Foton (or Photon) is the project name of two series of Russian science satellite and reentry vehicle programs. Although unmanned, the design was adapted from the manned Vostok spacecraft capsule. The primary focus of the Foton project is materials science research, but some missions have also carried experiments for other fields of research including biology. The original Foton series included 12 launches from the Plesetsk Cosmodrome from 1985 to 1999. The second series, under the name Foton-M, incorporates many design improvements over the original Foton, and is still in use. So far, there have been three launch attempts of the Foton-M. The first was in 2002 from the Plesetsk Cosmodrome, which ended in failure due to a problem in the launch vehicle. The last two were from the Baikonur Cosmodrome, one in 2005 and one in 2007, both were successful. Both the Foton and Foton-M series used Soyuz-U (11A511U and 11A511U2) rockets as launch vehicles.
The Foton capsule has limited thruster capability. As such, the reentry path and orientation can not be controlled after the capsule has separated from the engine system. This means that the capsule has to be protected from reentry heat on all sides, thus explaining the spherical design (as opposed to Project Mercury's conical design), which allows for maximum volume while minimizing the external surface. However, the lack of lift means the capsule experiences high forces on reentry, up to 8 to 9g.