On May 5, 1961, the same day the first American astronaut was launched, NASA proposed using Scout rockets to evaluate the Mercury tracking and real-time computer network in preparation for manned orbital missions. The proposal was approved and on June 13, 1961, the NASA Space Task Group issued detailed instrumentation requirements for the modified Scout, which became known as Mercury-Scout.
Each Mercury-Scout was to carry a lightweight communications payload into orbit to allow a simulation of the tracking through the Mercury global network of an actual Mercury capsule. Blue Scout II number D-8 was modified for the first – and what would turn out to be the last – Mercury-Scout mission, MS-1. The launch was conducted by the United States Air Force, which had already launched other Blue Scout rockets from Cape Canaveral, on November 1, 1961. But 28 seconds after liftoff, the rocket veered off course and had to be destroyed by the range safety officer.
Mercury program managers decided against further Mercury-Scout missions, and by the end of 1961 Mercury-Atlas missions MA-4 and MA-5 had demonstrated that actual orbiting Mercury capsules could be successfully tracked.