Terrestrial Technology Research Articles

As Bad as Things are for Radio Astronomy in the Protected Bands -- They are Worse for SETI!

ABSTRACTIf the funding that has been requested in NASA’s FY89 budget is forthcoming, the Search for Extraterrestrial Intelligence (SETI) will inaugurate its microwave search program on Columbus Day, 1992. This systematic search for evidence of narrowband microwave signals generated by another technology will continue at several sites around the world until at least 1998. The search will be conducted in two modes: a sensitive targeted search of selected solar type stars covering 1 to 3 GHz, and an all sky survey that covers 1 to 10 GHz. This region of the spectrum is the quietest in terms of natural background noise from astrophysical sources and/or the terrestrial atmosphere, which is why it was chosen. Unfortunately, at the same time that terrestrial technology has enabled this systematic search, it also threatens to render the search all but impossible from the surface of the Earth. Terrestrial transmissions generated for an enormous number of different purposes will be the signals most frequently detected by the SETI systems! This paper describes the design decisions and observing plans that the SETI Program is now making in order to have a chance of successfully “listening” throujgh this heavily utilized portion of the spectrum. We do not yet know precisely how heroic our efforts to discriminate against and identify RFI may have to be, but we have been accumulating observational experience and data that demonstrate convincingly that the situation is rapidly growing worse. Because of the real-time nature of the signal processing being planned, SETI systems will provide an excellent opportunity to monitor, and perhaps identify, sources of narrowband interference within the radio astronomy bands at each site where observations are being conducted.

Concepts for Lunar Outpost Development

This paper summarizes the results of a qualitative investigation to identify concepts for design and construction of near-term lunar facilities. Accomplishing such construction will require an adaptation or transfer of current terrestrial technology and methods. Discussions on modularization, geosynthetic materials, aluminum materials, static load analysis, and dynamic load analysis provide illustrative examples of how terrestrial technologies can be adapted to lunar applications. These discussions provide support for the development of a phased lunar construction strategy. The initial stage of construction is characterized by small self-supporting accommodation and laboratory modules. The assembly facility stage is characterized by the construction of a large pressurized module-assembly facility. The module production is characterized by the fitting together of terrestrial or low earth-orbit subassemblies into completed modules within the module assembly facility. The completed modules are also tested and moved to their final location in this stage. The lunar materials state is characterized by the construction of facilities with maximum use of lunar materials.

Radio frequency interference at Jodrell Bank observatory within the protected 21 cm band

Radio frequency interference (RFI) will provide one of the most difficult challenges to systematic Searches for Extraterrestrial Intelligence (SETI) at microwave frequencies. The SETI-specific equipment is being optimized for the detection of signals generated by a technology rather than those generated by natural processes in the universe. If this equipment performs as expected, then it will inevitably detect many signals originating from terrestrial technology. If these terrestrial signals are too numerous and/or strong, the equipment will effectively be blinded to the (presumably) weaker extraterrestrial signals being sought. It is very difficult to assess how much of a problem RFI will actually represent to future observations, without employing the equipment and beginning the search. In 1983 a very high resolution spectrometer was placed at the Nuffield Radio Astonomy Laboratories at Jodrell Bank, England. This equipment permitted an investigation of the interference environment at Jodrell Bank, at that epoch, and at frequencies within the 21 cm band. This band was chosen because it has long been “protected” by international agreement; no transmitters should have been operating at those frequencies. The data collected at Jodrell Bank were expected to serve as a “best case” interference scenario and provide the minimum design requirements for SETI equipment that must function in the real and noisy environment. This paper describes the data collection and analysis along with some preliminary conclusions concerning the nature of the interference environment at Jodrell Bank.

Common Characteristics of Terrestrial and Space Construction

The building of stationary facilities in space and on the lunar surface will bring humankind to the verge of a new era in its exploration of space. Many new and unprecedented construction problems have to be solved. Terrestrial construction technology, developed over centuries, had to overcome similar earthbound extremes. Viable examples include underwater construction and building on the frozen terrain of north and south poles. Many specialized techniques and kinds of equipment have emerged to meet those extreme conditions. This body of knowledge and technology may become a valuable resource for the design and construction of buildings in space. The objective of this paper is to demonstrate why experts from space technology and construction engineering should combine their specialized knowledge to benefit human advances into space.

Fifty Years of High-definition Television Transmission

High-definition television was described in 1935 by the Selsdon Committee as having not less than 240 lines per picture. Public transmission of an interlaced 405-line service commenced in 1936 and lasted until 1985, having been gradually displaced by 625-line colour. Today, high definition means more than 1000 lines, and is unlikely to be broadcast from conventional terrestrial transmitters.This Address reviews the development of terrestrial television transmission technology from the, pre-war Baird/Marconi-EMI trials, through the period of post-war Band I and III expansion to the introduction of u.h.f. and the ultimate realization in the United Kingdom of one of the most highly developed and effective colour transmission networks anywhere in the world.

Preferred frequencies for SETI observations

SETI observational programs conducted over the last two decades, and most of those planned for the near future, have concentrated on searching for signals at microwave frequencies. Considerations of signal-to-noise ratio at the receiving end indicate that this is the correct approach if the broadcasting society is not concerned with directionality and transmits into a fairly large solid angle. However, if that society desires to transmit only a highly directional beacon, then it is not now possible, given our lack of knowledge of advanced space technology, to predict reliably whether microwave or infrared wavelengths are to be preferred in an optimum search program. Given the realities of current terrestrial technology, either the centimeter or millimeter domain is to be preferred to the infrared, independent of considerations of directionality. In any event, there does not appear to be any cosmically unique (“magic”) frequency at which to conduct SETI.

Factors Governing Photovoltaic Technology Transfer: Terrestrial to Space

Environmental requirements, market size, and the fact that the power source is not the dominant portion of most space systems constrains the transfer of terrestrial photovoltaic developments to space use. Market size is the main reason for the two orders-of-magnitude difference in cost between space and terrestrial photovoltaic power systems. Terrestrial developments emphasizing performance rather than cost advantages are more likely to be adopted for space. Examples of such terrestrial technologies are presented and discussed.