NICMOS, the Near Infrared Camera and Multi-Object Spectrometer, is Hubble’s infrared instrument that has remained in hibernation since 2008. It detects near-infrared light, wavelengths longer than visible red light, allowing astronomers to see through dust and study cool or distant objects.
Astronauts installed NICMOS during Servicing Mission 2 in 1997. Its original solid-nitrogen coolant was exhausted by 1999, leaving the instrument dormant. Servicing Mission 3B revived it in 2002 by installing the NICMOS Cooling System, an experimental mechanical cooler that restored its infrared capability.
After a planned shutdown in September 2008, the cooling system failed to restart reliably. NASA chose to leave NICMOS dormant, in part because Hubble’s newer Wide Field Camera 3, installed in 2009, provided strong infrared capability without risking a difficult restart.
The common mix-up is to confuse NICMOS with WFC3’s infrared channel. WFC3 replaced much of NICMOS’s operational role, but NICMOS is the named instrument associated with the long-term hibernation.