Short answers, pulled from the story.
Operation Hardtack I's YUCCA test, detonated on the 28th of April 1958 at an altitude of 86,000 feet, is notable as the first nuclear test delivered by balloon. Starfish Prime in 1962, detonated at 400 kilometres, was the highest-altitude nuclear test ever conducted, with a yield of 1.4 megatons.
The 1962 Starfish Prime detonation, over Johnston Atoll at 400 kilometres altitude, generated an electromagnetic pulse felt 1,400 kilometres away in Hawaii, where roughly 300 streetlights immediately failed. A nuclear weapon detonated at that altitude produces an EMP with a radius of 2,200 kilometres, large enough to cover the continental United States.
Known deployments of weapons stationed in space include the Almaz space-station armament and the TP-82 Cosmonaut survival pistol, carried on Soyuz spacecraft as part of an emergency landing kit to protect cosmonauts from wild animals. The Soviet space station Salyut 3 was also fitted with a 23mm cannon, which was test-fired at target satellites at ranges of 500 to 3,000 metres.
The Outer Space Treaty entered into effect on the 10th of October 1967, signed by the United States, the United Kingdom, and the Soviet Union. It prohibits placing nuclear weapons or weapons of mass destruction in Earth orbit or on celestial bodies. As of the 1st of January 2005-98 states had ratified it.
The Global Positioning System is a satellite navigation network designed and controlled by the United States Department of Defense. It uses a constellation of at least 24 satellites in intermediate circular orbit. The first Block II satellite launched on the 14th of February 1989, and maintaining the system costs approximately 400 million US dollars per year.
The Strategic Defense Initiative, proposed by President Ronald Reagan in 1983, was a space-based system intended to protect the United States from strategic nuclear missile attack. Critics including astronomer Carl Sagan argued the Soviet Union could defeat it simply by building more missiles than it could intercept. Dr. Carol Rosin gave the programme the nickname "Star Wars", after the science-fiction franchise.