NASA isn't only focused on its mission to Mars. In fact, the space agency has something else to boast - and it's the only one in the world. Say hello to the world's biggest flying observatory, NASA's SOFIA.

Compared to the other Boeing 747SP, this airliner is rare and it's the only one of its kind. The 747-200 maybe 47 feet shorter but it's the world's' only flying astronomy laboratory that makes use of an infrared telescope.

The SOFIA, which stands for Stratospheric Observatory for Infrared Astronomy, was originally built for long haul routes. Now, NASA makes use of it to observe light in the infrared spectrum, which is not visible to the naked eye. Why is this important?

Infrared light sources have never been studied, not until SOFIA. Adding to its unique features, the SOFIA can provide data that any other telescope in ground or up in space can't pick up. The overall mission of SOFIA is "studying objects spanning the full gamut of astronomical topics including planets, moons, asteroids and comets in our solar system; star and planet formation; extra-solar planets and the evolution of planetary systems; the interstellar medium and interstellar chemistry; the nucleus of the Milky Way galaxy, and nearby normal and active galaxies," according to its project scientist Pamela Marcum.

Sometimes called the Vampire Jet, SOFIA is a multi-use observatory with a number of instruments that include spectrometers, photometers, and cameras. All these operate in a variety of infrared wavelengths, whereas others specifically study astronomical science phenomena.

Now, the SOFIA is based inside NASA's Armstrong Flight Research Center in California. However in the duration of the Northern Hemisphere summer, SOFIA is moved to the base at New Zealand.

NASA's SOFIA was a joint project between the space agency and the German Aerospace Center (DLR). It was designed in 2010. On that same year, the SOFIA operations begun.