NASA is set to send four astronauts — three from the United States and one from Canada — on a trip around the moon and back without landing there. This is the first time that anyone would travel this far from Earth since Apollo 17 in 1972.

If Artemis II succeeds, missions that return astronauts to the moon’s surface could follow later in the decade.

Here’s what to know about the mission, and the astronauts making the trip.

This is NASA’s big new rocket — the present-day equivalent of the Saturn V used during the Apollo moon landings. It is 322 feet tall and weighs 5.75 million pounds when filled with propellant. Launching from NASA’s Kennedy Space Center in Florida, it is capable of sending about 60,000 pounds of payload to the moon.

The design is a remix of technologies developed in the 1970s for the space shuttles.

NASA led the design of the Space Launch System rocket and the Orion capsule, and it hired the commercial companies SpaceX and Blue Origin to provide the lunar landers for future Artemis missions.

Four astronauts were selected for the mission in 2023 and have been training for their journey since then. The three NASA astronauts — the commander Reid Wiseman, the pilot Victor Glover and a mission specialist, Christina Koch — have been to the International Space Station. Mr. Glover is set to be the first Black man to travel around the moon, and Ms. Koch the first woman. A mission specialist from Canada, Jeremy Hansen, has not yet been to space. Mr. Hansen will be the first person who is not a NASA astronaut to make the trip.

Orion is the spacecraft that will carry the astronauts to the moon and back. The top part — the crew module — will return to Earth, splashing down in the Pacific Ocean, off the coast of San Diego.

After Neil Armstrong stepped on the moon, many felt that the space race with the Soviet Union was won and that new lunar missions were not worth the expense. In the decades since, NASA has focused on low-Earth orbit exploration with the space shuttles and the International Space Station.

During the first Trump administration, going back to the moon became a priority for NASA and the program continued under President Joseph R. Biden Jr. The Artemis missions aim to explore the moon for scientific discovery and mine it for resources like frozen water for later space missions, and helium-3 for future fusion power plants.

Artemis I: The first mission of the Artemis program, launched in November 2022, sent an uncrewed Orion capsule into orbit around the moon. Along the way, the mission deployed several small satellites known as CubeSats. Orion returned to Earth 26 days later.

Artemis II: This year’s mission aims to test the life-support and other critical systems on Orion. After separating from the upper stage of the rocket, the crew plans to test Orion’s ability to execute docking maneuvers for future flights. If any serious problems arise while Orion is still in Earth orbit, mission managers will bring the astronauts home.

Once the spacecraft heads to the moon, it will be on what is known as a “free return” trajectory — the moon’s gravity will swing the capsule directly back to Earth without the need for any firing of the engines. That means the Orion capsule could return to Earth even if there were a failure of the propulsion system.

As the Orion flies by the moon’s far side, the astronauts will make observations of the lunar surface, including parts that have never been seen by human eyes. (The Apollo missions were timed so that the near side of the moon, where the astronauts landed, was in daylight, so the far side then was largely in darkness.)

When the moon is between the spacecraft and Earth, communications with the astronauts will be interrupted for 30 to 50 minutes.

Future Artemis missions: In February, NASA upended its plans for what happens after Artemis II. Artemis III was supposed to be the keystone event, landing astronauts near the south pole of the moon by the end of 2028. Instead, it is now rescheduled to launch in mid-2027, and remain in Earth orbit as a test flight for practicing rendezvousing with one or both of the lunar landers that are under development by SpaceX and Blue Origin. And if it goes well, it could set up two landing attempts, Artemis IV and Artemis V, in 2028. That would meet President Trump’s goal of sending NASA astronauts back to the moon before the end of his second term.

Over the last two decades, NASA has spent more than $50 billion developing and building the Space Launch System, the Orion capsule and the accompanying ground systems needed to launch them. There is no simple price tag for just Artemis II, although a report by the NASA inspector general in 2021 said each launch of the Space Launch System and Orion capsule costs about $4.1 billion.

Residents were supposed to get a respite from the ankle-nipping mosquitoes that fueled a recent surge in dengue fever in Los Angeles County.

Typically, the invasive mosquitoes — called Aedes aegypti — essentially disappear from winter until early May in the region.

Instead, complaints to local agencies tasked with controlling the pests spiked recently.

“We have not seen them go away altogether like they have in previous years,” said Susanne Kluh, general manager for the Greater Los Angeles County Vector Control District.

Their unusual presence adds to the urgency of work going on in a 40-foot shipping container tucked away in Pacoima. It’s about to transform into a bustling nursery for tens of thousands of mosquitoes.

This May, the district is set for the third year in a row to release legions of sterilized male mosquitoes — which don’t bite — into parts of Sunland-Tujunga.

The last two years were promising, with the female population in two treated neighborhoods plunging by an average of more than 80%.

Yet business owners have signaled they’re not willing to pay to expand it.

That’s thrown uncertainty into officials’ goal of eventually bringing the approach to their whole service area, spanning 36 cities and unincorporated communities.

Steve Vetrone, assistant general manager at the Greater L.A. district.

