IMB, the Irvine-Michigan-Brookhaven detector, was a nucleon decay experiment and neutrino observatory located in a Morton Salt company's Fairport mine on the shore of Lake Erie in the United States 600 meters underground.
[2] IMB consisted of a roughly cubical tank about 17 × 17.5 × 23 meters, filled with 2.5 million gallons of ultrapure water which was surrounded by 2,048 photomultiplier tubes.
Ground was broken at the salt mine in 1979; the water tank for the detector itself was finished in 1981.
The project was delayed by funding problems and leaks in the water tank, but by the end of summer 1982 the detector was operating at full capacity.
This discovery was completely unexpected; supernovas as near as 1987a are extremely rare and virtually unpredictable.