The Roman Space Telescope is designed to directly image exoplanets using complex opto-mechanical systems developed by the Max Planck Institute for Astronomy
An artist’s concept of the Nancy Grace Roman Space Telescope.
© NASA/SVS
To the point
- News from Heidelberg: Engineers and scientists at the Max Planck Institute for Astronomy have contributed to the development of one of the Roman Space Telescope’s two main instruments, the Coronagraph Instrument (CGI).
- Immense stability of the optics: The so-called Position Alignment Mechanism (PAM) is a central component of the coronagraph and stabilizes its optical components. This makes it possible to resolve and photograph planets like Jupiter as point-sources next to their host stars. The requirements for this stabilization system make the CGI the most sophisticated optical observation instrument ever used for research in space.
- Towards imaging a second Earth: With the experience gained from this new camera design, it should be possible with future telescopes to image planets like Earth orbiting distant stars.
- Launch of the Roman Space Telescope: After a team at NASA’s Goddard Space Flight Center has integrated the instruments into the space telescope, the telescope will launch on August 30, 2026, at 07:26 am EDT aboard a SpaceX Falcon Heavy rocket.
The Roman Space Telescope has been under development for about a decade under NASA’s leadership and is scheduled to launch on August 30, 2026, at 07:26 am EDT. The telescope is named after Nancy Grace Roman, who was considered the architect of NASA’s modern science program and, among other efforts, dedicated herself to the success of the Hubble-Space-Telescope-Project. Roman’s destination is Lagrange point L2, a specific location 1.5 million kilometers from Earth that lies on the axis connecting the Sun and Earth on the side of Earth facing away from the Sun. At this point, the gravitational forces of the celestial bodies cancel each other out, allowing Roman to orbit the Sun without propulsion.
Photographing Planets Around Distant Stars
An optical Engineer performs an inspection of Roman’s Primary mirror, which has a diameter of 2,4 meters, just like the Hubble Space Telescope.
© NASA/Chris Gunn
The diameter of the Roman Space Telescope’s primary mirror is 2.4 meters, and it is a replica of the Hubble Space Telescope’s mirror. It carries two scientific instruments: The Wide Field Instrument has a detector area about 100 times larger than Hubble’s and, in just five years, will image an area of the sky 50 times larger than Hubble did over 30-years. And, together with the Euclid space telescope in orbit, Roman will set out to track down dark matter, which is widely distributed throughout the universe.
Thanks to the Wide Field Instrument’s high image resolution and sensitivity, researchers also plan to search large sections of the sky for cooler planets, which have not been as easy to find as opposed to hot, bright gas giants. They will use two methods for this: Using the so-called transit method, they aim to detect about 100,000 new planets as they pass in front of their star and cause a minimal but measurable dimming of the star’s light. Using another method based on the so-called microlensing effect, they hope to find an additional 1,000 exoplanets. Both methods detect distant worlds only indirectly.
Engineers are checking the optical path of the coronagraph instrument (CGI), which is one of the two instruments on the Roman Space Telescope, under cleanroom conditions. Light from the telescope will be directed into the coronagraph to capture images of relatively faint planets as small dots next to their much brighter host stars.
© Chris Gunn/ NASA JPL
The second instrument, the Coronagraph Instrument (CGI), is used to directly image and study exoplanets that have already been discovered using other methods. Coronagraphs use special masks to block out the bright host star, in order to reveal fainter celestial bodies, such as a planet orbiting closely around that star. These distant solar systems are so far away that the imaged planets appear only as small dots next to their host star, which is obscured by the coronagraph.
With previous coronagraphs on ground-based telescopes, this was only possible for particularly bright gas giants located at greater distances from their central stars – stars that are so hot that they emit infrared light and thus can be imaged with infrared cameras. With the CGI, however, researchers aim specifically to image cooler and smaller exoplanets, such as Jupiter, which primarily reflect the light of their host star. The planets that Roman aims to image appear, as seen from Earth, a billion times fainter than their host star. This roughly corresponds to the difference in brightness between Jupiter and the Sun. The CGI is designed to image exoplanets as point-sources that are about a thousand times fainter than what has been technically possible to date.
To achieve this, all optical components must be very precisely aligned with one another. The Max Planck Institute for Astronomy in Heidelberg has built opto-mechanical components specifically for this purpose, which form the Precision Alignment Mechanisms, or PAM for short. If this system proves successful, it could be used to photograph even smaller and fainter rocky planets, such as Earth, in the future, that orbit other stars.
Max Planck Institute for Astronomy Provides Key Optomechanics
One of six flight models of the Precision Alignment Mechanisms (PAMs) for the Coronagraph Instrument (CGI), a camera aboard the Nancy Grace Roman Space Telescope. The PAMs position and stabilize the optical elements of the CGI during observations.
© O. Krause / MPIA
The Max Planck Institute for Astronomy supplied six flight models of the positioning mechanism – that is, components that are permanently installed in the coronagraph and will be launched into space. Another six engineering models of the PAM are used for ground-based testing. The PAMs are essential for achieving the extreme precision of the optics required to photograph planets orbiting their stars in distant star systems. They ensure that the coronagraph’s built-in masks, as well as its filters and mirrors, tilt by no more than 40 milliarcseconds over an eight-hour period (3.6 million milliarcseconds equal one degree). This corresponds to the angle at which a person in Los Angeles would be perceived when viewed from Heidelberg.
