Nav: Home

Innovative planet-finding technology passes another hurdle

November 12, 2015

A potentially revolutionary instrument now being developed to first find Earth-like planets in other solar systems and then study their atmospheres to identify chemical signatures of life has just passed another technological hurdle that makes it an even stronger contender for a future astrophysics mission.

The instrument, called the Visible Nulling Coronagraph (VNC), combines an interferometer with a coronagraph -- in itself a first. It's well on its way to demonstrating operations over a broader spectral range, including the ultraviolet, visible, and near-infrared bands, said Brian Hicks, a fellow with NASA's Postdoctoral Program who is working with VNC Principal Investigators Rick Lyon and Mark Clampin, who are scientists at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

"The VNC is demonstrating the spectral range needed for planet characterization," Hicks said. "It will be more sensitive for finding fainter planets. It also will enable spectroscopy, which is what NASA will need to study the atmospheres of exoplanets to identify signatures of water, oxygen, carbon dioxide, methane, and ozone -- the chemistry we associate with habitability for life as we know it."

Currently, the Kepler Observatory uses indirect means to detect exoplanets, as will the James Webb Space Telescope and the Transiting Exoplanet Survey Satellite in the future.

The next logical step is direct detection using a next-generation space observatory equipped with highly sophisticated instruments, including a coronagraph or occulting star shade that would block starlight and allow the observatory to directly image faint Earth-like exoplanets.

The VNC, which Clampin and Lyon started developing nearly six years ago, is ideally suited to this task. Its pupil-based technique for separating star from planet light is naturally compatible with segmented or arbitrarily shaped telescope mirrors, similar to the one that will form the heart of the Webb Observatory. Such a mirror folds up for launch and then unfolds once the observatory reaches its orbital destination.

Instead of using internal masks and or an external occulter to block starlight -- techniques employed by more traditional coronagraphs -- the VNC relies on a two-armed interferometer that splits and then recombines collected light. Under this concept, starlight gathered by the observatory's primary, segmented mirror travels down the VNC's optical path to the first of two beamsplitters, which transmits light into one arm and reflects light into the other interferometer arm.

After traversing both arms, the light encounters a second beamsplitter that recombines the light to create two output paths known as the "bright" and "dark" channels. Starlight passes to the bright channel and planet light to the dark.

However, creating these two channels couldn't be possible without a technology called the multiple mirror array (MMA). This device, comprised of 163 tiny individual mirror segments that each measure about the width of six average human hairs and are perched atop tiny finger-like devices that allow them to piston, tip and tilt up to thousands of times per second, is placed in the interferometer arm that receives reflected light.

The MMA's job is to correct errors. It first senses and then corrects wavefront errors caused by vibration, dust, and thermal changes that prevent the bright starlight, collected by the primary mirror, from being perfectly "nulled" -- in other words, ultimately canceled in the dark channel.

A spectrograph and imager then would analyze the dark-channel light to determine the planet's physical properties.

Rhombs Provide Solution

In testing with the VNC testbed, the technique proved that it could achieve nearly billion-to-one contrast, but over a narrow band in the visible spectrum. "This first milestone still stands as the deepest contrast ever achieved with a nulling coronagraph," Lyon said, adding that this achievement was made possible by engineers Udayan Mallik, who set up all computer interfacing to control the devices, and Pete Petrone, who built the VNC hardware and optics. "It also clearly demonstrated nulling with a segmented aperture -- another significant milestone."

The team now is increasing VNC's sensitivity over a broader spectral range needed to detect and characterize Earth-like planets.

The group incorporated two pairs of identical prisms into both interferometer arms. These "squashed" rectangular-shaped, highly polished prisms, known as Fresnel rhombs, produce polarizing reflections -- similar to what happens to sunlight that reaches your eyes after reflecting off cars or pavement. "While this scattered light reduces contrast when driving without wearing sunglasses, the polarization effect is actually helpful in the VNC," Hicks said.

"The polarization effect achieved through the rhombs is something that can be used to make starlight suppression with the VNC work at high contrast over a broad spectral range," Hicks said. "Now we are working to demonstrate the instrument with 40 times the bandwidth," he added.

But the addition of the rhombs isn't the only new technology the team is pursuing to cement its possible inclusion in a next-generation mission.

Lyon, Clampin, Hicks, and others on the team received NASA technology-development funds to demonstrate the VNC on an actual segmented optical testbed, called the Segmented Aperture Interferometric Nulling Testbed, or SAINT for short, Lyon said. The work will begin in October.

Goddard engineer Matt Bolcar, Hicks, and Lyon also have received additional NASA funding to investigate the use of freeform optics, an emerging optics technology that allows light-gathering devices to take almost any shape, potentially providing improved image quality over a larger field of view -- all in a smaller package.

"One of the primary advantages of freeform optics is that they can reduce the total number of elements needed for a flight VNC. Most importantly, this would improve throughput, among other things," Lyon said. "By custom tailoring the shape of the optics we may achieve a wider field of view."

"Each of these is a significant improvement and could make the VNC a game changer when it comes to designing the future mission that will have characterizing exoplanets as one of its top priorities," Hicks said. "The goal is to use the improvements and the enabling technologies to make the VNC an even better choice for yielding the greatest science return."

For more Goddard technology news, go to https://gsfctechnology.gsfc.nasa.gov/newsletter/Current.pdf
-end-


NASA/Goddard Space Flight Center

Related Technology Articles:

How technology use affects at-risk adolescents
More use of technology led to increases in attention, behavior and self-regulation problems over time for adolescents already at risk for mental health issues, a new study from Duke University finds.
Hold-up in ventures for technology transfer
The transfer of technology brings ideas closer to commercialization. The transformation happens in several steps, such as invention, innovation, building prototypes, production, market introduction, market expansion, after sales services.
The ultimate green technology
Imagine patterning and visualizing silicon at the atomic level, something which, if done successfully, will revolutionize the quantum and classical computing industry.
New technology detects COPD in minutes
Pioneering research by Professor Paul Lewis of Swansea University's Medical School into one of the most common lung diseases in the UK, Chronic Obstructive Pulmonary Disease, has led to the development of a new technology that can quickly and easily diagnose and monitor the condition.
New technology for powder metallurgy
Tecnalia leads EFFIPRO (Energy EFFIcient PROcess of Engineering Materials) project, which shows a new manufacturing process using powder metallurgy.
New milestone in printed photovoltaic technology
A team of researchers at Friedrich-Alexander-Universit├Ąt have achieved an important milestone in the quest to develop efficient solar technology as an alternative to fossil fuels.
Gene Drive Technology: Where is the future?
For this episode of BioScience Talks, we're joined by Gene Drive Committee co-chair James P.
Could Hollywood technology help your health?
The same technology used by the entertainment industry to animate characters such as Gollum in 'The Lord of The Rings' films, will be used to help train elite athletes, for medical diagnosis and even to help improve prosthetic limb development, in a new research center at the University of Bath launched today.
Assessing carbon capture technology
Carbon capture and storage could be used to mitigate greenhouse gas emissions and thus ameliorate their impact on climate change.
New technology for dynamic projection mapping
It has been thought technically difficult to achieve projection mapping onto a moving/rotating object so that images look as though they are fixed to the object.

Related Technology Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".