By Colin Jacob
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The experience was a real adventure from start to finish, but only in the good sense of the word. From the time I was greeted by the Chilean border agent – who responded to the word “Paranal” with the proud exclamation, “The most advanced telescope in the world!” – until I was delivered safe and sound to the airport for my trip home, the experience was smooth. ESO take very good care of visiting astronomers. There was no logistics to manage, since all transport inside Chile is organised by ESO’s helpful staff, and all accommodation is at ESO facilities. I spent a week in Chile and never had a need to handle the local currency.
The Mountain
The logistics, and potential gotchas, of the trip to Paranal have been well covered elsewhere on this blog (which I strongly encourage anyone travelling to read), but I will add some of my impressions. Firstly as a tourist to the Atacama desert: The landscape was spectacular in many ways. I have never seen such a treeless country, with the Australian red centre seeming positively tropical in comparison. For some hours on the bus to the observatory, I don’t believe I spied a single tree. The only ones visible from the mountain are a sorry handful imported and set up at the entrance to the Residencia, where they no doubt cling to life only with the constant care of ESO staff. The dryness is certainly palpable, in the eyes, skin and nose, and on the glasses which steam up when one enters the building housing the pool. An indicator on the wall read 2.7% humidity, which would be low even by the standards of the area. It’s for good reason that the Wikipedia entry on the Atacama has a section “Comparison to Mars”!
What lives up there? Apart from some tiny bits of scrub there was little to be seen, but on one occasion I did see a soaring vulture. It must eat something, so I enquired about potential prey. Nobody was quite sure but there have been sightings of foxes around the telescope at night, so it just goes to show that even in the world’s driest desert, life finds a way.
The view from the mountain leaves a strong impression. The unique landscape, an ocean of cloud below in the distance, and the view over to Cerro Armazones where the groundwork is being laid for the E-ELT all make for some thought-provoking viewing. I regret not making time for the “star walk” from the Residencia up to the telescope. It would be good exercise as well as a chance to explore the landscape and, if you like, some true solitude.
The Observing
As a prelude to gathering our data, we were fortunate enough to be treated to a tour of the VLT. There are also opportunities to tag along at the beginning and end of the night when the checks are made inside the dome; I made sure to stick my nose in there whenever the opportunity presented itself. There’s no substitute for seeing the telescope up close; the scale is hard to appreciate from a picture. We were able to walk around inside the dome, and while there I was able to see both XShooter and MUSE on their respective Unit Telescopes. Seeing each UT the weight of a jumbo jet yet so finely balanced it could be moved with the push of a human hand and steered with the precision required for cutting-edge astronomy, inspired thoughts of gratitude. Thank you to the people of the world who funded instruments like this, so we handful of astronomers could gather data from a patch of sky a few arc seconds across!
Along with other visitoring astronomers I commend the suggestion of going outside during observations for the spectacular night view. The four LGS lasers on UT4 are clearly visible and make for an awe-inspiring sight. While I was there one of the targets was Io, so the four laser beams appeared to converge right on Jupiter in the sky. Several jokes were made about how the Jovians might interpret such a signal from their notoriously warlike Terran neighbours.
I understand that visitor mode may become less common at the VLT, and I don’t imagine it will be a common experience for the next generation of astronomers gathering data on thirty-meter class telescopes. In our case it was still a valuable exercise. It is true that the ESO staff, including some very helpful support astronomers, leave little room for error by a visiting astronomer. The ESO phase 2 tool is very good, and we were able to quite easily generate scripts to generate observing block files and import them into the tool where we, and the ESO astronomers, could see our targets were VLT-ready. Making on the fly changes was not difficult, and sending a target over to the queue for observation was a click of a button. On the night we were able to tell in almost real time that we could get clear redshifts for our targets and so reduce integration times. Our observing strategies on the night changed significantly; in some cases we switched between two prepared plans of a single slit across lens and source versus two slit positions. In the end we were able to observe more targets than originally expected due to the quality of the data and the ease of adjusting our plans. Future observations have now been finely calibrated and we can submit service mode proposals with greater confidence that the integration times will be adequate.
Visitor mode, of course, also has its risks. We lost a few hours on the first night due to cloud. The second night, a crash of the Telescope Control System required a bit of a scramble and the rousing of a few engineers, but without a clear indication from the logs of the cause of the issue, a restart was attempted. From then on we had no problems, with the loss of only an hour.
Tips
In addition to the other tips and tidbits I’ve seen, I’d add:
