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Harnessing the 2024 Eclipse for Ionospheric Discovery with HamSCI
3 min read
Harnessing the 2024 Eclipse for Ionospheric Discovery with HamSCIAs the total solar eclipse on April 8, 2024, draws closer, a vibrant community of enthusiastic amateur radio operators, known as “hams,” is gearing up for an exciting project with the Ham Radio Science Citizen Investigation (HamSCI) group. Our goal is clear and ambitious: to use the Moon’s shadow as a natural laboratory to uncover the intricacies of the ionosphere, a layer of Earth’s atmosphere crucial for radio communication.
This rare event offers an unmatched opportunity to observe the ionosphere’s response to the temporary absence of solar radiation during the eclipse. HamSCI, a collective of citizen scientists and professional researchers, plans to seize this opportunity by conducting radio experiments across North America.
This image captures the Moon passing in front of the Sun during an eclipse on Jan. 30, 2014, seen in space by NASA’s Solar Dynamics Observatory. NASA/SDOOur mission centers on two main activities: the Solar Eclipse QSO Party (SEQP) and the Gladstone Signal Spotting Challenge. For the SEQP, amateur radio operators across the continent will aim to establish as many radio contacts (called QSOs) as possible before, during, and after the eclipse, creating a lively scene filled with radio signals. This effort will generate a vast network of observations on radio wave behavior under the eclipse’s unique conditions. The SEQP, a competitive yet friendly event, encourages wide participation and adds an element of excitement.
The Gladstone Signal Spotting Challenge, named in honor of ham radio operator Philip Gladstone for his significant contributions to radio science, adopts a focused approach. Participants will use special equipment to monitor select radio frequencies, aiding in our observation of the ionosphere’s reaction to the eclipse. This crucial aspect of our project validates scientific models of the ionosphere and enriches our understanding of its interaction with solar radiation.
Amateur radio enthusiasts of all backgrounds and skill levels are invited to join these events, united by a shared enthusiasm for scientific exploration and a collective curiosity about the upper atmosphere. Through the support of the amateur radio community, HamSCI demonstrates the profound impact of citizen science in contributing to our scientific knowledge.
As the eclipse ends, our analytical work begins. We will delve into the collected data, interpret it, and publish our findings. These efforts are expected to significantly advance our understanding of the ionosphere and showcase the value of community involvement in scientific discovery.
HamSCI is an organization that aims to inspire wonder and encourage people to participate in scientific discovery. The community of citizen scientists associated with HamSCI believe that the seamless fusion of science and amateur radio is an excellent example of what can be achieved when people come together, driven by curiosity and a passion for exploration.
For more information about HamSCI and details on the SEQP and the Gladstone Signal Spotting Challenge, please visit:
- HamSCI’s Eclipse Information: https://hamsci.org/eclipse
- Contest Information: https://hamsci.org/contest-info
By McKenzie Denton
HamSCI Citizen Science Team Member
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How NASA’s Roman Telescope Will Measure Ages of Stars
Guessing your age might be a popular carnival game, but for astronomers it’s a real challenge to determine the ages of stars. Once a star like our Sun has settled into steady nuclear fusion, or the mature phase of its life, it changes little for billions of years. One exception to that rule is the star’s rotation period – how quickly it spins. By measuring the rotation periods of hundreds of thousands of stars, NASA’s Nancy Grace Roman Space Telescope promises to bring new understandings of stellar populations in our Milky Way galaxy after it launches by May 2027.
Stars are born spinning rapidly. However, stars of our Sun’s mass or smaller will gradually slow down over billions of years. That slowdown is caused by interactions between a stream of charged particles known as the stellar wind and the star’s own magnetic field. The interactions remove angular momentum, causing the star to spin more slowly, much like an ice skater will slow down when they extend their arms.
This effect, called magnetic braking, varies depending on the strength of the star’s magnetic field. Faster-spinning stars have stronger magnetic fields, which causes them to slow down more rapidly. Due to the influence of these magnetic fields, after about one billion years stars of the same mass and age will spin at the same rate. Therefore, if you know a star’s mass and rotation rate, you potentially can estimate its age. By knowing the ages of a large population of stars, we can study how our galaxy formed and evolved over time.
