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By European Space Agency
Asteroid 2024 YR4 made headlines earlier this year when its probability of impacting Earth in 2032 rose as high as 3%. While an Earth impact has now been ruled out, the asteroid’s story continues.
The final glimpse of the asteroid as it faded out of view of humankind’s most powerful telescopes left it with a 4% chance of colliding with the Moon on 22 December 2032.
The likelihood of a lunar impact will now remain stable until the asteroid returns to view in mid-2028. In this FAQ, find out why we are left with this lingering uncertainty and how ESA's planned NEOMIR space telescope will help us avoid similar situations in the future.
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By NASA
A funky effect Einstein predicted, known as gravitational lensing — when a foreground galaxy magnifies more distant galaxies behind it — will soon become common when NASA’s Nancy Grace Roman Space Telescope begins science operations in 2027 and produces vast surveys of the cosmos.
This image shows a simulated observation from NASA’s Nancy Grace Roman Space Telescope with an overlay of its Wide Field Instrument’s field of view. More than 20 gravitational lenses, with examples shown at left and right, are expected to pop out in every one of Roman’s vast observations. A journal paper led by Bryce Wedig, a graduate student at Washington University in St. Louis, Missouri, estimates that of those Roman detects, about 500 from the telescope’s High-Latitude Wide-Area Survey will be suitable for dark matter studies. By examining such a large population of gravitational lenses, the researchers hope to learn a lot more about the mysterious nature of dark matter.Credit: NASA, Bryce Wedig (Washington University), Tansu Daylan (Washington University), Joseph DePasquale (STScI) A particular subset of gravitational lenses, known as strong lenses, is the focus of a new paper published in the Astrophysical Journal led by Bryce Wedig, a graduate student at Washington University in St. Louis. The research team has calculated that over 160,000 gravitational lenses, including hundreds suitable for this study, are expected to pop up in Roman’s vast images. Each Roman image will be 200 times larger than infrared snapshots from NASA’s Hubble Space Telescope, and its upcoming “wealth” of lenses will vastly outpace the hundreds studied by Hubble to date.
Roman will conduct three core surveys, providing expansive views of the universe. This science team’s work is based on a previous version of Roman’s now fully defined High-Latitude Wide-Area Survey. The researchers are working on a follow-up paper that will align with the final survey’s specifications to fully support the research community.
“The current sample size of these objects from other telescopes is fairly small because we’re relying on two galaxies to be lined up nearly perfectly along our line of sight,” Wedig said. “Other telescopes are either limited to a smaller field of view or less precise observations, making gravitational lenses harder to detect.”
Gravitational lenses are made up of at least two cosmic objects. In some cases, a single foreground galaxy has enough mass to act like a lens, magnifying a galaxy that is almost perfectly behind it. Light from the background galaxy curves around the foreground galaxy along more than one path, appearing in observations as warped arcs and crescents. Of the 160,000 lensed galaxies Roman may identify, the team expects to narrow that down to about 500 that are suitable for studying the structure of dark matter at scales smaller than those galaxies.
“Roman will not only significantly increase our sample size — its sharp, high-resolution images will also allow us to discover gravitational lenses that appear smaller on the sky,” said Tansu Daylan, the principal investigator of the science team conducting this research program. Daylan is an assistant professor and a faculty fellow at the McDonnell Center for the Space Sciences at Washington University in St. Louis. “Ultimately, both the alignment and the brightness of the background galaxies need to meet a certain threshold so we can characterize the dark matter within the foreground galaxies.”
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This video shows how a background galaxy’s light is lensed or magnified by a massive foreground galaxy, seen at center, before reaching NASA’s Roman Space Telescope. Light from the background galaxy is distorted, curving around the foreground galaxy and appearing more than once as warped arcs and crescents. Researchers studying these objects, known as gravitational lenses, can better characterize the mass of the foreground galaxy, which offers clues about the particle nature of dark matter.Credit: NASA, Joseph Olmsted (STScI) What Is Dark Matter?
Not all mass in galaxies is made up of objects we can see, like star clusters. A significant fraction of a galaxy’s mass is made up of dark matter, so called because it doesn’t emit, reflect, or absorb light. Dark matter does, however, possess mass, and like anything else with mass, it can cause gravitational lensing.
When the gravity of a foreground galaxy bends the path of a background galaxy’s light, its light is routed onto multiple paths. “This effect produces multiple images of the background galaxy that are magnified and distorted differently,” Daylan said. These “duplicates” are a huge advantage for researchers — they allow multiple measurements of the lensing galaxy’s mass distribution, ensuring that the resulting measurement is far more precise.
