Integrated Science Instrument Module (ISIM) is a component of the James Webb Space Telescope, a large international infrared space telescope launched on 25 December 2021.[1] ISIM is the heart of the JWST, and holds the main science payload which includes four science instruments and the fine guidance sensor.[1]
ISIM is the spacecraft chassis and instruments that take the light from the main mirror and convert that into the science data that is then sent back to Earth.[1] The other two major sections of the JWST are the Optical Telescope Element (OTE) (mirrors and their structure) and the Spacecraft Element (SE), which includes the spacecraft bus and sunshield.[1] ISIM has a mass of 1400 kg (3086 lb),[2][3] about 23% of the mass of the JWST.
The infrared camera instrument integrated with ISIM passed its thermal tests in early 2016.[4] ISIM underwent intense thermal cold testing in late 2015 to early 2016.[5] NIRcam is extremely important to JWST, because it is not only a sensitive infrared camera, but it is also used to adjust the alignment of the main mirror segments.[4] The tests were very positive because NIRcam showed it was very stable through vibration and thermal testing.[4] NIRcam was installed into ISIM in March 2014, and then underwent integration and testing after that, as the telescope was readied for its originally planned 2019 launch.[4]