SUperb Seeing Instrument

SUSI and SUSI2 were very sensitive, high-resolution CCD cameras installed on the 3.5-metre New Technology Telescope (NTT) at ESO’s La Silla Observatory. They were optimised for periods of good seeing conditions.

The original instruments for the NTT comprised the ESO Multi-Mode Instrument (EMMI) and the infrared spectrometer IRSPEC, but their designers had not anticipated the spectacular first light images produced by the NTT. These images provided an excellent demonstration of what could be achieved by controlling the dome temperature and ventilation to optimise the local seeing, combined with a high quality site. It was quickly realised that the initial instruments would not be able to take full advantage of the superb atmospheric conditions, and so ESO rapidly developed a CCD camera that would be able to exploit these opportunities.

The new instrument was named the SUperb Seeing Imager, or SUSI for short. It saw first light in April 1991.

SUSI was used to study a variety of astronomical objects, including taking a long exposure of Halley’s comet (eso9404), observing a cosmic mirage (eso9606), taking snapshots of the dust jets of Comet Hale-Bopp (eso9624), and performing long exposures of patches of the southern sky to produce the NTT SUSI Deep Field (eso9801). In combination with EMMI, SUSI was also used to image the supernova 1995K, which was one of the supernovae observations that led to the suggestion of the accelerating expansion of the Universe (eso9511).

In February 1998, SUSI was replaced with its upgraded version. SUSI2 was identical in concept but with 4 times the field of view (5.5 x 5.5 arcmin). After many successful years of operation, SUSI2 was decommissioned in 2008.


The authoritative technical specifications as offered for astronomical observations are available from the Science Operation page.

Location: La Silla
Telescope: New Technology Telescope
Focus: Nasmyth A
Type: High-resolution imager
Wavelength coverage: 0.35 - 1.00 µm
Spatial resolution: 4.1 arcminutes x .4.1 arcminutes
Spectral resolution:
First light date: April 1991 (SUSI), February 1998 (SUSI2)
Science goal: To study a variety of astronomical objects with high spatial resolution in good seeing conditions
Images taken with the instrument: Link
Images of the instrument: Link

Videos of the instrument:


Press Releases with the instrument: Link