Physics – Optics
Scientific paper
May 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000eso..pres...14.&link_type=abstract
ESO Press Release, 05/2000
Physics
Optics
Scientific paper
The Nova-ESO VLTI Expertise Centre Opens in Leiden (The Netherlands)
European science and technology will gain further strength when the new, front-line Nova-ESO VLTI Expertise Centre (NEVEC) opens in Leiden (The Netherlands) this week.
It is a joint venture of the Netherlands Research School for Astronomy (NOVA) (itself a collaboration between the Universities of Amsterdam, Groningen, Leiden, and Utrecht) and the European Southern Observatory (ESO). It is concerned with the Very Large Telescope Interferometer (VLTI).
The Inauguration of the new Centre will take place on Friday, May 26, 2000, at the Gorlaeus Laboratory (Lecture Hall no. 1), Einsteinweg 55 2333 CC Leiden; the programme is available on the web. Media representatives who would like to participate in this event and who want further details should contact the Nova Information Centre (e-mail: jacques@astro.uva.nl; Tel: +31-20-5257480 or +31-6-246 525 46).
The inaugural ceremony is preceded by a scientific workshop on ground and space-based optical interferometry. NEVEC: A Technology Centre of Excellence
As a joint project of NOVA and ESO, NEVEC will develop in the coming years the expertise to exploit the unique interferometric possibilities of the Very Large Telescope (VLT) - now being built on Paranal mountain in Chile. Its primary goals are the
* development of instrument modeling, data reduction and calibration techniques for the VLTI;
* accumulation of expertise relevant for second-generation VLTI instruments; and
* education in the use of the VLTI and related matters.
NEVEC will develop optical equipment, simulations and software to enable interferometry with VLT [1]. The new Center provides a strong impulse to Dutch participation in the VLTI. With direct involvement in this R&D work, the scientists at NOVA will be in the front row to do observations with this unique research facility, bound to produce top-level research and many exciting new discoveries. The ESO VLTI at Paranal
ESO PR Photo 14a/00
ESO PR Photo 14a/00
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Caption : A view of the Paranal platform with the four 8.2-m VLT Unit Telescopes (UTs) and the foundations for the 1.8-m VLT Auxiliary Telescopes (ATs) that together will be used as the VLT Interferometer (VLTI). The three ATs will move on rails (yet to be installed) between the thirty observing stations above the holes that provide access to the underlying tunnel system. The light beams from the individual telescopes will be guided towards the centrally located, partly underground Interferometry Laboratory in which the VLTI instruments will be set up. This photo was obtained in December 1999 at which time some construction materials were still present on the platform; they were electronically removed in this reproduction.
The ESO VLT facility at Paranal (Chile) consists of four Unit Telescopes with 8.2-m mirrors and several 1.8-m auxiliary telescopes that move on rails, cf. PR Photo 14a/00 . While each of the large telescopes can be used individually for astronomical observations, a prime feature of the VLT is the possibility to combine all of these telescopes into the Very Large Telescope Interferometer (VLTI) .
In the interferometric mode, the light beams from the VLT telescopes are brought together at a common focal point in the Interferometry Laboratory that is placed at the centre of the observing platform on top of Paranal. In principle, this can be done in such a way that the resulting (reconstructed) image appears to come from a virtual telescope with a diameter that is equal to the largest distance between two of the individual telescopes, i.e., up to about 200 metres.
The theoretically achievable image sharpness of an astronomical telescope is proportional to its diameter (or, for an interferometer, the largest distance between two of its component telescopes). The interferometric observing technique will thus allow the VLTI to produce images as sharp as 0.001 arcsec (at wavelength 1 µm) - this corresponds to viewing the shape of a golfball at more than 8,000 km distance. The VLTI will do even better when this technique is later extended to shorter wavelengths in the visible part of the spectrum - it may ultimately distinguish human-size objects on the surface of the Moon (a 2-metre object at this distance, about 400,000 km, subtends an angle of about 0.001 arcsec).
However, interferometry with the VLT demands that the wavefronts of light from the individual telescopes that are up to 200 meters apart must be matched exactly, with less than 1 wavelength of difference. This demands continuous mechanical stability to a fraction of 1 µm (0.001 mm) for the heavy components over such large distances, and is a technically formidable challenge. This is achieved by electronic feed-back loops that measure and adjust the distances during the observations. In addition, continuous and automatic correction of image distortions from air turbulence in the telescopes' field of view is performed by means of adaptive optics [2]. VLTI technology at ESO, industry and institutes
The VLT Interferometer is based on front-line technologies introduced and advanced by ESO, and its many parts are now being constructed at various sites in Europe.
ESO PR Photo 14b/00
ESO PR Photo 14b/00
[Preview - JPEG: 359 x 400 pix - 72k] [Normal - JPEG: 717 x 800 pix - 200k] [High-Res - JPEG: 2687 x 3000 pix - 1.3M]
Caption : Schematic lay-out of the VLT Interferometer. The light from a distant celestial objects enters two of the VLT telescopes and is reflected by the various mirrors into the Interferometric Tunnel, below the observing platform on the top of Paranal. Two Delay Lines with moveable carriages continuously adjust the length of the paths so that the two beams interfere constructively and produce fringes at the interferometric focus in the laboratory.
In 1998, Fokker Space (also in Leiden, The Netherlands) was awarded a contract for the delivery of the three Delay Lines of the VLTI. This mechanical-optical system will compensate the optical path differences of the light beams from the individual telescopes. It is necessary to ensure that the light from all telescopes arrives in the same phase at the focal point of the interferometer. Otherwise, the very sharp interferometric images cannot be obtained. More details are available in the corresponding ESO PR 04/98 and recent video sequences, included in ESO Video News Reel No. 9 and Video Clip 04a/00 , cf. below.
Also in 1998, the company AMOS (Liège, Belgium) was awarded an ESO contract for the delivery of the three 1.8-m Auxiliary Telescopes (ATs) and of the full set of on-site equipment for the 30 AT observing stations, cf. ESO PR Photos 25a-b/98. This work is now in progress at the factory - various scenes are incorporated into ESO Video News Reel No. 9 and Video Clip 04b/00 .
Several instruments for imaging and spectroscopy are currently being developed for the VLTI. The first will be the VLT Interferometer Commissioning Instrument (VINCI) that is the test and first-light instrument for the VLT Interferometer. It is being built by a consortium of French and German institutes under ESO contract.
The VLTI Near-Infrared / Red Focal Instrument (AMBER) is a collaborative project between five institutes in France, Germany and Italy, under ESO contract. It will operate with two 8.2-m UTs in the wavelength range between 1 and 2.5 µm during a first phase (2001-2003). The wavelength coverage will be extended in a second phase down to 0.6 µm (600 nm) at the time the ATs become operational. Main scientific objectives are the investigation at very high-angular resolution of disks and jets around young stellar objects and dust tori at active galaxy nuclei with spectroscopic observations.
The Phase-Referenced Imaging and Microarcsecond Astrometry (PRIMA) device is managed by ESO and will allow simultaneous interferometric observations of two objects - each with a maximum size of 2 arcsec - and provide exceedingly accurate positional measurements. T
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