Under the Microscope: GHOSTS & Rainbows (Part 4)
National Research Council Canada / Conseil national de recherches Canada
A blog post by Alan McConnachie, Project Scientist for the GHOST spectrometer
GHOST - Commissioning begins for the next great instrument for Gemini Observatory!
More great storytelling with Alan McConnachie, an astronomer with the NRC’s Herzberg Astronomy and Astrophysics Research Centre. Over the last 10 years, Alan has been part of a team that has developed a new instrument for astronomers around the world, called GHOST – the Gemini High Resolution Optical SpecTrograph. GHOST is the new instrument for the Gemini South telescope, one half of the International Gemini Observatory.
Did you miss Part 3??You can read it here.
---
Friday, June 17, 2022, somewhere over the USA
Heading back to Chile. When last we spoke, we had the bench and all the optics, aligned and working well. We had rainbows – including the Sun’s! And they were beautiful. But we didn’t have the fully finished spectrograph. For that, Jordan, Jennifer and the team at Gemini needed to erect the enclosure all around it – basically a giant, thermally stable box that will keep GHOST working at the same temperature all the time, to within a tenth of a degree or better, so the rainbows never shift where they land on the detector, and so observations can be repeated at very high precision.
And they did that! Tony and Peter from Australia have spent the last few weeks verifying that the software works to operate GHOST. So now it’s going on the telescope for 9 nights, to be put through its paces, to be tested. To be commissioned.
And so I’m on a plane again.
---
Saturday, June 18, 2022, La Serena
Joining me from Victoria, BC this time are Chris and John. Chris, like me, is an astronomer (but younger, better, smarter). Scientists will be doing much of the observing during commissioning, supported by the engineering team that put GHOST together. That’s where John comes in. We’ll be meeting other astronomers who have helped with the planning of all this – Fletcher, Trystyn, Mike (one of the architects of GHOST) – as well as Tony, who is already at the telescope, and David from NOIRLab/Gemini.
I won’t comment on the journey, especially the time spent in Toronto Pearson Airport, except to say that Chris has arrived sans-luggage. We’re guessing it’s not going to arrive until Wednesday, when the next flight from Toronto lands in Santiago, and by that time we will be at 2,700 meters in the Andes...
…so he’s off to buy some clothes.
---
Tuesday, June 21, 2022, 7 am, Cerro Pachon summit hotel
Finishing a long day, but what a day! We left our hotel in La Serena about 26 hours ago, and drove to the AURA Recinto. AURA runs NOIRLab, and NOIRLab runs Gemini, and the Recinto is the headquarters of them all in La Serena. Every weekday at about 6 am, buses leave to take the day crews of the telescopes on the nearly 2-hour drive up to the summit of Cerro Pachon. A few of us hitched a ride with them, and the rest drove up with Manuel in a truck.
The bus is designed for sleep, so I happily volunteered for that.
It’s cold at the summit, much colder than when I was here a month or two ago. It’s also very windy. Not good, and my first sense that things might not go quite according to plan. After lunch, we left our new accommodations at the summit to go to the telescope to get ready for the night. It was great to see GHOST again, except now really all you see is an enormous ?? though good looking ?? ?big black box, hooked up to a big rack of electronics.
We connected remotely to the telescope operations room back at the HQ in La Serena, where some of the rest of the team are based, and then we started running calibrations, ready for the night ahead. At this time of year, the nights are long – the solstice is in a few days – and we can expect about 12 hours of very dark skies every night. Lots of time to do what we need to do.
If we can open the telescope.
Those high winds are very high. For safety reasons we can’t open the enormous dome of the observatory if winds are up near 20 m/s (about 70 km/h), and they were exceeding that. So we stayed closed for the first half hour. But then they reduced a bit. So we opened, but in very sub-ideal conditions, and unable to point at anything to the north in case the dome blows off (ok, maybe not, but pointing into gale-force winds is not a wise idea). High winds also mean the atmosphere is not stable, and so the stars are much more blurry and twinkly than what we want them to be.
And did I mention the clouds? We can see through some clouds, if they’re not too thick. The clouds tonight went from thin to thick and back again.
But we got to use GHOST on sky! Given the conditions, we focused on bright stuff, and kept it simple:
First, can we actually see anything when we point at a star? Answer: yes!
Second, does the software work? Answer: sort of!?
Much discussion about what we were seeing on the screen, and if things were working as we expected. Making a list of the bugs to fix before the next night. After the very basics, we moved to exploring some of the other functionalities of GHOST. Figuring out if all the buttons we have, but which were never pressed until now, do what we want them to do, and figuring out the right order to press them in.
And having to close again due to wind, before opening up an hour or two later. And getting some truly wonderful spectra on some very interesting stars! The fact GHOST is able to observe in these conditions is amazing by itself. The Gemini staff point out that it would be marginal whether anything else would be operating in weather like this.
By 4 am, I’m starting to fade, but Mike and Chris seem to have a second wind, and start figuring out coordinate transformations. More than I can do at this time of night! We finish the night by looking at a star we want to come back to over the following weeks and months, to check out the stability of our measurements.
And we finish as the Sun comes up at 7 am. Stormy weather, but a great first night for GHOST!
---
Wednesday, June 22, 2022, 2 am, Control Room, Gemini South
The rooms at the summit are designed for sleeping during the day. Much needed. Got up for breakfast, a.k.a. lunch, at about 1 pm, and back to the telescope to run calibrations. Thick clouds all day. Working on troubleshooting the bugs from last night and made great progress. Should be much easier when we get back on sky.
