The Fine Guidance Sensor for the James Webb Telescope

The second of four main instruments to fly aboard NASA's James Webb Space Telescope (Webb) has been delivered to NASA. The Fine Guidance Sensor (FGS) will enable the telescope to accurately and precisely point at the correct, intended objects for it to observe. The FGS is packaged together as a single unit with the Near-Infrared Imager and Slitless Spectrograph (NIRISS) science instrument.

From what I understand these instruments are now undergoing cryogenic testi