A year ago, I posted a rather uninspiring wallpaper describing the James Webb Telescope. If you’ve been following the development of the telescope, you’ve probably noticed that some of the terminology has shifted in response to changes made in the instruments.
For the past ten months, the mission team has been offering a “behind the scenes” look at the instruments and their performance at various testing sites via video podcast. Everything you ever wanted to know about mirrors in space—watch the videos and you will never need to ask another question on the subject.
The most recent video veers away from the subject of the telescope’s mirrors to talk about the “dynamic duo,” the paired instrument consisting of the Fine Guidance Sensor (FGS) and the Near-Infrared Imager and Slitless Spectrograph (NIRISS) instrument. It seems like an odd combination: the FGS is a guide camera responsible for the fine adjustments in the telescope’s guidance system, while the NIRISS is a four-way instrument that works as an imager, spectroscope/-graph, and interferometer. The FGS and NIRISS operate independently, but as the video linked above indicates, the NIRISS can take over some guidance functions, adding another level of redundancy to the instrument in case something goes wrong with the FGS.
Also: thank you, Canada.
