IRIS2 Goes to the AAT

These pages are an informal visual record of the IRIS2 Commssioning process.

Also available is Bridget Dawson's Diary.

October 23

IRIS2 arrived at the AAT on October 23rd in less than impressive weather conditions.
However, undaunted, the IRIS2 team proceeded to unload the instrument from its CSIRO "air ride" truck.

 
 

Carefully lowered out of the truck, IRIS2 was soon safely back on the ground.


On its way to the 4th floor and the telescope, the old met the new - IRIS2 on the right, and the venerable RGO spectrograph on the left. Note how the modern electro-polished stainless steel compares with dingy old UK Civil Service grey.

Instructed by the AAT staff to bring absolutely everything including the kitchen sink, we did just that. The ultrasonic kitchen sink - though to the uninitiated it does look a bit more like a chip fryer than a sink.
Then it was time to remove the bottom of the Cassegrain cage, and allow IRIS2 it's first date with destiny.
And its fits! A very happy John Dawson was smiles all over when the gamble to make IRIS2 the first AAT instrument in our history to have four locating pins paid off. All four fit perfectly! (And some doubters said it couldn' be done).

After its test fits, IRIS2 then went to the Coude West prep area for pumping, and preperation for cooling.

Wednesday night saw  the dewar undergo vacuum and leak testing, and pumping of the main dewar.

October 24, 2001

The next day saw the main dewar pumped down, with just a tiny leak present. A larger leak in the foredewar in the vacuum guage seal was tracked down and repaired.The dewar itself also migrated accross the floor, being parked in at least 4 positions (as cabling revealed yet more location restrictions).



However, by Thursday afternoon the cryo-coolers on the main dewar were connected to the AAT's new helium reticulation.

This impressive new piece of infrastructure will permit IRIS2 to maintained permanently cool once fully commissioned - at either the AAT Cassegrain focus, or in the Coude West instrument preperation area.
 

At Coude West the new system appears as a fairly simple set of connections. But one floor down, we find its pointy end....
A network of helium lines connecting a pair of helium compressors both to the Coude West prep area....

 


... and to a new cable wrap at the AAT's north bearing, from where the helium is then passed to ...
... another cable wrap on the western declination bearing, provide helium plumbed all the way onto the telescope (and on to the prime focus top ends).

This new helium system will permit both IRIS2 and 2dF/AAOmega to reside on the telescope, and stay cold, at the same time. IRIS2 in particular, is expected to stay permanently cold once final commissioning is completed. If it sounds like I'm making a big deal out of nothing, try thingking of it this way - we've just had the sewerage put on. Instead of having to get up several times in the middle of a cold night to head down to a thunderbox in the back yard to get your liquid nitrogen, cryogenic temperatures are right there on tap down the telescope.

Special thanks to Pat Sykes and Mark Wright of ATNF, who did the specialist helium reticulation plumbing, distribution panels, tractor modifications and installation and flexible preparation.  They did this in the AAT dome during winter often at temperatures around the value in your domestic refrigerator. ATNF also manufactured the cryodyne driver electronics for us. On the AAT side, Allan Lankshear worked with Pat Sykes on the system layout, designed the wraps and oversaw the project. Brendan, Wayne, Neville and contractors constructed and helped install the wraps as well as installing the AAT side of the project. Jonathan designed the coolant reticulation, co-ordinated the cryodyne driver manufacture with ATNF, designed and organised the local contractor to manufacture the alarm and interlock system.
 

With cryol-cooling started, the auxiliary liquid nitrogen cooling system was also plumbed in for main dewar cooling. At which point that kitchen sink we were told to bring finally came in handy as a drip tray.

Meanwhile the wheels were tested (warm) and all found to operate successfully.

By Thursday night the cryo-coolers on both dewars were operating, along with the detector controllers, and images (very hot ones) were being read out, as the dewars cooled.

Friday, October 25, 2001 : D-day

Over the course of the night of October 24th and the early morning of October 25th, IRIS2 was pumped and cooled to near operating temperature. By the time the day crew arrived all was lamost ready for IRIS2 to go on the telescope. This had initially been planned as a "lets see if we can get it on, then we'll use it on Saturday" excercise. In the end, the whole process went so smoothly we were ready to try and see light on Friday night!

With the Cassegrain cage removed again, IRIS2 was raised into 
position for mounting.

And it still fit!
Then a complex procedure was carried out to finally fix the mounting struts in place. Pins cooled (and so shrunk) in liquid nitrogen were pushed into place at the apex of the struts (where the masking tape is wrapped in the above right image). When these pins cool, they are locked in place (as are the struts) for eternity.
Which meant it was finally time for IRIS2 to say farewell to the carrying cradle in which it has nestled so comfortably for the last year or so, and live free on the AAT.
 
Kept company (of course) by its very own electronics rack
By 7pm that evening (the mechanical crew from Epping having headed off to the Imperial Hotel for a well earned rest), we attempted to align the pupil of IRIS2 with the pupil of the telescope (IRIS2 has its own internal and very cold replica of the telescope aperture.  By aligning this mask with the telescope's aperture we can ensure the hot telescope structure is not seen by IRIS2's infrared detector). But first we focussed the telescope on a bright star, to obtain every instrument's first image - an out of focus doughnut.We had first fuzz!

Thanks to a very clever pupil imager installed in IRIS2 and designed by Peter Gillingham, the pupil alignment process (which involves actually losening the mounting points shown in the picture at the top left, and inserting shims to slightly move the instrument) was very straighforward. Roger Haynes and I just kept looking at each other thinking it couldn't be this easy!
 


 
Now we really were ready for first light. We slewed to the 30 Doradus region of the Small Magellanic Cloud, and acquired the following image of the "Tarantula Nebula"  in the Ks passband - IRIS2's first light at 11:42pm on October 25 (as processed by the  loving hands of Stuart Ryder). 

After which we were ready for the whole team to join in the traditional toast to IRIS2's future success (the Epping team who'd been in the pub timed their return to perfection - they watched the pictures roll in and joined in the Scotch consumption).

The nights since (IRIS2 was on the telescope for the following 8 nights) have given us some successes and a few failures. It is clear that work on the reliability of the software will be essential, that we would like to get the Science grade device installed (instead of the Engineering grade device currently in place, and that some work is needed on optical alignment.

However some very good data has been taken - images of the cluster AC114, brown dwarf spectra and some data for several Shared Risks Sservice Observing programs.

All in all its been nowhere near as bad as I imagined - in fact far smoother than I could have believed. Which is all down to my amazing colleagues here at the Observatory. A jobs well done everyone. Not finished just yet, of course. But still well done.

Chris T. 4/11/2001

This page created by Chris Tinney