MIRI uses silicon arrays doped with arsenic to make observations at these wavelengths.[1] The imager is designed for wide views but the spectrograph has a smaller view.[1] Because it views the longer wavelengths it needs to be cooler than the other instruments (see Infrared astronomy), and it has an additional cooling system.[1] The cooling system for MIRI includes a Pulse Tube precooler and a Joule-Thomson Loop heat exchanger.[1] This allowed MIRI to be cooled down to a temperature of 7 kelvins during operations in space.[1]