Highlights and Video From NASA’s Artemis I Moon Mission Splashdown

The Orion spacecraft, which is to carry astronauts to and from the moon in coming years, splashed down in the Pacific Ocean Sunday after a successful test flight with no crew aboard.

Kenneth Chang

Suspended under parachutes, an astronaut capsule without astronauts made a gentle splash in the Pacific on Sunday, bringing NASA's Artemis I moon mission to a close.

The end of the uncrewed test flight coincided with the 50th anniversary of the landing of Apollo 17 on the moon, the last time that NASA astronauts walked there.

The Artemis program is the successor to Apollo, and after years of delays and a mounting price tag, the new rocket and spacecraft that will take astronauts back to the moon worked about as smoothly as mission managers could have hoped.

"This was a challenging mission," Mike Sarafin, the Artemis mission manager, said during a news conference after the splashdown. "And this is what mission success looks like."

The moon trip capped a year of spectacular successes for NASA. Its James Webb Space Telescope, which launched almost a year ago, began sending back breathtaking images of the cosmos this summer. Its DART mission showed in September that slamming into an asteroid on purpose could protect Earth in the future if a deadly space rock is discovered on a collision course with our planet.

With the conclusion of Artemis I, more attention will shift toward SpaceX, the private rocket company founded by Elon Musk. NASA is relying on a version of Starship, the company's next-generation spacecraft that has not yet flown to space, to land astronauts on the moon.

On Sunday, just after noon Eastern time, the Orion crew capsule — where astronauts will sit during future flights — re-entered the Earth's atmosphere at 24,500 miles per hour. This was the mission's last major objective: to demonstrate that the capsule's heat shield could withstand temperatures up to 5,000 degrees Fahrenheit.

By design, the capsule bounced off the upper layer of air before re-entering a second time. It was the first time that a capsule designed for astronauts had performed this maneuver, known as a skip-entry, which enables more precise steering toward the landing site. As expected, there were two blackouts in communications as the heat from the capsule's encounter with the atmosphere created electrically charged gases that blocked the radio signals.

Before and after the blackouts, live video from outside Orion's window showed impressive views of Earth getting larger and larger.

At 12:40 p.m. Eastern time, the capsule settled in the Pacific Ocean off Mexico's Baja peninsula. Recovery crews aboard the U.S.S. Portland experienced brisk winds and choppy seas with waves four to five feet high.

Over the next few hours, recovery crews worked to pull Orion out of the water. It will then head back to NASA's Kennedy Space Center in Florida for detailed inspection.

The capsule and the Space Launch System, a giant new rocket, are key pieces of Artemis, which aims to land astronauts on the moon near its south pole as early as 2025.

During the 26 days of Artemis I, glitches popped up as expected, but the flight appeared to be devoid of major malfunctions that would require a lengthy investigation and redesign.

"It's a great demonstration that this stuff works," said Daniel L. Dumbacher, the executive director of the American Institute of Aeronautics and Astronautics, in an interview. Mr. Dumbacher oversaw early work on the Space Launch System more than a decade ago when he was a top human spaceflight official at NASA.

While the mission was years behind schedule and billions of dollars over budget, the flight provided some validation of the traditional government-run approach that NASA took for the development of the complex space hardware.

"From my standpoint, it certainly measures up to the expectations, if not more," said Jeff Bingham, a former senior Republican aide on the Senate subcommittee that shaped legislation in 2010 directing NASA to build the Space Launch System, in an interview. "I feel good about the fact that what we intended is coming to fruition."

Even Lori Garver, a former deputy administrator of NASA who favored turning to private companies to come up with more innovative rocket designs that might have been built faster and cheaper, acknowledged that the Artemis I flight went smoothly.

"It's fantastic that it is working," she said in an interview. "It's a huge relief, and excitement, at NASA."

The space agency now appears to be in good shape to launch the next mission, Artemis II, as planned in 2024. That flight will send four astronauts to the moon, without landing, and then back to Earth.

Vanessa Wyche, director of the Johnson Space Center, said NASA planned to name the crew members for Artemis II early next year.

The moon landing is planned for the third Artemis mission, in which the Space Launch System and Orion will ferry four astronauts to a large looping orbit around the moon. That task will not require capabilities beyond those demonstrated during Artemis I and Artemis II.

Manufacturing the hardware for those missions is already well underway. The Orion capsule for Artemis II is already half-built at the Kennedy Space Center. The service module for Orion, built by Airbus as part of the European Space Agency's contributions to the moon missions, was delivered last year. This weekend, the bottom section for the rocket that will launch Artemis III arrived at Kennedy for installation of the engines.

"This isn't just a one-flight-and-we’re-done," said Jim Free, associate administrator of NASA's exploration systems development directorate.

But Artemis III will hinge on a third requisite piece: a lander built by SpaceX. And for that part of the mission, Mr. Musk's company will have to pull off a series of technological marvels that have never been achieved before.

"I think all eyes do start turning to the lander at some point," said Ms. Garver, whose work during the Obama administration helped lay the foundation for SpaceX's current program of taking astronauts to the International Space Station.

