And Then There Were Three …! – VLT MELIPAL Achieves Successful “First Light” in Record Time
ESO Education and Public Relations Dept.
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Text with all links, photos and a video clip are available on the ESO Website at URL:
http://www.eso.org/outreach/press-rel/pr-2000/pr-01-00.html
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For immediate release: 28 January 2000
ESO Press Release 01/00
And Then There Were Three …!
VLT MELIPAL Achieves Successful "First Light" in Record Time
This was a night to remember at the ESO Paranal Observatory! For the first time, three 8.2-m VLT telescopes were observing in parallel, with a combined mirror surface of nearly 160 m2.
In the evening of January 26, the third 8.2-m Unit Telescope, MELIPAL ("The Southern Cross" in the Mapuche language), was pointed to the sky for the first time and successfully achieved "First Light".
During this night, a number of astronomical exposures were made that served to evaluate provisionally the performance of the new telescope. The ESO staff expressed great satisfaction with MELIPAL and there were broad smiles all over the mountain.
The first images
ESO PR Photo 04a/00
Caption: ESO PR Photo 04a/00 shows the "very first light" image for MELIPAL. It is that of a relatively bright star, as recorded by the Guide Probe at about 21:50 hrs local time on January 26, 2000. It is a 0.1 sec exposure, obtained after preliminary adjustment of the optics during a few iterations with the computer controlled "active optics" system. The image quality is measured as 0.46 arcsec FWHM (Full-Width at Half Maximum).
ESO PR Photo 04b/00
Caption: ESO PR Photo 04b/00 shows the central region of the Crab Nebula, the famous supernova remnant in the constellation Taurus (The Bull). It was obtained early in the night of "First Light" with the third 8.2-m VLT Unit Telescope, MELIPAL. It is a composite of several 30-sec exposures with the VLT Test Camera in three broad-band filters, B (here rendered as blue; most synchrotron emission), V (green) and R (red; mostly emission from hydrogen atoms). The Crab Pulsar is visible to the left; it is the lower of the two brightest stars near each other. The image quality is about 0.9 arcsec, and is completely determined by the external seeing caused by the atmospheric turbulence above the telescope at the time of the observation. The coloured, vertical lines to the left are artifacts of a "bad column" of the CCD. The field measures about 1.3 x 1.3 arcmin2. This image may be compared with that of the same area that was recently obtained with the FORS2 instrument at KUEYEN (PR Photo 40g/99).
Following two days of preliminary adjustments after the installation of the secondary mirror, cf. ESO PR Photos 03a-n/00, MELIPAL was pointed to the sky above Paranal for the first time, soon after sunset in the evening of January 26. The light of a bright star was directed towards the Guide Probe camera, and the VLT Commissioning Team, headed by Dr. Jason Spyromilio, initiated the active optics procedure. This adjusts the 150 computer- controlled supports under the main 8.2-m Zerodur mirror as well as the position of the secondary 1.1-m Beryllium mirror. After just a few iterations, the optical quality of the recorded stellar image was measured as 0.46 arcsec (PR Photo 04a/00), a truly excellent value, especially at this stage!
Immediately thereafter, at 21:16 hrs local time (i.e., at 01:16 hrs UT on January 27), the shutter of the VLT Test Camera at the Cassegrain focus was opened. A 1-min exposure was made through a R(ed) optical filter of a distant star cluster in the constellation Eridanus (The River). The light from its faint stars was recorded by the CCD at the focal plane and the resulting frame was read into the computer.
Despite the comparatively short exposure time, myriads of stars were seen when this "first frame" was displayed on the computer screen. Moreover, the sizes of these images were found to be virtually identical to the 0.6 arcsec seeing measured simultaneously with a monitor telescope, outside the telescope enclosure. This confirmed that MELIPAL was in very good shape. Nevertheless, these very first images were still slightly elongated and further optical adjustments and tests were therefore made to eliminate this unwanted effect. It is a tribute to the extensive experience and fine skills of the ESO staff that within only 1 hour, a 30 sec exposure of the central region of the Crab Nebula in Taurus with round images was obtained, cf. PR Photo 04b/00.
The ESO Director General, Dr. Catherine Cesarsky, who assumed her function in September 1999, was present in the Control Room during these operations. She expressed great satisfaction with the excellent result and warmly congratulated the ESO staff to this achievement.
She was particularly impressed with the apparent ease with which a completely new telescope of this size could be adjusted in such a short time. A part of her statement on this occasion was recorded on ESO PR Video Clip 02/00 that accompanies this Press Release.
Three telescopes now in operation at Paranal
At 02:30 UT on January 27, 2000, three VLT Unit Telescopes were observing in parallel, with measured seeing values of 0.6 arcsec (ANTU — "The Sun"), 0.7 arcsec (KUEYEN — "The Moon") and 0.7 arcsec (MELIPAL).
MELIPAL has now joined ANTU and KUEYEN that had "First Light" in May 1998 and March 1999, respectively. The fourth VLT Unit Telescope, YEPUN ("Sirius") will become operational later this year.
While normal scientific observations continue with ANTU, the UVES and FORS2 astronomical instruments are now being commissioned at KUEYEN, before this telescope will be handed over to the astronomers on April 1, 2000.
The telescope commissioning period will now start for MELIPAL, after which its first instrument, VIMOS will be installed later this year.
Impressions from the MELIPAL "First Light" event
First Light for MELIPAL
ESO PR Video Clip 02/00 (3350 frames/2:14 min)
[MPEG Video+Audio; 160×120 pix; 3.1 Mb]
[MPEG Video+Audio; 320×240 pix; 9.4 Mb]
[RealMedia; streaming; 34kps]
[RealMedia; streaming; 200kps]
ESO Video Clip 02/00 shows sequences from the Control Room at the Paranal Observatory, recorded with a fixed TV-camera on January 27 at 03:00 UT, soon after the moment of "First Light" with the third 8.2-m VLT Unit Telescope (MELIPAL). The video sequences were transmitted via ESO’s dedicated satellite communication link to the Headquarters in Garching for production of the Clip. It begins with a statement by the Manager of the VLT Project, Dr. Massimo Tarenghi, as exposures of the Crab Nebula are obtained with the telescope and the raw frames are successively displayed on the monitor screen. In a following sequence, ESO’s Director General, Dr. Catherine Cesarsky, briefly relates the moment of "First Light" for MELIPAL, as she experienced it at the telescope controls.
ESO Press Photo 04c/00 ESO Press Photo 04d/00
The computer screen with the image ESO staff at the moment of "First of a bright star, as recorded by the Light" for MELIPAL in the evening of Guide Probe in the early evening of January 26. The photo was made in January 26; see also PR Photo the wooden hut on the telescope 04a/00. This image was used for the observing floor from where the initial adjustments by means of the telescope was controlled during the active optics system. (Digital first hours. (Digital Photo). Photo).
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