SDTV and high definition television (HDTV) are the two categories of display formats for digital television (DTV) transmissions, which are becoming the standard. In North America, digital SDTV is broadcast in the same 4:3 aspect ratio as NTSC signals with widescreen content being center cut.
Command pilot Neil Armstrong 's flight marked the second time a U.S. civilian flew into space (Joseph Albert Walker became the first U.S. civilian on X-15 Flight 90). Armstrong had resigned his commission in the United States Naval Reserve in 1960.
Endeavour, named for the first ship commanded by British explorer James Cook, rolled out of the assembly plant in Palmdale, California, in 1991 at a cost of $1.7 billion. Over the next 20 years, Endeavour flew some of the most high-profile shuttle missions in history. Endeavour flew 25 flights and nearly 123 million miles. It flew a spacelab mission and numerous International Space Station assembly missions and even rendezvoused with Russia's Mir Space Station.