4. PROGRAMS, MISSIONS, AND PAYLOADS

Orbiting Frog Otolith Program

The Orbiting Frog Otolith (OFO) Program was a part of the research program of NASA's Office of Advanced Research and Technology (OART). One of the goals of the OART was to study vestibular organ function in space and on the Earth.

     Man's ability to orient himself with respect to his environment and his ability to coordinate his bodily movements has evolved in the constant presence of gravity. Because of this, it was difficult to predict how astronauts would respond to extended stays in microgravity.

     The OFO experiment was designed to allow researchers to collect neurophysiological data on the response of the otolith to prolonged periods of weightlessness. The otolith is a part of the inner ear that is associated with equilibrium control: acceleration with respect to gravity as its primary sensory input.

     After the successful OFO-A mission in 1970, interest in the research continued. A project called Vestibular Function Research was initiated in 1975 to fly a vestibular experiment in an Earth-orbiting spacecraft. This flight project was eventually discontinued, but a number of ground studies were conducted. The research has given rise to several very useful offshoots, including the ground-based Vestibular Research Facility located at ARC.

Figure 4-15: Launch of the Orbiting Frog Otolith (OFO) capsule (see also Fig. 4-16).

The OFO Spacecraft

The OFO experiment was originally designed for flight within the Apollo Applications Program, which was established to make optimum use of hardware used in Apollo lunar missions. However, because the low acceleration levels needed for the experiment could not easily be maintained in a manned Apollo spacecraft, an unmanned satellite was later chosen as a more suitable vehicle. The satellite's design eliminated exposures to acceleration levels above 10-3g. This meant that the experimental specimens could experience an almost weightless state.

     The spacecraft had a diameter of approximately 30 in. and a length of 47 in. The octagonal lower section of the spacecraft housed the electronic apparatus. The upper section, which contained the experiment package, was shaped like a truncated cone. A heat shield covering this upper section protected the experiment during re-entry into the Earth's atmosphere. A "yo-yo" despin assembly was located around the girth of the spacecraft. Four booms, folded against the side of the spacecraft, were located radially around the satellite. After the spacecraft separated from the launch vehicle, the yo-yo despin subsystem slowed spacecraft rotation. The four booms were then released to extend from the side of the spacecraft. The extension of the booms increased the moment of inertia of the spacecraft, permitting the acceleration level to remain below 10-3g (Fig. 4-16).

Figure 4-16: Orbiting Frog Otolith (OFO) with booms. Booms out increased the moment of inertia.

     The spacecraft was launched by a Scout 1B rocket. The Scout 1B was a four-stage solid propellant rocket system, which was about 73 ft long and weighed about 40,000 pounds at lift-off. Also onboard was the Radiation Meteroid spacecraft to demonstrate and evaluate improved instrumentation and to gather near-Earth data of scientific interest.

Move to next section Orbiting Frog Otolith-A

Additional Reading

Gualtierotti, T. Vestibular Receptors in Space: Final Report. Contract NAS2-9871, 1979.

NASA. Orbiting Frog Otolith/ OFO-Project Press Kit. NASA News Release 70-132, 1970.

Space General Company. Orbiting Frog Otolith Satellite (OFO) Mission Performance Report. NASA CR-62083, December 1970.