The spirit of the holiday season is shining bright at Mauna Kea’s W.M. Keck Observatory.

The reason: Technical crews who worked through months of delays and tricky obstacles to upgrade a key telescope instrument finished just in time for a visiting team of astronomers to view the Christmas Comet.

Like the elves at Santa’s workshop preparing for the big night, the Keck team worked furiously to prepare for the historic flyby of 46P/Wirtanen Comet, nicknamed the Christmas Comet because of its fuzzy green appearance. It comes closest to Earth every 5-1/2 years or so.

“Instead of working toward the 25th of December, we were working to finish by the 16th of December,” said Greg Doppmann, the Keck astronomer who helped oversee the upgrade.

Dec. 16 was the day when the comet soared within 7.1 million miles of Earth, the closest the rocky and icy visitor would approach our planet in at least 70 years, according to NASA.

While that still might sound far away, astronomers say it’s nothing compared with the great distances they typically deal with. In fact, they said, this particular comet flyby was one of the closest in the last century.

Dec. 16 was also the day a group of highly regarded, NASA-sanctioned comet scientists arrived for two nights of long-planned observations.

Everything pretty much went off as planned for the astronomers. They successfully captured sharper-than-ever spectral data images using Keck’s newly upgraded spectrograph, a form of camera that separates light by its wavelengths and records the data.

But it could have gone sideways if the Keck team, which included a contingent from UCLA, where the instrument was originally built, hadn’t hustled to make the project right.

The planning and ordering in advance of the event began a couple of years ago. But first the observatory’s aging Near-Infrared Spectrograph, or NIRSPEC, needed an upgrade. It had been two decades since NIRSPEC was delivered to Keck Observatory, and the technology of such cameras had greatly improved.

Doppmann, Keck’s own support astronomer, began working on the multimillion-dollar project more than a year ago.

But a three-month delay in the manufacturing of the new optics with infrared detectors began to raise anxiety levels and put those involved in transforming the instrument under the gun.

“These are things you can’t buy off the shelf,” he said.

Doppmann said there was a contingency plan for moving ahead without that part of the upgrade, but the telescope’s efficiency would have suffered.

“Fortunately, we were able to get it installed a day or two before it would’ve been too late to meet our comet deadline. It was really down to the wire,” he said.

Work began in earnest at the beginning of August, when the spectrograph was taken off the telescope and placed on the floor of the observatory’s dome.

Usually, new instruments are constructed elsewhere and brought to the summit for installation. This time the decision was made to perform the camera upgrade right at the top of the 13,800-foot mountain to prevent any damage in transporting it up and down the bumpy summit road.

The work would not be easy at that altitude, considering the lack of oxygen and frosty temperatures hovering near freezing at sunset.

The spectrograph is encased in a dewar, a steel case that keeps the optics extraordinarily cold. To open up the case and reseal it, scientists need to pump out air and then cool it down to extreme temperatures reaching minus 370 degrees Fahrenheit.

It’s a slow process but a necessary one, Doppmann said, because the instrument is extremely sensitive to the heat signatures in the sky.

When it came time to seal it up, however, a leak was detected.

“The leak was at a low level, but it was unacceptable and we had to fix it,” he said.

Finding it became somewhat of a nightmare. The confounded scientists opened and closed the dewar, with pumping and cooling, five different times over a two-week period until the problem was finally discovered: a design flaw in the placement of an O-ring.

In the end the upgrade wasn’t finished until a week before the Christmas Comet flyby, leaving time for three nights of taking the spectrograph through a test run.

Meanwhile, Boncho Bonev, the American University research professor who led the comet project, said he wasn’t worried.

“Worrying would not help,” he said in an email. “My colleagues and I tried to remain full focus on what depended on us — to prepare as well as possible for this observing.”

Bonev’s research team is trying to figure out the comet’s chemical composition and, ultimately, looking for clues to the origins of life.

Bonev said his team was incredibly grateful to the NIRSPEC team for their “top effort” in making the spectrograph upgrades a reality.

“The NIRSPEC team not only completed the upgrade, but also provided a decisive help during the actual observations,” he said.

The only thing left to worry about was the weather.

But while it threatened to be frightful, it ultimately turned out to be mostly delightful, as the Christmas Comet streaked across the star-filled December sky and delivered a sackful of excellent data.