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By NASA
Advancing Single-Photon Sensing Image Sensors to Enable the Search for Life Beyond Earth
A NASA-sponsored team is advancing single-photon sensing Complementary Metal-Oxide-Semiconductor (CMOS) detector technology that will enable future NASA astrophysics space missions to search for life on other planets. As part of their detector maturation program, the team is characterizing sensors before, during, and after high-energy radiation exposure; developing novel readout modes to mitigate radiation-induced damage; and simulating a near-infrared CMOS pixel prototype capable of detecting individual photons.
Single-photon sensing and photon-number resolving CMOS image sensors: a 9.4 Mpixel sensor (left) and a 16.7 Mpixel sensor (right). Credit: CfD, RIT Are we alone in the universe? This age-old question has inspired scientific exploration for centuries. If life on other planets evolves similarly to life on Earth, it can imprint its presence in atmospheric spectral features known asbiosignatures. They include absorption and emission lines in the spectrum produced by oxygen, carbon dioxide, methane, and other molecules that could indicate conditions which can support life. A future NASA astrophysics mission, the Habitable Worlds Observatory (HWO), will seek to find biosignatures in the ultraviolet, optical, and near-infrared (NIR) spectra of exoplanet atmospheres to look for evidence that life may exist elsewhere in the universe.
HWO will need highly sensitive detector technology to detect these faint biosignatures on distant exoplanets. The Single-Photon Sensing Complementary Metal-Oxide-Semiconductor (SPSCMOS) image sensor is a promising technology for this application. These silicon-based sensors can detect and resolve individual optical-wavelength photons using a low-capacitance, high-gain floating diffusion sense node. They operate effectively over a broad temperature range, including at room temperature. They have near-zero read noise, are tolerant to radiation, and generate very little unwanted signal—such as dark current. When cooled to 250 K, the dark current drops to just one electron every half-hour. If either the read noise or dark current is too high, the sensor will fail to detect the faint signals that biosignatures produce.
A research team at the Rochester Institute of Technology (RIT) Center for Detectors (CfD) is accelerating the readiness of these SPSCMOS sensors for use in space missions through detector technology maturation programs funded by NASA’s Strategic Astrophysics Technology and Early Stage Innovations solicitations. These development programs include several key goals:
Characterize critical detector performance metrics like dark current, quantum efficiency, and read noise before, during, and after exposure to high-energy radiation Develop new readout modes for these sensors to mitigate effects from short-term and long-term radiation damage Design a new NIR version of the sensor using Technology Computer-Aided Design (TCAD) software SPSCMOS sensors operate similarly to traditional CMOS image sensors but are optimized to detect individual photons—an essential capability for ultra-sensitive space-based observations, such as measuring the gases in the atmospheres of exoplanets. Incoming photons enter the sensor and generate free charges (electrons) in the sensor material. These charges collect in a pixel’s storage well and eventually transfer to a low-capacitance component called the floating diffusion (FD) sense node where each free charge causes a large and resolved voltage shift. This voltage shift is then digitized to read the signal.
Experiments that measure sensor performance in a space relevant environment use a vacuum Dewar and a thermally-controlled mount to allow precise tuning of the sensors temperature. The Dewar enables testing at conditions that match the expected thermal environment of the HWO instrument, and can even cool the sensor and its on-chip circuits to temperatures colder than any prior testing reported for this detector family. These tests are critical for revealing performance limitations with respect to detector metrics like dark current, quantum efficiency, and read noise. As temperatures change, the electrical properties of on-chip circuits can also change, which affects the read out of charge in a pixel.