Measuring Stellar Rotation
How do astronomers measure the rotation rate of a distant star? They look for changes in the star’s brightness due to starspots. Starspots, like sunspots on our Sun, are cooler, darker patches on a star’s surface. When a starspot is in view, the star will be slightly dimmer than when the spot is on the far side of the star.
This image of our Sun was taken in August 2012 by NASA’s Solar Dynamics Observatory. It shows a number of sunspots. Other stars also experience starspots, which cause the star’s observed brightness to vary as the spots rotate in and out of view. By measuring those changes in brightness, astronomers can infer the star’s rotation period. NASA’s Nancy Grace Roman Space Telescope will collect brightness measurements for hundreds of thousands of stars located in the direction of the center of our Milky Way galaxy, yielding information about their rotation rates.Credit: NASAIf a star has a single, large spot on it, it would experience a regular pattern of dimming and brightening as the spot rotated in and out of view. (This dimming can be differentiated from a similar effect caused by a transiting exoplanet.) But a star can have dozens of spots scattered across its surface at any one time, and those spots vary over time, making it much more difficult to tease out periodic signals of dimming from the star’s rotation.
Applying Artificial Intelligence
A team of astronomers at the University of Florida is developing new techniques to extract a rotation period from measurements of a star’s brightness over time, through a program funded by NASA’s Nancy Grace Roman Space Telescope project.
They are using a type of artificial intelligence known as a convolutional neural network to analyze light curves, or plots of a star’s brightness over time. To do this, the neural network first must be trained on simulated light curves. University of Florida postdoctoral associate Zachary Claytor, the science principal investigator on the project, wrote a program called “butterpy” to generate such light curves.
A star can have dozens of spots scattered across its surface at any one time, causing irregular brightness fluctuations that make it difficult to tease out periodic signals of dimming due to the star’s rotation. This graph of data from the butterpy program shows how the observed brightness of a simulated star would vary over a single rotation period. NASA’s Roman Space Telescope will be able to measure the light curves, and therefore rotation rates, of hundreds of thousands of stars, bringing new insights into stellar populations in our galaxy.Credit: NASA, Ralf Crawford (STScI)“This program lets the user set a number of variables, like the star’s rotation rate, the number of spots, and spot lifetimes. Then it will calculate how spots emerge, evolve, and decay as the star rotates and convert that spot evolution to a light curve – what we would measure from a distance,” explained Claytor.
The team has already applied their trained neural network to data from NASA’s TESS (Transiting Exoplanet Survey Satellite). Systematic effects make it more challenging to accurately measure longer stellar rotation periods, yet the team’s trained neural network was able to accurately measure these longer rotation periods using the TESS data.
Roman’s Star Survey
The upcoming Roman Space Telescope will gather data from hundreds of millions of stars through its Galactic Bulge Time Domain Survey, one of three core community surveys it will conduct. Roman will look toward our galaxy’s center – a region crowded with stars – to measure how many of these stars change in brightness over time. These measurements will enable multiple science investigations, from searching for distant exoplanets to determining the stars’ rotation rates.
The specific survey design is still being developed by the astronomical community. The NASA-funded study on stellar rotation promises to help inform potential survey strategies.
“We can test which things matter and what we can pull out of the Roman data depending on different survey strategies. So when we actually get the data, we’ll already have a plan,” said Jamie Tayar, assistant professor of astronomy at the University of Florida and the program’s principal investigator.
“We have a lot of the tools already, and we think they can be adapted to Roman,” she added.
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 and Caltech/IPAC in Southern 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 Christine Pulliam
Space Telescope Science Institute, Baltimore, Md.
Media Contact:
Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, Md.
301-286-1940
Christine Pulliam
Space Telescope Science Institute, Baltimore, Md.
