A second space lab, Tiangong 2, launched on 15 September 2016, 22:04:09 (UTC+8). The launch mass was 8,600 kg, with a length of 10.4m and a width of 3.35m, much like the Tiangong 1. Shenzhou 11 launched and rendezvoused with Tiangong 2 in October 2016, with an unconfirmed further mission Shenzhou 12 in the future. The Tiangong 2 brings with it the POLAR gamma ray burst detector, a space-Earth quantum key distribution, and laser communications experiment to be used in conjunction with the Mozi 'Quantum Science Satellite', a liquid bridge thermocapillary convection experiment, and a space material experiment. Also included is a stereoscopic microwave altimeter, a space plant growth experiment, and a multi-angle wide-spectral imager and multi-spectral limb imaging spectrometer. Onboard TG-2 there will also be the world's first-ever in-space cold atomic fountain clock.