The Orbiting Frog Otolith (OFO) was a NASA space program which resulted in the successful launch in 1970 of the Orbiting Frog Otolith spacecraft (OFO-A mission), sending two bullfrogs into orbit for the study of weightlessness. The name, derived through common use, was a functional description of the biological experiment carried by the satellite. Otolith referred to the frog's inner-ear balance mechanism.