NASA Achieves Milestone for Engines to Power Future Artemis Missions
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater) NASA conducted a full-duration RS-25 hot fire April 3 on the Fred Haise Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi, achieving a major milestone for future Artemis flights of NASA’s SLS (Space Launch System) rocket. It marked the final test of a 12-test series to certify production of new RS-25 engines by lead contractor Aerojet Rocketdyne, an L3Harris Technologies company, to help power NASA’s SLS rocket on Artemis missions to the Moon and beyond, beginning with Artemis V. NASA/Danny Nowlin Crews transport RS-25 developmental engine E0525 to the Fred Haise Test Stand at NASA’s Stennis Space Center on Aug. 30, 2023, for the second and final certification test series.NASA/Danny Nowlin A crane lifts developmental engine E0525 onto the Fred Haise Test Stand at NASA’s Stennis Space Center on Aug. 30, 2023, in preparation for a series of 12 tests to collect performance data for lead SLS (Space Launch System) engines contractor Aerojet Rocketdyne, an L3Harris Technologies company, to produce engines that will help power the SLS rocket, beginning with Artemis V.NASA/Danny Nowlin Crews prepare to place RS-25 engine E0525 on the engine vertical installer on the Fred Haise Test Stand at NASA’s Stennis Space Center on Aug. 30, 2023. NASA/Danny Nowlin Team members ready RS-25 engine E0525 for full installation on the Fred Haise Test Stand at NASA’s Stennis Space Center on Aug. 30, 2023, for a second certification test series to collect data for the final RS-25 design certification review.NASA/Danny Nowlin The second – and final – RS-25 certification test series begins Oct. 17, 2023. When the liquid hydrogen and liquid oxygen propellants mix and ignite, an extremely high temperature exhaust, of up to 6,000-degrees Fahrenheit, mixes with water to form steam that exits the flame deflector and rises into the atmosphere, forming a cloud that subsequently cools.NASA/Danny Nowlin A cloud of steam is visible at NASA’s Stennis Space Center during an Oct. 17, 2023, hot fire that marks the first test in the critical series to support future SLS (Space Launch System) missions to deep space.NASA/Danny Nowlin An RS-25 hot fire at NASA’s Stennis Space Center on Nov. 15, 2023, marks the second test of a 12-test engine certification series. The NASA Stennis test team typically fires the certification engine for 500 seconds, the same amount of time engines must fire to help launch the SLS (Space Launch System) rocket to space with astronauts aboard the Orion spacecraft. NASA/Danny Nowlin Operators fire the RS-25 engine at NASA’s Stennis Space Center on Nov. 15, 2023, up to the 113% power level. The first four Artemis missions are using modified space shuttle main engines that can power up to 109% of their rated level. New RS-25 engines will power up to the 111% level to provide additional thrust, so testing up to the 113% power level provides a margin of operational safety.NASA/Danny Nowlin NASA demonstrates a key RS-25 engine capability necessary for flight of the SLS (Space Launch System) rocket during a hot fire on Nov. 29, 2023. Crews gimbaled, or pivoted, the RS-25 engine around a central point during the almost 11-minute (650 seconds) hot fire on the Fred Haise Test Stand at NASA’s Stennis Space Center.NASA/Danny Nowlin The first RS-25 engine test of 2024 takes place on Jan. 17, 2024, at NASA’s Stennis Space Center as crews complete a 500-second hot fire on the Fred Haise Test Stand. NASA/Danny Nowlin A remote field camera offers a head-on view of an RS-25 engine hot fire on the Fred Haise Test Stand at NASA’s Stennis Space Center on Jan. 23, 2024.NASA/Danny Nowlin NASA marks the halfway point of its second RS-25 certification series on Jan. 27, 2024, with the sixth test of the series on the Fred Haise Test Stand at NASA’s Stennis Space Center. For each Artemis mission, four RS-25 engines, along with a pair of solid rocket boosters, power the SLS (Space Launch System) rocket, producing more than 8.8 million pounds of thrust at liftoff. NASA/Danny Nowlin Teams at NASA’s Stennis Space Center install a second production nozzle, left, on Feb. 6, 2024, to gather additional performance data on the RS-25 certification engine at the Fred Haise Test Stand.NASA/Danny Nowlin A new RS-25 engine production nozzle is lifted on the Fred Haise Test Stand at NASA’s Stennis Space Center on Feb. 6, 2024. Crews used specially adapted procedures and tools to swap out the nozzles with the engine in place on the stand.NASA/Danny Nowlin Operators fire RS-25 engine E0525 for 550 seconds and up to a power level of 113% on the Fred Haise Test Stand at NASA’s Stennis Space Center on Feb. 23, 2024. The hot fire test was the first featuring a new engine