Part way through the IONS 2004 program, persistent fog had delayed aircraft that should have delivered additional supplies of O3 sensors. With only a few sensors left, completion of O3 profiling on Sable Island was at risk. So the captain of the Ceol Mor, a small sailing boat scheduled to visit the island in late July, was contacted for assistance. The Ceol Mor arrived on July 24th, and anchored off the north side of the island.