Observed target on search radar. Ground speed about 25000 kt, altitude at least 30000ft. recorded on scope camera. observed by other radar sites across Canada. I was an early warning radar operator in the USAF on St Lawrence Island. We observed a target, unidentified, in Soviet airspace heading east at high speed. Our first thought was that it was some type of missile. We turned on the scope camera and notified the site commander. The object was estimated at 25000kt. The first contact was at about 200 miles, which would make it very high or very large.