nozzle, allowing engineers to collect and compare performance data on a second production unit.NASA/Danny Nowlin The third RS-25 hot fire of 600 seconds or more is conducted March 6, 2024, at NASA’s Stennis Space Center. The full-duration test on the Fred Haise Test Stand marked the ninth in a 12-test certification series for production of new engines to help power NASA’s SLS (Space Launch System) rocket on Artemis missions to the Moon and beyond, beginning with Artemis V. NASA/Danny Nowlin The test team at NASA’s Stennis Space Center conduct the first RS-25 hot fire of spring 2024 on March 22, powering the engine for a full duration 500 seconds and up to a power level of 113%.NASA/Danny Nowlin NASA closes in on a milestone for production of new RS-25 engines to help power future Artemis missions to the Moon and beyond following a successful full duration test on March 27, 2024, at NASA’s Stennis Space Center. The hot fire marked the 11th test of a 12-test series.NASA/Danny Nowlin NASA conducted a full-duration RS-25 hot fire April 3 on the Fred Haise Test Stand at NASA’s Stennis Space Center near Bay St. Louis, Mississippi.NASA/Danny NowlinNASA achieved a major milestone April 3 for production of new RS-25 engines to help power its Artemis campaign to the Moon and beyond with completion of a critical engine certification test series at NASA’s Stennis Space Center near Bay St. Louis, Mississippi.
The 12-test series represents a key step for lead engines contractor Aerojet Rocketdyne, an L3Harris Technologies company, to build new RS-25 engines, using modern processes and manufacturing techniques, for NASA’s SLS (Space Launch System) rockets that will power future lunar missions, beginning with Artemis V.
“The conclusion of the certification test series at NASA Stennis is just the beginning for the next generation of RS-25 engines that will help power human spaceflight for Artemis,” said Johnny Heflin, SLS liquid engines manager. “The newly produced engines on future SLS rockets will maintain the high reliability and safe flight operational legacy the RS-25 is known for while enabling more affordable high-performance engines for the next era of deep space exploration.”
Through Artemis, NASA will establish the foundation for long-term scientific exploration at the Moon; land the first woman, first person of color, and first international partner astronaut on the lunar surface; and prepare for human expeditions to Mars for the benefit of all.
Contributing to that effort, the NASA Stennis test team conducted a full-duration, 500-second hot fire to complete the 12-test series on developmental engine E0525, providing critical performance data for the final RS-25 design certification review. The April 3 hot fire completed a test series that began in October 2023.
RS-25 engines are evolved space shuttle main engines, upgraded with new components to produce the additional power needed to help launch NASA’s SLS rocket. The first four Artemis missions are using modified space shuttle main engines also tested at NASA Stennis. For each Artemis mission, four RS-25 engines, along with a pair of solid rocket boosters, power the SLS rocket, producing more than 8.8 million pounds of total combined thrust at liftoff.
“This was a critical test series, and credit goes to the entire test team for their dedication and unique skills that allowed us to meet the schedule and provide the needed performance data,” said Chip Ellis, project manager for RS-25 testing at NASA Stennis. “The tests conducted at NASA Stennis help ensure the safety of our astronauts and their future mission success. We are proud to be part of the Artemis mission.”
The E0525 developmental engine featured new key components – including a nozzle, hydraulic actuators, flex ducts, and turbopumps – that matched design features of those used during an initial certification test series completed at NASA Stennis last summer.
The two certification test series helped verify the new engine components meet all Artemis flight requirements moving forward. Aerojet Rocketdyne is using techniques such as 3D printing to produce new RS-25 engines more efficiently, while maintaining high performance and reliability. NASA has awarded the company contracts to provide 24 new engines, supporting SLS launches for Artemis V through Artemis IX.
“Successfully completing this rigorous test series is a testament to the outstanding work done by the team to design, implement and test this upgraded version of the RS-25 that reduces the cost by 30% from the space shuttle program,” said Mike Lauer, RS-25 program director at Aerojet Rocketdyne. “We tested the new RS-25 engines to the extreme limits of operation to ensure the engines can operate at a higher power level needed for SLS and complete the mission with margin.”
