Imaging and Slitless Spectroscopy Instrument for Surveys (ISSIS)

ISSIS design

ISSIS is being developed in Spain by SENER Ingenería y Sistemas S.A.( The instrument will carry out UV and optical diffraction limited imaging of astronomical objects. The current ISSIS design includes two acquisition channels for imaging and slitless spectroscopy:

  • The Far Ultraviolet Channel (FUV), providing the optimum sensitivity in the 1150-1750 Å interval, and equipped with a CsI MCP detector.
  • The Near Ultraviolet Channel (NUV) covering wavelegnths in the 1850-3200 Å range; the detector is a CsTe MCP.


The different operation modes are selected through the mode selection mechanism:

  •  Imaging: flat mirrors aligned to direct the light into the selected channel (FUV or NUV) are used. The optical filters are accomodated on two wheels for each channel: there are long-pass filters and narrow band filters for specific investigations, as well as two neutral filters for each channel, to increase the dynamical range.
  • Spectroscopy: the beam is directed to the reflection gratings. The FUV diffraction grating has peak efficiency at 1400 Å and groove density of 450 lines/mm, while the NUV one has the peak at 2300 Å and 250 lines/mm.
  • Calibration: a shutter is used to block the light from the telescope, and the beam is directed to the calibration subsystem in order to take flat field images on a pixel-to-pixel basis.