Space Electronics: Satellites and ET EM Waves
May 1961 Popular Electronics[Table of Contents]People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Popular Electronics was published from October 1954 through April 1985. All copyrights (if any) are hereby acknowledged.
Prior to around 1960, the nature of electromagnetic radiation outside the Earth's atmosphere was entirely a matter of scientific conjecture. As is evidenced by this 1961 article, at the time it was still not known for certain whether electromagnetic energy outside the bands transmitted through the ionosphere existed for sure. There was of course no reason to believe that low frequency, long wavelength radio waves were not present along with the rest of the spectrum, but experiments needed to be developed that would launch satellites above the atmosphere to detect probable out-of-band signals and then re-transmit them on frequencies known to easily penetrate the 'ether.' Many failures occurred along the way, but persistence paid off in what is today a very well explored and documented outer space. Prior to the last half decade, groups like NASA were more interested in conducting research than wasting precious allocated funds on unrelated projects like the utterly unrelated studies regarding the end of western civilization and outreaches to certain religious groups.
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A monthly report on satellite electronics and communication in interstellar space.
By Oliver P. Ferrell
The atmosphere we breathe has a dual purpose-it supplies life-sustaining oxygen and serves as an "invisible shield" to protect earthlings from the harmful radiation abounding in outer space. This shield does have one tremendous disadvantage: radiation that cannot pierce the shield from without is therefore probably unknown to us - and part of this radiation is in the radio-frequency band below 500 kc. Scientists have long wondered if by any chance there are radio signals outside the earth's atmosphere in the very-long-wave band. The only way to find out is to go outside the atmosphere and listen.
Apparently damaged during the unfolding of Explorer IX, the beacon transmitter di not operate. It was powered by solar cells.
Explorer IX was carefully packed into nose of Scout II rocket and launched by NASA. Test was only partially successful.
Spinning satellite, built by Hughes Aircraft, is an "active" repeater. It weighs 32 pounds and is powered by silicon cells.
The Transit satellites are navigational beacons operating on paired frequencies. Transit III-B is on 54, 162, 216, and 324 mc.
The "neck" joining Transit III-B and the NRL LOFTI satellite failed to separate after February 21 launch.
Scientists reason that long-wave reception should be pretty good 1000 miles above the surface. Lightning static which prohibits low-frequency reception of weak signals will probably be largely screened off by the ionospheric "shield."
A "reverse" of this experiment was conducted during the lifetime of satellite Explorer VI (launched August 7, 1959). Aboard the payload was a U. S. Navy receiver tuned to NSS on 15.5 kc. Apparently the idea was to determine the strength of this low-frequency signal - the results have never been made known. Some Navy technicians say that satellites may provide the answer to communicating with underwater submarines, but just how remains a mystery in our eyes - packing "Big Jim," the Navy's present megawatt long-wave transmitter, into a satellite doesn't seem quite possible.
A second attempt to monitor powerful signals on the low frequencies was made with the LOFTI satellite - launched February 21, 1961. LOFTI contained a U. S. Navy receiver tuned to the 300,000-watt signal of NBA. This station is on 18 kc. from the Canal Zone. This satellite rode "piggy-back" on Transit III-B (see photo above). One of the two low-frequency receivers aboard LOFTI is working and the characteristics of 18-kc. reception are being recorded.
Satellite Briefings. Although the Russians have widely publicized the "fact" that their Venus probe satellite operates on 922.8 mc., it has not been heard by monitors in North America. The British receiving station at Jodrell Bank was given sufficient information to track this satellite in late February. However, the Russian Venus probe did not respond to "ground command" signals after February 22nd (it was launched February 12th). Keyed to respond every five days, the Venus probe could not be heard on Monday, February 27th, nor Saturday, March 4th.
The Venus probe is supposed to have carried four antennas - one non-directional, two moderately wide beams, and one very sharp beam antenna. The latter beam had been designed to unfold to a six-foot diameter when the probe reached the vicinity of Venus.
A 12-foot polka-dot balloon was launched by NASA from Wallops Island on February 16. Called Explorer IX, the beacon transmitter - operating on 136 mc. - was damaged as the balloon unfolded from the rocket's fourth stage. Several days later the satellite was "found" through optical means and is now in orbit. Explorer IX is too small for Echo-type communications and was launched to measure air drag on balloon satellites in the upper atmosphere.
Three new satellites can be added to the list of "Radio Signals from the Satellites" appearing on page 65 of our April column. They are Discoverer XXI, gathering infrared data, Transit III-B, and LOFTL. Frequencies used by Discoverer XXI have not been revealed. Transit III-B is putting out weak signals on exactly 54, 162, 216 and 324 mc. (the same as Transit II-A), plus a special transmitting setup on 224, 421 and 448 mc. LOFTI is on 136.0 mc.
As we mentioned last month, Echo-type satellites are also called "passive" satellites - meaning that they simply reflect radio signals. Active satellites contain radio receivers and transmitters to rebroadcast signals upon command from ground stations. The Courier I-B is a good example of a working "active" satellite.
Vastly improved passive satellites have been suggested by the Ryan Aeronautical people. Some of their proposed designs are shown at the bottom. Included are the corner reflector, wide-band multi-helix, and resonant dipoles with dual polarization. Each design has been calculated to be more efficient than the spherical balloon. Engineers and space experimenters hope that the resonant dipole idea will be exploited in a satellite launching later in 1961.
Because of interference problems near the 108 mc. frequency used by the American satellites, all launchings after June 1961 will be tracked with beacons operating between 136 and 137 mc. Minitrack stations (to be discussed in a later column) are being converted to receive 136-mc. signals.
Space Studies. Two frequencies have been allocated to the ITT Laboratories, Nutley, N.J., for study of space communications theory. The authorization is for 2120 and 2299.5 mc., although the latter channel will be the only one available after July 1.
According to reports, ITT will bounce signals from passive satellites (and possibly the moon) in order to study interference to conventional earthbound systems. All transmissions will be from Nutley, N. J., with a power of about 10 kw.
At Minus-One. Two California scientists have recommended that a special radio transmitter be included in our Mars and Venus probes. This transmitter would not be operated by any personnel sent on such expeditions, but would be a "last gasp" transmitter - should the probe be destroyed by intelligent beings!
Suggested designs for passive or Echo-type satellites worked up by Ryan Aeronautical Company. At the top is a corner reflector fitted into a sphere. In the center, 26 cones have been formed into helical antennas. At bottom, dipole strips have been attached to the balloon - they are at right angles to one another to counteract polarization changes as the satellite spins and wobbles in orbit.
Posted April 17, 2014