12:25 PM EDT, August 5, 2011:
The five SRBs (solid rocket boosters) on the giant ATLAS V Launch Vehicle ignite and the flight of NASA’s new Jupiter probe began.
Juno, named after the Roman god for Jupiter’s wife, will spend five years en route to the gas giant. Once there it will take up station in orbit around Jupiter for a year to make the most detailed measurements of the Jovian environment ever. When its mission is over, it will plunge into the planet’s thick atmosphere, still sending back data until it burns up or is crushed by atmospheric pressure.
Juno was launched by a launch vehicle (LV) developed and built not by NASA but by a commercial consortium consisting of Boeing Aircraft and Lockheed Martin Aircraft. The consortium is called the United Launch Alliance (ULA). The ATLAS V is the largest, most powerful LV currently available. Ironically, it uses Russian engines in its first stage to generate 800,000 pounds of thrust. The five SRBs add another 300,000 plus pounds of thrust.
The second stage is an upgraded NASA design—the LH2 powered Centaur. This commercial combo sent Juno on its way.
Juno is a four ton, 11.5 ft tall spacecraft. It is unique for a trip to an outer planet because it will be solar powered. All other craft sent beyond Mars have used atomic power (radioisotope thermoelectric generators) because solar energy was too weak 400,000 miles out. But solar technology has come a long way this century. Juno’s solar panels can generate 450 watts at Jupiter, plenty for the spacecraft’s energy efficient instruments.