NASA awarded SpaceX a $2.9 billion contract in 2021 to develop and build the lunar lander, which is a variation of the giant Starship rocket, for Artemis III.

A long-promised test launch of Starship to orbit has yet to occur, although a hubbub of activity at the company's development site in South Texas indicates that SpaceX is getting closer.

For Artemis III, the lander will dock with the Orion spacecraft above the moon.

Two astronauts will move over to the lander and head to the south polar region of the moon, spending close to a week on the surface.

But getting the lander to lunar orbit will be far from easy.

For one, it will require at least three different Starships. The Starship system is a two-stage rocket: a reusable booster known as the Super Heavy with the Starship spacecraft on top. After reaching orbit, the tanks of the second stage — the Starship spacecraft — will be almost empty, with not enough propellant to head to the moon.

Thus, SpaceX will first launch a Starship that will essentially serve as a gas station in orbit. Then, it will conduct a series of launches — Mr. Musk has said no more than eight will be needed — of a tanker version of Starship to carry propellant to the gas station Starship.

The final launch is to be the lunar lander Starship, which will sidle up to the gas station Starship in orbit and fill up its tanks. The lunar lander will then finally be ready to head to the moon.

While NASA's Space Launch System rocket flies just once and all of the pieces fall into the ocean as litter, SpaceX's Starship is designed to be entirely reusable. That will make the launches frequent and cheap, Mr. Musk says.

Before Artemis III, SpaceX is to conduct an uncrewed test first to show that it can indeed perform a quick succession of Starship launches, reliably transfer propellants in orbit and safely land on the moon.

The idea of refueling in space dates back decades but remains largely untested.

"Knowing what I think I know about the state of our research into microgravity propellant transfer, we have a long way to go," Mr. Dumbacher said.

Rocket launches also remain risky, so the multitude of Starship launches needed for Artemis III raises the chances that one of them fails, scuttling the entire endeavor.

By turning over development of the lunar lander to SpaceX, NASA hopes that the innovative approach of Mr. Musk's company will provide a lander more quickly at a lower cost than a NASA-led program could.

The flip side is that if SpaceX finds the technical challenges more difficult than expected, NASA will not have an immediate alternative to turn to. The agency just received proposals from other companies for a second lander design, but the second lander design is intended for later moon mission. (In November, NASA awarded SpaceX an additional $1.15 billion to provide the lander for Artemis IV.)

Mr. Musk has also added to his portfolio of companies with the purchase of Twitter, where the turmoil that has followed his takeover of the social media company is now consuming much of his time and attention.

"That is new," Ms. Garver said. "The Elon concerns have escalated," although she said she was not sure how much those directly affect work at SpaceX.

The Information and CNBC reported last month that SpaceX has shaken up the leadership of its Texas Starship operation with Gwynne Shotwell, SpaceX's president, and Mark Juncosa, the company's vice president of vehicle engineering, now overseeing the site.

Last week, Mr. Musk said on Twitter that he continues to oversee both SpaceX and Tesla, his electric car company, "but the teams there are so good that often little is needed from me."

Mr. Bingham said he hoped for Starship to succeed, but "It's a lot of uncertainty in there, and it's worrisome."

During the news conference, Bill Nelson, the NASA administrator, said he asked Mr. Free all of the time whether SpaceX was on schedule. "And the answer comes back to me, ‘Yes, and in some cases, exceeding,’" Mr. Nelson said.

Michael Roston

We’re wrapping up our live coverage of today's NASA Artemis mission splashdown. You can sign up for more space and astronomy coverage, including reminders on your personal digital calendar, at nytimes.com/spacecalendar

Michael Roston

Bill Nelson says that SpaceX's Starship is meeting expectations for timelines with NASA and in some cases exceeding them. "Thus far, I am told, they are on schedule," he said. He says there will be a few test flights in South Texas, and then once they are confident in the spacecraft, they will do launches from Cape Canaveral.

Michael Roston

Melissa Jones, the NASA landing and recovery director who is sitll aboard the U.S.S. Portland, said that many extra hours are being spent recovering the spacecraft from the ocean for testing purposes, and that if astronauts were aboard it would typically take less than two hours.

Michael Roston

Mr. Sarafin says that Orion's parachutes sank in the ocean after the landing before they could be recovered. He added that it's almost didn't matter because they were deployed as planned when the spacecraft landed.

Michael Roston

"I’m not worried about the support from Congress," said Bill Nelson, the NASA Administrator and former Florida senator, who says it will endure as the Artemis program continues. He also said that the excitement around the astronauts announced for future moon missions will get levels of public attention comparable to the seven Mercury astronauts in 1959.

Michael Roston

Vanessa Wyche, director of NASA Johnson Space Center, says that the goal is to name astronauts for the Artemis II mission "in early 2023."

Michael Roston

"Our work has really just begun," said Emily Nelson, chief flight director after highlighting forthcoming efforts to develop systems that will help Artemis II and future missions to succeed.

Michael Roston

The capsule landed within 2.1 nautical miles of the target NASA picked in the Pacific Ocean, said Howard Hu, the Orion program manager.

