Coronas is an international project to study the Sun and its interaction with Earth using spacecraft launched by Russia and carrying experiments developed by Russia and Ukraine with involvement from scientists in other European countries and the United States. Coronas satellites are equipped to study solar activity, including flares and mass ejections, in various regions of the spectrum from radio waves to gamma rays. Coronas-I reentered the atmosphere on 4 March 2001, two days before Mir was de-orbited, leaving Russia temporarily without a single working science payload in orbit. Coronas-F carries three main groups of instruments, to obtain high resolution X-ray images of solar active regions, measure the strength and polarization of radiation coming from active regions and flares, and measure the flux of solar particles. Both satellites were launched by Tsyklon rockets from Pletesk.