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Comparison of a WFPC2 Thermal Vacuum Globular Cluster-Mask Image to Wfpc1
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By European Space Agency
The second of the Meteosat Third Generation Imagers, MTG-I2, has passed some important milestones in the cleanroom facilities at Thales Alenia Space in Cannes, southern France.
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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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By NASA
X-ray: NASA/CXC/Univ. of Hong Kong/S. Zhang et al.; Radio: ATNF/CSIRO/ATCA; H-alpha: UK STFC/Royal Observatory Edinburgh; Image Processing: NASA/CXC/SAO/N. Wolk In 2009, NASA’s Chandra X-ray Observatory released a captivating image: a pulsar and its surrounding nebula that is shaped like a hand.
Since then, astronomers have used Chandra and other telescopes to continue to observe this object. Now, new radio data from the Australia Telescope Compact Array (ATCA), has been combined with Chandra’s X-ray data to provide a fresh view of this exploded star and its environment, to help understand its peculiar properties and shape.
At the center of this new image lies the pulsar B1509-58, a rapidly spinning neutron star that is only about 12 miles in diameter. This tiny object is responsible for producing an intricate nebula (called MSH 15-52) that spans over 150 light-years, or about 900 trillion miles. The nebula, which is produced by energetic particles, resembles a human hand with a palm and extended fingers pointing to the upper right in X-rays.
Labeled Version of the ImageX-ray: NASA/CXC/Univ. of Hong Kong/S. Zhang et al.; Radio: ATNF/CSIRO/ATCA; H-alpha: UK STFC/Royal Observatory Edinburgh; Image Processing: NASA/CXC/SAO/N. Wolk The collapse of a massive star created the pulsar when much of the star crashed inward once it burned through its sustainable nuclear fuel. An ensuing explosion sent the star’s outer layers outward into space as a supernova.
The pulsar spins around almost seven times every second and has a strong magnetic field, about 15 trillion times stronger than the Earth’s. The rapid rotation and strong magnetic field make B1509-58 one of the most powerful electromagnetic generators in the Galaxy, enabling it to drive an energetic wind of electrons and other particles away from the pulsar, creating the nebula.
In this new composite image, the ATCA radio data (represented in red) has been combined with X-rays from Chandra (shown in blue, orange and yellow), along with an optical image of hydrogen gas (gold). The areas of overlap between the X-ray and radio data in MSH 15-52 show as purple. The optical image shows stars in the field of view along with parts of the supernova’s debris, the supernova remnant RCW 89. A labeled version of the figure shows the main features of the image.
Radio data from ATCA now reveals complex filaments that are aligned with the directions of the nebula’s magnetic field, shown by the short, straight, white lines in a supplementary image. These filaments could result from the collision of the pulsar’s particle wind with the supernova’s debris.
Complex Filaments Aligned with the Directions of the Nebula’s Magnetic FieldX-ray: NASA/CXC/Univ. of Hong Kong/S. Zhang et al.; Radio: ATNF/CSIRO/ATCA; H-alpha: UK STFC/Royal Observatory Edinburgh; Image Processing: NASA/CXC/SAO/N. Wolk By comparing the radio and X-ray data, researchers identified key differences between the sources of the two types of light. In particular, some prominent X-ray features, including the jet towards the bottom of the image and the inner parts of the three “fingers” towards the top, are not detected in radio waves. This suggests that highly energetic particles are leaking out from a shock wave — similar to a supersonic plane’s sonic boom — near the pulsar and moving along magnetic field lines to create the fingers.
The radio data also shows that RCW 89’s structure is different from typical young supernova remnants. Much of the radio emission is patchy and closely matches clumps of X-ray and optical emission. It also extends well beyond the X-ray emission. All of these characteristics support the idea that RCW 89 is colliding with a dense cloud of nearby hydrogen gas.
However, the researchers do not fully understand all that the data is showing them. One area that is perplexing is the sharp boundary of X-ray emission in the upper right of the image that seems to be the blast wave from the supernova — see the labeled feature. Supernova blast waves are usually bright in radio waves for young supernova remnants like RCW 89, so it is surprising to researchers that there is no radio signal at the X-ray boundary.
MSH 15–52 and RCW 89 show many unique features not found in other young sources. There are, however, still many open questions regarding the formation and evolution of these structures. Further work is needed to provide better understanding of the complex interplay between the pulsar wind and the supernova debris.
A paper describing this work, led by Shumeng Zhang of the University of Hong Kong, with co-authors Stephen C.Y. Ng of the University of Hong Kong and Niccolo’ Bucciantini of the Italian National Institute for Astrophysics, has been published in The Astrophysical Journal and is available at https://iopscience.iop.org/article/10.3847/1538-4357/adf333.
NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
Read more from NASA’s Chandra X-ray Observatory Learn more about the Chandra X-ray Observatory and its mission here:
https://www.nasa.gov/chandra
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Visual Description
This release features a composite image of a nebula and pulsar that strongly resembles a cosmic hand reaching for a neon red cloud.
The neon red cloud sits near the top of the image, just to our right of center. Breaks in the cloud reveal interwoven strands of gold resembling spiderwebs, or a latticework substructure. This cloud is the remains of the supernova that formed the pulsar at the heart of the image. The pulsar, a rapidly spinning neutron star only 12 miles in diameter, is far too small to be seen in this image, which represents a region of space over 150 light-years across.
The bottom half of the image is dominated by a massive blue hand reaching up toward the pulsar and supernova cloud. This is an intricate nebula called MSH 15-52, an energetic wind of electrons and other particles driven away from the pulsar. The resemblance to a hand is undeniable. Inside the nebula, streaks and swirls of blue range from pale to navy, evoking a medical X-ray, or the yearning hand of a giant, cosmic ghost.
The hand and nebula are set against the blackness of space, surrounded by scores of gleaming golden specks. At our lower left, a golden hydrogen gas cloud extends beyond the edges of the image. In this composite, gold represents optical data; red represents ATCA radio data; and blue, orange, and yellow represent X-ray data from Chandra. Where the blue hand of the nebula overlaps with the radio data in red, the fingers appear hazy and purple.
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Last Updated Aug 20, 2025 EditorLee MohonContactCorinne M. Beckingercorinne.m.beckinger@nasa.gov Related Terms
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By NASA
This NASA Hubble Space Telescope image features a dense and dazzling array of blazing stars that form globular cluster ESO 591-12.NASA, ESA, and D. Massari (INAF — Osservatorio di Astrofisica e Scienza dello Spazio); Processing: Gladys Kober (NASA/Catholic University of America) A previously unexplored globular cluster glitters with multicolored stars in this NASA Hubble Space Telescope image. Globular clusters like this one, called ESO 591-12 or Palomar 8, are spherical collections of tens of thousands to millions of stars tightly bound together by gravity. Globular clusters generally form early in the galaxies’ histories in regions rich in gas and dust. Since the stars form from the same cloud of gas as it collapses, they typically hover around the same age. Strewn across this image of ESO 591-12 are a number of red and blue stars. The colors indicate their temperatures; red stars are cooler, while the blue stars are hotter.
Hubble captured the data used to create this image of ESO 591-12 as part of a study intended to resolve individual stars of the entire globular cluster system of the Milky Way. Hubble revolutionized the study of globular clusters since earthbound telescopes are unable to distinguish individual stars in the compact clusters. The study is part of the Hubble Missing Globular Clusters Survey, which targets 34 confirmed Milky Way globular clusters that Hubble has yet to observe.
The program aims to provide complete observations of ages and distances for all of the Milky Way’s globular clusters and investigate fundamental properties of still-unexplored clusters in the galactic bulge or halo. The observations will provide key information on the early stages of our galaxy, when globular clusters formed.
Image credit: NASA, ESA, and D. Massari (INAF — Osservatorio di Astrofisica e Scienza dello Spazio); Processing: Gladys Kober (NASA/Catholic University of America)
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By NASA
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Hubble Observations Give “Missing” Globular Cluster Time to Shine
This NASA Hubble Space Telescope image features a dense and dazzling array of blazing stars that form globular cluster ESO 591-12. NASA, ESA, and D. Massari (INAF — Osservatorio di Astrofisica e Scienza dello Spazio); Processing: Gladys Kober (NASA/Catholic University of America)
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A previously unexplored globular cluster glitters with multicolored stars in this NASA Hubble Space Telescope image. Globular clusters like this one, called ESO 591-12 or Palomar 8, are spherical collections of tens of thousands to millions of stars tightly bound together by gravity. Globular clusters generally form early in the galaxies’ histories in regions rich in gas and dust. Since the stars form from the same cloud of gas as it collapses, they typically hover around the same age. Strewn across this image of ESO 591-12 are a number of red and blue stars. The colors indicate their temperatures; red stars are cooler, while the blue stars are hotter.
Hubble captured the data used to create this image of ESO 591-12 as part of a study intended to resolve individual stars of the entire globular cluster system of the Milky Way. Hubble revolutionized the study of globular clusters since earthbound telescopes are unable to distinguish individual stars in the compact clusters. The study is part of the Hubble Missing Globular Clusters Survey, which targets 34 confirmed Milky Way globular clusters that Hubble has yet to observe.
The program aims to provide complete observations of ages and distances for all of the Milky Way’s globular clusters and investigate fundamental properties of still-unexplored clusters in the galactic bulge or halo. The observations will provide key information on the early stages of our galaxy, when globular clusters formed.
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Last Updated Jul 03, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
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