On the Path to Discovering a Second Earth
/ Press release from the Max Planck Institute for Solar System Research
astronews.com
August 15, 2024
In Heidelberg, central optical components for the Coronagraph Instrument of the Nancy Grace Roman Space Telescope have been developed and are now being handed over to NASA at the Jet Propulsion Laboratory. The instrument will be used to test an innovative camera design that could provide the first direct evidence of a second Earth.
The Nancy Grace Roman space telescope (formerly known as WFIRST) has been in development for about a decade under NASA’s guidance. The main mirror measures 2.4 meters in diameter, mirroring the Hubble Space Telescope’s mirror. For one of its two scientific instruments, the Coronagraph Instrument (CGI), the Max Planck Institute for Astronomy (MPIA) in Heidelberg, led by Oliver Krause, constructed key opto-mechanical components. The CGI represents a technical study aimed at testing a new measurement design for detecting exoplanets through direct imaging. If it successfully images gas giants similar to Jupiter near their parent stars as points of light, this method could be employed by future space telescopes to detect and study rocky planets like Earth.
The MPIA provided six flight models and six additional engineering models of the Precision Alignment Mechanisms (PAM), which align and stabilize optical components such as mirrors and filters for the CGI observations. These components were designed by engineers at the MPIA and manufactured and tested in their workshops and laboratories, with support from von Hoerner & Sulger of Schwetzingen. Oliver Krause, head of the infrared space astronomy research group, and his team have been gradually delivering these essential CGI components to the Jet Propulsion Laboratory (JPL) at the California Institute of Technology (CalTech) in Pasadena, USA. The JPL is part of NASA and plays a key role in the technical development of space probes.
The MPIA is a direct partner of NASA and JPL in the CGI project. Their outstanding achievements in designing and manufacturing mechanisms for NIRSpec and MIRI, the central measuring instruments of the James Webb space telescope, greatly impressed NASA and JPL. NIRSpec and MIRI have been providing spectacular images and data since mid-2022. The PAM flight models have already been installed in the CGI for space use and thoroughly tested. The identical engineering models are being used to verify the specifications on the ground, including a lifetime model that has already undergone over 27,000 movements. This is about twice the load experienced by a flight model during ground tests and the mission in space. Another milestone was the delivery of the CGI to NASA’s Goddard Space Flight Center on May 19, 2024. There, the instrument will be integrated into the telescope and undergo further extensive functional and stress testing.
The CGI is the first instrument to combine two common observation techniques for space applications: coronagraphy and adaptive optics. Coronagraphs use special masks to block bright objects, allowing fainter celestial bodies in their vicinity to become visible. This method is currently used to detect exoplanets through direct imaging. However, the masks can create significant image artifacts, restricting reliable detection of potential exoplanets reflecting their parent star’s light to relatively large distances. Consequently, astronomers predominantly discover giant gas planets, similar to Jupiter, orbiting far from their central star. To detect smaller planets with closer orbits, minimizing these artifacts is crucial.
To address this challenge, the CGI incorporates adaptive optics, which enhances brightness contrast between the star and the planet. This technology is typically employed in ground-based telescopes to reduce atmospheric turbulence effects. In the CGI, it minimizes interference from the optical system of the telescope. However, the computational power required presents new challenges for space cameras. Overall, this combination should allow scientists to visualize exoplanets like never before, as bright points of light near their bright parent stars. The CGI is specifically designed to detect a planet whose parent star is a billion times brighter—comparable to the brightness difference between Jupiter and the Sun. This marks an improvement of up to a thousand times over current capabilities. A built-in spectrograph will then enable researchers to study these planets’ atmospheric composition.
To achieve this, the PAMs manufactured by the MPIA must provide an extraordinarily high level of accuracy and stability in positioning optical elements such as filters, coronagraphs, and mirrors over extended periods. During operation, the PAMs may tilt by no more than 40 milliarcseconds over eight hours (3.6 million milliarcseconds make up one degree). This corresponds to the angle needed to see a person’s size in Los Angeles from Heidelberg. These exacting requirements and the complexity of the CGI make it the most intricate and costly scientific instrument ever to be placed in space. If the initial tests in space are successful, the CGI will be available to astronomers for exoplanet research.
