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By NASA
5 min read
Ultra-low-noise Infrared Detectors for Exoplanet Imaging
A linear-mode avalanche photodiode array in the test dewar. The detector is the dark square in the center. Michael Bottom, University of Hawai’i One of the ultimate goals in astrophysics is the discovery of Earth-like planets that are capable of hosting life. While thousands of planets have been discovered around other stars, the vast majority of these detections have been made via indirect methods, that is, by detecting the effect of the planet on the star’s light, rather than detecting the planet’s light directly. For example, when a planet passes in front of its host star, the brightness of the star decreases slightly.
However, indirect methods do not allow for characterization of the planet itself, including its temperature, pressure, gravity, and atmospheric composition. Planetary atmospheres may include “biosignature” gases like oxygen, water vapor, carbon dioxide, etc., which are known to be key ingredients needed to support life as we know it. As such, direct imaging of a planet and characterization of its atmosphere are key to understanding its potential habitability.
But the technical challenges involved in imaging Earth-like extrasolar planets are extreme. First such planets are detected only by observing light they reflect from their parent star, and so they typically appear fainter than the stars they orbit by factors of about 10 billion. Furthermore, at the cosmic distances involved, the planets appear right next to the stars. A popular expression is that exoplanet imaging is like trying to detect a firefly three feet from a searchlight from a distance of 300 miles.
Tremendous effort has gone into developing starlight suppression technologies to block the bright glare of the star, but detecting the light of the planet is challenging in its own right, as planets are incredibly faint. One way to quantify the faintness of planetary light is to understand the photon flux rate. A photon is an indivisible particle of light, that is, the minimum detectable amount of light. On a sunny day, approximately 10 thousand trillion photons enter your eye every second. The rate of photons entering your eye from an Earth-like exoplanet around a nearby star would be around 10 to 100 per year. Telescopes with large mirrors can help collect as much of this light as possible, but ultra-sensitive detectors are also needed, particularly for infrared light, where the biosignature gases have their strongest effects. Unfortunately, state-of-the-art infrared detectors are far too noisy to detect the low level of light emitted from exoplanets.
With support from NASA’s Astrophysics Division and industrial partners, researchers at the University of Hawai’i are developing a promising detector technology to meet these stringent sensitivity requirements. These detectors, known as avalanche photodiode arrays, are constructed out of the same semiconductor material as conventional infrared sensors. However, these new sensors employ an extra “avalanche” layer that takes the signal from a single photon and multiplies it, much like an avalanche can start with a single snowball and quickly grow it to the size of a boulder. This signal amplification occurs before any noise from the detector is introduced, so the effective noise is proportionally reduced. However, at high avalanche levels, photodiodes start to behave badly, with noise exponentially increasing, which negates any benefits of the signal amplification. Late University of Hawai’i faculty member Donald Hall, who was a key figure in driving technology for infrared astronomy, realized the potential use of avalanche photodiodes for ultra-low-noise infrared astronomy with some modifications to the material properties.
University of Hawai’i team members with cryogenic dewar used to test the sensors. From left to right, Angelu Ramos, Michael Bottom, Shane Jacobson, Charles-Antoine Claveau. Michael Bottom, University of Hawai’i The most recent sensors benefit from a new design including a graded semiconductor bandgap that allows for excellent noise performance at moderate amplification, a mesa pixel geometry to reduce electronic crosstalk, and a read-out integrated circuit to allow for short readout times. “It was actually challenging figuring out just how sensitive these detectors are,” said Michael Bottom, associate professor at the University of Hawai’i and lead of development effort. “Our ‘light-tight’ test chamber, which was designed to evaluate the infrared sensors on the James Webb Space Telescope, was supposed to be completely dark. But when we put these avalanche photodiodes in the chamber, we started seeing light leaks at the level of a photon an hour, which you would never be able to detect using the previous generation of sensors.”
The new designs have a format of one megapixel, more than ten times larger than the previous iteration of sensors, and circuitry that allows for tracking and subtracting any electronic drifts. Additionally, the pixel size and control electronics are such that these new sensors could be drop-in replacements for the most common infrared sensors used on the ground, which would give new capabilities to existing instruments.
