Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Future Looks Bright for Interferometry

19.09.2008
First Light for the PRIMA instrument

The PRIMA instrument [1] of the ESO Very Large Telescope Interferometer (VLTI) recently saw "first light" at its new home atop Cerro Paranal in Chile. When fully operational, PRIMA will boost the capabilities of the VLTI to see sources much fainter than any previous interferometers, and enable astrometric precision unmatched by any other existing astronomical facility. PRIMA will be a unique tool for the detection of exoplanets.

"PRIMA is specifically designed to see if one star 'wobbles' to and fro because it is has unseen planetary companions", says instrument scientist Gerard van Belle. "This allows us to not only detect exoplanets, but to measure their mass." PRIMA's expected astrometric precision of tens of micro-arcseconds is unmatched by any other existing astronomical facility, whether on the ground or in orbit [2]. In addition to taking astrometric measurements PRIMA will be the key to the imaging of faint sources with the VLTI using the science instruments AMBER and MIDI.

Interferometry combines the light received by two or more telescopes, concentrating on tiny differences between the signals to measure angles with exquisite precision. Using this technique PRIMA can pick out details as sharply as a single telescope with a diameter equivalent to the largest distance between the telescopes. For the VLTI, the distance between the two telescope elements is about 200 metres.

The PRIMA instrument is unique amongst the VLTI instruments, in that it is effectively two interferometers in one. PRIMA will take data from two sources on the sky simultaneously: the brighter source can be used for tracking, allowing the interferometer to "stare" at the fainter source for longer than is now possible with conventional interferometers. Although there have been earlier pathfinder experiments to test this technique, PRIMA represents the first facility-class instrument of its kind that is open to all astronomers.

PRIMA parts arrived at the summit at Paranal at the end of July and were integrated and tested during the following month. On 2 September 2008, as a first milestone, starlight from two VLTI 1.8-m Auxiliary Telescopes was fed into the PRIMA system, and interference fringes were detected on PRIMA's Fringe Sensor Unit. Three days later the system was routinely using active tracking on the fringes, compensating for atmospheric turbulence.

First light - or, in the case of interferometric instruments, first fringes - actually occurred ahead of the ambitious schedule set out by lead engineer Francoise Delplancke: "There were many activities that all had to be successful simultaneously for this to happen, but the assembly, integration, and verification went smoothly - I was pleased by how easy and reliable the fringe tracking was, for our first try."

All PRIMA sub-systems [3] have been installed successfully for use with two Auxiliary Telescopes and will now be submitted to intensive commissioning tests before being offered to the community of users for routine observations [4].

Notes

[1]: PRIMA stands for "Phase Referenced Imaging and Microarcsecond Astrometry". AMBER and MIDI are two instruments of the VLTI.

[2]: When a planet orbits a star, its gravity effectively pulls the star, making it "wobble". This wobbling is generally measured by looking at the variations of the radial velocity of a star, but if precise enough measurements of the position of the star can be made, it should be possible to see this wobble directly. PRIMA should be precise enough to make these measurements for Jupiter-like planets. PRIMA will be able to measure angular differences of about ten micro-arcseconds - roughly, the angular thickness of the width of a human hair seen at a distance of 1 km.

[3]: The PRIMA facility uses a number of components along the VLTI pipeline, including Star Separators (STSs) for the telescopes, Differential Delay Lines (DDLs), laser Metrology and two Fringe Sensor Units (FSUs). The Star Separators collect the light from two distinct stars to be sent through the interferometer. The DDLs, built by a consortium (Geneva Observatory, MPIA Heidelberg and Landessternwarte Heidelberg) compensate for slight differences in path lengths due to the separate positions on the sky of the two sources. Each Fringe Sensor Unit recombines light from both telescopes for the two sources separately to form interferometric fringes. These fringes are alternate dark and bright bands with widths that can be related to the angular separation of the sources. The Metrology system ties everything together at the 1-nm level by sending light back through the system from the FSUs to the STSs and back again.

[4]: Four commissioning runs are scheduled for PRIMA over the next six months and will concentrate on testing and characterising the fringe tracking on a single star. Observations of two distinct stars will begin next year and will extend these tests to the dual-star mode. These tests will also result in PRIMA's first astrometric measurements. Soon afterwards PRIMA will begin serious operations in planet-finding surveys.

The PRIMA project is a joint effort led by ESO and includes contributions from Geneva Observatory, MPIA Heidelberg, Landessternwarte Heidelberg, Leiden University, Ecole Polytechnique Fédérale de Lausanne, Institute of Microtechnology of Neuchâtel and MPE Garching; industrial partners on the PRIMA project include TNO and Thales Alenia Space.

Henri Boffin | alfa
Further information:
http://www.eso.org/public/outreach/press-rel/pr-2008/pr-29-08.html

Further reports about: Interferometer Interferometry Landessternwarte MIDI MPIA Observatory Sensor Telescope VLTI

More articles from Physics and Astronomy:

nachricht When AI and optoelectronics meet: Researchers take control of light properties
20.11.2018 | Institut national de la recherche scientifique - INRS

nachricht How to melt gold at room temperature
20.11.2018 | Chalmers University of Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Nonstop Tranport of Cargo in Nanomachines

Max Planck researchers revel the nano-structure of molecular trains and the reason for smooth transport in cellular antennas.

Moving around, sensing the extracellular environment, and signaling to other cells are important for a cell to function properly. Responsible for those tasks...

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Optical Coherence Tomography: German-Japanese Research Alliance hosted Medical Imaging Conference

19.11.2018 | Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

 
Latest News

Nonstop Tranport of Cargo in Nanomachines

20.11.2018 | Life Sciences

Researchers find social cultures in chimpanzees

20.11.2018 | Life Sciences

When AI and optoelectronics meet: Researchers take control of light properties

20.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>