Michael Roston

Mr. Sarafin paraphrased a plaque left by the Apollo 17 astronauts when they left the moon 50 years ago: "May the spirit of peace in which we came be reflected in the lives of all mankind."

Michael Roston

"This is what mission success looks like," said Mike Sarafin, the Artemis mission manager at NASA.

Michael Roston

Jim Free, the associate administrator for Exploration Systems Development at NASA, said that "This isn't just one flight and we’re done," after highlighting that components are already being built up through the Artemis V mission, with an eye on a lunar base and then Mars.

Michael Roston

NASA is starting a post-landing news conference which you can watch in the YouTube video player now embedded above.

Michael Roston

NASA has concluded its live commentary on the mission. There is a news conference scheduled for 3:30 p.m. and until then we’ll provide additional live footage in the embedded YouTube player above as the crews work to pull the spacecraft from the ocean.

Michael Roston

Applause at mission control at Johnson Space Center in Houston as the team their officially concludes their work on the Artemis I mission. Soon it will be time to pull the Orion spacecraft onto the U.S.S. Portland in the Pacific Ocean.

Kenneth Chang

transcript

Five, four, three, two, one, ignition. We have liftoff. Acknowledge software. FC2 please prepare for Section 35, OAC, SE1 and LVN.

The next time American astronauts land on the moon, they will be stepping out of a spacecraft built by SpaceX. (The SpaceX lander is so big — as tall as a 16-story building — that the astronauts will not so much be stepping out onto the surface as taking an elevator down to it.)

For several years, SpaceX has been working on Starship, a stainless steel behemoth that would be the most powerful rocket ever built. Together with a booster stage, it will stand nearly 400 feet high, taller than the Statue of Liberty and its pedestal.

Starship will also — unlike any previous orbital rocket — be entirely reusable. That fact has the potential to cut the cost of sending payloads to orbit — less than $10 million to take 100 tons to space, Elon Musk, the company's founder, has said.

While Mr. Musk first set out to build Starship with eventual trips to Mars in mind, NASA will use a version of the rocket to ferry astronauts to the surface of the moon from its orbit. Beating out two competitors, SpaceX won a $2.9 billion contract for the mission, Artemis III.

The lunar mission will require about 10 Starship launches. First, SpaceX plans to launch a propellant depot version of Starship — think of it as a gas station — into orbit around Earth. Then, a tanker Starship filled with liquid oxygen and liquid methane propellants will sidle up to the propellant depot Starship. Once the tanker has transferred its load, it will return to Earth.

According to Mr. Musk, no more than eight Starship tanker flights are needed to fill the propellant depot. Then, the lunar lander Starship will launch from Earth, meet up with the propellant depot and fill its tanks before departing for lunar orbit. There, it will wait for the arrival of four astronauts riding in NASA's Orion spacecraft.

When Orion and Starship dock above the moon, two astronauts will move to Starship and head to the lunar south polar region, while the other two will stay in orbit on the Orion spacecraft.

Starship and the two moon-walking astronauts will spend about a week on the surface. They will then blast off to dock again with Orion, and Orion will take the astronauts back to Earth. SpaceX has not said what it plans do with the lunar lander Starship once its NASA mission is complete.

The moon landing is scheduled for 2025, but it is expected to be delayed. Before then, SpaceX is to conduct a demonstration landing of Starship, without any astronauts, on the moon. (That uncrewed demonstration is to show that Starship can land, but taking off again is not a requirement.)

Before SpaceX can even think about getting to the moon, it needs to get to low-Earth orbit. Short test flights of Starship prototypes went to high altitudes and exploded before one successfully landed undamaged in May 2021. The next test flight will go into space, with the booster trying a controlled landing in the Gulf of Mexico, while the Starship stage will try to set down in the Pacific Ocean off Hawaii after flying to orbit.

In June, the Federal Aviation Administration granted environmental approval for the test flight from a site in South Texas, and detailed actions SpaceX must complete before launching. Spacecraft and booster tests are occurring on a regular basis, and in October, a NASA official told a NASA Advisory Council committee that SpaceX was aiming to launch Starship to orbit for the first time in early December.

Since then, Mr. Musk added to his portfolio of companies with the purchase of Twitter, which is now consuming much of his time and attention. CNBC reported last month that SpaceX has shaken up the leadership of its Texas Starship operation with Gwynne Shotwell, SpaceX's president, and Mark Juncosa, the company's vice president of vehicle engineering, now overseeing the site. Last week, Mr. Musk said on Twitter that "little is needed from me," at SpaceX.

On Nov. 29, SpaceX conducted a test of the booster, firing 11 of its engines on the launchpad. It is not known when the company plans the orbital test launch.

Booster 7 completed a long-duration static fire test of 11 Raptor 2 engines on the orbital launch pad at Starbase pic.twitter.com/fFnKR00XNo

Kenneth Chang

The uncrewed Artemis I test flight is over, but Artemis II — what will be the first with astronauts aboard — will not be until at least 2024.

In an interview this summer, Bill Nelson, the NASA administrator, vented about the gap between Artemis I and Artemis II. "I have been raising Cain," he said. "If this first mission is successful and meets the goals and is safe for the astronauts, why can't we get it quicker than two years?"