Roman’s 300-megapixel camera, known as its Wide Field Instrument, will allow researchers to accurately determine the bending of the background galaxies’ light by as little as 50 milliarcseconds, which is like measuring the diameter of a human hair from the distance of more than two and a half American football fields or soccer pitches.
The amount of gravitational lensing that the background light experiences depends on the intervening mass. Less massive clumps of dark matter cause smaller distortions. As a result, if researchers are able to measure tinier amounts of bending, they can detect and characterize smaller, less massive dark matter structures — the types of structures that gradually merged over time to build up the galaxies we see today.
With Roman, the team will accumulate overwhelming statistics about the size and structures of early galaxies. “Finding gravitational lenses and being able to detect clumps of dark matter in them is a game of tiny odds. With Roman, we can cast a wide net and expect to get lucky often,” Wedig said. “We won’t see dark matter in the images — it’s invisible — but we can measure its effects.”
“Ultimately, the question we’re trying to address is: What particle or particles constitute dark matter?” Daylan added. “While some properties of dark matter are known, we essentially have no idea what makes up dark matter. Roman will help us to distinguish how dark matter is distributed on small scales and, hence, its particle nature.”
Preparations Continue
Before Roman launches, the team will also search for more candidates in observations from ESA’s (the European Space Agency’s) Euclid mission and the upcoming ground-based Vera C. Rubin Observatory in Chile, which will begin its full-scale operations in a few weeks. Once Roman’s infrared images are in hand, the researchers will combine them with complementary visible light images from Euclid, Rubin, and Hubble to maximize what’s known about these galaxies.
“We will push the limits of what we can observe, and use every gravitational lens we detect with Roman to pin down the particle nature of dark matter,” Daylan said.
The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA’s Jet Propulsion Laboratory in Southern California; Caltech/IPAC in Pasadena, California; the Space Telescope Science Institute in Baltimore; and a science team comprising scientists from various research institutions. The primary industrial partners are BAE Systems, Inc. in Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.
By Claire Blome
Space Telescope Science Institute, Baltimore, Md.
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Last Updated Jun 12, 2025 EditorAshley BalzerContactAshley Balzerashley.m.balzer@nasa.govLocationNASA Goddard Space Flight Center Related Terms
Nancy Grace Roman Space Telescope Astrophysics Dark Matter Galaxies Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research The Universe Explore More
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By European Space Agency
The European Space Agency’s (ESA) newest planetary defender has opened its ‘eye’ to the cosmos for the first time. The Flyeye telescope’s ‘first light’ marks the beginning of a new chapter in how we scan the skies for new near-Earth asteroids and comets.
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By NASA
NASA Teams responsible for preparing and launching Artemis II at NASA’s Kennedy Space Center in Florida are set to begin a series of integrated tests to get ready for the mission. With the upper stage of the agency’s SLS (Space Launch System) integrated with other elements of the rocket, engineers are set to start the tests to confirm rocket and ground systems are working and communicating as planned.
While similar to the integrated testing campaign conducted for NASA’s uncrewed Artemis I test flight, engineers have added tests ahead of Artemis II to prepare for NASA’s first crewed flight under the Artemis campaign – an approximately 10-day journey by four astronauts around the Moon and back. The mission is another step toward missions on the lunar surface and helping the agency prepare for future astronaut missions to Mars.
Interface Verification Testing
Verifies the functionality and interoperability of interfaces across elements and systems. Teams will conduct this test from the firing room in the Launch Control Center and perform health and status checks of various systems and interfaces between the SLS core stage, the solid rocket boosters, and the ground systems. It will ensure different systems, including core stage engines and booster thrust control, work as planned. Teams also will perform the same series of tests with the interim cryogenic propulsion stage and Orion before conducting a final interface test with all segments.
Program Specific Engineering Test
Teams will conduct separate engineering tests for the core stage, rocket boosters, and upper stage following the interface verification tests for each part of the rocket.
End-to-End Communications Testing
Integrated test of SLS core and upper stages, and Orion command and telemetry radio frequencies with mission control at NASA’s Johnson Space Center in Houston to demonstrate flight controllers’ ability to communicate with the ground systems and infrastructure. This test uses a radio frequency antenna in the Vehicle Assembly Building (VAB), another near the launch pad that will cover the first few minutes of launch, as well as a radio frequency that use the Tracking Data Relay Satellite and the Deep Space Network. Teams will do two versions of this test – one with the ground equipment communicating with a radio and telemetry station for checkouts, and one with all the hardware and equipment communicating with communications infrastructure like it will on launch day.
