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By NASA
Explore Hubble Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Hubble and Artificial Intelligence Explore the Night Sky Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts Multimedia Images Videos Sonifications Podcasts e-Books Online Activities 3D Hubble Models Lithographs Fact Sheets Posters Hubble on the NASA App Glossary News Hubble News Social Media Media Resources More 35th Anniversary Online Activities 2 min read
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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NASA’s Goddard Space Flight Center, Greenbelt, MD
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Last Updated Jul 03, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
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Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
Hubble’s Cosmic Adventure
Hubble’s Night Sky Challenge
Hubble’s 35th Anniversary
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By European Space Agency
Astronomers using the European Space Agency’s Cheops mission have caught an exoplanet that seems to be triggering flares of radiation from the star it orbits. These tremendous explosions are blasting away the planet’s wispy atmosphere, causing it to shrink every year.
This is the first-ever evidence for a ‘planet with a death wish’. Though it was theorised to be possible since the nineties, the flares seen in this research are around 100 times more energetic than expected.
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By NASA
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
The SWOT satellite is helping scientists size up flood waves on waterways like the Yellowstone River, pictured here in October 2024 in Montana. SWOT measures the height of surface waters, including the ocean, and hundreds of thousands of rivers, lakes, and reservoirs in the U.S. alone.NPS In a first, researchers from NASA and Virginia Tech used satellite data to measure the height and speed of potentially hazardous flood waves traveling down U.S. rivers. The three waves they tracked were likely caused by extreme rainfall and by a loosened ice jam. While there is currently no database that compiles satellite data on river flood waves, the new study highlights the potential of space-based observations to aid hydrologists and engineers, especially those working in communities along river networks with limited flood control structures such as levees and flood gates.
Unlike ocean waves, which are ordinarily driven by wind and tides, and roll to shore at a steady clip, river waves (also called flood or flow waves) are temporary surges stretching tens to hundreds of miles. Typically caused by rainfall or seasonal snowmelt, they are essential to shuttling nutrients and organisms down a river. But they can also pose hazards: Extreme river waves triggered by a prolonged downpour or dam break can produce floods.
“Ocean waves are well known from surfing and sailing, but rivers are the arteries of the planet. We want to understand their dynamics,” said Cedric David, a hydrologist at NASA’s Jet Propulsion Laboratory in Southern California and a coauthor of a new study published May 14 in Geophysical Research Letters.
SWOT is depicted in orbit in this artist’s concept, with sunlight glinting off one of its solar panels and both antennas of its key instrument — the Ka-band Radar Interferometer (KaRIn) — extended. The antennas collect data along a swath 30 miles (50 kilometers) wide on either side of the satellite.CNES Measuring Speed and Size
To search for river waves for her doctoral research, lead author Hana Thurman of Virginia Tech turned to a spacecraft launched in 2022. The SWOT (Surface Water and Ocean Topography) satellite is a collaboration between NASA and the French space agency CNES (Centre National d’Études Spatiales). It is surveying the height of nearly all of Earth’s surface waters, both fresh and salty, using its sensitive Ka-band Radar Interferometer (KaRIn). The instrument maps the elevation and width of water bodies by bouncing microwaves off the surface and timing how long the signal takes to return.
“In addition to monitoring total storage of waters in lakes and rivers, we zoom in on dynamics and impacts of water movement and change,” said Nadya Vinogradova Shiffer, SWOT program scientist at NASA Headquarters in Washington.
Thurman knew that SWOT has helped scientists track rising sea levels near the coast, spot tsunami slosh, and map the seafloor, but could she identify river height anomalies in the data indicating a wave on the move?
She found that the mission had caught three clear examples of river waves, including one that arose abruptly on the Yellowstone River in Montana in April 2023. As the satellite passed overhead, it observed a 9.1-foot-tall (2.8-meter-tall) crest flowing toward the Missouri River in North Dakota. It was divided into a dramatic 6.8-mile-long (11-kilometer-long) peak followed by a more drawn‐out tail. These details are exciting to see from orbit and illustrate the KaRIn instrument’s uniquely high spatial resolution, Thurman said.
Sleuthing through optical Sentinel-2 imagery of the area, she determined that the wave likely resulted from an ice jam breaking apart upstream and releasing pent-up water.
The other two river waves that Thurman and the team found were triggered by rainfall runoff. One, spotted by SWOT starting on Jan. 25, 2024, on the Colorado River south of Austin, Texas, was associated with the largest flood of the year on that section of river. Measuring over 30 feet (9 meters) tall and 166 miles (267 kilometers) long, it traveled around 3.5 feet (1.07 meters) per second for over 250 miles (400 kilometers) before discharging into Matagorda Bay.
The other wave originated on the Ocmulgee River near Macon, Georgia, in March 2024. Measuring over 20 feet (6 meters) tall and extending more than 100 miles (165 kilometers), it traveled about a foot (0.33 meters) per second for more than 124 miles (200 kilometers).
“We’re learning more about the shape and speed of flow waves, and how they change along long stretches of river,” Thurman said. “That could help us answer questions like, how fast could a flood get here and is infrastructure at risk?”
Complementary Observations
Engineers and water managers measuring river waves have long relied on stream gauges, which record water height and estimate discharge at fixed points along a river. In the United States, stream gauge networks are maintained by agencies including the U.S. Geological Survey. They are sparser in other parts of the world.
“Satellite data is complementary because it can help fill in the gaps,” said study supervisor George Allen, a hydrologist and remote sensing expert at Virginia Tech.
If stream gauges are like toll booths clocking cars as they pass, SWOT is like a traffic helicopter taking snapshots of the highway.