Mr. Nelson said that years ago, to save money, NASA decided to reuse some of the electronics equipment, known as avionics, from the Artemis I Orion capsule in the new Orion capsule for Artemis II. "It takes them two years to take the avionics out and redo them," Mr. Nelson said, "which is very frustrating to me, but it is what it is."

There will be four astronauts aboard Artemis II. Three will be from NASA, and one will be Canadian, part of the agreement spelling out the Canadian Space Agency's participation in the Artemis program. NASA has not yet announced who will fly on the mission.

The trajectory of Artemis II will be fairly simple. After launch, the second stage of the Space Launch System will push Orion into an elliptical orbit that loops as far out as 1,800 miles above Earth, giving the astronauts time to see how Orion's systems work.

Then, when Orion speeds around again, its engine will fire to send it toward the moon. For Artemis II, the Orion spacecraft will not enter orbit around the moon; it will instead use the moon's gravity to sling back to Earth for a Pacific Ocean splashdown. The entire trip should take around 10 days.

The big event will be Artemis III, currently scheduled for no earlier than 2025.

During the Apollo moon landings in the 1960s and 1970s, the lunar lander was packed into the Saturn V rocket. The lander for Artemis III will be a version of a Starship rocket built by SpaceX. The lunar Starship will be launched separately. Additional Starships would then launch to refill the propellant tanks of the lunar Starship before it left Earth orbit.

At the moon, the Starship lander will enter what is known as a near-rectilinear halo orbit, or N.R.H.O.

Halo orbits are influenced by the gravities of two bodies — in this case, the Earth and the moon — which help to make the orbit highly stable, minimizing the amount of propellant needed to keep a spacecraft circling the moon. A spacecraft in this orbit also never passes behind the moon, where communications with Earth are cut off.

Once Starship is in orbit around the moon, the Space Launch System rocket will send four astronauts in an Orion capsule to the same near-rectilinear halo orbit. The Orion will dock with the Starship. Two of the astronauts will move to the Starship rocket, landing somewhere near the moon's South Pole, while the other two astronauts will remain in orbit in Orion.

After about a week on the surface, the two moon-walking astronauts will blast off in Starship and rendezvous with Orion in orbit. Orion will then take the four astronauts back to Earth.

In August, NASA announced 13 potential landing sites near the moon's south pole.

The astronauts aboard Artemis IV will head to Gateway, a space station-like outpost that NASA will build in the same near-rectilinear halo orbit used for Artemis III. That mission will use a Space Launch System rocket with an upgraded second stage, providing enough power to take along Gateway's habitat module.

Originally, NASA planned for Artemis IV to focus on construction of Gateway. But this year, it decided that the mission would also include a trip to the lunar surface. Last month, NASA announced SpaceX would provide the lander for Artemis IV.

For Artemis V and later missions, the lunar lander will be docked at Gateway. Astronauts will arrive at the Gateway on Orion, then move to the lander for the journey to the lunar surface.

NASA is now considering bids for a different company to provide the lander for Artemis V.

Among the companies that may be bidding to build a competing lander are Blue Origin, the rocket company started by Jeff Bezos, the founder of Amazon.

NASA would then run a competition for future lunar landers similar to how it hired companies to take cargo and astronauts to the International Space Station.

By the end of this decade, humans could walk on the moon once again. Here's how NASA plans to send them there.

Michael Roston

NASA reports that the Orion spacecraft is floating stably in the ocean. Navy helicopters see no damage to the spacecraft or fuel leaking from it. Crews will soon approach the capsule on small boats. It will be hours until it is pulled up out of the water.

Kenneth Chang

Unofficial splashdown time: 12:40:30 p.m. ET.

Kenneth Chang

Splashdown!

Splashdown. After traveling 1.4 million miles through space, orbiting the Moon, and collecting data that will prepare us to send astronauts on future #Artemis missions, the @NASA_Orion spacecraft is home. pic.twitter.com/ORxCtGa9v7

Kenneth Chang

About a minute to splashdown

Kenneth Chang

The three main parachutes are out.

Kenneth Chang

The small drogue parachutes have been deployed.

Kenneth Chang

The last big milestone will be the deployment of the parachutes.

Kenneth Chang

The second blackout is over. More footage from the camera aboard the capsule. That's a sign that the heatshield worked and everything looks great so far.

Kenneth Chang

The second blackout period has begun after Orion performed its "skip re-entry" maneuver.

Kenneth Chang

Why should NASA repeat what it did half a century ago?

NASA officials argue that the moon missions are central to its human spaceflight program — not simply a do-over of the Apollo moon landings from 1969 to 1972.

"It's a future where NASA will land the first woman and the first person of color on the moon," Bill Nelson, the NASA administrator, said during a news conference earlier this year. "And on these increasingly complex missions, astronauts will live and work in deep space and will develop the science and technology to send the first humans to Mars."

NASA is also hoping to jump-start companies looking to set up a steady business of flying scientific instruments and other payloads to the moon and to inspire students to enter science and engineering fields.

For scientists, the renewed focus on the moon promises a bonanza of new data in the coming years. There is a particular interest in the amount of water ice on the moon, which could be used for astronauts’ water and oxygen supplies in the future and could provide fuel for missions deeper into space.