The two figures show results for SPSCMOS devices. The figure on the left shows a photon counting histogram with peaks that correspond to photon number. The figure on the right shows the dark current for a SPSCMOS device before and after exposure to 50 krad of 60 MeV protons. Credit: CfD, RIT The radiation-rich environment for HWO will cause temporary and permanent effects in the sensor. These effects can corrupt the signal measured in a pixel, interrupt sensor clocking and digital logic, and can cause cumulative damage that gradually degrades sensor performance. To mitigate the loss of detector sensitivity throughout a mission lifetime, the RIT team is developing new readout modes that are not available in commercial CMOS sensors. These custom modes sample the signal over time (a “ramp” acquisition) to enable the detection and removal of cosmic ray artifacts. In one mode, when the system identifies an artifact, it segments the signal ramp and selectively averages the segments to reconstruct the original signal—preserving scientific data that would otherwise be lost. In addition, a real-time data acquisition system monitors the detector’s power consumption, which may change from the accumulation of damage throughout a mission. The acquisition system records these shifts and communicates with the detector electronics to adjust voltages and maintain nominal operation. These radiation damage mitigation strategies will be evaluated during a number of test programs at ground-based radiation facilities. The tests will help identify unique failure mechanisms that impact SPSCMOS technology when it is exposed to radiation equivalent to the dose expected for HWO.
Custom acquisition electronics (left) that will control the sensors during radiation tests, and an image captured using this system (right). Credit: CfD, RIT While existing SPSCMOS sensors are limited to detecting visible light due to their silicon-based design, the RIT team is developing the world’s first NIR single-photon photodiode based on the architecture used in the optical sensors. The photodiode design starts as a simulation in TCAD software to model the optical and electrical properties of the low-capacitance CMOS architecture. The model simulates light-sensitive circuits using both silicon and Mercury Cadmium Telluride (HgCdTe or MCT) material to determine how well the pixel would measure photo-generated charge if a semiconductor foundry physically fabricated it. It has 2D and 3D device structures that convert light into electrical charge, and circuits to control charge transfer and signal readout with virtual probes that can measure current flow and electric potential. These simulations help to evaluate the key mechanisms like the conversion of light into electrons, storing and transferring the electrons, and the output voltage of the photodiode sampling circuit.
In addition to laboratory testing, the project includes performance evaluations at a ground-based telescope. These tests allow the sensor to observe astronomical targets that cannot be fully replicated in lab. Star fields and diffuse nebulae challenge the detector’s full signal chain under real sky backgrounds with faint flux levels, field-dependent aberrations, and varying seeing conditions. These observations help identify performance limitations that may not be apparent in controlled laboratory measurements.
In January 2025, a team of researchers led by PhD student Edwin Alexani used an SPSCMOS-based camera at the C.E.K. Mees Observatory in Ontario County, New York. They observed star cluster M36 to evaluate the sensor’s photometric precision, and the Bubble Nebula in a narrow-band H-alpha filter. The measured dark current and read noise were consistent with laboratory results.
The team observed photometric reference stars to estimate the quantum efficiency (QE) or the ability for the detector to convert photons into signal. The calculated QE agreed with laboratory measurements, despite differences in calibration methods.
The team also observed the satellite STARLINK-32727 as it passed through the telescope’s field of view and measured negligible persistent charge—residual signal that can remain in detector pixels after exposure to a bright source. Although the satellite briefly produced a bright streak across several pixels due to reflected sunlight, the average latent charge in affected pixels was only 0.03 e–/pix – well below both the sky-background and sensor’s read noise.
Images captured at the C.E.K. Mees Observatory. Left: The color image shows M36 in the Johnson color filters B (blue), V (green), and R (red) bands (left). Right: Edwin Alexani and the SPSCMOS camera (right). Credit: : CfD, RIT As NASA advances and matures the HWO mission, SPSCMOS technology promises to be a game-changer for exoplanet and general astrophysics research. These sensors will enhance our ability to detect and analyze distant worlds, bringing us one step closer to answering one of humanity’s most profound questions: are we alone?
For additional details, see the entry for this project on NASA TechPort.
Project Lead(s): Dr. Donald F. Figer, Future Photon Initiative and Center for Detectors, Rochester Institute of Technology (RIT), supported by engineer Justin Gallagher and a team of students.
Sponsoring Organization(s): NASA Astrophysics Division, Strategic Astrophysics Technology (SAT) Program and NASA Space Technology Mission Directorate (STMD), Early Stage Innovations (ESI) Program
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Last Updated Sep 02, 2025 Related Terms
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Written by Michael Allen
An international team of astronomers using NASA’s IXPE (Imaging X-ray Polarimetry Explorer), has challenged our understanding of what happens to matter in the direct vicinity of a black hole.
With IXPE, astronomers can study incoming X-rays and measure the polarization, a property of light that describes the direction of its electric field.
