The experiment was designed to study the adaptability of the otolith to sustained weightlessness, to provide information for human spaceflight.

The otolith is a structure in the inner ear that is associated with equilibrium control: acceleration with respect to gravity as its primary sensory input.

However, because the low acceleration levels needed for the experiment could not easily be maintained in a crewed Apollo spacecraft, an uncrewed satellite was later chosen as a more suitable vehicle.

The objective of the experiment was to investigate the effect of microgravity on the otolith, a sensory organ that responds to changes in an animal's orientation within the Earth's gravitational field.

The water medium served to cushion the vibration and acceleration of launch, and to facilitate gas exchange with the organisms.

"[3] Local Congressman (and future four-term governor) Edwin Edwards helped connect the agency with Rayne, six miles east of his hometown of Crowley.

[3] A total of 20 Rayne frogs were sent to NASA for evaluation, where they were narrowed to a group of four—two of which would go into orbit and two who would remain as a backup crew.

The frogs were demotorized by cutting their limb nerves to prevent them from dislodging their implanted electrodes, and to reduce their metabolic rates.

The flight hardware unit, the FOEP, was a pressure-tight canister containing a water-filled centrifuge that housed the two frogs.

Carbon dioxide entering the gas loop was removed by an absorbent and the purified oxygen returned to the pump for recirculation.

An amplifier system in the FOEP increased voltage output from the microelectrodes implanted in the animals to the level required by the telemetry apparatus.

Surgical preparation of the flight frogs was completed about 12 hours before launch, and the animals were sealed inside the FOEP.

Two equipment malfunctions occurred during the flight: pressure in the canister increased to 11 pounds per square inch (76 kPa), and the temperature decreased to 55 °F (13 °C) for nine hours.

[6] NASA reported that the frogs died shortly before noon, Washington time, on November 15 after more than six days in orbit.

The bottom closure and removable top lid are both slightly domed to prevent implosion should pressure reversals be encountered.

The inner assembly structure is fastened to a support ring approximately 6 inches from the bottom of the canister and consists of upper and lower bulkheads joined by a cylinder.

The cylinder is mounted perpendicular to the canister and supported by ball bearings housed in the upper and lower bulkheads.

The rotational axis of the centrifuge is formed by shafts centrally located in the vertical plane at right angles to the cylinder, held in place by the ball bearings.

The water serves as a cushion for the high accelerations and vibrations of launch and as a medium for gas exchange via the frogs' skin.

A bubble of air trapped in the polyethylene tubing which contains the probe adds buoyancy and makes the electrode the same density as the nerve in which it is implanted, thereby allowing the two to move together.

Nerve impulses detected by the microelectrodes are fed into a preamplifier directly attached to the frog's jaw, and passed on to a post-data amplifier for spacecraft telemetry.

The interface between loops occurs at a selectively permeable membrane of silicon rubber which separates the liquid and gas.

A double layer of polyurethane foam lining the interior of the centrifuge prevents frog waste matter from fouling the water circulation system.

The water supply for the evaporator is contained in a rubber bladder supported by a ring in the canister immediately above the lower dome.

When water temperature exceeds the nominal 60 °F, a ground command actuates a timing circuit operating a valve.