The Integrated Science Instrument Module (ISIM) is the part of JWST that contains the science instruments, the Fine Guidance Sensor, and the data-handling computer.
The Integrated Science Instrument Module (ISIM) is the observatory element that contains the 4 science instruments as well as the Fine Guidance Sensor (FGS). The ISIM includes the electronics that control the instrument detectors and mechanisms and maintains the thermal environment, and also provides command and data processing for the science instruments and the FGS. See Figures 1 and 2.
The ISIM Command and Data Handling (ICDH) computer provides the basic command and telemetry routing, and processing functions for all of the science instruments. It also provides for event-driven mission timeline execution by an observation plan executive (OPE), and science instrument (including the FGS) applications for science operations and target acquisition. The ICDH computer oversees the operation of the instruments and manages the event-driven operation of the Observatory through the execution of the Observation Plan and on-board scripts, and coordinates ISIM and Spacecraft activities by sending requests for services, such as slews, to the Spacecraft. The ICDH performs readout mode processing of the science data, that is formatting of the science data, before transfer to the Spacecraft Solid State Recorder. Software resident on the ICDH analyzes portions of the data for target acquisition purposes. The ICDH computer is located on the Spacecraft Bus.
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Near Infrared Camera, NIRCam
Mid-Infrared Instrument, MIRI
Near Infrared Spectrograph, NIRSpec
Near Infrared Imager and Slitless Spectrograph, NIRISS
Fine Guidance Sensor, FGS
JWST Acronyms and Abbreviations