The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument for the Thirty Meter Telescope (TMT). It combines a diffraction limited imager and an integral field spectrograph. This paper focuses on the electrical system of IRIS. With an instrument of the size and complexity of IRIS we face several electrical challenges. Many of the major controllers must be located directly on the cryostat to reduce cable lengths, and others require multiple bulkheads and must pass through a large cable wrap. Cooling and vibration due to the rotation of the instrument are also major challenges. We will present our selection of cables and connectors for both room temperature and cryogenic environments, packaging in the various cabinets and enclosures, and techniques for complex bulkheads including for large detectors at the cryostat wall.
With the successful completion of our preliminary design phase, we will present an update on all design aspects of the IRIS near-infrared integral field spectrograph and wide-field imager for the Thirty Meter Telescope (TMT). IRIS works with the Narrow Field Infrared Adaptive Optics System (NFIRAOS) to make observations at the diffraction limit of TMT at wavelengths between 0.84 and 2.4 microns. The imager has been expanded to a 34 arcsec field of view and the spectrograph has a wide range of filter and spectral format combinations with a contiguous field of view up to 112x128 spatial elements. Among the many challenges the instrument faces, and has tried to address in its design, are atmospheric dispersion up to 100 times the sampling scale, unprecedented saturation issues in crowded fields, and the need for integrated on-instrument wavefront sensors. But the scientific payoff is enormous and IRIS on TMT will open entirely new opportunities in all areas of astrophysical science.