Jürgen's cunning plan for re-aligning the blue CCD was put into action today. The blue dewar had to be removed & relocated to the clean room for the procedure.
Dr Bramall briefed the patient on what was about to happen.
Then securely lashed it to the optical table to prevent any movement during the alignment procedure.
A green laser was set up behind a target with a hole in the centre. The laser + target was mounted on a tripod equipped with a nifty geared head stage assembly which would allow fine adjustment of the laser & support the screen that we would view the return-spots on.
The laser shines through the central hole in the target, to the CCD window (which consists of two concave surfaces - the outer one being spherical & the inner one cylindrical), then reflects off the chip & travels back through the window to the screen/target.
We know that the chip's tilted, but the lens hasn't moved so the laser needs to be set up to be in auto-collimation with the lens. Then the chip can be adjusted with the three micrometers until the return-spot from the CCD lands back on the laser.
Some careful tweaking was needed to get the relatively faint return-spots from the two lens surfaces to land on the central spot where the laser emerges. At this point the laser was squared up with respect to the CCD window & the chip was clearly way off to the lower left.
David could then open up the micrometer hatches again & make the necessary adjustments to get the bright spot from the reflection off the CCD to line up with the other spots & the outgoing beam.
Reassuringly, it was only the two micrometers that had lost the ball bearings that needed adjusting.
It was possible to steer the return to line up perfectly with the outgoing beam in the centre of the target.
All looking Much better, even though it's tricky to judge when looking through the highly curved surfaces of the field-flattener lens (that doubles as the CCD window).
Then time to read & lock the micrometers again.
Here you can see the various spots, including the one on the target being reflected by the mirror-like CCD.
We also tried moving the tripod back a couple of metres to see if we could refine the alignment by using a longer baseline. The fainter spots required the lights to be switched off (yielding a neat photo-op!), but they were also much bigger & hence not of much use.
Still - we're really pleased about how sensitive this technique turned out to be & we're optimistic that this will have done the trick...
With that, the patient was gently ferried back to the ward.
& connected up to the relevant life-support systems, specifically the vacuum pump & the CCD controller. We'll again have to wait until tomorrow to be able to take images & see whether we've succeeded in re-aligning the detector.
The other important job for today was getting the low-down on all the HRS software from Eddy before he left. Sadly, he's flying home tomorrow so Luke drove him down to Cape Town this evening. This probably explains Luke's glum expression, but perhaps we need to start working on our Happy Face again?
Neat to be able to run various things from the SALT control room for the first time!
Have a safe trip back Eddy - So Long & Thanks For All The Software (& Whisky)! We look forward to seeing you back here sometime in the next couple of months :)