Image of the Palomar-2 globular cluster located in the constellation of Auriga, taken with the linear-mode avalanche photodiode arrays, taken from the first on-sky testing of the sensors using the University of Hawai’i’s 2.2 meter telescope. Michael Bottom, University of Hawai’i Last year, the team took the first on-sky images from the detectors, using the University of Hawai’i’s 2.2-meter telescope. “It was impressive to see the avalanche process on sky. When we turned up the gain, we could see more stars appear,” said Guillaume Huber, a graduate student working on the project. “The on-sky demonstration was important to prove the detectors could perform well in an operational environment,” added Michael Bottom.
According to the research team, while the current sensors are a major step forward, the megapixel format is still too small for many science applications, particularly those involving spectroscopy. Further tasks include improving detector uniformity and decreasing persistence. The next generation of sensors will be four times larger, meeting the size requirements for the Habitable Worlds Observatory, NASA’s next envisioned flagship mission, with the goals of imaging and characterizing Earth-like exoplanets.
Project Lead: Dr. Michael Bottom, University of Hawai’i
Sponsoring Organization: NASA Strategic Astrophysics Technology (SAT) Program
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Last Updated Feb 18, 2025 Related Terms
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By Space Force
The Department of the Air Force released the memorandum DEI and Gender Ideology Publication Review.
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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
2 Min Read More Than 400 Lives Saved with NASA’s Search and Rescue Tech in 2024
NASA Artemis II crew members are assisted by U.S. Navy personnel as they exit a mockup of the Orion spacecraft in the Pacific Ocean during Underway Recovery Test 11 (URT-11) on Feb. 25, 2024. Credits: NASA/Kenny Allen NASA’s Search and Rescue technologies enabled hundreds of lives saved in 2024.NASA/Dave Ryan Did you know that the same search and rescue technologies developed by NASA for astronaut missions to space help locate and rescue people across the United States and around the world?
NASA’s collaboration with the international satellite-aided search and rescue effort known as Cospas-Sarsat has enabled the development of multiple emergency location beacons for explorers on land, sea, and air.
Of the 407 lives saved in 2024 through search and rescue efforts in the United States, NOAA (National Oceanic and Atmospheric Administration) reports that 52 rescues were the result of activated personal locator beacons, 314 from emergency position-indicating radio beacons, and 41 from emergency locator transmitters. Since 1982, more than 50,000 lives have been saved across the world.
Using GPS satellites, these beacons transmit their location to the Cospas-Sarsat network once activated. The beacons then provide the activation coordinates to the network, allowing first responders to rescue lost or distressed explorers.
NASA Artemis II crew members are assisted by U.S. Navy personnel as they exit a mockup of the Orion spacecraft in the Pacific Ocean during Underway Recovery Test 11 (URT-11) on Feb. 25, 2024, while his crewmates look on. URT-11 is the eleventh in a series of Artemis recovery tests, and the first time NASA and its partners put their Artemis II recovery procedures to the test with the astronauts.NASA/Kenny Allen The Search and Rescue Office, part of NASA’s SCaN (Space Communications and Navigation) Program, has assisted in search and rescue services since its formation in 1979 Now, the office is building on their long legacy of Earth-based beacon development to support crewed missions to space.
The beacons also are used for emergency location, if needed, as part of NASA’s crew launches to and from the International Space Station, and will support NASA’s Artemis campaign crew recovery preparations during future missions returning from deep space. Systems being tested, like the ANGEL (Advanced Next-Generation Emergency Locator) beacon, are benefitting life on Earth and missions to the Moon and Mars. Most recently, NASA partnered with the Department of Defense to practice Artemis II recovery procedures – including ANGEL beacon activation – during URT-11 (Underway Recovery Test 11).
Miniaturized Advanced Next-Generation Emergency Locator (ANGEL) beacons will be attached to the astronauts’ life preserver units. When astronauts Reid Wiseman, Victor Glover, Christina Koch, and CSA (Canadian Space Agency) astronaut Jeremy Hanse splash back down to Earth — or in the unlikely event of a launch abort scenario — these beacons will allow them to be found if they need to egress from the Orion capsule.NASA The SCaN program at NASA Headquarters in Washington provides strategic oversight to the Search and Rescue office. NOAA manages the U.S. network region for Cospas-Sarsat, which relies on flight and ground technologies originally developed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. U.S. region rescue efforts are led by the U.S. Coast Guard, U.S. Air Force, and many other local rescue authorities.
