The NOTS-EV-2 Caleb, also known as NOTS-500, Hi-Hoe and SIP was an expendable launch system, which was later used as a sounding rocket and prototype anti-satellite weapon. It was developed by the United States Navy's Naval Ordnance Test Station (NOTS) as a follow-up to the NOTS-EV-1 Pilot, which had been abandoned following ten consecutive launch failures. Two were launched in July and October 1960, before the cancellation of the project.