Orbiting Frog Otolith
Encyclopedia
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
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
Otolith
An otolith, , also called statoconium or otoconium is a structure in the saccule or utricle of the inner ear, specifically in the vestibular labyrinth of vertebrates. The saccule and utricle, in turn, together make the otolith organs. They are sensitive to gravity and linear acceleration...
referred to the frog's inner-ear balance mechanism.
The Orbiting Frog Otolith Program was a part of the research program of NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
'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.
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.
The Frog Otolith Experiment (FOE) was developed by Dr. Torquato Gualtierotti of the University of Milan
University of Milan
The University of Milan is a higher education institution in Milan, Italy. It is one of the largest universities in Europe, with about 62,801 students, a teaching and research staff of 2,455 and a non-teaching staff of 2,200....
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, when he was assigned so the Ames Research Center as a resident Research Associate sponsored by the National Academy of Sciences. The experiment was designed to study the adaptability of the otolith
Otolith
An otolith, , also called statoconium or otoconium is a structure in the saccule or utricle of the inner ear, specifically in the vestibular labyrinth of vertebrates. The saccule and utricle, in turn, together make the otolith organs. They are sensitive to gravity and linear acceleration...
to sustained weightlessness
Weightlessness
Weightlessness is the condition that exists for an object or person when they experience little or no acceleration except the acceleration that defines their inertial trajectory, or the trajectory of pure free-fall...
, to provide information for manned space flight. Originally planned in 1966 to be included on an early Apollo mission, the experiment was deferred when that mission was canceled. In late 1967 authorization was given to orbit the FOE when a supporting spacecraft could be designed. The project, part of NASA's Human Factor Systems program, was officially designated "OFO" in 1968. After a series of delays, OFO was orbited 9 November 1970.
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
NASA Ames Research Center
The Ames Research Center , is one of the United States of America's National Aeronautics and Space Administration 10 major field centers.The centre is located in Moffett Field in California's Silicon Valley, near the high-tech companies, entrepreneurial ventures, universities, and other...
.
OFO should not to be confused with similar acronyms describing the Orbiting Observatory series of spacecraft, such as Orbiting Geophysical Observatory
Orbiting Geophysical Observatory
Orbiting Geophysical Observatory refers to the six satellites launched by the United States that were in use from September 1964 to 1972, designed to study the Earth's magnetosphere. The satellites successfully studied the interactions between the Earth and the Sun, despite a number of technical...
(OGO), Orbiting Solar Observatory
Orbiting Solar Observatory
The Orbiting Solar Observatory Program was the name of a series of nine American science satellites primarily intended to study the Sun, though they also included important non-solar experiments. Eight were launched successfully by NASA between 1962 and 1975 using Delta rockets...
(OSO), and Orbiting Astronomical Observatory
Orbiting Astronomical Observatory
The Orbiting Astronomical Observatory satellites were a series of four American space observatories launched by NASA between 1966 and 1972, which provided the first high-quality observations of many objects in ultraviolet light...
(OAO).
The OFO spacecraft
Apollo Applications program
The Apollo Applications Program was established by NASA headquarters in 1968 to develop science-based manned space missions using surplus material from the Apollo 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
Yo-yo de-spin
frame|[[Payload Assist Module|PAM-D]] upper stage with the [[Phoenix |Phoenix]] spacecraft. The [[Star 48|Star 48-B]] engine is shown being spun, fired, yo-yo de-spun and jettisoned....
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
Moment of inertia
In classical mechanics, moment of inertia, also called mass moment of inertia, rotational inertia, polar moment of inertia of mass, or the angular mass, is a measure of an object's resistance to changes to its rotation. It is the inertia of a rotating body with respect to its rotation...
of the spacecraft, permitting the acceleration level to remain below 10-3g.
Orbiting Frog Otolith-A
Mission: OFO-A Mission Duration: 6 days Date: November 9-15, 1970 (not recovered) Life Sciences Research Objectives:To study the effect of microgravity on the vestibular organ Life Sciences Investigations:Neuroscience ( OFO-1.1, 1.2, 1.3) Organisms Studied:Rana catesbeiana Bullfrog The American bullfrog , often simply known as the bullfrog in Canada and the United States, is an aquatic frog, a member of the family Ranidae, or “true frogs”, native to much of North America. This is a frog of larger, permanent water bodies, swamps, ponds, and lakes, where it is usually found... (bullfrog) Flight Hardware: Frog Otolith Experiment Package (FOEP)
Launch vehicle: Scout B Scout (rocket) The Scout family of rockets were launch vehicles designed to place small satellites into orbit around the Earth. The Scout multistage rocket was the first orbital launch vehicle to be entirely composed of solid fuel stages.... LV configuration: Scout B S178C |
The OFO-A mission was launched on November 9, 1970 (06:00 GMT) from Wallops Island
Wallops Island
Wallops Island is a island off the east coast of Virginia, part of the barrier islands that stretch along the eastern seaboard of the United States of America.It is located in Accomack County, Virginia...