Countdown Demonstration Test
Teams will conduct a launch day demonstration with the Artemis II astronauts to test launch countdown procedures and make any final necessary adjustments ahead of launch. This test will be divided into two parts. The first will be conducted while SLS and Orion are in the VAB and include the Artemis II crew departing their crew quarters after suiting up at the Neil A. Armstrong Operations and Checkout Building and driving to the VAB where they will enter Orion like they will on launch day and practice getting strapped in. Part two will be completed once the rocket is at the launch pad and will allow the astronauts and Artemis launch team to practice how to use the emergency egress system, which would be used in the event of an unlikely emergency at the launch pad during launch countdown.
Flight Termination System End-to-End Test
Test to ensure the rocket’s flight termination system can be activated in the event of an emergency. For public safety, all rockets are required to have a flight termination system. This test will be divided into two parts inside the VAB. The first will take place ahead of Orion getting stacked atop SLS and the second will occur before the rocket and spacecraft roll out to the launch pad.
Wet Dress Rehearsal
Teams will practice loading cryogenic liquid propellant inside SLS once it’s at the launch pad and run through the launch countdown sequences just prior to engine ignition. The rehearsal will run the Artemis II launch team through operations to load liquid hydrogen and liquid oxygen into the rocket’s tanks, conduct a full launch countdown, demonstrate the ability to recycle the countdown clock, and also drain the tanks to give them an opportunity to practice the timelines and procedures they will use for launch.
Teams will load more than 700,000 gallons of cryogenic, or super cold, propellants into the rocket at the launch pad on the mobile launcher according to the detailed timeline they will use on the actual launch day. They will practice every phase of the countdown, including weather briefings, pre-planned holds in the countdown, conditioning and replenishing the propellants as needed, and validation checks. The Artemis II crew will not participate in the rehearsal.
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By NASA
6 Min Read A Defining Era: NASA Stennis and Space Shuttle Main Engine Testing
The numbers are notable – 34 years of testing space shuttle main engines at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, 3,244 individual tests, more than 820,000 seconds (totaling more than nine days) of cumulative hot fire.
The story behind the numbers is unforgettable.
“It is hard to describe the full impact of the space shuttle main engine test campaign on NASA Stennis,” Center Director John Bailey said. “It is hundreds of stories, affecting all areas of center life, within one great story of team achievement and accomplishment.”
NASA Stennis tested space shuttle main engines from May 19, 1975, to July 29, 2009. The testing made history, enabling 135 shuttle missions and notable space milestones, like deployment of the Hubble Space Telescope and construction of the International Space Station.
The testing also:
Established NASA Stennis as the center of excellence for large propulsion testing. Broadened and deepened the expertise of the NASA Stennis test team. Demonstrated and expanded the propulsion test capabilities of NASA Stennis. Ensured the future of the Mississippi site. The first space shuttle main engine is installed on May 8, 1975, at the Fred Haise Test Stand (formerly A-1). The engine would be used for the first six tests and featured a shortened thrust chamber assembly.NASA Assignment and Beginning
NASA Stennis was not the immediate choice to test space shuttle main engines. Two other sites also sought the assignment – NASA’s Marshall Flight Center in Alabama and Edwards Air Force Base in California. However, following presentations and evaluations, NASA announced March 1, 1971, that the test campaign would take place in south Mississippi.
“(NASA Stennis) was now assured of a future in propulsion testing for decades,” summarized Way Station to Space, a history of the center’s first decades.
Testing did not begin immediately. First, NASA Stennis had to complete an ambitious project to convert stands built the previous decade for rocket stage testing to facilities supporting single-engine hot fire.
Propellant run tanks were installed and calibrated. A system was fashioned to measure and verify engine thrust. A gimbaling capability was developed on the Fred Haise Test Stand to allow operators to move engines as they must pivot in flight to control rocket trajectory. Likewise, engineers designed a diffuser capability for the A-2 Test Stand to allow operators to test at simulated altitudes up to 60,000 feet.
NASA Stennis teams also had to learn how to handle cryogenic propellants in a new way. For Apollo testing, propellants were loaded into stage tanks to support hot fires. For space shuttle, propellants had to be provided by the stand to the engine. New stand run tanks were not large enough to support a full-duration (500 seconds) hot fire, so teams had to provide real-time transfer of propellants from barges, to the run tanks, to the engine.
The process required careful engineering and calibration. “There was a lot to learn to manage real-time operations,” said Maury Vander, chief of NASA Stennis test operations. “Teams had to develop a way to accurately measure propellant levels in the tanks and to control the flow from barges to the tanks and from the tanks to the engine. It is a very precise process.”
