The Roman Space Telescope’s Mirrors Have Been Integrated
One of NASA’s biggest goals is to find habitable exoplanets. The ultimate goal of NASA’s Exoplanet Program is to find unmistakable signs of current life. Exoplanets’ own skies could hold such signs, waiting to be revealed by detailed analysis of the atmospheres of planets well beyond our solar system. While the James Webb Space Telescope is very impressive, it’s an infrared telescope primarily intended for early universe and star studies.
Thankfully, NASA has been making progress on the Roman Space Telescope. The Roman Space Telescope is an observatory designed to settle essential questions in the areas of dark energy, exoplanets, and infrared astrophysics. Just a few days ago the agency announced that the telescope’s massive primary and secondary mirrors were integrated together.
At this point, the observatory is not too far from completing its crucial build phase. From here, it will go through a very thorough and extensive testing phase before launch. Expected to join Webb at L2, the Roman Space Telescope will have a long journey ahead of it. Here I will go more in-depth into the recent telescope progress, the significance of its design, what to expect in the near future, and more.
Mirror Integration
The process of constructing a next generation space telescope is an immensely complex process that takes quite a bit of time. However, only a few days ago on the second, NASA tweeted saying, “Roman’s primary and secondary mirrors have been integrated together at @L3HarrisTech to create the Forward Optical Assembly! In honor of #Groundhogday, our partners have tested the optics over and over again to make sure they are just right!” This included images of the two mirrors coming together. While not as big as Webb’s primary mirror, it still is 2.4 meters in diameter (7.9 feet). Enough to discover some incredible things when combined with its distant location at L2.
The Roman Space Telescope will have two instruments, the Wide Field Instrument, and the Coronagraph Instrument. The Wide Field Instrument will have a field of view that is 100 times greater than the Hubble infrared instrument, capturing more of the sky with less observing time. As the primary instrument, the Wide Field Instrument will measure light from a billion galaxies over the course of the mission lifetime. It will perform a microlensing survey of the inner Milky Way to find ~2,600 exoplanets. The Coronagraph Instrument will perform high contrast imaging and spectroscopy of individual nearby exoplanets. The Roman Space Telescope will have a primary mission lifetime of 5 years, with a potential 5 year extended mission.
More specifically, the Wide Field Instrument (WFI) is a 300-megapixel infrared camera that will allow scientists to explore the cosmos all the way from the edge of our solar system to the farthest reaches of space. Peering far across the universe is like looking back in time to when the universe was much younger. Seeing the universe in its early stages will help unravel how it has expanded throughout its history, which will hint at how it may continue to evolve. Each Roman image will capture a patch of the sky bigger than the apparent size of a full Moon. Hubble’s infrared images, taken with its Wide Field Camera 3, are about 200 times smaller. Even Hubble’s widest exposures, taken with the Advanced Camera for Surveys, are nearly 100 times smaller. Over the first five years of observations, Roman will image over 50 times as much sky as Hubble covered in its first 30 years.
Most excitingly, the Coronagraph Instrument on the Nancy Grace Roman Space Telescope demonstrates technology that allows astronomers to directly image planets in orbit around other stars by greatly reducing the glare from the host star. It will be far more powerful than any other coronagraph ever flown, capable of seeing planets that are almost a billion times fainter than their star. Results from the Roman Coronagraph, which is being built at NASA’s Jet Propulsion Laboratory, will demonstrate the technology that will enable future missions to observe and characterize rocky planets in the habitable zone of their star – the range of orbital distances where liquid water could potentially exist on a planet’s surface. Studying the physical properties of exoplanets that are more similar to Earth will take us a step closer to discovering habitable planets and possibly learning whether we are alone in the cosmos.
As of recently, Roman is scheduled to be launched on a Falcon Heavy launch vehicle under a contract specifying readiness by October 2026 in support of a NASA launch commitment of May 2027. The total cost for NASA to launch the Roman telescope is approximately $255 million, which includes the launch service and other mission related costs.
