Visiting Cerro Paranal in Chile

I visited the ESO Paranal Observatory in August 2003. Cerro Paranal is located 130 km south of the city of Antofagasta and 12 km inland from the Pacific Coast, in what is the driest area on Earth. ESO operates the Very Large Telescope (VLT) on Cerro Paranal with four 8.2-m telescopes (the Unit Telescopes or short UTs) at an altitude of 2635 meters. Each UT provides one Cassegrain and two Nasmyth focus stations for facility instruments. In addition each UT is equipped with a Coude focus station from which the light can be coherently combined in the interferometric focus. Image quality is impressive with a record 0".18 FWHM, 1 sec. exposure in the I-band with FORS2 at UT2, and the sky is photometric in 78 % of the night time. Active Optics techniques get down to the near-IR diffraction limit of an 8 m (< 0".05), even when seeing is in its more normal 0".5-1".0 range. The Very Large Telescope Interferometer (VLTI), with its own suite of instruments, ultimately provide imagery at the milli arcsecond level as well as astrometry at 10 micro arcsecond precision. Proposals received by ESO request more than four times the available observable time at Paranal Observatory, and research articles based on VLT data are in the mean quoted twice as often as the average. With two scientific papers being published every day, the ESO Observatories are in fact the most productive ground-based astronomical facilities in the world.

The following are the Mapuche names for each UT and their meanings, with the date when each UT achieved first light:
UT1 (ANTU, The Sun) 25-26 May 1998
UT2 (KUEYEN, The Moon) 1 Mar 1999
UT3 (MELIPAL, The Southern Cross) 26 Jan 2000
UT4 (YEPUN, Venus, as evening star) 3-4 Sep 2000

View of the clouds down below from Cerro Paranal

Melipal, UT3 The 2.6-m VLT Survey Telescope (VST) Yepun, UT4

From left to right: Antu, Kueyen and Melipal

Melipal, UT3 Antu, Kueyen and Melipal

Antu with Yepun in the background

Antu with Yepun in the background The Zerodur primary mirror of Antu, UT1

The secondary mirror of Antu, UT1

The secondary mirror of Antu The Nasmyth-platform of Antu

Antu

FORS1 in the background at the Cassegrain focus of Antu, and I

Closeup of FORS1 at the Cassegrain focus of Antu

FORS1 at the Cassegrain focus of Antu (middle and right)

The astronomical instruments in operation at the VLT cover all major observing modes required to tackle current front-line research topics:
- FORS1 (FOcal Reducer and Spectrograph) annd its twin, FORS2, are multi-mode instruments that can be used for imaging in the visible and for low-resolution spectroscopy.
- ISAAC (Infrared Spectrometer And Array Camera) is a cryogenic infrared imager and spectrometer, observing in the 1 to 5 µm range.
- UVES (Ultra-violet and Visible Echelle Spectrograph) is the high-dispersion spectrograph of the VLT, observing from 300 nm to 1100 nm, with a maximum spectral resolution of 110,000.
- NACO is an Adaptive Optics facility produucing images as sharp as if taken in space.
- VIMOS (VIsible Multi-Object Spectrograph), a four-channel multiobject spectrograph and imager, allows obtaining low-resolution spectra of up to 1000 galaxies at a time.
- FLAMES (Fibre Large Array Multi-Element Spectrograph) offers the unique capability to study simultaneously and at high spectral resolution hundreds of individual stars in nearby galaxies.
- VISIR (Vlt Imager and Spectrometer for thhe mid-InfraRed) provides diffraction-limited imaging at high sensitivity in the two mid infrared (MIR) atmospheric windows (8 to 13 µm and 16.5 to 24.5 µm).
- SINFONI is a near-infrared (1 - 2.5 ╞m) integral field spectrograph fed by an adaptive optics module.
- CRIRES (CRyogenic high-resolution InfraRed Echelle Spectrograph) provides a resolving power of up to 100,000 in the spectral range from 1 to 5 μm.
- HAWK-I (High Acuity Wide field K-band Imaager) is a near-infrared imager with a relatively large field of view.