Should the CGI mission succeed, the applied technology could be further refined for future space telescopes, such as the Habitable Worlds Observatory. Directly imaging a second Earth would then become achievable. The Roman Space Telescope, initially named WFIRST (Wide-Field Infrared Survey Telescope), honors astronomer Nancy Grace Roman, who led NASA’s astronomical research programs for decades, including overseeing the scientific planning for the Hubble space telescope. The launch of the Roman telescope is scheduled for 2027.
On the Way to Discovering the Second Earth
In Heidelberg, central optical elements for the Coronagraph Instrument of the Nancy Grace Roman Space Telescope
have been developed and are now at the Jet Propulsion Laboratory, handed over to NASA. The instrument will be used to test
an innovative camera design that has the potential to provide the first direct evidence of a second Earth.
The Development of the Nancy Grace Roman Space Telescope
The Nancy Grace Roman Space Telescope (formerly WFIRST) has been under development for about a decade under the direction of NASA.
With a main mirror diameter of 2.4 meters, it mirrors the Hubble Space Telescope’s capabilities. The Max Planck Institute for Astronomy (MPIA),
led by Oliver Krause, played a pivotal role in developing key optical components for the Coronagraph Instrument (CGI). This instrument represents
a groundbreaking study to test a new measurement design for direct imaging of exoplanets, with the goal of identifying rocky planets similar to Earth.
Precision Alignment Mechanisms (PAM)
MPIA has supplied six flight models and six engineering models of the Precision Alignment Mechanisms (PAM) that align and stabilize
optical components such as mirrors and filters for the CGI. These mechanisms have undergone extensive testing and are crucial for the
accuracy needed in space observations.
Collaboration with NASA and JPL
The MPIA is a direct partner of NASA and JPL in developing the CGI project. After impressive performance with the NIRSpec and MIRI
instruments for the James Webb Space Telescope, NASA was confident in MPIA’s capabilities. The PAM flight models are installed and
extensively tested for functionality in various conditions.
Understanding Coronagraphy and the CGI
The CGI combines coronagraphy and adaptive optics to enhance the direct imaging of exoplanets. Coronagraphs mask bright objects to make
fainter celestial bodies visible. While effective, this method generates image artifacts that pose limitations on detecting smaller planets
close to their stars.
Adaptive Optics Technology
To counteract potential issues with image clarity, the CGI incorporates adaptive optics. This technology minimizes interference and
increases contrast, allowing for superior visibility of exoplanets—potentially revealing planets that are billion times fainter than the
bright light of their parent stars.
Unprecedented Detection Capabilities
The CGI’s groundbreaking technology aims to achieve an accuracy of position adjustments to within 40 milliarcseconds over extended
periods. This incredible precision allows detection abilities that can efficiently manage high-contrast scenarios, opening the door to
discovering smaller exoplanets that share basic characteristics with Earth.
Milestones and Future Potential
If successful, the CGI mission will pave the way for future advancements in exoplanet observation technologies, with aspirations to
refine methods used in the anticipated Habitable Worlds Observatory. The Roman Space Telescope’s launch is slated for 2027,
promising exciting opportunities for astronomical research.
Technology Impact on Astronomy
The implications of the CGI and its innovative approach could transform our understanding of exoplanets. By enabling scientists to
directly image Earth-like planets in habitable zones, humanity stands on the threshold of finding potential new homes beyond our solar system.
Key Specifications of the CGI
| Specification | Description |
|---|---|
| Primary Mirror Diameter | 2.4 meters |
| Precision Alignment | 40 milliarcseconds |
| Detection Contrast | 1 billion times brighter star |
| Planned Launch | 2027 |
| Exoplanet Detection Goals | Rocky planets similar to Earth |
The Legacy of Nancy Grace Roman
Named after astronomer Nancy Grace Roman, who was pivotal in the scientific planning of the Hubble Space Telescope and subsequent
astronomical research programs, the Nancy Grace Roman Space Telescope embodies her legacy of exploration and discovery in astrophysics.
