China launched a Long March-2D carrier rocket into space on Thursday evening carrying a wheel-like formation of four remote sensing satellites, the first formation of its kind in the world. The satellites of the PIESAT-1 constellation were launched at 6:50 p.m. (Beijing Time) from the Taiyuan Satellite Launch Center in northern China's Shanxi Province, and then entered a preset orbit. The four satellites are equipped with interferometric synthetic aperture radars (InSARs), which are effective tools to measure changes in land surface. Compared to traditional InSARs, a wheel formation can generate more interference baselines, thus increasing mapping efficiency.