Three More Satellites Silenced

Press, Volume CVIII, Issue 31780, 10 September 1968, Page 21

Three More Satellites Silenced

The day has already arrived when a man seated at a console can push a button and perform an assassination several hundred miles away. And what is moij?, he can alter a few] controls to select a n«w victim and press the'button again with equally fatal results. On August 29 this dastardly act was carried out not once but three times—with separate victims. However, to avoid causing alarm it should be mentioned that the victims had been under sentence of death for many months and were sacrificed that others might live. They were, in fact, three orbiting satellites which had to be permanently silenced. Their radio voices had lasted too long and were occupying precious radio channels required for newer spacecraft. The silenced satellites are the three members of the Pegasus series. They did not succumb te anything as crude as a bullet or knife. Instead, they were put out of action permanently by specially coded radio signals broadcast to them cm their command frequencies by a station on earth. They are now dead and cannot be revived. In each case the lethal command turned off electric power supplying all internal systems including the command receiver. It is exactly analogous to total failure of the heart and central nervous system of a human being. Until the day when their orbits decay and they reenter the earth’s atmosphere

and burn up, the three Pegasus satellites will remain lifeless pieces of space junk. Pegasus 3 should remain in orbit for another five or six years, while the first two, which are in higher orbits, should stay aloft until well into the 1980 s. Fluctuating Brilliance The three Pegasus satellites are among the largest ever placed in orbit, measuring 96 feet across the span of their huge “wings.” Since their i launching in February, May and July, 1965, they have been seen by millions of people round the world. From our latitudes they are often visible after dark as they cross from west to east low in the northern sky. Next to the giant Echo 2 balloon satellite they are the brightest artificial satellites at present in orbit Unlike Echo 2 they fluctuate rapidly in brilliance as the sun’s rays glint from their outstretched wings. The Pegasus satellites were the first scientific payloads placed in orbit by the giant Saturn 1 rocket Each Pegasus weighs one ton and a half and no other American rocket was at the time capable of lifting them into space. The total weight in orbit exceeded 10 tons if the final rocket stage is included. Primary function of the Pegasus satellites was to register and report collisions with meteoroidal material in space. This data was sought to assist the design of manned spacecraft The three satellites have achieved their purpose magnificently. It is now known that the Apollo spacecraft are adequately protected for flights to the moon and back. At the same time the Pegasus

findings indicate that vehicles intended for long voyages into space will require considerably better protection. This presents quite a formidable design problem for spaceprobes journeying to the outer planets or for manned vehicles venturing on return trips to Mars or Venus. Penetrations Recorded In their first year of operation the three Pegasus satellites recorded a total of over 1000 impacts by meteoroids large enough to penetrate the aluminium panels on their wings. Each satellite has a total of 416 panels measuring 20 by 40 inches, but of varying thickness. On the back of each panel is a sheet of mylar plastic insulation covered by a thin layer of copper. The copper and aluminium form the plates of an electrical capacitor which was charged to 40 volts. Impact by a meteroid large enough to penetrate the aluminium plate caused a discharge current which was recorded and relayed to Earth. By mounting the panels in pairs, back-to-back, any penetration of the copper layer did not matter. The Pegasus satellites were designed to operate for 18 months. At the end of their design life-time they were functioning perfectly, so it was decided to keep them in operation for a further year. This further assignment was such a success that a study was commenced to find out why the complex systems on board each Pegasus were operating with such high reliability. No Faults Engineers and scientists at the Marshall Space Flight Centre in Alabama then began to use the three satellites primarily to gather performance data to assist future spacecraft designs. They began an exhaustive programme of testing by ground command. For example the data processing equipment in the Pegasus satellites has a memory unit which employs 30.080 magnetic cores together with associated electronics for transferring the stored data in and out when required. Last year every core on each Pegasus was individually checked. Not a single failure of the cores or their electronics was detected. After months of work, a clear picture has been gained of the condition of each of the 90 major electronic subassemblies in each Pegasus satellite. With a vast harvest of reliability data in hand the performance study was discontinued and with much regret the order was given to de-activate these three outstanding satellites. The Fairchild Stratos Corporation, which manufactured and tested them, can feel justly proud that all three served faithfully to the very end—they even died faultlessly. I