NASA's infrared eye leaves Earth trailing behind it, not orbiting it

Before dawn on August 25, 2003, a Delta II 7920H rocket lifted off from Cape Canaveral's Launch Complex 17B carrying NASA's newest observatory into the dark. At 05:35:39 UTC, the Spitzer Space Telescope reached a heliocentric, Earth-trailing orbit rather than circling the planet, a design choice meant to keep it cold without heavy shielding. Its 85-centimeter beryllium mirror, cooled to 5.5 degrees above absolute zero, was built to see infrared light no ground telescope could catch. Mission planners hoped for two and a half years of science; it ran for more than sixteen…