At last we're seeing the first images from the land-based Vera Rubin Observatory, after years of effort and frantic last-minute fixes that pushed the new observatory to completion. This has been reported in a new alert in the most recent email update from the American Astronomical Society - some of which I share in this post.
No, this telescope isn't out in space like the James Webb telescope. The newly constructed Vera C. Rubin Observatory lies at the summit of Cerro Pachón. The remote Chilean mountain is home to fatigued yet focused scientists who regularly gather in the observatory’s control room. They’ve been monitoring the systems around the 8.4-meter telescope while waiting to troubleshoot a problem: The telescope’s camera is overheating. It's only May, just weeks before the observatory is set to release its first images to the public.
Those images have since been unveiled during a June 23rd “first
look” event, are just the beginning. Every three nights for the next 10
years, the fast-moving and unprecedentedly sensitive telescope will complete a
scan of the Southern Hemisphere’s sky, generating 60 million gigabytes of data.
Named for the astronomer Vera
Rubin - well known for her discovery of firm evidence for dark matter - the
observatory will generate survey images that consist of exposures of 15 or 30
seconds, using six filters to cover the full visible range as well as
near-infrared wavelengths (330–1080 nanometers).
Eventually, those scans will help create a time-lapse “movie”
of the universe known as the Legacy Survey of Space and Time (LSST).
Its goal will include demystifying dark matter and dark energy, catching
fast-moving or ever-changing objects in the night sky, and mapping the universe
around us.
However, taking these initial images has been no small feat. Since construction began in 2015, highly customized components built in labs around the world have been coming together on the remote mountaintop, with an array of technical problems having to be solved on-site.
In the words of Fernanda Urrutia, an astrophysicist working on Rubin’s education and public outreach team:
“The last month was a crazy month, we're working very hard.”
This was soon after the AAS reporter arrived at the summit, noting:
"The scientists’ work during my visit was focused on trying to fix the cooling systems for the Rubin digital camera, the largest in the world. At the same time shutting down the camera provides great opportunity to conduct engineering tests which the teams can't do while actively observing the sky. Admitted Kevin Fanning, a member of the science and camera teams 'Admittedly there isn't a good understanding of the situation today.'"
The AAS reporter goes on:
"Nevertheless neither he or other members are bogged down by
the uncertainty. What they do know is that different parts of the camera need
to be kept at different temperatures. If any of their respective cooling
systems malfunction, the camera can overheat relatively quickly. So whenever on-site
scientists see the camera temperature climbing – even as the outside temperature
drops in the middle of the night- they’re quick to shut it down an begin problem
solving."
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We're informed that by evening, the temperature graphs on the screens in the
summit control room stabilized and engineers established a plan for the
night. They wanted to wait until the outside temperatures dropped again before
operating the camera, to determine if the cold air outside is responsible for
the cooling system’s malfunction. This test was expected to be a slow one, and
some of the observing scientists settled around to play Uno as night fell on
the mountain.
For months before the First Look press conference, scientists
had been hard at work in Rubin’s summit control room, making sure the
telescope (pictured on their screen below) was ready to begin its 10-year survey of the
cosmos.
The cooling systems were always “the big pickle” for
engineers working on the LSST Camera, in the parlance of research engineer Claire Juramy
(French National Institute of Nuclear and Particle Physics). Different parts of
the camera needed to be kept at different temperatures. If any of their
separate cooling systems malfunctioned, the camera could overheat relatively
quickly. So, when on-site scientists saw the camera’s temperature climbing even
as the outside air temperature dropped in the middle of the night, they were
quick to shut it down and start problem-solving
The AAS News reporter again:
"But behind us, the many graphs on screen suggest the outside
temperature is not falling at all — it's getting hotter. “Weather forecasts for
mountaintops are notoriously difficult to do,” Fanning explains."
"As it became clear they would have to wait another night to complete the test, the scientists recount the camera’s installation in March, when they had to place the camera at just the right place relative to the primary and secondary mirrors to capture in-focus images."
“By dead reckoning, we placed this camera within maybe three millimeters [off where it should be],” says Robert Lupton, who works with scientific software at Rubin as the LSST’s pipeline scientist. "
We then learn that due to the very wide (3.5 degrees) field of view, if the camera is just slightly out of place, the engineering images turn up donuts of light where there should be stars. Commissioning images provided the information needed to tweak the camera’s placement until it was just right.
Slow and steady seems to do well as a guiding principle for the observatory. The same principle applies to fixing the cooling system, according to Aaron Roodman (Stanford University), who leads the camera team. In his workds;
“Take a step and then discuss,”
He advises the others via video call the next morning as
they formulate a new plan.
It turns out that cold night air was involved. In the following weeks, the team further insulated the cooling systems and explored heating options to keep parts of the camera warm on cold nights. The fixes bring the observatory one step closer to the first-look images seen in this post.
Now, those images showcase the observatory’s potential. Wide
fields that are an astounding 3.5° across focus on patches of sky full of
galaxy clusters and nebulae, showing not only how deeply the camera can gaze
into the universe but also giving a taste of how many objects there still are
to discover and understand. The full survey of the Southern Hemisphere sky is
slated to begin later this year.
In Chile, the celebrations are just one more step in the continuing collaborative process of getting the high-profile observatory up and running.
Another small part of the Virgo cluster. Visible are two prominent spiral galaxies (lower right), three merging galaxies (upper right), several groups of more distant galaxies, many stars in the Milky Way Galaxy, and more. NSF / DOE / Vera C. Rubin Observatory
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