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Aviation History
1959
1959 - 1918.PDF
28 August 1959 71 Missiles and Space flight ^«# ^ MAPPING OUTER SPACE ... telemetered data was obtained. Pioneer 4 was tracked to a distanceof about 400,000 miles before its batteries became exhausted. Prior to a space-probe launch, details of the expected trajectoryare supplied to Jodrell Bank from the U.S.A. In the case of a lunar-probe firing from Cape Canaveral the probe would appearover the Jodrell horizon to the south-west and be picked up by the radio telescope about ten minutes after launching, after whichit would take a further 20 min to attain an elevation of some 30 deg to the south. The exact position of the probe is checkedat ten-minute intervals by moving the telescope off track and scanning back through the maximum-intensity position, in bothazimuth and elevation. The co-ordinates at which the maximum signal is received indicate the angular position of the probe withan accuracy which depends on the beamwidth and hence on the frequency. At a frequency of 1,000 Mc/s the beamwidth is20 min of arc and the probe can be located to within a few minutes of arc. Satellites and probes, although perhaps the most publicizedinterest of the Jodrell Bank establishment, are not its main con- cern. As a university department possessing the world's mostpowerful radio-astronomical tool of its type, Prof. LovelPs group is basically concerned with exploring and mapping the vast spacesof the universe. There are several areas, however, in which data from satellites and probes are of direct use in these basic studies. The resident group concerned with satellites at Jodrell Bank,led by Dr. John Thomson, works closely together with Dr. John Evans' team responsible for Moon and planetary echo research.The reception of signals from Vanguard 1 (whose solar-powered transmitters are expected to continue to operate indefinitely) isproviding detailed information on the nature of the ionosphere, including a study of the way in which the polarization plane ofthese signals rotates in passing through the ionosphere. This phenomenon was first observed in radio echoes from the Moon.In addition, much of the telemetered information from space probes (the prime concern of the U.S. team at Jodrell) is relevantto the station's basic research, in fields such as micrometeorite experiments, radiation and magnetic fields and cosmic rayintensity. In much of their normal programme of work the Jodrell Bankscientists are looking a long way ahead of the satellites and space- probes. In one of the small buildings, for instance, a radio"contour map" of the Andromeda galaxy, some 1^ million light- years distant, is being built up from simultaneous traverses acrossthe galaxy on three frequencies. This is part of a broad study of the position, distance, size, distribution and origin of radio sourcesboth inside our own Milky Way system and in extra-galactic space. Specific investigations include an examination of thegalaxies on the frequency of the hydrogen line (a radio emission from neutral hydrogen gas), which enables the motion of hydrogenclouds to be studied. Nearer to Earth, a number of ionospheric and other projects onwhich much work was done during the International Geophysical Year are being continued, with certain changes in emphasis. Thesubjects include the scintillation or twinkling of radio stars, the drift of meteor trails in the E region (about 100 km altitude), amonitoring of solar phenomena on three frequencies, and radar studies of auroras and of the ionized trails of meteors entering theatmosphere. In most of these programmes the massive steerable radio tele-scope plays an important part. Its time is allocated to the various projects according to a pre-arranged schedule, and the instrumentnormally works a 24-hour day (including maintenance and aerial changing between experiments). At the time of Flight's visit toJodrell Bank recently a twelve-hour period of measuring the William Young (right), of Space Technology Laboratories, leader of the U.S. team at Jodrell Bank, talking to R. G. Lascelles, special assistant to the director "Flight" photograph \ Professor A. C. B. Love//, director of the Jodrell Bank station and Professor of Radio Astronomy at Manchester University. The model is of Pioneer 1, and seen through the window is the vast structure of the 250ft steerable radio telescope angular diameter of radio sources with the bowl in the fixedposition (i.e., making a transit with the Earth's revolution) was followed by a survey of one discrete source.From the control room in the centre of the low brick building about 200yd from the telescope, the movement of the instrumentis electronically controlled. Steering instructions are determined by an electronic analogue computer which solves the 14 differentequations needed to give accurate control of the instrument over all parts of the sky. To keep the telescope automatically trained on a star, forexample, seven of these equations are used to translate the position and movement of the star, as given by the celestial co-ordinates ofright ascension and declination, into terms of telescope azimuth and elevation. The remaining seven equations deal with the caseof a scan along or across the Milky Way, for which the frame of reference is that of galactic latitude and longitude, which againmust be expressed as a steering instruction to the telescope in terms of azimuth and elevation. Amplified signals determine thespeed of the various electric motors which control the movement of the telescope through two Ward Leonard motor generator setshoused just above the central pivot bearing. The steering of the telescope is carried out from the maincontroller's console, where a safety interlock system gives visual warning of the position of men who may be working on thetelescope structure. About six feet away on each side of the control desk is a bank of 15 large dials. Those on the right ofthe controller show him the actual and computed positions of the telescope (elevation and azimuth); while on the left the dialsindicate celestial co-ordinates (right ascension and declination) and galactic co-ordinates (galactic latitude and longitude). Thisinformation is accurate to at least one minute of arc; and universal and sidereal time are also displayed. New achievements at Jodrell Bank this year have included thetransmission of voice messages to Cambridge, Massachusetts, via the Moon; and the switching off and on of the telemetry trans-mitters in the "paddlewheel" satellite while in orbit by the S.T.L. team. In the near future it is hoped to reflect a radar echo fromVenus. To visit the skilled young practitioners of the young science ofradio astronomy at Jodrell Bank, and to hear about their work, is to realize the incredibly vast new realm of knowledge which theirthinking and experimental techniques are making possible. Radio astronomy already forms an important part of astronautics today,and Prof. Lovell himself has indicated the probable development over the next ten years. "I believe the next decade in space research will see develop-ments in astronomical work which were inconceivable only a short time ago," he said. "During this period one can confidentlyexpect that both radio and optical telescopes will be carried on Earth satellites so that the universe can be studied from above theinterfering regions of the Earth's atmosphere. One can even hope that remotely controlled telescopes may be operated from theMoon within this period. In connection with space probes, it seems clear that such vehicles will be able to approach andpossibly sample the atmospheres and surfaces of some of the planets. The contributions which can be expected to result toour knowledge of the conditions and evolution of the solar system are at present almost incalculable."
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