(Ronaldo Bolanos / Los Angeles Times)

“Unfortunately, that’s going to be a rather expensive endeavor,” said Steve Vetrone, an assistant general manager for the district. “I can tell you right now that’s not something that we can do with our current operating budget.”

A need, an ask and a disappointing answer

Aedes aegypti are a new-ish local fixture. Native to Africa, the black-and-white striped mosquitoes were first detected in California in 2013 and landed in L.A. County the following year.

“Despite our best efforts, they’ve been able to just outpace us, and they’re now in every city and community within our district,” and all of Southern California, Vetrone said. In fact, the low-flying, day-biting mosquitoes are present in nearly half of California’s counties, including Shasta in the far north.

Desperate to find a solution, many are trying the so-called sterile insect technique — including vector control districts serving Orange and San Bernardino counties, as well as the San Gabriel Valley — and “we kind of all hope that this is going to be our silver bullet,” Kluh said.

The idea is fairly simple: unleash sterile males so that they far outnumber wild ones — say, 10 to 1 or even 100 to 1. The goal is for the altered males to mate with females, producing eggs that don’t hatch.

Kluh’s district uses X-rays to sterilize males but there are other methods, such as using genetically modified insects or ones infected with bacteria.

Female mosquitoes are fed different types of blood — pig and cow — to see which leads to the most eggs.

(Ronaldo Bolanos / Los Angeles Times)

The technique, while promising, requires time and money.

In California, property owners foot the bill for local mosquito (and other pest) control, with some paying an annual fee called a benefit assessment.

Levying a new fee requires approval from home, apartment and business owners, in accordance with Proposition 218.

To unleash sterile male mosquitoes in a broader swath of the Greater L.A. district, officials are seeking up to $20 a year per single family home. That would be on top of $18.97 that homeowners now pay for the agency’s services.

Last April, the district sent out 50,000 sample ballots to property owners, asking if they’d support the increase.

Only 47% of those returned were in favor.

“Data showed that single family homeowners were pretty supportive, but fewer business owners with larger parcels and potentially higher dues did not see the benefit in the additional expense,” Kluh said in an email.

Business owners might not live in the area, but their vote — if their property spans several acres — is weighted more heavily.

Times readers, commenting on a story from last year about the proposal, responded favorably.

“I hate mosquitos because they love me so much,” one reader said. “I would happily spend $20 to reduce their populations! I probably spend more [than] that on repellent.”

Officials haven’t given up, and plan to send out another round of sample ballots next year.

Kluh already has talking points for businesses in her back pocket: Restaurant owners should have an interest in making outdoor dining more pleasant, while apartment owners could lose revenue if their renters are sickened by an outbreak of Zika, chikungunya or yellow fever — all diseases transmitted by Aedes aegypti, she said.

Making mosquitoes that can’t reproduce

On a recent tour of the Pacoima insectary, Nicolas Tremblay, a senior vector ecologist with the district, whipped out a small container filled with a handful of what looked like vitamins.

But the clear pill cases were filled with about 6,500 mosquito eggs and bovine liver powder.

Nicolas Tremblay, senior vector ecologist, tapes trays to indicate pill capsules filled with mosquito eggs were placed in water.

(Ronaldo Bolanos / Los Angeles Times)

The pills are dropped into trays of water, where the eggs hatch and the larvae feed on the powder. It takes about nine days to go from egg to buzzing adult.

The males are then chauffeured to Garden Grove, where they’re zapped with X-rays. Then they’re driven back and set free the next day.

“It’s crazier around August, September, is when we’ll probably reach our peak production” of up to 72,000 mosquitoes a week, he said. “All these [trays] would be full of water and mosquitoes.”

In 2024, the district launched its pilot, releasing nearly 600,000 sterilized males in two Sunland-Tujunga neighborhoods over about five months.

The population of Aedes aegypti females dropped by an average of 82% compared with a control area.

The stakes became clear that year, when California reported 18 locally acquired dengue cases — a sharp rise from the first-ever cases confirmed the year before.

Last year, the pilot saw similar success, though there was also a natural drop in activity districtwide.

On the recent visit to the insectary, several hundred mosquitoes flew around in white mesh cages, serving as participants in a study to see which blood they prefer — pig or cow.

“We haven’t completed the trials yet, but it seems like they didn’t care,” he said.

One thing scientists already know: Aedes aegypti love biting people.

A highly adaptive foe

The invasive mosquitoes can lay their eggs in tiny amounts of water. A bottle cap or crease in a potato chip bag is fair game.

What’s more, mosquitoes in the Greater L.A. district are resistant to a lot of pesticides.

Now, there might be a new concern. Typically, the invasive mosquitoes go into a type of hibernation every year.

Kluh said it appeared that they may have mutated in a way that allows them to stay active through the winter.

A warming climate has already expanded their season and allowed them to move into formerly inhospitable regions.

Releasing sterilized males involves no pesticides, and also leverages the insect’s biology: Males in lust are adept at finding females.

Many residents are thrilled by the promising tool, but others bristle at the idea of manipulating nature.

“There’s folks that are in favor and then there are folks that are just absolutely opposed because it’s like, ‘You’re playing God,’” Vetrone said.