The polarization degree is a measurement of how aligned those vibrations are to each other. Scientists can use a black hole’s polarization degree to determine the location of the corona – a region of extremely hot, magnetized plasma that surrounds a black hole – and how it generates X-rays.
This illustration of material swirling around a black hole highlights a particular feature, called the “corona,” that shines brightly in X-ray light. In this depiction, the corona can be seen as a purple haze floating above the underlying accretion disk, and extending slightly inside of its inner edge. The material within the inner accretion disk is incredibly hot and would glow with a blinding blue-white light, but here has been reduced in brightness to make the corona stand out with better contrast. Its purple color is purely illustrative, standing in for the X-ray glow that would not be obvious in visible light. The warp in the disk is a realistic representation of how the black hole’s immense gravity acts like an optical lens, distorting our view of the flat disk that encircles it. NASA/Caltech-IPAC/Robert Hurt In April, astronomers used IXPE to measure a 9.1% polarization degree for black hole IGR J17091-3624, much higher than they expected based on theoretical models.
“The black hole IGR J17091-3624 is an extraordinary source which dims and brightens with the likeness of a heartbeat, and NASA’s IXPE allowed us to measure this unique source in a brand-new way.” said Melissa Ewing, the lead of the study based at Newcastle University in Newcastle upon Tyne, England.
In X-ray binary systems, an extremely dense object, like a black hole, pulls matter from a nearby source, most often a neighboring star. This matter can begin to swirl around, flattening into a rotating structure known as an accretion disc.
The corona, which lies in the inner region of this accretion disc, can reach extreme temperatures up to 1.8 billion degrees Fahrenheit and radiate very luminous X-rays. These ultra-hot coronas are responsible for some of the brightest X-ray sources in the sky.
Despite how bright the corona is in IGRJ17091-364, at some 28,000 light-years from Earth, it remains far too small and distant for astronomers to capture an image of it.
“Typically, a high polarization degree corresponds with a very edge-on view of the corona. The corona would have to be perfectly shaped and viewed at just the right angle to achieve such a measurement,” said Giorgio Matt, professor at the University of Roma Tre in Italy and a co-author on this paper. “The dimming pattern has yet to be explained by scientists and could hold the keys to understanding this category of black holes.”
The stellar companion of this black hole isn’t bright enough for astronomers to directly estimate the system’s viewing angle, but the unusual changes in brightness observed by IXPE suggest that the edge of the accretion disk was directly facing Earth.
The researchers explored different avenues to explain the high polarization degree.
In one model, astronomers included a “wind” of matter lifted from the accretion disc and launched away from the system, a rarely seen phenomenon. If X-rays from the corona were to meet this matter on their way to IXPE, Compton scattering would occur, leading to these measurements.
Fast Facts
Polarization measurements from IXPE carry information about the orientation and alignment of emitted X-ray light waves. The high the degree of polarization, the more the X-ray waves are traveling in sync. Most polarization in the corona come from a process known as Compton scattering, where light from the accretion disc bounces off the hot plasma of the corona, gaining energy and aligning to vibrate in the same direction. “These winds are one of the most critical missing pieces to understand the growth of all types of black holes,” said Maxime Parra, who led the observation and works on this topic at Ehime University in Matsuyama, Japan. “Astronomers could expect future observations to yield even more surprising polarization degree measurements.”
Another model assumed the plasma in the corona could exhibit a very fast outflow. If the plasma were to be streaming outwards at speeds as high as 20% the speed of light, or roughly 124 million miles per hour, relativistic effects could boost the observed polarization.
In both cases, the simulations could recreate the observed polarization without a very specific edge-on view. Researchers will continue to model and test their predictions to better understand the high polarization degree for future research efforts.
More about IXPE
IXPE, which continues to provide unprecedented data enabling groundbreaking discoveries about celestial objects across the universe, is a joint NASA and Italian Space Agency mission with partners and science collaborators in 12 countries. IXPE is led by NASA’s Marshall Space Flight Center in Huntsville, Alabama. BAE Systems, Inc., headquartered in Falls Church, Virginia, manages spacecraft operations together with the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder.