Scientists do not really know how much water is on the moon or how easy it will be to extract the water from the surrounding rock and soil. Future missions could help to resolve that question.

Kenneth Chang

Orion is back in radio contact, and briefly transmitted some amazing video from the spacecraft's cabin camera looking down at the Earth.

We will soon perform the skip entry maneuver. Orion is currently traveling about 16,000 mph. pic.twitter.com/ZSDFqJVq9j

Kenneth Chang

Orion has entered the upper part of Earth's atmosphere. The spacecraft is also in its first temporary blackout of communications with the flight controllers on Earth, lasing about four minutes.

We have now entered the entry phase. The @NASA_Orion spacecraft is traveling just under 25,000 miles per hour. #Artemis pic.twitter.com/Q488mhgfCS

Kenneth Chang

The re-entry is the last key test for this mission. Coming back from the moon is faster and hotter than a re-entry from low-Earth orbit. Orion will enter the atmosphere at a speed just under 25,000 mph and temperatures around the spacecraft will reach 5,000 degrees Fahrenheit or so.

Kenneth Chang

Half an hour to splashdown

Kenneth Chang

Orion just fired its thrusters to make a final tweak of its trajectory.

Kenneth Chang

Orion will perform a "skip re-entry," where it will enter the atmosphere, bounce out and then re-enter a second time. That allows more precise steering toward the landing site. It also means there will be two communication blackouts where the heat creates electrically charged gases around the capsule, blocking radio signals.

Kenneth Chang

18 minutes until Orion enters Earth's atmosphere

Kenneth Chang

The service module has separated from the crew capsule, a key step in the spacecraft's return to Earth. The service module is part of Orion with the main engine, solar panels and other systems that aren't needed for re-entry. It was provided by the European Space Agency, a key shift from earlier missions where NASA made sure it was in charge of all of the pieces on the "critical path."

Thanks for the ride, @esa. 🥹 We should do this again soon. pic.twitter.com/p1mkbGYA4O

Kenneth Chang

Spacecraft can safely return to Earth on land or water, but astronauts who fly on Orion to and from the moon will be splashing down in the Pacific Ocean.

For NASA, it will be a return to historical precedent. During the 1960s and 1970s, the agency's Mercury, Gemini and Apollo astronaut capsules all splashed down in the ocean, while Soviet capsules all ended their trips on land. Russia's current Soyuz crew capsules continue to make ground landings, as do China's astronaut-carrying Shenzhou capsules.

When the Apollo era ended, NASA switched to the space shuttle, which launched like an upright rocket does but landed like an airplane on a runway does. When the space shuttle program ended, NASA eventually replaced it with smaller astronaut capsules.

Crew Dragon, built by SpaceX, has safely completed water landings in the Atlantic Ocean or the Gulf of Mexico for five NASA astronaut missions as well a pair of private astronaut flights.

Another capsule, Starliner, which Boeing built for NASA, will return its astronaut crews on land in New Mexico. While Boeing has safely landed two uncrewed Starliners, problems with testing and launching the capsule have delayed its first astronaut flight to 2023.

One difference between the new Orion spacecraft and the Apollo command modules of the 1960s and 1970s is that it will perform what NASA calls a skip re-entry. During the skip re-entry, the capsule will enter the upper atmosphere, oriented at angle where the capsule generates enough aerodynamical lift to bounce back up out of the atmosphere. It will then re-enter a second time. It's almost like throwing a rock that bounces off the surface of a pond before sinking.

A skip re-entry has not been attempted before for a spacecraft made to carry humans. The maneuver reduces the peak heating and the forces that future astronauts will experience. But because of the longer duration passing through the atmosphere, the total amount of energy absorbed by the heat shield will be greater. The maneuver also allows more precise steering toward a landing site closer to the coast.

Michael Roston

The capsule is getting ready to separate from the service module section that has been powering Orion during its trip around the moon.

Solar wings are being moved into position ahead Orion's crew module separating from the @ESA service module. We're now 10 minutes from separation. 5000 miles / 8000 km from Earth. pic.twitter.com/5KH1s84Nup

Kenneth Chang

One hour until splashdown.

Kenneth Chang

Launching to space is dangerous. Historically, NASA and other space agencies conduct a test flight of a new rocket without passengers before risking the lives of astronauts. During the 1960s, there were two uncrewed flights of the Saturn V before three astronauts boarded Apollo 8, which circled the moon 10 times on Christmas Eve in 1968.

While there were no humans aboard Orion for this journey to the moon, the capsule's seats were not empty. One was filled with a full-size mannequin named Commander Moonikin Campos in honor of Arturo Campos, a Mexican American engineer who played a key role in bringing the crippled Apollo 13 spacecraft safely back to Earth.

The moonikin, wearing the same spacesuit that astronauts will don in future missions, was equipped with two radiation sensors. Additional sensors behind its headrest and under its seat recorded the vibrations and forces that astronauts will experience during the mission.

