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Aviation History
1964
1964 - 0839.PDF
478 FUGHT Internationa/, 26 March 1964 Missiles and Spaceflight The UK-2 satellite, pictured during its extensive test programme University/Met-office Pay load for UK-2 EXPERIMENTS from Cambridge University, ManchesterUniversity and the Meteorological Office are aboard thesecond joint US/UK satellite, scheduled to be launched today (March 26) by Scout vehicle from Wallops Island, Virginia. A 51° orbit ranging from about 170 to 930 miles, and with a period of 103min, is planned for the spacecraft. The first US/UK satellite, Ariel, was launched on April 26, 1962. The US National Aeronautics and Space Administration has designed, built and tested the spacecraft at the Goddard Space Flight Center in Maryland, will launch the satellite from Wallops Island, and is responsible for tracking and acquiring data. Britain has provided the three experiments for the craft which are designed to measure galactic radio noise, vertical distribution of ozone, and micrometeoroid flux. Known as UK-2 or UK-C prior to launch, the satellite was to be named—probably Ariel 2—on achieving orbit. The Milliard Radio Astronomy Observatory of the University of Cambridge, under the supervision of Dr F. Graham Smith, fur- nished the galactic radio experiment. This is designed to measure the intensity of galactic radio noise (radiation emissions from celestial bodies). These signals from distant stars are very weak by the time they have been filtered through the ionosphere and reach radio telescopes on Earth. The UK-2 experiment will provide an aerial in space for clear reception of these signals. By going above the ionosphere this experiment will be able to measure these signals between 0.75 and 3Mc/s under known con- ditions of receiver sensitivity, ionospheric effects of propagation and aerial impedance. The experiment also will be free from artificial or man-made signals present below the ionosphere. The equipment has been developed and produced by GEC (Stanmore) Ltd, with special wire for the long aerial produced by British Insulated Calender's Cables. A second experiment, provided by Dr R. Frith and Dr K. H. Stewart of the Air Ministry's Meteorological Office, Bracknell, will measure the vertical distribution of ozone in the Earth's atmo- sphere. The ozone layer is that portion of the atmosphere created through a chemical reaction when the Sun's ultra-violet radiation reaches oxygen in the Earth's atmosphere. This conversion process saps the power of the ultra-violet rays which would otherwise be lethal to Earth inhabitants. The ozone-layer measurements should add to the knowledge of the processes which form and destroy ozone, of the air motions which distribute it and of the effects of ozone on the thermal equilibrium of the upper atmosphere. Measurements will be made of the intensity of solar rays at selected wavelengths absorbed by ozone. These will be made at times when the satellite is entering or leaving the Earth's shadow and the solar rays must pass through the Earth's atmosphere to reach the satellite. The optical-mechanical equipment has been manufactured by R. and J. Beck Ltd, the electronic units have been developed and produced by British Aircraft Corporation, and a photo-cell with a special cathode was developed by Rank-Cintel. The third experiment was designed by Dr R. C. Jennison of Manchester University's Nuffield Radio Astronomy Laboratories at Jodrell Bank, to detect and measure micrometeoroids encountered by the satellite. Holes formed in a thin metallic film by the impact of micrometeoroids will be detected by sunlight passing through them and falling upon a photo-sensitive strip of solar cells. The solar cells will give a signal for each hole. The number and size of the penetrating micrometeoroids can then be deduced. Knowledge of micrometeoroids is necessary in understanding the total mass and history of the solar system and predicting their erosion effects on future spacecraft and space stations. The equip- ment has been developed and produced by Ferranti Ltd. The three experiments, chosen by the British National Committee on Space Research in consultation with NASA, complement several previous NASA projects. Vanguard 3, Pioneer 5, Explorer 7, Explorer 16 and Mariner 2 all carried instruments for collecting data on micrometeoroids. The rocket probes P-21 and P-21A and Explorer 8 were among experiments for investigating the ionosphere. Currently the Canadian satellite Alouette, a swept-frequency topside ionosphere sounder, is sending data on the structure of the ionosphere. The Experiments The galactic-noise experiment will measure the cosmic background noise level in the frequency range of 0.75-3.0Mc/s. The receiver will sweep repeatedly over this range with each sweep requiring about 15sec. The minimum data- sampling rate averages about 15 per sec. A lower data rate, about one per sec, will be obtained from a smoothed output and tape- recorded over as much of the satellite orbit as possible. Dipole and ferrite-loop aerials will be used for this experiment. The 130ft dipole aerial will provide optimum reception. The aerial wire will be deployed using centrifugal force to pull the wire off a drum. Payout is controlled by a constant-speed motor. The wire will be led out from the body of the satellite by means of booms on either side, and its deployment helps to de-spin the satellite. At one fixed frequency at the high end of the frequency range, the ferrite-loop aerial will be used. This consists of two ferrite rods about 12in long and lin square placed on opposite sides of the satellite shell parallel to the spin axis. The output of the ferrite-loop aerial will provide useful data should the dipole aerial fail to deploy. The ozone experiment is designed to measure the vertical distri- bution of ozone in the Earth's atmosphere as often and at as many places as possible. The attenuation of solar rays will be measured as they pass on a tangent through the atmosphere at twilight, using wavelengths absorbed by ozone (2,500-4,000A). Broadband and scanning measuring techniques will be used. The broadband technique consists of the measurement of the current produced in two photocells with appropriate filters. The ozone experiment will give reasonably accurate and useful infor- mation if the solar spectrum in the middle and near-ultra-violet does not vary significantly from that found by rocket experiments and ground observations, and the scattering properties of the Earth's atmosphere do not vary too much from theoretical models. The scanning technique uses a simple prism spectrometer to project a solar spectrum on a photomultiplier. The spectrum is
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