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Aviation History
1963
1963 - 1395.PDF
FLIGHT International, 8 August 1963 215 Missiles and Spaceflight Artist's impression of the S-66 ionospheric beacon satellite. Bar magnets interacting with the Earth's magnetic field keep the reflector section of quartz prisms facing towards the Earth while the satellite is in the northern hemisphere. Aerials are carried at the tips of the four solar-cell panels MAPPING THE IONOSPHERE An ambitious attempt to discover the structure of the ionosphere on a worldwide basis and to study its variation with solar activity and with time is.scheduled to get off the pad from Point Arguello, California, on August 15 at the earliest. This will be the launch into circular, polar orbit of the National Aeronautics and Space Admini- strations's S-66 ionosphere beacon satellite, and its subsequent observation by scientists from 19 countries. If successfully placed in orbit, the satellite will presumably become Explorer 18. Also aboard the satellite will be a laser experiment—the first to be carried in a satellite and one in which, according to NASA, "chances of initial success are marginal." The launch vehicle will be the all-solid, four-stage Scout. The radio beacon experiment is only one of a number of satellite- borne ionospheric experiments conducted by NASA, but its signi ficance lies in the simplicity of read-out equipment needed (aerial, radio receiver, timing device and recorder). This means that scientists all over the world will be able to participate. Over 40 Principle of operation of the laser experiment aboard the S-66 satellite PROGRAMABtE 'RACKING TEtESCOPE AND DETECTOR 'AH ANGLE 'EAD OUT SYSTEM REFLECTED / / SATELLITE PULSE / / OPTICAL / / REFLECTOR / / / ^''TRANSMITTED PULSE LASER TRANSMITTER TRANSMITTED PULSE RECEIVED PULSE RANGE READ OUT SYSTEM experimenters have volunteered to take part in the programme— the largest co-operative group yet to take a direct part in a NASA space satellite experiment. The planned orbit for the satellite is at an inclination of 80° to the Equator and is circular at about 600 miles. The various ground stations will record the manner in which certain radio emissions from the satellite change as they pass through the ionosphere. By studying these changes, the participating scientists expect (1) to relate ionospheric behaviour to the solar radiation which produces the ionozation; (2) to learn the bulk behaviour of the ionosphere as it varies in time and space; (3) to measure the electron content in the ionosphere between the satellite and Earth as related to latitude, season and diurnal time; and (4) to determine the geometry and distribution of small-scale irregularities in the ionosphere. The satellite is an adaptation of the US Navy's Transit naviga tional satellite, and was designed and built for NASA by the Applied Physics Laboratory of Johns Hopkins University. It is octagonal and weighs about 1201b. A bar magnet, half-an-inch wide and lOin long, will be carried inside the spacecraft and will passively orient the satellite along the Earth's magnetic field. This will ensure that the laser reflectors point continuously towards Earth (while the satellite is in the northern hemisphere), and provide more stable radio signals for the ionospheric experiments. Four blades, covered with solar cells to convert the Sun's energy into electricity to recharge the nickel-cadmium batteries, extend from the sides of the spacecraft. They each measure 66in by lOin, and are adequate to provide power to operate the satellite equip ment for about three years. The spacecraft shell, 18in in diameter and 12in high, is made of honeycomb nylon and glass-fibre. An electron probe extends from both the top and the bottom of the satellite. Two 5ft whip antennas and two dipole antennas for the transmitter extend from the ends of opposite blades, and a whip antenna for the satellite's command receiver extends from the bottom of the craft. In the launch configuration, the four blades are folded down over the fourth stage of the Scout vehicle, and are held in place by the cables of the de-spin weight assembly. The fourth-stage adapter contains switches which are timed to release the de-spin cables about 7min after motor burn-out and injection into orbit. The adapter also contains a small rocket which is ignited some 2sec after separation to deflect the fourth stage so that it will not collide with the payload or its extended solar blades.
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