Learn more about IXPE’s ongoing mission here:
https://www.nasa.gov/ixpe
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Last Updated Aug 12, 2025 EditorBeth RidgewayContactCorinne Edmistoncorinne.m.edmiston@nasa.govLocationMarshall Space Flight Center Related Terms
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By NASA
An artist’s concept of the Moon (right) and Mars (center) against the starry expanse of space. A sliver of the Earth’s horizon can be seen in the foreground.Credit: NASA NASA is accepting U.S. submissions for the second phase of the agency’s LunaRecycle Challenge, a Moon-focused recycling competition. The challenge aims to develop solutions for recycling common trash materials – like fabrics, plastics, foam, and metals – that could accumulate from activities such as system operations, industrial activities, and building habitats in deep space.
Phase 2 of the LunaRecycle Challenge is divided into two levels: a milestone round and the final round. Submissions for the milestone round are open until January 2026, with finalists from that round announced in February. Up to 20 finalists from the milestone round will compete in the challenge’s in-person prototype demonstrations and final judging, slated for the following August. Cash prizes totaling $2 million are available for successful solutions in both rounds.
“NASA is eager to see how reimagining these materials can be helpful to potential future planetary surface missions,” said Jennifer Edmunson, acting program manager for Centennial Challenges at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “I’m confident focusing on the most critical trash items – and integration of the prototype and digital twin competition tracks – will yield remarkable solutions that could enable a sustainable human presence off-Earth and transform the future of space exploration.”
Estimates indicate a crew of four astronauts could generate more than 2,100 kilograms (4,600 pounds) of single-use waste – including food packaging, plastic films, foam packaging, clothing, and more – within 365 days. Successful solutions in LunaRecycle’s Phase 2 should manage realistic trash volumes while minimizing resource inputs and crew time and operating safely with minimal hazards.
Phase 2 is only open to U.S. individuals and teams. Participants can submit solutions regardless of whether they competed in the earlier Phase 1 competition.
All Phase 2 participants are expected to build a physical prototype. In addition, participants can submit a digital twin of their prototype for additional awards in the milestone and final rounds.
The LunaRecycle Challenge is a NASA Centennial Challenge, part of the Prizes, Challenges and Crowdsourcing Program within NASA’s Space Technology Mission Directorate. LunaRecycle Phase 1 received record-breaking interest from the global innovator community. The challenge received more than 1,200 registrations – more than any competition in the 20-year history of Centennial Challenges – and a panel of 50 judges evaluated nearly 200 submissions. Seventeen teams were selected as Phase 1 winners, representing five countries and nine U.S. states. Winners were announced via livestream on NASA Marshall’s YouTube channel.
LunaRecycle is managed at NASA Marshall with subject matter experts primarily at the center, as well as NASA’s Kennedy Space Center in Florida and NASA’s Ames Research Center in California’s Silicon Valley. NASA, in partnership with The University of Alabama College of Engineering, manages the challenge with coordination from former Centennial Challenge winner AI SpaceFactory and environmental sustainability industry member Veolia.
To learn more about LunaRecycle’s second phase, including registration for upcoming webinars, visit:
https://www.nasa.gov/lunarecycle
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Jasmine Hopkins
NASA Headquarters, Washington
321-432-4624
jasmine.s.hopkins@nasa.gov
Taylor Goodwin
Marshall Space Flight Center, Huntsville, Ala.
256-544-0034
taylor.goodwin@nasa.gov
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Last Updated Aug 11, 2025 LocationNASA Headquarters Related Terms
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By NASA
Science: NASA, ESA, CXC, Yi-Chi Chang (National Tsing Hua University); Image Processing: Joseph DePasquale (STScI) NASA’s Hubble Space Telescope and NASA’s Chandra X-ray Observatory teamed up to identify a new possible example of a rare class of black holes, identified by X-ray emission (in purple) in this image released on July 24, 2025. Called NGC 6099 HLX-1, this bright X-ray source seems to reside in a compact star cluster in a giant elliptical galaxy. These rare black holes are called intermediate-mass black holes (IMBHs) and weigh between a few hundred to a few 100,000 times the mass of our Sun.
Learn more about IMBHs and what studying them can tell us about the universe.
Image credit: Science: NASA, ESA, CXC, Yi-Chi Chang (National Tsing Hua University); Image Processing: Joseph DePasquale (STScI)
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