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DSSI Speckle Camera

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Overview of Capabilities

DSSI (Differential Speckle Survey Instrument, Elliott Horch, Southern Conn. St. Univ.) provides simultaneous diffraction-limited optical imaging (FWHM~0.02" at 650nm) of targets as faint as V~16-17, in 2 channels over a ~2.8 - 5.6 arcsecond field-of-view.

DSSI was built in 2008 and more recently upgraded with two new Andor Ixon Electron-Multiplying CCDs (EMCCDs). The EMCCDs are 512x512 pixels each with plate scales of 0.011 arcsec/pixel at Gemini. DSSI collimates the input beam and splits it, using a dichroic, into blue and red components which are passed through filters and then focused onto the two EMCCDs.

The standard procedure at Gemini is to operate the EMCCDs using 60 msec exposures, and gather images in sets of 1000 frames (yielding total exposure times of integer minutes). This readout rate is made possible by windowing the readouts for each camera to a 256x256 pixel region (ie. a 2.8"x2.8" field, which is the largest practical field to match an isoplanatic patch of atmosphere). The photon-multiplying properties of the EMCCDs produce effectively very low read-noise data, enabling speckle imaging of much fainter targets than has been historically possible. The diffraction-limited resolution possible at Gemini (0.016" FWHM at 500nm or 0.025" at 800nm) offers proposers unique capabilities.

The visiting instrument team will take all observations and will provide their standard pipeline-reduced data products to PIs. There is no requirement to collaborate with the instrument PI for this level of service. If you need more than this, then the PI would appreciate an offer to collaborate. After the standard proprietary period, all raw and reduced data will be made available via the Gemini Observatory Archive (in a reduced-effort mode).

The PI for the Gemini Speckle program is Steve Howell (NASA Ames Research Center).


DSSI is no longer offered at Gemini since it has been replaced by the permanently mounted Zorro and 'Alopeke in Gemini South and North, respectively. Please consult those instruments pages if you are interested in speckle interfereometry at Gemini.

DSSI Science Highlights

Press release image

How to Use These Pages

The DSSI pages are organized as follows:

DSSI block diagram

Gemini Observatory Participants