From: Allen Thomson (thomsona@netcom.com) Subject: Nuking LEO (yet again) Newsgroups: sci.space.policy Date: 1998/10/15 Last week's Space News contained an interesting letter on the consequences of a high-altitude nuclear burst, a topic that has occasionally been discussed here. The author is the former Lt. Col. Glenn Kweder of the Radiation Sciences Directorate of the Defense Nuclear Agency (now incorporated into the Defense Threat Reduction Agency). In 1994-1995 he was responsible for briefing "Third World Threat to Low Earth Orbit Satellites" to a number of US government agencies. He was also a member of the team briefing "The Role of Radiation Tolerant Micro- electronics in Support of the U.S. Satellite Industrial Base." Both Space News and Mr. Kweder have given permission to reproduce the letter in its entirety. -------------------------------------------------------------- Nuclear Threat Letters Space News, Oct. 5-11, 1998, p.14 I would like to comment on the article urging protective measures for U.S. satellites ["Report Urges Use of Stealth, Deployment Alternatives to Protect U.S. Satellites," Sept. 7-13, page 41]. I was surprised to see no mention of a nuclear weapon detonated at high altitude, over 100 kilometers, which would have a devastating effect on hundreds of low- Earth-orbit (LEO) satellites. A high-altitude nuclear detonation releases a tremendous number of high- energy electrons. These electrons, trapped in Earth's magnetosphere, rapidly populate all LEO orbital space. As a result, hundreds of LEO satellites are exposed to electron levels up to 10,000 times higher than the natural LEO space environment . This enhanced electron radiation damages critical electronic circuits in satellites, leading to the demise of LEO constellations in weeks or a few months. Furthermore, most of the protection solutions mentioned in the report detailed in the article would be ineffective against this threat. On- orbit spares would suffer the same fate as the primary satellites, while launching replacement satellites also would be ineffective since the enhanced radiation levels can persist for several months to a year. This ultimate anti-satellite weapon also is extremely low-tech. All that is required is a small nuclear weapon and a launch vehicle with a timer. Because the effect is global, no fancy guidance system and no homing sensors are required. No satellite needs to be directly attacked since the damaging electrons rapidly move out from the point of explosion. This leads to another attractive feature of this nuclear approach: deniability. An aggressor country could launch an attack near its own territory and claim it was only doing a test and had no knowledge or intent to harm satellites. Sanctions could be imposed on the country, but it is unlikely that a direct military response would be aimed at it since the high-altitude explosion killed no one and no cities were destroyed. The primary means of defeating this threat is to make sure that satellites [are equipped with] a combination of shielding and radiation- hardened electronics. Such an approach, if implemented in the beginning of a satellite program, would only add a small percentage to development costs. Remember the problems caused when Galaxy 4 failed earlier this year? Imagine if hundreds of satellites failed in the timespan of a few weeks and replacements could not be launched for a year. It would be a nightmare. Glenn Kweder Space systems analyst Logicon RDA Alexandria, VA