RS-25 Final Certification Test Series by the NumbersAll RS-25 engines are tested and proven flightworthy at NASA Stennis prior to use on Artemis missions. RS-25 tests at the center are conducted by a diverse team of operators from NASA, Aerojet Rocketdyne, and Syncom Space Services, prime contractor for site facilities and operations.
Facebook logo @NASASTENNIS @NASASTENNIS Instagram logo @NASASTENNIS Share Details Last Updated Apr 04, 2024 EditorNASA Stennis CommunicationsContactC. Lacy Thompsoncalvin.l.thompson@nasa.gov / (228) 688-3333LocationStennis Space Center Related Terms Explore More 3 min read NASA to Continue Testing for New Artemis Moon Rocket Engines Article 1 month ago 2 min read NASA Marks Halfway Point for Artemis Moon Rocket Engine Certification Series Article 2 months ago 3 min read NASA Stennis Continues Preparations for Future Artemis Testing Article 4 months ago Keep Exploring Discover More Topics from NASA StennisDoing Business with NASA Stennis
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Eclipses Near and Far
On April 8, 2024, North America will witness its last total solar eclipse for more than twenty years. Other parts of the world will experience the rare celestial event in the coming decade. A total solar eclipse occurs when the Moon passes directly between the Sun and the Earth, blocking its disk from view but making its corona visible in a dazzling display. Although spectacular when seen from the ground, observed from space, solar eclipses appear as large shadows moving across the face of the Earth. The unique geometry of the Earth-Sun-Moon system allows total solar eclipses to occur. Eclipses also occur outside the Earth-Moon system, although the geometries of those worlds rarely if ever produce the stunning display visible on Earth. Spacecraft exploring other worlds have documented these extraterrestrial eclipses.
Left: Schematic geometry of a solar eclipse; sizes and distances not to scale. Right: Path of the April 8, 2024, total solar eclipse. Image credit: courtesy Sky & Telescope.
A solar eclipse occurs when the Moon passes between the Sun and the Earth, with the Moon casting its shadow on its home planet. Although the Sun is much larger than the Moon, it is also much farther away. As seen from Earth, the Sun and Moon have roughly the same angular diameter and appear roughly the same size in the sky. A total eclipse occurs when the Moon blocks out the Sun’s disk entirely. Because the Moon does not orbit in a perfect circle around the Earth, it appears smaller at its farthest point thus creating annular eclipses. Moons around other planets can also create eclipses although their different sizes relative to the Sun do not create our familiar eclipses. Planets with multiple moons can have more than one eclipse occur at the same time.
Left: Gemini XII astronauts photograph the total solar eclipse from Earth orbit in November 1966. Middle: Surveyor 3 observes a solar eclipse from the Moon in April 1967. Right: In November 1969, Apollo 12 astronauts returning from Moon experienced a solar eclipse as the Earth blocked the Sun shortly before splashdown.
Gemini XII astronauts James A. Lovell and Edwin E. “Buzz” Aldrin for the first time photographed a solar eclipse from Earth orbit on Nov. 12, 1966. Sixteen hours into their flight, the nearly total eclipse came into view as they flew over the Galapagos Islands and Aldrin took several photographs and a short film clip. Calculations showed that Gemini XII passed within 3.4 miles of the center of the eclipse’s path that traversed South America. The Surveyor 3 spacecraft observed the first solar eclipse from the Moon on April 24, 1967. Unlike solar eclipses observed on Earth, this time the Earth itself blocked the Sun – observers on Earth saw the event as a lunar eclipse as the Moon passed through the Earth’s shadow. In November 1969, as Apollo 12 astronauts Charles “Pete” Conrad, Richard F. Gordon, and Alan L. Bean neared Earth on their return from the second lunar landing – during which they visited Surveyor 3 – orbital mechanics had a show in store for them. Their trajectory passed through Earth’s shadow, treating them to a total solar eclipse. From their perspective, the Earth appeared about 15 times larger than the Sun. Gordon radioed Mission Control, “We’re getting a spectacular view at eclipse,” and Bean proclaimed it a “fantastic sight.” Conrad reported on the rapidly changing scenery, with the Sun illuminating the Earth’s atmosphere in a 360-degree ring with ever-changing colors while the planet remained pitch black. In the darkness, they could see flashes of lightning in thunderstorms appearing as fireflies. As their eyes adapted to the dark portion of the Earth, they saw landmasses such as India and even city lights. In the center of the Earth’s dark disc they reported seeing a large bright circle that turned out to be the glint of the full Moon reflecting off the Indian Ocean.