launch site. The satellite carrying the OFO-A experiment remained in orbit for almost seven days. Recovery of the spacecraft was not planned. The payload was the Frog Otolith Experiment Package (FOEP).
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.
Two bullfrog
Bullfrog
The American bullfrog , often simply known as the bullfrog in Canada and the United States, is an aquatic frog, a member of the family Ranidae, or “true frogs”, native to much of North America. This is a frog of larger, permanent water bodies, swamps, ponds, and lakes, where it is usually found...
s (Rana catesbeiana) were used as experimental subjects in the flight experiment. The bullfrog was chosen for study because its labyrinth
Labyrinth
In Greek mythology, the Labyrinth was an elaborate structure designed and built by the legendary artificer Daedalus for King Minos of Crete at Knossos...
is very similar to that of humans. Since it is an amphibian, preflight surgery could be performed above water, but it could be kept in water during the flight. The water medium served to cushion the vibration and acceleration of launch, and to facilitate gas exchange with the organisms.
Both flight frogs had electrocardiogram
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(ECG) electrodes implanted in their thoracic cavities
Thoracic cavity
The thoracic cavity is the chamber of the human body that is protected by the thoracic wall ....
and microelectrodes implanted in their vestibular nerve
Vestibular nerve
The vestibular nerve is one of the two branches of the Vestibulocochlear nerve . It goes to the semicircular canals via the vestibular ganglion...
s. The frogs were demotorized (by cutting their limb nerves http://lis.arc.nasa.gov/lis/Hardware_App/foep_lss.html) to prevent them from dislodging their implanted electrodes, and to reduce their metabolic rates. With this lowered metabolic activity, the frogs could survive in good health without being fed for as long as one month. Immersion in water allowed the frogs to breathe through their skin. The water medium also helped to move carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and heat away from the animals.
Hardware
The flight hardware unit, the FOEP, was a pressure-tight canister containing a water-filled centrifugeCentrifuge
A centrifuge is a piece of equipment, generally driven by an electric motor , that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis...
that housed the two frogs. The centrifuge was a cylindrical structure that rotated the frogs' heads at scheduled intervals. The FOEP also contained a life support system which could maintain a regulated environment for the frogs. This system consisted of two closed loops, one containing liquid and the other containing gas. The interface between the two loops was a selectively permeable silicone rubber
Silicone rubber
Silicone rubber is an elastomer composed of silicone—itself a polymer—containing silicon together with carbon, hydrogen, and oxygen. Silicone rubbers are widely used in industry, and there are multiple formulations...
that acted as an artificial lung. Oxygen passed through the membrane from the gas to the liquid side, and carbon dioxide from the liquid to the gas side. The frogs were immersed in the liquid loop. A pump circulated oxygen through the gas-containing loop. Carbon dioxide entering the gas loop was removed by an absorbent and the purified oxygen returned to the pump for recirculation. A water evaporator and an electric heater maintained the water temperature at about 60 °F (15 °C). An amplifier system in the FOEP increased voltage output from the microelectrodes implanted in the animals to the level required by the telemetry apparatus.
Operations
The centrifuge was activated as soon as possible once the satellite was in orbit and stabilized at 10-3g (10 mm/s²). The centrifuge applied gravity stimuli in cycles. Each cycle lasted about 8 minutes, and consisted of the following: a 1-minute period without acceleration, an 8-second period when rotation slowly began, 14 seconds of constant 0.6 g (6 m/s²), an 8-second period when rotation slowly stopped, and a 6-minute period when aftereffects of rotation could be measured. Cycles were performed every 30 minutes during the initial 3 hours in orbit, and less frequently during the rest of the flight.
The OFO experiment continued until the seventh day in orbit, at which time the onboard battery failed. Recovery of the OFO spacecraft and FOEP hardware were not required.