But that will not be tonight. It’s getting colder and snow is forecast to start in a few hours. As much as we love being at the telescope, none of us want to be at the telescope in the middle of the night during a snow storm. So we’re packing it in for the night and getting back to our accommodations before the road becomes dangerous.
---
Thursday, June 23, 2022, 2 am, Cerro Pachon summit hotel
So this happened:
The road up to where we are, and further up to the telescope, is a maintained dirt road. It’s twisty and bumpy and requires careful driving at the best of times. Today is not the best of times. Anytime there is snow, the day crew are delayed until a safety call is made on the road. Turns out that the day crew did make it to the telescope in the afternoon, but it was very windy when they got there. As such, they were unable to inspect the dome (which requires climbing out onto the dome, very high off the ground) and so they were unable to clear it of ice and snow. And if they can’t do that, we can’t use the telescopes, because you definitely don’t want lumps of ice falling on the big mirror.
So tonight we did some more remote troubleshooting from our hotel rooms. Useful, but… sigh.
---
领英推荐
Friday, June 24, 2022, 2 am, Control Room, Gemini South
Cake!
The day crew brought cake to celebrate commissioning! Very good of them and very tasty! Helped set us up for the night ahead.
And there was a form of progress tonight ?? - instead of not observing any stars from our hotel rooms, tonight we didn’t observe any stars from the telescope! The dome got cleared, but winds and clouds hung around. Again, making reasonable use of the time by getting useful calibrations and sorting out software, but we really need to be doing on-sky tests, instead of these winds, clouds, snow…
…and earthquake! At about 11:55 pm (GMT-4), a magnitude 5.0 earthquake. That was exciting.
---
Saturday, June 25, 2022, 5 am, Cerro Pachon summit hotel
We got back on sky!
The winds stayed strong, but not as strong, and we were able to open. And the clouds were patchy, much like our first night, so we were able to continue with some of the tests we wanted to do. At least, we could check things worked, but in these kinds of conditions, you can’t see faint things, and we can’t determine just how well things are working.
And we had to close early, because the clouds got too thick.
---
Sunday, June 26, 2022, 1 pm, Cerro Pachon summit hotel
We started last night with the most beautiful sunset I’ve ever seen:
Clouds over the Andes at sunset. Very photogenic. The key word here is “clouds.”
And wind! We nearly got blown away coming to the telescope, and we were having gusts up to 140 km/hr while we were there!
At this point it won’t surprise you to learn we didn’t observe anything last night.
And there is another snow storm rolling in. Scheduled for Monday. They are closing the roads tonight in preparation for very bad conditions. Monday night observing will certainly be canceled. Some of us have flights on Wednesday. If it's a bad storm, we might be stuck here. So we’ve made the call to drive down to the base facility back in La Serena and continue from there. Only tonight and Tuesday night remain. Not convinced this is going to be enough…we’ve yet to start on any precision tests, they require good conditions, not back-to-back snowstorms. This weather is actually pretty rare. In the winter you lose nights to the weather, of course, but usually bad weather doesn’t hang around for more than a few days…
Before we left the telescope this morning, we said goodbye to GHOST – we won’t see it again in person for a while, now we are heading to the base facility.
---
Tuesday, June 28, 2022, La Recinto
So big news! We’ve been extended until Friday! This is becoming a marathon observing run. But so far we’ve had 8 nights, on-sky for 2 of them, both times in extremely bad conditions (Sunday was clouded, again, and Monday was cancelled due to snow). The snow yesterday was not as bad as was anticipated, and its looking like it’ll be clear tonight. In fact, Tuesday, Wednesday and Thursday all have a great-looking forecast, and everyone involved, including Gemini management, agreed it makes sense to take advantage of those nights and us being here. Several of the team – John, Mike and Trystyn ?? ?need to leave as scheduled, but Chris and I have been able to change our flights, and Fletcher is based here anyway for the next several months. Tonight is the last of our regularly scheduled nights. Fingers crossed!
---
Thursday, June 30, 8 am, La Recinto
Awesome. Just awesome. On Tuesday after my last post, I went to the control room. I had to ask the telescope operator if the wind monitor was working. It was showing only a few m/s.?Apparently, that’s what it’s supposed to be like! And no clouds, all night! So we really started doing what we wanted to do all along – pushing GHOST to its limits!
We observed bright and, more importantly, some really faint stars (for astronomers: nearly 20th magnitude). And we got some great data for them all. GHOST can easily find them in the sky (“acquiring” its targets), and the quality of the data we get even after relatively short exposures looks fantastic. We started later on Wednesday – Gemini had some other high priority observations they needed to do at the start of the night – but again it was a fabulous night.
At this rate, if things go ok tonight, we won’t need Friday night.
What a difference a few clear nights make!
---
Friday, July 1, 2022, 9 am, La Recinto
Happy Canada Day!
We are done! GHOST rocks, and now we just need to do the final analyses of the data to show it to the world! Another fabulous night with excellent conditions. We did some of our most challenging observations yet, including sitting for a long time on some very faint stars, something I expect will be very common for GHOST in the future. We observed our first quasar, our first solar-system object, and a bunch of other interesting objects to showcase GHOST, as well as finishing off the observations we needed to ensure GHOST meets all of its requirements.
And we found time to toast the success of GHOST! Certainly the longest observing run I have been on, and it was threatening to be badly impacted by weather, but by the end I’d say it’s certainly the most successful and satisfying time at the telescope that I have ever spent.
And the Gemini crew were fantastic.
Next up: presenting the results to the world…there is a meeting in a few weeks in Montreal that is the perfect venue.
But first, time to go home.
---
Whether you’re an astronomer, an engineer, or just interested in science and astronomy – make sure to follow the NRC and?#GHOSTinstrument ?on social media, to learn more.