Left: The Moon’s shadow photographed from Mir during the August 1999 eclipse. Image credit: courtesy French space agency CNES. Middle: NASA astronaut Donald R. Pettit observed the first solar eclipse from the International Space Station during Expedition 6 in December 2002. Right: Pettit’s second eclipse during Expedition 31 in May 2012.
The credit belongs to French astronaut Jean-Pierre Haigneré for taking the first photograph from Earth orbit of the Moon’s shadow during a solar eclipse. He photographed the Aug. 11, 1999, total eclipse pass over England while onboard the Russian space station Mir as an Expedition 27 flight engineer. NASA astronaut Donald R. Pettit claims the title as the first person to photograph an eclipse from the International Space Station when he observed the Dec. 2, 2002, total eclipse during Expedition 6. As an additional claim, on May 20, 2012, Pettit observed his second eclipse from the space station during Expedition 31, this one an annular eclipse over the Western Pacific Ocean.
Left: Expedition 12 image of the March 2006 total eclipse over the eastern Mediterranean Sea. Middle: Expedition 52 image of the August 2017 total eclipse over North America. Right: Expedition 63 image of the June 2020 annular eclipse.
Left and middle: Two views of the eclipse over Antarctica in December 2021, from the Expedition 66 crew aboard the space station, left, and from the Deep Space Climate Observatory (DSCOVR) satellite. Right: DSCOVR image of the October 2023 annular solar eclipse over North America.
Space station crews have observed and documented a number of solar eclipses in addition to Pettit’s two sightings, their ability to see the Moon’s shadow as it traverses the Earth’s surface determined by their orbital trajectory. Expedition 12 observed the total eclipse on March 29, 2006, Expedition 43 documented the total eclipse on March 25, 2015, Expedition 52 observed the most recent total eclipse visible from North America on Aug. 21, 2017, Expedition 61 observed the annular eclipse on Dec. 26, 2019, Expedition 63 saw the annular eclipse on June 21, 2020, Expedition 66 imaged the total eclipse over Antarctica on Dec. 4, 2021, and Expedition 70 viewed the annular eclipse visible in North America on Oct. 14, 2023. Positioned nearly one million miles away at the L1 Earth-Sun Lagrange point, the National Oceanic and Atmospheric Administration’s Deep Space Climate Observatory (DSCOVR) satellite keeps a watchful eye on Earth’s climate. NASA’s Earth Polychromatic Imaging Camera (EPIC), a camera and telescope aboard DSCOVR, has taken stunning images of the Moon’s shadow during eclipses as well as the Moon transiting across the face of the Earth.
Mars
Beyond the Earth-Moon system, eclipses do not occur on Mercury and Venus since they lack natural satellites to block out the Sun. Mars has two small satellites, Phobos and Deimos, both too small to fully eclipse the Sun, even though it appears only half as big as on Earth. Several rovers have captured Phobos and Deimos as they form annular eclipses. Some astronomers contend that due to the small sizes of the Martian satellites, especially Deimos, compared to the Sun, these are technically transits, not eclipses, but no formal definition exists. The Mars Exploration Rover Opportunity imaged the first eclipses from the surface of Mars shortly after its arrival on the planet, first of Deimos on March 4, 2004, followed by Phobos three days later. More recently, the Mars 2020 Perseverance rover imaged the annular eclipse of Phobos on April 20, 2022, and the eclipse (or transit) of Deimos on Jan. 22, 2024.
Left: Mars Exploration Rover Opportunity images of Deimos, left, and Phobos crossing in front of the Sun. Middle: Perseverance image of a Phobos annular eclipse in April 2022. Right: Perseverance image of a Deimos eclipse (or transit) in January 2024.
