As almost each evening, I am contemplating the magical transformation of the Paranal landscape into a subtle collection of reds, oranges and browns while the sky turns to deep blue. This is also the time of question and expectation: what seeing, how much ground layer and wind tonight ? The program is ready, we will start with the quasar and then move to other interesting objects before finishing to the now obligatory on/off sequence, now nickname snake.
But as a sailing boat does not decide on the direction and strength of the wind, observation at a ground based telescope has to cope with some part of unpredictability, some hasard, which is inherent to the atmospheric behaviour.
Indeed, at start, we were not able to point to the quasar because of pointing restriction due to strong wind from the East. This was unexpected because most of the time the strong winds come from the North and thus two days ago we changed on purpose to a South target to be on the safe side. We had to wait that the object pass meridian and in the meantime perform a snake sequence to measure the AO performance. Seeing was terrible, almost 2-3 arc second but the system manage to put it back to 1.2-1.5 arc second, not great though in absolute terms.
When it was possible we then moved to the quasar, but the measured image quality was even poorer. Even if the AOF was still closing all the loops, the image quality indicator went off the high limits and disappear from the monitoring screen ! We still performed the expected exposures but with such a poor image quality we were not sure what will be coming out of it.
Outside, wind was blowing like a hell and the ground layer vanished, AOF was desesperatly trying to keep the tip/tilt star in its box. In an heroic attempt, we keep trying to perform some measurements all nights, but at 4 a.m we decide to leave the boat.
In the meantime, as a consolation, Peter processed the date obtained the previous night on the ULIRG and produced a beautiful image that we are happy to share with you. Look to the finer detail and improved sharpness when comparing with an early observations obtained a few years ago at the science verification.
After a good sleep and a quick breakfast, it is time for all of us to debrief at the meeting room of the residencia. Despite the poor weather of the last nights, we have been able to perform all key tests and improved the system. A first evaluation of the performance demonstrate that our expectation are met. What was almost a dream 16 years ago is now a palpable reality.
With our data in hands we can say that image sharpness that were extremely rarely measured in MUSE or even impossible to obtain, will be obtain in normal conditions, say more than 50% of the time. Moreover, in average, the worst the atmospheric conditions, the better the improvement, resulting in a much higher probability for the science user to obtain excellent image quality, even for very long integration. Of course, this must be confirmed in the long term by using the system in various atmospheric conditions, but it is likely that the combination of MUSE and AOF will improve the quality of the produced MUSE datacubes and, ultimately, boost the scientific productivity.
One of the most complex systems ever build for an optical ground based telescope is now at our disposal. We are all excited and impatient to use it to question the Universe and get more hints and insights to try to answer its many mysteries.
On behalf of present and future users that will have a chance to get access to this great facility, I would like to thank all of you, and you are many, that have been part of this great technical and scientific development. It is a unique and major collective achievement, you can be proud of it.
This last night marks the end of the MUSE plus GALACSI commissioning. It has been a privilege and an immense pleasure to share with you, commissioning companions, these two runs. There are no successful scientific and technical achievement which is not also a human successful aventure, and this one is not an exception.
Note also that, August 2, ESO will communicate to the world a press release with some of the great images we have obtained.
I will close this blog for some time. It was great to share with all of you this moments. This is already the second episode of the series: first light and commissioning of MUSE stand alone was the first one (see here). But wait, this is not the end, in hardly a year we will be back to continue our adventure, with the expectation to push forward the system to another level: the so-called MUSE narrow field mode will be coupled with a full laser tomography adaptive optics system. The aim is to improve the sharpness of MUSE images by almost an order of magnitude in a small field of view and we expect exciting results when scrutinising astronomical objects.
Stay tuned, we will be back !