ESPRESSO First light

ESPRESSO has successfully observed its first star last Monday November 27th, 2017 around 21:30 local chilean time. The numerous team involved in this important milestone was composed of technical staff, including software specialists and astronomers.

The first star observed by ESPRESSO was Tau Ceti. This was achieved through the UT1 telescope. The full chain from the star to the data archiving worked fine. This represents a quite complex chain involving the telescope, the Coudé Train, the Front-End, the spectrograph and then the instrument and data reduction software. The Coudé Train optical relay brought the photons from the M3 mirror to the combined Coudé Laboratory, where its L11 lens refocused properly the image in the Front-End. Before reaching the Front-End, the light passed through the ADC12 Atmospheric Dispersion Corrector.


The Front-End, where most of the moving and dissipating elements are located, collected the light from the proper telescope(s), stabilized the image and the pupil, added the selected calibration light, and sent them to the spectrograph through optical fibers. In the spectrograph itself, the light was processed by several optical components. In the image below right, we see on the right the Echelle Grating,  in the middle the dichroic separating the blue and red photons, and in the background the Main Collimator reflecting others optical elements.

The spectrograph then projected two echelle spectra on the two red and blue detectors. We see here below the Vacuum Vessel with the two cameras chimneys and the detectors cryostats. Their images were then processed electronically and saved as a raw FITS file (below right).

The raw spectra were then reduced by the automatic reduction process to show a very nice high resolution spectrum. We see below one order of the spectrum and a zoom in this order.

 Pictures credit: G. Calderone (INAF – Trieste), D. Mégevand (Univ. Geneva)

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