Jupiter
Left: Hubble Space Telescope infrared image of a triple eclipse on Jupiter on March 28, 2004, with moons Ganymede, Io, and Callisto casting shadows on the planet. Middle: Hubble Space Telescope image of the Jan. 24, 2015, multiple eclipse on Jupiter, with five of its moons – Callisto, Io, Europa, Amalthea, and Thebe – casting shadows on the planet. Right: Europa eclipses Io in December 2014, as observed through an Earth-based telescope. Image credit: courtesy Jen Miller and Joy Chavez, Gemini Observatory.
Since the outer gas giant planets do not have solid surfaces, no spacecraft has imaged an actual eclipse by one of the multitude of moons orbiting these worlds. What we can observe, through ground-based and orbiting telescopes and spacecraft are the shadows cast by the moons on their home planets. Eclipses on Jupiter are not exceptionally rare given the planet’s large size compared to its many moons and greater distance from the Sun. Only five of Jupiter’s moons, Amalthea, Io, Europe, Ganymede, and Callisto are either large enough or close enough to the planet to completely occult the Sun. And given the low tilts of the moons’ orbits, they cast a shadow on every revolution. Double, triple and multiple simultaneous eclipses are not uncommon. The Hubble Space Telescope has observed numerous such events. Given the number of Jupiter’s moons, especially the four large Galilean moons, and that their orbits all lie very close to Jupiter’s equatorial plane, they occasionally eclipse each other, with the outer moons passing between the Sun and the inner moons. When Earth passes through Jupiter’s equatorial plane, fortunate observers can capture these rare events using ground-based telescopes, sometimes accidentally as they observe the Galilean moons for other reasons.
Left: Juno image of Io’s shadow on Jupiter in September 2019. Right: Juno image of Jupiter’s moon Ganymede casting its shadow on the planet in February 2022.
The Juno spacecraft, in orbit around Jupiter since 2016, has returned stunning images of Jupiter’s cloud patterns. On Sept. 11, 2019, it captured a spectacular image of Io’s shadow on Jupiter’s colorful cloud tops. On Feb. 25, 2022, Juno imaged the largest moon Ganymede’s shadow.
Saturn and beyond
Left: As it orbited Saturn, in November 2009 Cassini imaged eclipses of moons Titan, center, and Enceladus, lower right of Titan, and the planet’s rings. Middle: Titan casts its shadow, elongated by the planet’s curvature, on Saturn in this November 2009 image from the Cassini orbiter. Right: Sequential Hubble Space Telescope February 2009 images of a quadruple eclipse, as Saturn’s moons Enceladus, Dione, Titan, and Mimas cast their shadows on the planet.
Like Jupiter, dozens of moons orbit around the ringed planet Saturn, providing ample opportunities for telescopes and spacecraft to observe them passing in front of and casting their shadows onto the planet. The Cassini spacecraft, in orbit around Saturn between 2004 and 2017, captured thousands of images of the planet, its rings, and its moons. On many occasions, Cassini passed behind the planet and its moons, creating artificial eclipses, while at other times the spacecraft imaged the moons’ shadows on the planet’s cloud tops. The Hubble Space Telescope captured a series of images of a rare quadruple eclipse on Feb. 24, 2009, as Saturn’s moons Enceladus, Dione, Titan, and Mimas transited across the planet, casting their shadows on the cloud tops.
The Cassini spacecraft created this artificial eclipse of Saturn in November 2013 as it traveled beyond Saturn during one of its orbits, with many objects, including Earth, made visible.
On July 19, 2013, Cassini took a series of images from a distance of about 750,000 miles as Saturn eclipsed the Sun. In the event dubbed The Day the Earth Smiled, people on Earth received notification in advance that Cassini would be taking their picture from 900 million miles away, and were encouraged to smile at its camera. In addition to the Earth and Moon, Cassini captured Venus, Mars, and seven of Saturn’s satellites in the photograph.
Left: Composite image showing the relative apparent sizes of the Sun and a selection of planetary moons. Image credit: courtesy sdoisgo.blogspot.com. Middle: July 2006 Hubble Space Telescope image of Uranus and its moon Ariel casting a shadow on the planet. Right: The New Horizons spacecraft created an artificial eclipse as it flew behind Pluto during its July 2015 flyby, the Sun’s rays highlighting its tenuous atmosphere.
