Satellite reentry

Plans for satellite reentry are normally developed for implementation by national authorities and should include provision to address heightened public concerns. 

Earth to space (satellite) to earth communication links are relatively insensitive to ionospheric disturbances. Communications between earth and manned space vehicles are barely affected by plasmas when the spaceships are well away from the atmosphere, eg, in orbit or in a translunar trajectory. However, during reentry of a spaceship, a low temperature plasma forms around the vehicle and interrupts the communication links to it (183). Plasmas are incidental to the performance of modem rockets used to explore the solar system. 

To evaluate the thermodynamic and radiation properties of a natural or perturbed state of the upper atmosphere or ionosphere, the thermal and transport properties of heated air are required. Such properties are also of particular interest in plasma physics, in gas laser systems, and in basic studies of airglow and the aurora. In the latter area the release of certain chemical species into the upper atmosphere results in luminous clouds that display the resonance electronic-vibrational-rotational spectrum of the released species. Such spectra are seen in rocket releases of chemicals for upper-atmosphere studies and on reentry into the atmosphere of artificial satellites. Of particular interest in this connection are the observed spectra of certain metallic oxides and air diatomic species. From band-intensity distribution of the spectra and knowledge of the /-values for electronic and vibrational transitions, the local conditions of the atmosphere can be determined.1... 

Nuclear weapons production and testing facilities (Hanford, WA, Savannah River, GA, Rocky Flats, CO, and The Nevada Test Site, in the United States, and Mayak in the former Soviet Union), also released small amounts. The releases occurred in accidents with nuclear weapons, the reentry of satellites that used Pu-238, and by the Chernobyl nuclear reactor accident. 

Satellites and other spacecraft rrse radionuclides as a power source. Some spacecraft have power reactors, and there have been a few instances in which these reactors have returned to Earth, which cairsed some contarrtina-tion to be spread. One notable example is when a COSMOS satellite disintegrated on reentry into the atmosphere, which distributed radioactivity in northern Canada in 1978. A more common energy sorrrce is Pu (half-life = 88 yr), which generates energy as it decays to power some satellite systems. There are few examples of this radionuclide reentering the earth s atmosphere, and its relatively short half-life makes it only a small potential sonrce relative to background levels. 

Accidents with radioactive sources or material include found radioactive material or contaminated areas or items, a lost or missing radioactive source, unshielded source, accidents in a laboratory, transport accidents involving radioactive sources or material, accidents with X-ray machines and particle accelerators, and an accidental reentry of a nuclear-powered satellite, which may lead to impact on the earth s surface and the spread of contamination. Radiological emergencies that could result from deliberate acts, such as terrorist activities... 

Carbon-carbon composites are used in high temperature service for aerospace and aircraft applications as well as for corrosion-resistant industrial pipes and housings. Applications include rocket nozzles and cases, aircraft brakes, and satellite structures. Carbonized phenolic resin with graphite fiber functioned effectively as the ablative shield in orbital reentry vehicles for many years (113). 

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