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By Space Force
The visit offered a deeper understanding of local space operations, and underscore the installation’s growing role in advancing national defense through innovation and enlisted force development.
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By NASA
Dr. Compton J. Tucker – a senior researcher at NASA’s Goddard Space Flight Center (GSFC) – joins 149 newly elected members to the National Academy of Sciences (NAS) – see Photo. NAS is one of the highest honors in American science. Compton gave a virtual presentation at GSFC on July 21, 2025, in which he showed highlights from his 50 years of research and reflected on the honor of being selected as an NAS fellow. He admitted that he was surprised upon learning of his election in April 2025 – despite his prestigious career.
Photo 1. Compton Tucker uses satellites to address global environmental challenges. Photo credit: Colorado State University In some ways this award brings Compton’s career full circle. He first came to GSFC as a NAS postdoc in 1975 after having earned his Bachelor’s of Science degree at Colorado State University (CSU) in 1969. He followed with his Master’s of Science degree and Ph.D. from CSU’s College of Forestry in 1973 and 1975 respectively. Two years later, he joined NASA as a civil servant. After a prestigious 48 years of public service, Compton has decided to retire in March 2025.
Compton is a well-known pioneer in the field of satellite-based environmental analysis, using data from various U.S. Geological Survey–NASA Landsat missions and from the National Oceanographic and Atmospheric Administration’s (NOAA) Advanced Very High Resolution Radiometer (AVHRR) instrument, the prototype of which launched aboard the Television Infrared Observation Satellite–N (TIROS-N) in 1978, with launches continuing on NOAA and European polar orbiting satellites throughout the next 40 years. The last two AVHRR instruments, which launched on the European Organisation for the Exploitation of Meteorological Satellites’ (EUMETSAT) Meteorological Operational satellites (METOP–B and -C) in 2012 and 2018 respectively, are still operational today.
Photo 2. Earth scientist Compton Tucker, who has studied remote sensing of vegetation at NASA Goddard for 50 years, has been elected to the National Academy of Sciences. Photo credit: Compton Tucker In his GSFC presentation, Compton described how, in the course of doing their research, he and his colleague(s) realized the original plans for AVHRR resulted in Channel 1 and 2 overlapping one another. In short, he explained that his input helped persuade NOAA management to change the design for Channel 1 of AVHRR – beginning with NOAA-7. It is fair to say that this change had a lasting impact, with 16 more AVHRR instruments (with slight modifications over time) launched over the next four decades.
Compton’s research has focused on global photosynthesis on land (e.g., grass-dominated savannas), determined land cover (i.e., forest fragmentation, deforestation, and forest condition), monitored droughts and food security, and evaluated ecologically coupled disease outbreaks. From 2005 to 2010, he was the co-chair of two Interagency Working Groups for Observations and Land Use and Land Cover Change. Compton was active in NASA’s Space Archaeology Program, participating in ground-based radar and magnetic surveys in Turkey, particularly at Troy, the Granicus River Valley, and Gordion. Over the course of his 50-year career, he has authored or co-authored more than 400 scholarly articles that have appeared in scientific journals – and in his presentation he hinted that more might be in store after retirement.
Compton has received numerous scientific awards and honors. He was elected to a fellow of the American Geophysical Union in 2009 and to the American Association for the Advancement of Science in 2015. He received the Senior Executive Service Presidential Rank Award for Meritorious Service (2017), the Vega Medal from the Swedish Society of Anthropology and Geography (2014), the Galathea Medal from the Royal Danish Geographical Society (2004), the William T. Pecora Award from the U.S. Geological Survey (1997), the Michael Collins Trophy for Current Achievement from the National Air and Space Museum (1993), the Henry Shaw Medal from the Missouri Botanical Garden (1992), and the Exceptional Scientific Achievement Medal from NASA (1987).
Compton enjoyed sharing his knowledge with the next generation of scientists. He served as an adjunct professor at the University of Maryland (1994–2024) and a consulting scholar at the University of Pennsylvania Museum of Archeology and Anthropology (2005–2024).
Congratulations to Compton on earning this prestigious – and well-earned – recognition from NAS. Best wishes to him in whatever is next on his journey.
The National Academy of Sciences is a private, nonprofit institution that was established under a congressional charter signed by President Abraham Lincoln in 1863. It recognizes achievement in science by election to membership, and – with the National Academy of Engineering and the National Academy of Medicine – provides science, engineering, and health policy advice to the federal government and other organizations.
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
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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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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