Months after its scheduled re-entry into Earth's atmosphere — and a surprise cameo appearance in hit space flick Gravity — China's first space station boosted into a higher orbit. It still speeds around the planet, doing … what, exactly?

No one outside of China's popular but opaque space program seems to know.

Tiangong, or "heavenly palace," blasted off atop a Long March 2F booster in 2011. "Chinese Gen. Chang Wanquan, commander of China's manned space program, declared the launch a success from a control center in Beijing, drawing applause from assembled Chinese politicians and dignitaries,"Spaceflight Now reported.

During spaceflights Shenzhou 9 and Shenzhou 10, three-person Chinese crews lived aboard Tiangong's small habitat for as long as 15 days at a stretch.