Orbiting Frog Otolith - The OFO Spacecraft

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 (10 mm/s²). This meant that the experimental specimens could experience an almost weightless state.

The spacecraft had a diameter of approximately 30 in (760 mm) and a length of 47 in (1,190 mm) 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 de-spin 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.