Two other seats are occupied by model female torsos, named Zohar and Helga, that consist of 38 slices of plastic that mimic the density of bones, muscles and organs. Each torso contains 5,600 tiny crystal sensors to measure the amount of radiation absorbed during the mission. The torsos also contain battery-powered sensors that measured radiation exposure moment by moment.

Zohar wore a protective radiation vest made by an Israeli company; Helga did not. The experiment tested how well the vest is for shielding the greater amounts of radiation astronauts were exposed to, especially observing the effects on radiation-sensitive organs, like the breasts and ovaries of women.

"What I like to say is that the vest is a gender equalizer," said Oren Milstein, the chief executive of StemRad, which manufactured the vest. The vest should reduce the radiation exposure by half, Dr. Milstein said.

Another passenger is a small Snoopy, the Peanuts character, wearing an orange spacesuit with gloves, boots and a NASA patch. Snoopy served as the zero-gravity indicator, a tradition of bringing up an object — often a stuffed animal — that starts floating once the spacecraft has reached orbit.

And although there are no people aboard, there are living organisms. Orion carried experiments to measure the effects of deep space radiation on yeast, algae, fungi and plant seeds.

While most test flights have been uncrewed, the debut journey of the space shuttle was a notable exception. Two astronauts flew Columbia during its first trip to orbit in 1981.

At the request of the Trump administration in 2017, NASA studied whether to put astronauts on the first Space Launch System mission, then known more blandly as Exploration Mission-1 instead of Artemis. NASA concluded that it would be feasible, but it would add between $600 million and $900 million to the cost, and the mission, which was scheduled for 2020, would be delayed.

Flying Artemis I without astronauts gave NASA more flexibility. The mission stretches into December — longer than the Orion spacecraft is designed to work in deep space. NASA would have been able to continue with the mission if circumstances arose like a partial failure of a power or propulsion system. If there were astronauts aboard, mission managers would regard that as too risky.

During a news conference this summer, Mike Sarafin, the Artemis I mission manager, said NASA would have proceeded with the engine firing to send the spacecraft toward the moon "unless we’re sure that we’re going to lose the vehicle."

As an example, if Orion's solar array did not fully deploy, "We would proceed," Mr. Sarafin said. "And that is something that we wouldn't necessarily do on a crewed flight."

Michael Roston

There are 4 to 5 foot waves in the part of the Pacific Ocean where the Orion capsule will be recovered. "Just another day in the park for us," said Wayne Shearer, a Navy diver who will be involved in recovering the spacecraft from the water, during the NASA broadcast.

Michael Roston

NASA has started their live video program today with footage from Apollo 17. 50 years ago today, that mission set down on the moon, the last time astronauts visited that world.

Kenneth Chang

Orion went, orbited the moon and is now coming back after 26 days.

For the most part, the mission has been a success with no major malfunctions. Some systems, like the solar panels, performed better than designed.

That does not mean nothing went wrong, but mission managers generally described issues that they encountered as "funnies" — systems that did not quite work as expected, necessitating some investigation and sometimes some adjustments in their procedures.

NASA had three primary objectives during this Artemis I mission:

Demonstrate that the new giant Space Launch System rocket works to deliver the Orion crew capsule into orbit.

See how Orion operates during three weeks in space, enveloped in vacuum and pelted by radiation.

Verify that Orion's heat shield can survive the re-entry into Earth's atmosphere, arriving at a velocity of 24,600 miles per hour. As it slams into the air, the heat shield will reach temperatures up to 5,000 degrees Fahrenheit.

By Sunday, almost all of the objectives had been achieved except the last one: a safe return to Earth. Mission managers even added more test objectives. For example, Orion is designed to fly with its tail end, where the solar panels are, pointed at the sun. One of the additional tests was seeing how the spacecraft behaved when it was about 20 degrees out of this alignment, in particular how the angle affected the warming of the spacecraft by sunlight.

As Orion swung behind the moon, it fired its engine to be captured by moon's gravity. It passed within 80 miles of the surface before heading toward what is known as a distant retrograde orbit. (Distant because the orbit was 40,000 miles from the moon, retrograde because the direction was opposite the moon's motion around the Earth.)

Another engine firing pushed Orion into the distant orbit, and it then circled halfway around the moon. Then the process was essentially reversed: an engine firing to push Orion out of the distant retrograde orbit to another close powered flyby of the lunar surface that sent the spacecraft on a slingshot trajectory back to Earth.

The small glitches that occurred included star trackers that were momentarily confused when the thrusters fired and produced sparkles of propellant and a 45-minute loss of communication because NASA's Deep Space Network of radio antennas was configured incorrectly.

With modern video cameras, Orion was able to capture sharp images of itself with the moon and Earth in the background.

The New York Times

If you missed the launch that started the journey of the Artemis mission to the moon, no one could blame you: It happened at 1:47 a.m. Eastern time on Nov. 16.

To finally send the giant Space Launch System rocket and the uncrewed Orion capsule to space, NASA had to overcome several obstacles. Technical problems grounded the flight in August and again in September, then Hurricane Ian forced rolling the vehicle off the launchpad and delayed the flight to November. That month's late-season Hurricane Nicole also caused a brief postponement of the mission.

