Long-time Slashdot reader Kreuzfeld writes: Thursday marks the final mission of NASA’s Spitzer Space Telescope. Conceived of as an infrared-optimized “Great Observatory,” Spitzer has spent the last 6002 days providing Earthlings with an unprecedented view into other galaxies, our own solar system, and (unexpected to its designers!) planets around other stars. But in its Earth-trailing solar orbit, Spitzer is now over…