About the Author
Kendall Murphy
Technical WriterKendall Murphy is a technical writer for the Space Communications and Navigation program office. She specializes in internal and external engagement, educating readers about space communications and navigation technology.
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Last Updated Feb 06, 2025 EditorGoddard Digital TeamContactKatherine Schauerkatherine.s.schauer@nasa.govLocationNASA Goddard Space Flight Center Related Terms
Goddard Space Flight Center Artemis Communicating and Navigating with Missions Space Communications & Navigation Program Space Communications Technology Explore More
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By NASA
NASA’s VIPER (Volatiles Investigating Polar Exploration Rover) sits outside a testing chamber after completing its thermal vacuum testing in the fall of 2024. Credit: NASA/JSC David DeHoyos To advance plans of securing a public/private partnership and land and operate NASA’s VIPER (Volatiles Investigating Polar Exploration Rover) mission on the Moon in collaboration with industry the agency announced Monday it is seeking U.S. proposals. As part of the agency’s Artemis campaign, instruments on VIPER will demonstrate U.S. industry’s ability to search for ice on the lunar surface and collect science data.
The Announcement for Partnership Proposal contains proposal instructions and evaluation criteria for a new Lunar Volatiles Science Partnership. Responses are due Thursday, Feb. 20. After evaluating submissions, any selections by the agency will require respondents to submit a second, more detailed, proposal. NASA is expected to make a decision on the VIPER mission this summer.
“Moving forward with a VIPER partnership offers NASA a unique opportunity to engage with the private sector,” said Nicky Fox, associate administrator in the Science Mission Directorate at NASA Headquarters in Washington. “Such a partnership provides the opportunity for NASA to collect VIPER science that could tell us more about water on the Moon, while advancing commercial lunar landing capabilities and resource prospecting possibilities.”
This new announcement comes after NASA issued a Request for Information on Aug. 9, 2024, to seek interest from American companies and institutions in conducting a mission using the agency’s VIPER Moon rover after the program was canceled in July 2024.
Any partnership would work under a Cooperative Research and Development Agreement. This type of partnership allows both NASA and an industry partner to contribute services, technology, and hardware to the collaboration.
As part of an agreement, NASA would contribute the existing VIPER rover as-is. Potential partners would need to arrange for the integration and successful landing of the rover on the Moon, conduct a science/exploration campaign, and disseminate VIPER-generated science data. The partner may not disassemble the rover and use its instruments or parts separately from the VIPER mission. NASA’s selection approach will favor proposals that enable data from the mission’s science instruments to be shared openly with anyone who wishes to use it.
“Being selected for the VIPER partnership would benefit any company interested in advancing their lunar landing and surface operations capabilities,” said Joel Kearns, deputy associate administrator for exploration in the Science Mission Directorate. “This solicitation seeks proposals that clearly describe what is needed to successfully land and operate the rover, and invites industry to propose their own complementary science goals and approaches. NASA is looking forward to partnering with U.S. industry to meet the challenges of performing volatiles science in the lunar environment.”
The Moon is a cornerstone for solar system science and exoplanet studies. In addition to helping inform where ice exists on the Moon for potential future astronauts, understanding our nearest neighbor helps us understand how it has evolved and what processes shaped its surface.
To learn more about NASA’s lunar science, visit:
https://www.nasa.gov/moon
-end-
Karen Fox
Headquarters, Washington
202-358-1100
karen.fox@nasa.gov
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Last Updated Feb 03, 2025 Related Terms
Missions VIPER (Volatiles Investigating Polar Exploration Rover) View the full article
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By NASA
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Equipped with state-of-the-art technology to test and evaluate communication, navigation, and surveillance systems NASA’s Pilatus PC-12 performs touch-and-go maneuvers over a runway at NASA’s Armstrong Flight Research Center in Edwards, California on Sept. 23, 2024. Researchers will use the data to understand Automatic Dependent Surveillance-Broadcast (ADS-B) signal loss scenarios for air taxi flights in urban areas. To prepare for ADS-B test flights pilots and crew from NASA Armstrong and NASA’s Glenn Research Center in Cleveland, ran a series of familiarization flights. These flights included several approach and landings, with an emphasis on avionics, medium altitude air-work with steep turns, slow flight and stall demonstrations.NASA/Steve Freeman As air taxis, drones, and other innovative aircraft enter U.S. airspace, systems that communicate an aircraft’s location will be critical to ensure air traffic safety.