The delays also caused NASA to lose prime viewing hours — the August and September launch attempts were scheduled for the daytime when most people in the United States could be expected to be awake.

If there was any consolation for the late-night flight, the rocket's blast really popped in the dark.

"I’m telling you we’d never seen such a tail of flame," Bill Nelson, the NASA administrator, said after the flight in November.

You can see it for the first time the video above — or enjoy it again if you managed to catch the launch live.

Michael Roston

Right now in the video player embedded above, you can see a beautiful live image of our planet from the approaching Orion capsule.

Flight Day 26. Orion is returning to Earth. 20,000 miles / 32,000 km from Earth. Traveling at 9,600 mph / 15,500 kmh and accelerating. pic.twitter.com/EWCKXkChjg

Michael Roston

Looks like a nice day out in the Pacific Ocean near where the Orion capsule will splash down in about two hours.

Astronaut Shannon Walker releases a weather balloon aboard the USS Portland with the 45th Weather Squadron. @NASA_Orion is on its last full day in space with splashdown targeted for 11:39 a.m. CST (12:39 p.m. EST) today, Dec. 11. pic.twitter.com/JPNjDsAxwX

Kenneth Chang

CREW module

Can hold four people

launch abort system

Can carry the crew module to safety if there is an emergency during launch

Solar arrays

5 ft.

Spacecraft

adapter

Motors

service module

Provides power and propulsion to the crew module

5 ft.

launch

abort system

Can carry the crew module to safety if there is an emergency during launch

Motors

CREW module

Can hold four people

Solar

arrays

Spacecraft

adapter

service module

Provides power and propulsion to the crew module

CREW module

Can hold four people

launch abort system

Can carry the crew module to safety if there is an emergency during launch

Solar arrays

Spacecraft

adapter

Motors

service module

Provides power and propulsion to the crew module

10 ft.

Source: NASA

By Eleanor Lutz

The NASA spacecraft returning to Earth is called Orion. It has been on a 26-day journey to the moon and back to test how ready it will be when astronauts board for a similar, shorter voyage no earlier than 2024.

Development of the Orion crew capsule started in 2006 as part of Constellation, an earlier moon program started under President George W. Bush. Costs for Constellation soared, and the Obama administration tried to cancel it entirely in 2010.

However, Congress rebelled against that decision, leading to a revival of Orion and Ares V, the heavy-lift rocket that was planned for Constellation, which turned into the Space Launch System.

The Orion capsule is designed for trips that last multiple weeks in deep space beyond low-earth orbit. That means that the vehicle, while bigger than the Crew Dragon capsule that carries astronauts to the International Space Station, has a bit less space on the inside to make room for more robust life support systems.

But Orion can't get to the moon on its own. Astronauts will need a big rocket, in the form of the Space Launch System — the most powerful one since Saturn V took NASA astronauts to the moon in the 1960s and 1970s. The one that carried Artemis I was 322 feet tall and weighed 5.5 million pounds when filled with propellants.

It will be able to lift more than 200,000 pounds to low-Earth orbit and send nearly 60,000 pounds of payload to the moon.

The rocket, known as S.L.S., resembles a stretched external tank that was used by the retired space shuttles, and the side boosters that help it get to space look a lot like engines the shuttles used.

This is by design: To simplify development of its new moon rocket, NASA reused much of its 1970s space shuttle technology. The rocket's central stage is the same 27.6-foot diameter as the 1970s shuttle's external tank, and it is covered with the same orange insulation.

The four engines in the core stage are the same as the space shuttle main engines. In fact, the first three Artemis missions will actually use engines that were pulled from the old shuttles and refurbished. But because none of the S.L.S. rockets will be used more than once, NASA will run out of old shuttle engines after Artemis IV and will need new engines for Artemis V and later missions.

The side boosters are longer versions of those that were used for space shuttle flights. During the shuttle era, NASA recovered and reused similar boosters. But for the Space Launch System, which will launch only about once a year, the agency decided it would be easier and more economical to let the boosters sink into the ocean and use new ones for each flight.

The second stage of the S.L.S., which propelled the Orion capsule on a path to the moon once it reached low-Earth orbit, is essentially a modification of the one used for another rocket called Delta IV. A new upgraded second stage will be used for Artemis IV, making the rocket even more powerful.

Kenneth Chang

Another day, another rocket launch by SpaceX, and another spacecraft going to the moon. All those seem commonplace these days.

SpaceX has already launched its Falcon 9 rocket more than 50 times this year. NASA's Artemis I, an uncrewed test flight that is a precursor to future astronaut missions, returned to Earth after orbiting the moon. CAPSTONE, a small NASA-sponsored CubeSat, is still orbiting the moon after being launched in June. A robotic South Korean orbiter, Danuri, was launched to the moon in August.

But the lunar lander that was carried by a Falcon 9 rocket from Cape Canaveral, Fla., on Sunday is not a NASA mission. Instead, known as M1, it is from a small Japanese company, Ispace. The payloads on M1 include a rover from the United Arab Emirates and a small two-wheeled Transformers-like robot for the Japanese space agency.

While the mission lifted off at 2:38 a.m. Eastern time, you’ll have to wait until April to see if these robotic explorers make it there, possibly becoming the first cargo successfully carried to the lunar surface by a private company.

