Extremely cool to get to see the primary mirror cleaning system in action today! A huge arm with a nozzle attached swings over the array, blasting CO2 snow over the segments.
I also relished the chance to play with a fisheye lens again, what a treat :) Note the plume of CO2 just to the left of the centre of the array.
Back in the clean room, Eben & James had finished installing the framework for attaching the dial gauges & LVDTs to the SAC.
We also spent time testing a new setup for measuring the reflectivity of M5. This involved shining a red laser down through the hole in the super-structure platform & getting the return to land on a photodiode mounted next to it. The effect of the laser hitting M4 along the way is shown below - the translucent gold-coloured Zerodur that the mirrors are made of lights up beautifully!
Further effort went into adjusting the CGH fringes obtained with the interferometer...
The incredible sensitivity of the interferometer's essential to us, but being capable of measuring to fractions of a wavelength of light also has its drawbacks! The system easily registers the disturbance caused by a car driving up towards the plateau, let alone the effects that pumps, fans, people & wind have on the building.
We decided that more weight on the NRS simulator might help damp out some of the jittering so a posse rushed down to the gym & made off with all the weights. The poor little bakkie barely made it back up the hill again...
Other than the exhausting amounts of pool being played, this was the most exercise we've had in a month. It added a whole new dimension to Clean Room Olympics, but alas did little to stabilize the fringes.
That's it for now - we're heading back to Cape Town tomorrow for a much needed recharge, tune in again when we return on 1 June!