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Illustration of an exoplanet near its star

Despite the pandemic, staff at STScI’s Russell B. Makidon Optics Laboratory continued their work to advance state-of-the-art tools for future flagship missions.

A central orange circle is encircled by yellow and purple, on an orange and purple background
A processed image, like this one, is the output of the lab’s High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed. It shows an image of an artificial star that is blocked by a coronagraph at the center. The starlight has been almost canceled out in the circular purple area. This is where potential planets could be identified. In this case, the light is from a wide range of wavelengths, known as broadband light, which is necessary to study Earth-like planets around distant stars.

Good planning pays off: Since scientists at the institute’s Russell B. Makidon Optics Lab know they have to be prepared to run experiments in an empty lab (to ensure complete darkness) at any hour of the day, they were already well prepared to begin working remotely in March. Throughout the year, staff added several refinements to make it even easier to execute experiments through remote control.

The lab’s work centers on advancing technologies for future generations of segmented space telescopes, in particular in the areas of optical mirror alignment, wavefront sensing and control, and coronagraphy needed to capture images of distant worlds. To do this on a small scale, staff run experiments on testbeds in rooms that are completely sealed off from any light sources to mimic the conditions in space.

This year, staff also coordinated with their partners and several scientists at other institutions whose labs were closed due to COVID-19, providing more opportunities for them to use the lab to continue their own experiments. This allowed our staff to work with scientists outside the Baltimore region and increase their international collaborations. One graduate student in particular joined to continue her experiments in support of her PhD projects.

Significant Strides in the Lab’s Performance

Staff in the lab work to improve how telescopes with an instrument known as a coronagraph block starlight, which help researchers study a range of phenomena, like the dusty disks around stars or planets that orbit a star. To do so, they’ve set up tabletop experiments: miniature versions of telescope mirrors with lasers acting as starlight to test the requirements and limits for these instruments and procedures, and manipulate light with deformable mirrors.

This year, the Optics Lab team made important advancements in coronagraphy using the lab’s High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed. Their 2019 achievement was blocking all light but 1 part in 10 million in one wavelength of light. They surpassed this in 2020 by achieving a light suppression of 5 parts in 100 million for single wavelengths of light. Next, they added a new factor to the experiment by controlling for broadband light, which includes multiple wavelengths, and blocking all light but 1 part in 10 million for these experiments.

Another project addressed improvements to wavefront sensing and control, which are techniques that sense and correct for light distortions introduced by imperfect or misaligned telescope optics. Specifically, a collaborator from Princeton demonstrated a contrast steadiness of 5 parts in 100 million while actively introducing disturbances to the experiment. These are essential improvements since natural thermal drift occurs for all space-based telescopes. This issue is similar to what the upcoming Nancy Grace Roman Space Telescope will encounter at its eventual position about 1 million miles (1.5 million kilometers) from Earth. Small disturbances or temperature changes within the telescope will impact the ability of its instruments to maintain a dark zone. By using its small deformable mirrors in the light path within the telescope, scientists can counteract these small disturbances and consistently maintain the dark zone.

Finally, the Optics Lab team, which is able to periodically access the lab at the institute, installed a segmented deformable mirror on the HiCAT testbed—the only fully segmented, optical testbed dedicated to this problem. The lab’s many collaborators will work to recalibrate the fully segmented testbed to include a dark zone for the new experiment in the upcoming year. These tests are a critical step in the global effort to discover Earth-like exoplanets.