The Earth occupies a unique position with the nearly equal apparent diameters of the Moon and the Sun, providing opportunities for annular and total solar eclipses. As viewed from planets farther in the solar system, the Sun’s apparent diameter diminishes, with the apparent sizes of the moons orbiting those planets either larger or smaller than the Sun. Eclipses as we know them do not exist elsewhere in the solar system. Spacecraft exploring those remote worlds easily create artificial eclipses by passing through the planets’ shadows, often revealing important information, such as New Horizons imaging the tenuous atmosphere surrounding Pluto.
Paths of solar eclipses between 2021 and 2030. Image credit: courtesy Greatamericaneclipse.com.
The next total solar eclipse visible in North America will not occur until 2044, but over the next few years, several eclipses visible in other parts of the world will no doubt be targets of opportunity for astronauts’ cameras aboard the space station. And spacecraft exploring planets in the solar system will continue to document eclipses in those faraway places.
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Europe’s next rocket, Ariane 6, passed all its qualification tests in preparation for its first flight, and the full-scale test model has been removed from the launch pad to make way for the real rocket that will ascend to space.
The test model at Europe’s Spaceport in Kourou, French Guiana, stood 62 m high. It is exactly the same as the ‘production model’ Ariane 6 rockets that will soon be launched, except that its boosters do not need to be tested as part of the complete rocket, so the boosters are not fuelled.
Teams preparing Ariane 6 for its inaugural flight successfully completed for the first time a launcher preparation and countdown sequence, on 18 July. Representatives of ESA, Ariane 6 prime contractor ArianeGroup and launch base prime contractor and test conductor CNES completed important objectives for system qualification and performed a series of actions fully representative of a launch chronology.
The launch simulation included the removal of the mobile gantry, the chill-down of ground and launcher fluidic systems, the filling of the upper and core stage tanks with liquid hydrogen (–253°C) and liquid oxygen (–183°C), and at the end of the test, the successful completion of a launch chronology up to the ignition of the Vulcain 2.1 engine thrust chamber by the ground system.
On 5 September 2023 the Vulcain 2.1 engine was ignited, fired for four seconds as planned and switched off before its liquid oxygen and liquid hydrogen fuels were drained to their separate underground tanks. The exercise showed again that the system can be kept safe in the event of a launch abort, as already demonstrated during the 18 July test.
A nighttime full-scale wet rehearsal for Ariane 6 was completed on 24 October 2023, the rocket was fuelled and then drained of its fuel. The test lasted over 30 hours with three teams working in shifts of 10 hours each.
A major full-scale rehearsal was conducted on 23 November 2023 in preparation for its first flight, when teams on the ground went through a complete launch countdown followed by a seven-minute full firing of the core stage’s engine, as it would fire on a launch into space.
A third combined test loading occurred on 15 December 2024 that included a launch countdown to qualify the launch system in degraded conditions and ensure its robustness in preparation for operations. This test sequence included qualification tests of several launch system functions in case of aborted launch and included one ignition of the Vulcain 2.1 engine thrust chamber. It was the fifth countdown run to include loading Ariane 6 with cryo-propellants since July.
On 30 January 2024, the cryogenic connection system passed a last system test of the liftoff disconnection operations lines – the yellow arms supporting the fuel lines to the upper stage to power the Vinci orbital engine. Simultaneously at the bottom of the central core the connection system for the main stage also disconnected.
On 5 February, it was the turn of the electrical umbilical lines to be disconnected. These lines supply the launcher and the satellites inside Ariane 6 with electrical power but also host the digital signals for communications with the informatics system as well as carrying sensor information to ensure the flight system is in good shape for liftoff.
The largest components for the first flight model of Europe’s new rocket Ariane 6 arrived at the port of Pariacabo in Kourou, French Guiana on 21 February 2024 via the novel ship, Canopée (canopy in French). The Ariane 6 stages and components are all manufactured across Europe.
The two central stages for Ariane 6’s first flight were then assembled in the launcher assembly building (BAL) at Europe’s Spaceport. The core stage and the upper stage for Europe’s new rocket Ariane 6 are set to fly in the Summer of 2024. Once assembled, the stages will be transferred to the launch pad.
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