NASA's Roman Telescope: How James Webb's successor will map universe with colossal amounts of data

NASA's next big space telescope will be the Nancy Grace Roman Space Telescope
NASA's next big space telescope will be the Nancy Grace Roman Space Telescope   -  Copyright  NASA's Goddard Space Flight Center
By Luke Hurst

The James Webb Space Telescope is continuing to unravel the beauty and mystery of the cosmos since delivering its first images in July last year - but the mission to deploy the next big space telescope is already well underway.

The Nancy Grace Roman Space Telescope will be the next big space telescope to launch following the deployment of the latest NASA telescope, which itself was the successor to the still-active Hubble telescope.

Roman’s launch will usher in "a new age for astronomy," one of the European Space Agency (ESA) scientists working on the project told Euronews Next; it will gather more data than any other NASA mission launched before, and attempt to answer some of the biggest questions in astrophysics.

Scheduled to launch by 2027 at the latest, it will be able to capture "a more panoramic view of the universe and to allow more statistical studies," explained Marco Sirianni, ESA’s Science Operations Development Manager who is working on the project with NASA.

While a NASA-led mission, ESA is contributing some of the technology and expertise to the mission, in return for access to the unprecedented amount of data that it will deliver.

Here’s a look at what to expect from the next big NASA space telescope.

How will Roman differ from Hubble and James Webb?

While Hubble and Webb are extremely good at zooming in to get a detailed look at small parts of the sky, Roman is going to have a much wider field of view.

It will be able to create infrared images that are 200 times larger than Hubble while providing the same rich level of detail with its similarly sized 2.4-metre diameter mirror.

So while it will be able to produce "exquisite" images, the likes of which we have gotten used to from Hubble and Webb, it is mainly "going to be a telescope dedicated for surveys," said Sirianni.

"In order to look for the star population in a nearby galaxy, which is very large for the field of view of Hubble, we have to stitch and do mosaics of very different shots. With Roman, we can take a picture of the full galaxy in one single shot," he says.

For example, a recent “mosaic" of our neighbouring galaxy Andromeda was put together with 400 individual images taken by Hubble. Roman will be able paint the same vast picture with the same level of detail with just two images. And these much larger images means there will be an unprecedented amount of data collected.

"Just to give you an idea, in 30 years of Hubble operating we have gathered something like 170 terabytes of data," explained Sirianni. "For Webb, we expect in five years to have 1,000 terabytes. And for the 5 years nominal life for Roman we expect to have 20,000 terabytes".

Ultimately, it will gather data on billions of galaxies to create a "3D model of the universe".

Answering cosmic mysteries

With this panoramic view of the universe, NASA and its partners are hoping to answer some of the biggest questions facing astrophysics.

One of the goals is to test Albert Einstein’s theory of general relativity, which is well tested against the scale of our solar system for example, but less so on larger cosmological scales.

Visible matter within the universe should, according to the theory, slow down the expansion of the universe, so scientists attribute the speed of expansion of the universe to a mysterious component - dark energy - which they believe makes up roughly 68 per cent of the universe.

Roman will give us data that can accurately measure the position and distance of millions of galaxies and will help us to understand the expansion rate of the universe in different areas.

Ultimately, the results will tell us if Einstein's theory of gravity needs modification.

Exoplanet census

Another of Roman’s top goals is to spot thousands of new exoplanets within our galaxy, using a technique called gravitational microlensing.

"If two stars align to each other, the one in front will distort and magnify the light of the star behind. And if the star in the foreground has a planet, we will see the impact of that planet on the light of the star behind it," said Sirianni.

Given Roman will count billions of stars, it will provide a "very good census of how many stars will have exoplanets," he added.

Not only will it spot new exoplanets, but Roman will carry a second main instrument - called a coronagraph - which aims to image exoplanets that are close to their parent star. "This is a very difficult technique because the starlight has to be suppressed - it is orders of magnitude brighter than the objects that you want to study, the nearby planet," said Sirianni.

The coronagraph on Roman will attempt to directly capture large planets similar to Jupiter, conducting live corrections to improve image quality.

It will be a demonstration instrument - and if it proves to work, it will form the baseline for the technology to be used on future space observatories that will be attempting to directly image Earth-like planets in the habitable zone of their parent star.

ESA's contribution to Roman

ESA is contributing three key pieces of technology to the Roman mission, in return for access to the data and a seat at the table during the mission.

The space agency will provide "star trackers," small telescopes in the spacecraft that constantly determine its position in the sky by tracking stars. Then it will provide batteries to help power the spacecraft before its solar panels are deployed.

And finally, it will also supply detectors for the coronagraph onboard.

Furthermore, ESA’s own mission to measure the expansion of the universe and reveal more about dark energy is launching this summer.

The Euclid space telescope will gather the information that will then be complementary to the data gathered by Roman.

Like ESA’s contribution to Roman, NASA is making small contributions to the Euclid mission too.