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