The company started as one of the competitors for the Google Lunar X Prize, a competition that offered a $20 million prize for the first private spacecraft to land on the moon, travel 500 meters and send back video from the lunar surface.

At the time, the Japanese group, known as Team Hakuto, focused on developing a rover, and it was to rely on a competing team from India for the ride to the surface of the moon. If that had worked, the two rovers would have been racing to see which could travel the 500 meters first.

However, the Lunar X Prize expired before any of the teams made it to the launchpad. An Israeli competitor, SpaceIL, launched its craft in 2019, but its moon lander crashed on the lunar surface.

The group known as Team Hakuto evolved into Ispace, attracting sizable investment, and the company plans to launch a series of commercial moon landers in the coming years.

For Sunday's mission, the payloads include the Rashid lunar rover from the Mohammed Bin Rashid Space Center in Dubai; a two-wheeled "transformable lunar robot" from JAXA, the Japanese space agency; a test module for a solid-state battery from NGK Spark Plug Company; an artificial intelligence flight computer; and 360-degree cameras from Canadensys Aerospace.

As a vestige of its Lunar X Prize heritage, it is also carrying a panel engraved with the names of people who provided crowdfunding support and a music disc with a song performed by the Japanese rock band Sakanaction.

The Japanese company's lander is not the only passenger on Sunday's flight. A secondary payload on the Falcon 9 is a small NASA mission, Lunar Flashlight, which is to enter an elliptical orbit around the moon and use an infrared laser to probe the deep, dark craters at the moon's polar regions.

Much like some other recent moon missions, M1 is taking a circuitous, energy-efficient trip to the moon and will not land, in the Atlas Crater in the Northern Hemisphere of the moon, until late April. The fuel-efficient trajectory allows the mission to pack in more payload and carry less fuel.

As part of the Artemis I mission, NASA's Orion spacecraft traveled to, then orbited, the moon. It returned to Earth later on Sunday, with a splashdown into the Pacific Ocean.

A small NASA-financed mission called CAPSTONE also arrived recently to explore an orbit in which NASA plans to build a lunar outpost where astronauts will stop on the way to the moon.

And while it hasn't arrived yet, the moon will get a third new visitor next month. Danuri, a South Korean space probe, was launched in August and is due to enter lunar orbit on Dec. 16. The spacecraft will help the development of technology for future Korean missions, and it also carries scientific instruments to study the moon's chemical composition and magnetic field.

A NASA program called Commercial Lunar Payload Services, or CLPS, has been looking to send experiments to the surface to the moon. The first two missions, from Intuitive Machines of Houston and Astrobotic Technology of Pittsburgh, plan to launch next year after considerable delays. Intuitive Machines’ lander, which could be launched as early as March, could even beat Ispace to the moon because it's using a quick six-day trajectory.

Because it is not an American company, Ispace could not directly participate in the NASA program. However, it is part of a team led by Draper Technologies of Cambridge, Mass., that has won a CLPS mission from NASA. That mission is scheduled to be launched in 2025.

Kenneth Chang

And on the 26th day, the moon capsule returned to Earth.

During the early hours of Nov. 16, NASA launched a giant rocket toward the moon. The rocket reached orbit and sent a small capsule, this time with no astronauts on board, on its way to the moon. This was the beginning of Artemis I, a mission to test NASA's ability to return astronauts to the moon 50 years after it last accomplished that feat.

On Sunday, Artemis I will come to an end when that vehicle splashes back down in the Pacific Ocean.

The splashdown is expected 12:39 p.m. Eastern time. NASA Television will begin streaming coverage of the return at 11 a.m. Eastern time on Sunday, or you can watch on a video player we will provide here. In the video player above you can view occasional live video from the Orion capsule in space until NASA's coverage of the splashdown begins.

NASA will hold a news conference at 3:30 p.m. Eastern time after the splashdown.

The primary goal of Artemis I was a crucial shakedown of NASA's new space hardware, including Orion, a spacecraft for carrying astronauts to deep space, including lunar orbit. Orion is unoccupied this time, but it will take astronauts to the moon in the coming years.

During its nearly monthlong journey to and from the moon, Orion got within 80 miles of the lunar surface. It also extended its orbit tens of thousands of miles from the moon. If all goes well on Sunday, the mission will complete its most important objective: proving that the spacecraft can safely re-enter Earth's atmosphere on the way back from the moon, and then splashing down under parachutes in the Pacific Ocean to the west of Mexico's Baja Peninsula.

The Orion spacecraft will perform what NASA calls a skip re-entry. During the skip re-entry, the capsule will enter the upper atmosphere, oriented at an angle where the capsule generates enough aerodynamic lift to bounce back up out of the atmosphere. It will then re-enter a second time. It's almost like throwing a rock that bounces off the surface of a pond before sinking. The maneuver allows more precise steering toward a landing site closer to the coast.

NASA officials argue that the moon missions are central to its human spaceflight program — not simply a do-over of the Apollo moon landings from 1969 to 1972.

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Highlights and Video From NASA’s Artemis I Moon Mission Splashdown