Results
The experiment was successful. ECG indices showed the flight frogs to be in good health during the entire flight. Vestibular recordings were made as expected. Two equipment malfunctions occurred during the flight: pressure in the canister increased to 11 psi, and the temperature decreased to 55°F for nine hours. However, control experiments performed on the ground showed that these malfunctions had little effect on the outcome of the flight experiment.Several vestibular response changes were noted during the early period in weightlessness. All of the observed changes reverted to normal during the last 10 to 20 hours of the flight, suggest acclimatization
Acclimatization
Acclimatisation or acclimation is the process of an individual organism adjusting to a gradual change in its environment, allowing it to maintain performance across a range of environmental conditions...
.
Frog Otolith Experiment Package (FOEP)
Life Support System (LSS): The LSS maintains a regulated environment within the FOEP to assure the survival and normal functioning of two demotorized frogs. The lower bulkhead of the inner assembly structure provides mounting space for all life support equipment.
The package's dimensions were 18 in (457 mm) diameter × 18 in length, weighed 91 lb (41 kg) when loaded. Data acquisition consisted of ECG, body temperature, and vestibular activity. There was also a ground-based FOEP test unit which the FOEP could be connected preflight for ventilation and verification of environmental conditions prior to loading in the spacecraft.
Canister
The outer housing of the FOEP is a pressure-tight canister 181⁄16 inches (458.8 mm) in diameter and 18½ inches (470 mm) long. 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. Cutouts in the cylinder permit access to the centrifuge, which houses the frogs. Near the top of the canister are two electrical feed-through receptacles for the power supply and data line.Centrifuge
The centrifuge is a hollow cylinder 6 inches in diameter and 13.5 inches long with both end caps in place. 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. Thin, shallow-domed end caps are bolted to each end of the centrifuge with intervening rubber gaskets to prevent leakage. In the center of each cap is a fitting which allows frog specimens to be fully instrumented and mounted directly to the end caps before insertion into the centrifuge, and immersion. 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. The centrifuge is locked in position and not released until after the spacecraft orbit is fully stabilized. The motor which drives the centrifuge is mounted to the upper bulkhead. Signal amplifiers and an accelerometer are mounted on the centrifuge.Neutral-buoyancy electrode
The micro-electrode consists of a probe of tungsten wire 50 µm in diameter, sharpened electrically to a point less than 1 µm in diameter and completely insulated to the tip. 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. A section of paraffin is used to connect the electrode to a handle which is used only during the implantation process, then removed. 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.Life support system (LSS)
The LSS primarily consists of two closed loops: one containing liquid and the other containing gas. The lower bulkhead of the inner assembly structure provides mounting space for all LSS equipment. The oxygen supply system operates through these loops and includes a 4.5 cm³ capacity oxygen bottle, a pressure reducer and regulator, an artificial lung, CO2 absorber, and water supply. Limited control over the temperature of the frogs' environment is available by means of a water evaporator/heater.
Artificial lung
The interface between loops occurs at a selectively permeable membrane of silicon rubber which separates the liquid and gas. This membrane, called the lung, passes oxygen from the gas loop to the liquid loop, and CO2 from the liquid loop to the gas loop.Liquid loop
The frogs, housed in the centrifuge, are in the liquid loop. Moving from the lung to the frogs, the loop contains water and dissolved oxygen; moving from the frogs back to the lung, it contains water and free CO2. A double layer of polyurethane foam lining the interior of the centrifuge prevents frog waste matter from fouling the water circulation system. Water is circulated through the liquid loop using a small pump and must pass through the filter before leaving the centrifuge.Gas loop
The gas loop consists of a circuit in the lower bulkhead through which oxygen is circulated by a small pump. The pump delivers pure oxygen to the lung where some of it passes into the liquid loop, while the remainder becomes mixed with the CO2 coming from the liquid loop. From the lung, the oxygen-CO2 mixture is passed through a bed of Baralyme which absorbs the CO2. Pure oxygen is returned from the Baralyme to the pump and recirculated. The oxygen supply is replenished by gas from the small oxygen tank.Evaporator/heater
Augmented by the thermal environment of the spacecraft, the water evaporator and 8 Watt electric heater will maintain water temperature at 60±5 °F (15.5±3 °C). 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. As a result of the ambient pressure inside the canister, water is forced from the bladder through the valve and into the evaporator. Internal heat loads are transferred through a heat exchanger to the evaporator and are dissipated in evaporating the water.External links
- Orbiting Frog Otolith Program, NASA Life into Space website
- OFO-A, NASA Life into Space website
- SP-4402 Origins of NASA Names, II. SATELLITES, NASA History site
- NSSDC 1970-094A