Designers and engineers at the Heidelberg Institute designed the PAM modules and subsequently manufactured and tested them in the institute’s own workshops and laboratories. The company von Hoerner & Sulger from Schwetzingen, Germany, supported the construction. “When the individual parts of the flight model were lying in front of me, it really hit me that I was holding components that would fly into space and explore it,” says Monica Ebert. At the Max Planck Institute in Heidelberg, she oversaw the design and assembly of the mission-critical stabilization system for the instrument optics. “The assembly required utmost concentration.”
A version of the Precision Alignment System by the Max Planck Institute for Astronomy that holds a series of color filters in place. Light from the opposite side is blocked by the filters that appear dark. Infrared light, however, passes through the filters that appear reddish.
© Chris Gunn/ NASA JPL
Among the twelve versions of the PAM-system is also a so-called service-life model. This model was tested for long-term stress and performed over 27,000 movements during the test. This is roughly equivalent to twice the stress placed on a flight model. Through such tests, the teams minimize potential errors and problems with the mechanism installed in the Roman Space Telescope. Once launched, the telescope cannot be reached and repaired, as was possible with Hubble back then.
“The CGI aboard the Roman Space Telescope is the most sophisticated optical observation instrument ever used for research in space,” says Oliver Krause, head of the research group for Infrared Astronomy at the Max Planck Institute for Astronomy. If the initial tests in space are successful, the CGI will be made available to astronomers for the study of exoplanets.
Space-based optics that self-corrects in real time
In order for the CGI to directly image smaller and cooler exoplanets that orbit closer to their host stars than any previously observed, a greater brightness contrast between the star and the planet is needed than it has been possible to date. The challenge, therefore, was to suppress the image artifacts and optical turbulence that have historically dominated images from coronagraphs.
To achieve this, the engineers relied on adaptive optics. This technology is typically used in telescopes on Earth. The Extremely Large Telescope, currently under construction, for example, will change the shape of one of its mirrors a thousand times per second to eliminate the wobble of the starry sky – a phenomenon visible even to the naked eye as the twinkling of the stars. Even though there is no air in space to distort the Roman Telescope’s image, the optical system within the telescope itself is subject to distorting effects. These are suppressed by a small mirror that can be deformed in real time. This requires a great deal of computing power – a resource that is limited on board of a satellite. Solving this problem was therefore considered a challenge in its own right.
“To be able to find and study a second Earth in the future, we’ll need a powerful coronagraph that incorporates the full complexity of CGI,” says Oliver Krause. “Technologically, the CGI is a milestone on the way.” However, this would also require a telescope with significantly higher image resolution, such as the Habitable Worlds Observatory, whose initial designs call for a mirror at least six meters in diameter.
Ready for data from space
Once operations begin, the Max Planck Institute for Astronomy will continue to participate in the development of the data analysis software for the Roman Telescope’s technical and scientific data and will assist in planning and preparing the observations. The measurements themselves are coordinated by a NASA committee known as the Community Participation Program, whose core team also includes Oliver Krause. Shortly after launch, members of the committee – based in the U.S., Japan, and Europe – will gradually bring the telescope online. To do this, they will analyze the data the telescope sends to Earth during its journey to its destination continuously for 24 hours.
In total, the commissioning process will take 90 days – roughly the same amount of time it takes the Roman Space Telescope to reach the Lagrange point L2. The first scientific images are expected in early 2027. However, some of the observation programs themselves will take years to complete, such as the survey of the plane of our Milky Way in search of previously unknown planets and black holes.
Background Information
Oliver Krause and his team have been gradually shipping these core components of the instrument to the Jet Propulsion Laboratory (JPL) at the California Institute of Technology (Caltech) in the United States since 2022. JPL is part of NASA and is responsible for the technical development of space probes. On May 19, 2024, JPL in turn delivered the completed coronagraph (CGI) to NASA’s Goddard Space Flight Center. There, teams installed the instrument into the telescope and subjected it to further extensive functional and stress tests.
The Max Planck Institute for Astronomy (MPIA) is a direct partner of NASA and JPL in the CGI project. Not least, the outstanding achievements in the design and fabrication of the mechanisms for NIRSpec and MIRI-the James Webb Space Telescope’s primary scientific instruments-have impressed NASA and JPL. NIRSpec and MIRI have been delivering spectacular images and data since mid-2022.
The CGI team at MPIA consists of Oliver Krause (PAM project manager), Friedrich Müller (systems engineer and assembly manager), Monica Ebert (design and assembly), Ralf-Rainer Rohloff (design and component selection), Christopher Ritz (design and assembly), Armin Böhm (head of the precision mechanics workshop), Tobias Stadler and colleagues from the precision mechanics workshop (manufacturing of mechanical parts), Lars Mohr and Frank Whrel (electronics workshop-PAM EGSE construction), Ulrich Klaas (deputy project manager and documentation), Clemens Plank (Project Manager in 2021 and 2022), Christopher Lee (Project Manager in 2020), Theodoros Anagnos (Test Engineer and Test Automation), and Arnim Wolf (Purchasing and Shipping).
