Un succes (explications ci dessous)

Les premieres franges d’interferences

obtenues en recombinant la lumiere venant des 2 telescopes Keck1 et Keck2,

a l’aide de fibres optiques monomodes.

This is the first time that fibers are successfully used

as a replacement for mirrors to bring the light from

different telescopes to a common interferometric focus.

C’est une premiere

this feels like a wonderful achievement right now,

these first fringes are also the start of an

exciting and promising experimental adventure.

Les premieres franges,

Sujet: Premieres franges

De: Guy Perrin <guy.perrin@obspm.fr>

A: ….

Date: Sam, 18 Juin 2005, 17:12

Chers tous,

nous avons enfin obtenu ces premieres franges 'OHANA. Et dans des

conditions une nouvelle fois difficiles. Ciel quasi totalement couvert.

Plus un florilege de petits problemes.

Les premieres franges ont ete obtenues sur une etoile de magnitude 4,6

en K, 107 Hercule (voir ci-dessous). La sensibilite n'etait pas

mauvaise compte-tenu des conditions. La dispersion visible dans les

franges n'est pas due aux fibres 'OHANA mais aux deux dichroiques de

Keck 1 et Keck 2 de nature differentes !

Il est pour nous temps d'aller dormir apres cette tres tres longue

journee.

Merci a tous ceux qui ont travaille et apporte leur soutien a 'OHANA.

C'est une premiere etape qui en verra d'autres.

Guy et toute l'equipe 'OHANA.

………………….

Sujet: `Ohana fringes at Keck!

De: "Olivier Lai <Olivier Lai" <lai@cfht.hawaii.edu>

A: ohana@cfht.hawaii.edu

Date: Mar, 21 Juin 2005, 23:38

Dear OHANA Committee and extended `Ohana,

It is with great pleasure that I am writing to you on behalf of the

entire `Ohana team on this happy and important occasion. Indeed on

Saturday June 18th, at 00:26 am, fringes were obtained with the OHANA

fibers at the Keck Interferometer: these were obtained on a K = 4.61

star (we picked a star bright enough to ensure a high SNR to maximise

our chances to find the fringes, of course!), 107 Hercules, and the

sensitivity was very encouraging (more quantitative details forthcoming

once we all get some rest!). This is the first time that fibers are

successfully used as a replacement for mirrors to bring the light from

different telescopes to a common interferometric focus.

The preceding two weeks were filled with alignment, internal fringes,

vibration damping, more alignement and beautiful weather. Once again,

`Ohana suffered from clouds on Mauna Kea, but for once these were cirrus

rolling in on the second half of the night, so this is an improvement

over our last 4 runs! We did loose some time to varying absorption (at

4:00am, the moon was completely hidden), and with the usual unexpected

problems that had to be solved in real time.

We learnt many things in one short night, both on our injection modules

and ways to improve our observing efficiency but also on the Keck AO and

interferometer systems. As can be duly expected, our efficiency was not

very high during the beginning of this very first night of operation

(but it did improve towards the end). The prototpype OHANA requires a

lot of operations with two injection modules, two AOs, and an

interferometer. The injection modules had to be realigned to a very high

level of precision on a regular basis to ensure maximum coupling into

the fibers. Slight temperature drifts in the interferometric lab

required the OHANA fibers to be recentered with respect to the Keck

system. These are normal procedures that would need to be streamlined

and improved during a commissioning phase.

Dispersion is present in these very first fringes due to different

dichroics in the two Keck AO systems (the internal fringes showed none)

thus reducing the fringe contrast; however, this did not prevent from

finding them which is encouraging. In any case, we see clear ways on how

to improve our subsystems, and so while this feels like a wonderful

achievement right now, these first fringes are also the start of an

exciting and promising experimental adventure.

Aloha,

Olivier on behalf of the entire `Ohana team