NASA Stennis teams conduct a hot fire of the space shuttle Main Propulsion Test Article in 1979 on the B-2 side of the Thad Cochran Test Stand. The testing involved installing a shuttle external fuel tank, a mockup of the shuttle orbiter, and the vehicle’s three-engine configuration on the stand, then firing all three engines simultaneously as during an actual launch.NASA Testing the Way
The biggest challenge was operation of the engine itself. Not only was it the most sophisticated ever developed, but teams would be testing a full engine from the outset. Typically, individual components are developed and tested prior to assembling a full engine. Shuttle testing began on full-scale engines, although several initial tests did feature a trimmed down thrust chamber assembly.
The initial test on May 19, 1975, provided an evaluation of team and engine. The so-called “burp” test did not feature full ignition, but it set the stage for moving forward.
“The first test was a monstrous milestone,” Vander said. “Teams had to overcome all sorts of challenges, and I can only imagine what it must have felt like to go from a mostly theoretical engine to seeing it almost light. It is the kind of moment engineers love – fruits-of-all-your-hard-labor moment.”
NASA Stennis teams conducted another five tests in quick succession. On June 23/24, with a complete engine thrust chamber assembly in place, teams achieved full ignition. By year’s end, teams had conducted 27 tests. In the next five years, they recorded more than 100 annual hot fires, a challenging pace. By the close of 1980, NASA Stennis had accumulated over 28 hours of hot fire.
The learning curve remained steep as teams developed a defined engine start, power up, power down, and shutdown sequences. They also identified anomalies and experienced various engine failures.
“Each test is a semi-controlled explosion,” Vander said. “And every test is like a work of art because of all that goes on behind the scenes to make it happen, and no two tests are exactly the same. There were a lot of knowledge and lessons learned that we continue to build on today.”
NASA Stennis test conductor Brian Childers leads Test Control Center operations during the 1000th test of a space shuttle main engine on the Fred Haise Test Stand (formerly A-1). on Aug. 17, 2006.NASA Powering History
Teams took a giant step forward in 1978 to 1981 with testing of the Main Propulsion Test Article, which involved installing three engines (configured as during an actual launch), with a space shuttle external tank and a mock orbiter, on the B-2 side of the Thad Cochran Test Stand.
Teams conducted 18 tests of the article, proving conclusively that the shuttle configuration would fly as needed. On April 12, 1981, shuttle Columbia launched on the maiden STS-1 mission of the new era. Unlike previous vehicles, this one had no uncrewed test flight. The first launch of shuttle carried astronauts John Young and Bob Crippen.
“The effort that you contributed made it possible for us to sit back and ride,” Crippen told NASA Stennis employees during a post-test visit to the site. “We couldn’t even make it look hard.”
Testing proceeded steadily for the next 28 years. Engine anomalies, upgrades, system changes – all were tested at NASA Stennis. Limits of the engine were tested and proven. Site teams gained tremendous testing experience and expertise. NASA Stennis personnel became experts in handling cryogenics.
Following the loss of shuttles Challenger and Columbia, NASA Stennis teams completed rigorous test campaigns to ensure future mission safety. The space shuttle main engine arguably became the most tested, and best understood, large rocket engine in the world – and NASA Stennis teams were among those at the forefront of knowledge.
NASA conducts the final space shuttle main engine test on July 29, 2009, on the A-2 Test Stand at NASA Stennis. The Space Shuttle Program concluded two years later with the STS-135 shuttle mission in July 2011.NASA A Foundation for the Future
NASA recognized the effort of the NASA Stennis team, establishing the site as the center of excellence for large propulsion test work. In the meanwhile, NASA Stennis moved to solidify its future, growing as a federal city, home to more than 50 resident agencies, organizations, and companies.
Shuttle testing opened the door for the variety of commercial aerospace test projects the site now supports. It also established and solidified the test team’s unique capabilities and gave all of Mississippi a sense of prideful ownership in the Space Shuttle Program – and its defining missions.
No one can say what would have happened to NASA Stennis without the space shuttle main engine test campaign. However, everything NASA Stennis now is rests squarely on the record and work of that history-making campaign.
“Everyone knows NASA Stennis as the site that tested the Apollo rockets that took humans to the Moon – but space shuttle main engine testing really built this site,” said Joe Schuyler, director of NASA Stennis engineering and test operations. “We are what we are because of that test campaign – and all that we become is built on that foundation.”
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Last Updated May 19, 2025 EditorNASA Stennis CommunicationsContactC. Lacy Thompsoncalvin.l.thompson@nasa.gov / (228) 688-3333LocationStennis Space Center Related Terms
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