g. St. Robert), and at least one has been found as a result of door-to-door canvassing (Prairie Meteorite Search, summer 2000). In spite of the dearth of native meteorite specimens, the interest in meteoritics is shared by many amateur and professional scientists in Canada. There are substantial numbers of meteorites in the National Collection, Geological Survey of Canada, at the University of Alberta, and at the Royal Ontario Museum. The Meteorites and Impacts Advisory Committee (MIAC) to the Canadian Space Agency is the body which coordinates meteoritical research in Canada, and further information is available on its website.
Sandia Labs, New Mexico, has an interest in fireball phenomena, although the driving force for them may not be an interest in meteorites as such. To the mutual benefit of the U.S. military and meteorite enthusiasts, Sandia Labs has, in recent years, developed simple but effective all-sky camera systems for detecting bright meteors (fireballs and bolides). Those camera systems are being provided at no cost on a limited-time contractual basis to amateurs and professionals in the U.S.A. and Canada. In particular, there is now a network covering southwestern B.C. and Washington State, another network in Saskatchewan, and a third close to full operation in north-central Alberta.
Each system consists of an 18-inch diameter reflecting hemisphere located at the base of a tetrapod which supports a small video camera. The system at Ed Majden’s observatory is illustrated at http://www.amsmeteors.org/spectro.html Data are normally fed to a bank of three VHS tape recorders. Each tape recorder runs for 8 hours in sequence with the others. Date and time are superposed on each image.
The Alberta system was acquired at the instigation of Martin Connors. Cameras have been installed on the campus of Athabasca University (approximately 135 kilometres north of Edmonton), at The King's University College Observatory (approximately 20 kilometres east of Edmonton), and on the roof of the Physics Building, University of Alberta (within Edmonton). The latter camera will eventually be installed at the Devon Astronomical Observatory (approximately 20 kilometres southwest of Edmonton).
As part of his duties as an undergraduate summer student working with Doug Hube, Jason Hessels was assigned to the all-sky camera project. Many of the results of his labours can be found at http://www.ualberta.ca/~jhessels/meteor.html Jason has developed the procedures for digitizing images from the VHS tapes. He used C++ Builder in writing software which allows one to call up an image, and then click on a feature on the image such as a point on a fireball. The X-Y coordinates (pixel location) of that feature are then automatically converted to position on the celestial sphere, namely, RA-Dec and altitude-azimuth. Calibration of that coordinate conversion is necessary, and that has been achieved by observing Iridium satellite ‘flares’. (The Iridium satellites do have some value for the astronomical community!) In principle, the calibration can also be done using the Moon, planets and stars. In practice, glare from the Moon reduces the precision with which its position can be measured, and none of the stars or planets is bright enough to be detected, with the exception of Venus. The menu-driven, graphical user interface is extremely convenient to use. The program may be downloaded from the website given above. Questions regarding its use should be directed to Jason Hessels. Links to other websites of interest will be found on his website.
To better understand the next step in the process and because of difficulties in making the available programs run on his computer, Jason has been developing software which will convert multi-site observations of a given fireball into the flightpath through the atmosphere, followed by a prediction of the fall zone.
An inconvenient feature of the basic Sandia system is that one is required to change VHS tapes every day. That precludes placing the cameras at unattended remote dark sites. One of us (BM) is adapting frame grabbing technology developed for the broadcast industry as an alternative data storage method. The camera signal will be sent directly to a Pentium computer equipped with a fast frame grabber. At least a week’s worth of continuously-recorded images can be saved on a ~20GB hard drive. In the VCR format the data tapes are reused on a 10-day duty cycle. In the frame grabber approach the contents of the hard drive will be overwritten on a comparable cycle. Normally, reports of fireballs of any interest to us are received from the public within a day of their occurrence. On such occasions, images on the relevant tapes, or on the relevant portion of a disc, will be retrieved and saved for analysis.
In the late-Summer of 1999 there were two very bright fireballs over Alberta, both of which were observed from locations beyond, as well as within, the borders of the Province. The characteristics of those events were such as to suggest a high probability that both resulted in the fall of meteorites. Interestingly, the predicted fall zones for the two events were nearly coincident southeast of Red Deer. In spite of wide publicity, interviewing, and limited searches, those meteorites have not been recovered. Had Sandia cameras been operating at that time in both the Edmonton and Calgary regions, we are confident that a meteorite would have been recovered. Unfortunately, during the few months which have elapsed since the installation of the first camera in Alberta there have been no reports of fireballs.
ACKNOWLEDGMENTS. We thank Richard Spalding, Sandia Labs, for arranging delivery of the camera systems, and for replacing one faulty reflector. Jeremy Tatum provided assistance with the mathematics needed for the coordinate conversions. Tyler Foster assisted Jason Hessels in the creation of the ASCP software.