Join Webb At L2
Now that we know more about some of the progress and the telescope’s two main instruments, we can take a closer look at its destination and goal. To make Roman’s sensitive measurements possible, the telescope will observe from a vantage point about 930,000 miles (1.5 million km) away from Earth in the direction opposite the Sun. At this special place in space, called the second Sun-Earth Lagrange point, or L2, gravitational forces balance to keep objects in steady orbits with very little assistance. Roman’s barrel-like shape will help block out unwanted light from the Sun, Earth, and Moon, and the spacecraft’s distant location will help keep the instruments cool. The thermal stability of an observatory at L2 will provide a ten-fold improvement beyond Hubble in much of the data Roman will gather.
The amount of detail these observations will reveal is directly related to the size of the telescope’s mirror, since a larger surface gathers more light. Roman’s primary mirror is 7.9 feet (2.4 meters) across. While it’s the same size as the Hubble Space Telescope’s main mirror, it is less than one-fourth the weight. Roman’s mirror weighs only 410 pounds (186 kilograms) thanks to major improvements in technology.
Once in position, the Roman Space Telescope can use a light-bending phenomenon to study planets beyond our solar system, known as exoplanets. In a process called microlensing, a foreground star in our galaxy acts as the lens. When its motion randomly aligns with a distant background star, the lens magnifies, brightens and distorts the background star. As the lensing star drifts along in its orbit around the galaxy and the alignment shifts, so does the apparent brightness of the star. The precise pattern of these changes can reveal planets orbiting the lensing star because the planets themselves serve as miniature gravitational lenses. Such alignments must be precise and last only hours.
The Roman Space Telescope’s microlensing survey will monitor 100 million stars for hundreds of days and is expected to find about 2,500 planets. This planet-detection method is sensitive enough to find planets smaller than Mars, and will reveal planets orbiting their host stars at distances ranging from closer than Venus to beyond Pluto. These results will make the Roman Space Telescope an ideal companion to missions like NASA’s Kepler and the upcoming Transiting Exoplanet Survey Satellite (TESS), which are best suited to find larger planets orbiting closer to their host stars. Together, discoveries from these three missions will help complete the census of planets beyond our solar system, helping us learn how planets form and migrate into systems like our own.
Roman aims to prove that direct imaging technologies that have worked well on ground-based telescopes can perform even better in space. The mission will also extend current observations, which are primarily limited to infrared light, by seeing visible light. This will help astronomers see cooler planets for the first time via the visible light they reflect from their host stars, and even detect clouds. Roman’s Coronagraph Instrument will offer a crucial stepping stone on the journey to finding life on other worlds. Current direct imaging efforts are limited to enormous, bright planets. These worlds are typically super-Jupiters that are less than a hundred million years old – so young that they’re still glowing from heat leftover from their formation, which makes them detectable in infrared light. They also tend to be very far away from their host star because it’s easier to block the star’s light and see planets in more distant orbits.
But scientists would like to directly image planets that are similar to our own – Earth-sized, rocky planets in the habitable zone of Sun-like stars. To do so, NASA points out we need to be able to see smaller, cooler, dimmer planets orbiting much closer to their host stars than current telescopes are capable of detecting. Roman will move us a step closer by observing planets that are Jupiter’s size circling Sun-like stars, orbiting about as far as Jupiter is from the Sun. The mission will be able to image planets spanning ages up to several billion years – something that has never been done before – demonstrating technology that could be used by future missions to study worlds that are even more Earth-like. It will also offer a complementary way to probe planetary systems by taking images of faint disks of gas and dust surrounding nearby Sun-like stars. Roman may even be able to reveal structures in the disks, such as gaps created by unseen planets.
Conclusion
The Hubble Space Telescope once repaired revealed incredible things within the galaxy for the first time ever. Hubble’s big brother the Roman Space Telescope is a much more advanced and capable telescope with an even better destination. We will have to wait and see how it progresses and the impact it has on the space industry.
