The Euclid space telescope, a mission by the European Space Agency to map the geometry of the dark universe, released its first set of images on May 23, 2024.

What was the total exposure time or duration required to capture the data for these newly released Euclid images? In other words, how long did Euclid's instruments need to integrate and collect light from these distant galaxies to produce the images? Any information from credible sources on this would be appreciated.


1 Answer 1


From this paper: https://arxiv.org/pdf/2405.13500 :

Euclid takes its data in multiples of a so called reference observing sequence (ROS). Each of with consists of the following exposures:

An ROS field is composed of four dither pointings designed to fill the detector gaps. For each dither, the same measurement sequence is executed. First comes a VIS $I_E$-band nominal science exposure of 566 s, with a concurrent NISP spectroscopic exposure of 574 s in one of the four red-grism orientations. These are followed by a sequence of three NISP images in the $J_E$, $H_E$, and $Y_E$ bands, each lasting 112 s. For the ERO programme, each dither also included an $I_E$ short-science exposure of 95 s simultaneously to the $Y_E$ exposure, yielding four such images per ROS;

So per ROS you get $(4\,\times\,566)+95 = 2359\,$s for the I-channel of the VIS instrument and $4\times112=448\,$s for the J, H & Y-channels of the NISP instrument. This is also nicely illustrated in Fig. 8 of this earlier paper https://arxiv.org/abs/2108.01201 :

enter image description here (As this was written 3 yrs earlier, before the launch, I wouldn't worry about the few seconds difference.)

Those are then combines as RGB channels for the different images. The press release has some information on which channel, besides the I-channel, was used for which color in each image.

On top, for the early data release, each source gets between one and three of those ROSs, according to the table below. I leave the remaining math of adding up all those seconds as an exercise to the reader.

Another caveat would be that this is how observations where planned. Stuff like a solar flare can make some data unusable so for the precise exposure time of each image, one should consult also the papers mentioned in the table below.

enter image description here


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