The wave speeds that SWOT helped determine were similar to those calculated using gauge data alone, Allen said, showing how the satellite could help monitor waves in river basins without gauges. Knowing where and why river waves develop can help scientists tracking changing flood patterns around the world.
Orbiting Earth multiple times each day, SWOT is expected to observe some 55% of large-scale floods at some stage in their life cycle. “If we see something in the data, we can say something,” David said of SWOT’s potential to flag dangerous floods in the making. “For a long time, we’ve stood on the banks of our rivers, but we’ve never seen them like we are now.”
More About SWOT
The SWOT satellite was jointly developed by NASA and CNES, with contributions from the Canadian Space Agency (CSA) and the UK Space Agency. NASA’s Jet Propulsion Laboratory, managed for the agency by Caltech in Pasadena, California, leads the U.S. component of the project. For the flight system payload, NASA provided the Ka-band radar interferometer (KaRIn) instrument, a GPS science receiver, a laser retroreflector, a two-beam microwave radiometer, and NASA instrument operations. The Doppler Orbitography and Radioposition Integrated by Satellite system, the dual frequency Poseidon altimeter (developed by Thales Alenia Space), the KaRIn radio-frequency subsystem (together with Thales Alenia Space and with support from the UK Space Agency), the satellite platform, and ground operations were provided by CNES. The KaRIn high-power transmitter assembly was provided by CSA.
News Media Contacts
Jane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0307 / 626-379-6874
Written by Sally Younger
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Last Updated May 21, 2025 Related Terms
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3 min read Devil’s in Details in Selfie Taken by NASA’s Mars Perseverance Rover
Article 2 hours ago 5 min read NASA’s Perseverance Mars Rover to Take Bite Out of ‘Krokodillen’
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Spectrum is a shared resource. Since the discovery of radio waves and the invention of the telegraph, humanity has exponentially increased its use of the radio frequency (RF) spectrum. Consider how many wireless devices are around you right now. You’re probably reading this on a smartphone or laptop connected to the internet through Wi-Fi or 5G. You might be listening to music on Bluetooth headphones. If you are in a car or bus, the driver may be using signals from GPS satellites. To meet this increasing need, RF engineers and regulators continue to develop ways to enable users to share the same frequencies at the same time in the same place — think of modern cell phone technology. Avoiding or lessening interference between users requires regulators and users alike to maintain and enforce the ‘rules of the road’ that describe who can use which frequencies where, when, and how. NASA, like all other users, must comply with these regulations and collaborate with other users to ensure our use of the RF spectrum can continue and evolve.
Just as architects design taller buildings to accommodate more residences on the same plot of land, radio frequency engineers design methods to allow more users on the same frequency, at the same place and time.NASA Supporting and Protecting NASA’s Spectrum Users
NASA’s spectrum professionals work with users early in the project planning phase to understand the type, location, and duration of their data, and in turn determine what kind of antennas, transmitters, and receivers will be required. With that information, a spectrum manager helps to define the spectrum requirements, such as bandwidths, modulation, and other technical characteristics of the radio signals to be used. Understanding a project’s objectives helps define the appropriate service allocation and potential frequency ranges.
Once these spectrum requirements are determined, NASA’s spectrum professionals work with other relevant spectrum users within and beyond NASA to coordinate the use of the spectrum.
In the unfortunate event of harmful RF interference, working to identify, resolve, and report the interference is another critical function of NASA’s spectrum professionals. For example as Jeff Hayes — NASA’s current SCaN (Space Communications and Navigation) Program liaison to the Science Mission Directorate and the former program executive for operating missions in the Heliophysics and Astrophysics Divisions — recounts, “The NICER (Neutron Star Interior Composition Explorer) observatory did actually experience bouts of RF interference over certain parts of the world. As NICER uses GPS to understand where it is pointing to in the sky, interference can make the location information of the source imprecise, and that impacts the quality of the data collected. That data could potentially be attributed to the wrong star.”
When NASA identifies interference to a mission like NICER or to a device at an agency center or facility, NASA center and facility spectrum managers work to identify, resolve, and report the interference.
Identifying and reporting sources of interference helps to raise awareness of the impacts and causes of interference. When the sources of interference are international, which is especially common for space systems like NICER, SCaN’s spectrum management team works with U.S. regulators to report the incident to international regulators. These interference reports can be used to advocate for regulatory protections that help ensure the integrity of valuable science data and the safety of human spaceflight activities.
Advocating for NASA’s Current and Future Spectrum Use
NASA’s spectrum analysts and engineers perform analyses and simulations to support spectrum planning and management activities. For example, passive remote sensing instruments like the radiometer on the Soil Moisture Active Passive mission detect natural energy (radiation) emitted or reflected by an object or scene being observed. This energy is much fainter than human-generated radio signals and require highly sensitive radiometers that are susceptible to interference from more powerful signals. The spectrum management team works to ensure regulatory protections are in place and followed to ensure the integrity of NASA’s scientific missions.
Sometimes NASA’s future missions envision new ways and places to use radio waves. For example, when NASA’s Artemis campaign began taking steps to return humans to the Moon, SCaN’s spectrum professionals began working with other stakeholders to develop a RF architecture that enables the use of radio waves for science data, communications, positioning, navigation, and timing while also limiting the risk of interference with systems on or orbiting Earth. NASA’s spectrum professionals further the agency’s spectrum management goals and objectives by analyzing potential changes in international or domestic regulations and proposing technical solutions that promote collaborative spectrum use with both foreign and domestic partners.
NASA’s technical expertise is critical to ensuring domestic and international regulators are well informed as they develop new or revised regulations that effectively enable the exciting innovation and exploration central to NASA’s mission.
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Last Updated Apr 23, 2025 Related Terms
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