NASA’s next great space observatory is almost ready to get to work. The Nancy Grace Roman Space Telescope has entered its science commissioning phase, the final stretch of testing before it begins routine science operations, the agency announced on Thursday, October 22.

The milestone means Roman has completed a comprehensive checkout of the observatory and its primary instrument. “We’ve established that the observatory is fully functional,” Julie McEnery, Roman’s senior project scientist at NASA’s Goddard Space Flight Center, said in the NASA update. “The telescope can guide and take exposures, data flows appropriately, and we can slew from one place to another for observations. So now we’re drilling into the fine details of the quality of the images we’re collecting.”

What “commissioning” actually means

Every new space telescope goes through a careful break-in period after launch. Engineers check that the spacecraft can point accurately, that its instruments respond to light as expected and that data flows smoothly back to Earth. Only after that do scientists start the long-term observing programs the mission was built for.

Roman’s team says it is now running a series of carefully planned test observations to characterize the observatory’s performance, calibrate how its instruments respond to light and refine image quality before the switch to science operations.

Passing a tricky test

One early worry was how Roman would handle crowded or dusty parts of the sky. The telescope locks onto targets by holding steady on individual guide stars, and scientists were concerned that in regions packed with stars, or wrapped in thick dust, the fine guidance system might get confused.

“But test observations of such regions have shown that Roman performs wonderfully in all cases,” said Tom Barclay, Roman’s operations project scientist at Goddard.

Why image consistency is everything

Roman’s science depends on comparing huge numbers of images taken over time. If some frames came out blurrier or brighter than others because of the telescope itself, astronomers could not tell whether a cosmic object was truly changing.

“To achieve the groundbreaking science we expect from Roman, we need to have a crystal clear window into space, not one marred by pointing jitter or out-of-focus images,” said Josh Schlieder, Roman’s Wide Field Instrument scientist. “Even very small flaws could mask the small signals we are aiming to measure.”

Roman’s superpower: speed

The most exciting early takeaway is how fast Roman works. According to NASA, the initial test observations have gone so well that the team is already seeing what it calls the telescope’s superpower.

“During commissioning, we are taking several test observations of famous parts of the sky,” said Jeremy Perkins, Roman’s observatory integration and test scientist. “I am marveling at the level of detail Roman provides in very short time periods.”

That speed is the whole point of the mission. Roman’s Wide Field Instrument has a field of view about 100 times larger than Hubble’s infrared camera, so it can capture enormous slices of the sky in a single shot. NASA says large mosaics that used to be reserved for special occasions will soon become routine.

“In a typical observation with Roman’s Wide Field Instrument, we’ll see objects that are a hundred million times fainter than the human eye can detect,” Schlieder said. “So just imagine what strange and unexpected things might be buried in all that data.”

What Roman will study

Once science operations begin, Roman’s wide, deep surveys are designed to help astronomers investigate some of the biggest open questions in cosmology:

  • Dark energy, the mysterious influence that appears to be speeding up the expansion of the universe
  • Dark matter, the unseen material whose gravity shapes galaxies
  • Exoplanets, including worlds found by watching how the gravity of foreground stars briefly magnifies light from background stars
  • Everything in between, from objects in our own solar system to galaxies near the edge of the observable universe

NASA also noted that some of the observatory’s systems are performing even better than required, which could open up new scientific capabilities beyond the original plan.

Named for the “mother of Hubble”

The telescope honors Nancy Grace Roman, NASA’s first chief of astronomy, who championed space telescopes at a time when many doubted they were possible and played a key role in making the Hubble Space Telescope a reality.

The bottom line

Roman has passed its checkup with flying colors and is now fine-tuning its view. If commissioning keeps going this smoothly, astronomers are about to be hit with a flood of data, and NASA’s own scientists are openly excited about what might be hiding in it. Stay tuned as Roman moves from testing to full science operations.

Image: Nancy Grace Roman Space Telescope (2020-35-4665) by IMAGE: NASA, NASA-GSFC via Wikimedia Commons, Public Domain Mark 1.0