The Federal Aviation Administration (FAA) requires aircraft to communicate their locations to other aircraft and air traffic control in real time using an Automatic Dependent Surveillance-Broadcast (ADS-B) system. NASA is currently evaluating an ADS-B system’s ability to prevent collisions in a simulated urban environment. Using NASA’s Pilatus PC-12 aircraft, researchers are investigating how these systems could handle the demands of air taxis flying at low altitudes through cities.
When operating in urban areas, one particular challenge for ADS-B systems is consistent signal coverage. Like losing cell-phone signal, air taxis flying through densely populated areas may have trouble maintaining ADS-B signals due to distance or interference. If that happens, those vehicles become less visible to air traffic control and other aircraft in the area, increasing the likelihood of collisions.
NASA pilot Kurt Blankenship maps out flight plans during a pre-flight brief. Pilots, crew, and researchers from NASA’s Armstrong Flight Research Center in Edwards, California and NASA’s Glenn Research Center in Cleveland are briefed on the flight plan to gather Automatic Dependent Surveillance-Broadcast signal data between the aircraft and ping-Stations on the ground at NASA Armstrong. These flights are the first cross-center research activity with the Pilatus-PC-12 at NASA Armstrong.NASA/Steve Freeman To simulate the conditions of an urban flight area and better understand signal loss patterns, NASA researchers established a test zone at NASA’s Armstrong Flight Research Center in Edwards, California, on Sept. 23 and 24, 2024.
Flying in the agency’s Pilatus PC-12 in a grid pattern over four ADS-B stations, researchers collected data on signal coverage from multiple ground locations and equipment configurations. Researchers were able to pinpoint where signal dropouts occurred from the strategically placed ground stations in connection to the plane’s altitude and distance from the stations. This data will inform future placement of additional ground stations to enhance signal boosting coverage.
“Like all antennas, those used for ADS-B signal reception do not have a constant pattern,” said Brad Snelling, vehicle test team chief engineer for NASA’s Air Mobility Pathfinders project. “There are certain areas where the terrain will block ADS-B signals and depending on the type of antenna and location characteristics, there are also flight elevation angles where reception can cause signal dropouts,” Snelling said. “This would mean we need to place additional ground stations at multiple locations to boost the signal for future test flights. We can use the test results to help us configure the equipment to reduce signal loss when we conduct future air taxi flight tests.”
Working in the Mobile Operations Facility at NASA’s Armstrong Flight Research Center in Edwards, California, NASA Advanced Air Mobility researcher Dennis Iannicca adjusts a control board to capture Automatic Dependent Surveillance-Broadcast (ADS-B) data during test flights. The data will be used to understand ADS-B signal loss scenarios for air taxi flights in urban areas.NASA/Steve Freeman The September flights at NASA Armstrong built upon earlier tests of ADS-B in different environments. In June, researchers at NASA’s Glenn Research Center in Cleveland flew the Pilatus PC-12 and found a consistent ADS-B signal between the aircraft and communications antennas mounted on the roof of the center’s Aerospace Communications Facility. Data from these flights helped researchers plan out the recent tests at NASA Armstrong. In December 2020, test flights performed under NASA’s Advanced Air Mobility National Campaign used an OH-58C Kiowa helicopter and ground-based ADS-B stations at NASA Armstrong to collect baseline signal information.
NASA’s research in ADS-B signals and other communication, navigation, and surveillance systems will help revolutionize U.S. air transportation. Air Mobility Pathfinders researchers will evaluate the data from the three separate flight tests to understand the different signal transmission conditions and equipment needed for air taxis and drones to safely operate in the National Air Space. NASA will use the results of this research to design infrastructure to support future air taxi communication, navigation, and surveillance research and to develop new ADS-B-like concepts for uncrewed aircraft systems.
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Last Updated Jan 23, 2025 EditorDede DiniusContactLaura Mitchelllaura.a.mitchell@nasa.govLocationArmstrong Flight Research Center Related Terms
Armstrong Flight Research Center Advanced Air Mobility Aeronautics Air Mobility Pathfinders project Airspace Operations and Safety Program Ames Research Center Glenn Research Center Langley Research Center Explore More
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