Rick Binzel had three key messages to convey to attendees at the start of a workshop held in April at a European Space Agency center in the Netherlands: “Apophis will miss the Earth. Apophis will miss the Earth. Apophis will miss the Earth.”

Apophis, a near-Earth asteroid about 350 meters across, will skim by the Earth on April 13, 2029, coming within 32,000 kilometers — closer than satellites in geostationary orbit. Observations have ruled out any chance of an impact in 2029 and for at least the next 100 years.

Apophis, rather than posing a threat to Earth, instead presents an opportunity for researchers like Binzel, a professor of planetary science at MIT and one of the organizers of the Apophis T-5 Years workshop. He and others at the conference said asteroids as large as Apophis fly this close to the Earth only once every thousand years, making it a seemingly unmissable opportunity to easily study an asteroid up close.

“Apophis stands out. It’s one of the easiest to reach,” said Richard Moissl, head of ESA’s Planetary Defence Office, at the workshop. “There’s not a reason against it.”

There is, as the workshop revealed, no shortage of ideas for missions to study Apophis before and after the 2029 flyby. However, a shortage of funding means there is no guarantee any of those missions will fly, with timing running out to decide their fates.


So far, only one mission is slated to visit Apophis around the time of the flyby, and that spacecraft is already in space. Two years ago, NASA approved an extension for its OSIRIS-REx asteroid sample return mission. While a capsule containing 121.6 grams of material from the asteroid Bennu landed in Utah in September 2023, the main spacecraft flew by Earth on a trajectory that will allow it to rendezvous with Apophis shortly after the asteroid’s 2029 flyby. The spacecraft, rechristened OSIRISAPEX (for “Apophis Explorer”), will be able to spend about 18 months at Apophis, said Michael Nolan, deputy principal investigator for the mission. That will include taking high-resolution imagery of the asteroid’s surface and measurements of its shape and mass. OSIRIS-APEX will also approach the surface and fire its thrusters. “We’ll be able to go investigate what we do to the surface and what’s underneath,” he said.

Scientists, though, want to send one or more spacecraft to Apophis before the 2029 flyby. The goal is to characterize the asteroid before its close approach to the Earth and compare it to what OSIRIS-APEX sees to determine if tidal forces from Earth’s gravity reshape Apophis in any way.

Understanding any changes in Apophis, Binzel said, is important not just for science but also for planning planetary defense. “This is why this Apophis encounter, this once-per-thousand-year event, is a knowledge opportunity for the science of planetary defense.”

Perhaps the best prospect for studying Apophis before its flyby will come from a pair of smallsats currently in storage. Janus would have launched as a rideshare on the Psyche mission to the main belt asteroid of the same name, with the smallsats going by two pairs of binary asteroids.

However, delays in Psyche’s launch meant that Janus could no longer carry out its planned mission, and the revised launch date did not provide any viable alternative missions. NASA decided in July 2023 to cancel the mission and put the spacecraft, which were essentially complete, into storage.

Dan Scheeres, the principal investigator for Janus at the University of Colorado, believes the spacecraft could be repurposed to fly by Apophis before the 2029 close approach. “A Janus Apophis mission addresses, in our minds, the need to observe Apophis prior to its Earth closest approach, because that would take full advantage of the planned OSIRIS-APEX mission,” he said at the workshop.

The spacecraft would fly as-is, with the same instruments, although he said some additional testing would be necessary. The mission identified several opportunities for launching the spacecraft to get them to Apophis before April 2029, such as a rideshare on the launch of the NEO Surveyor space telescope in late 2027.

Blue Ring around Apophis

The workshop showed there is considerable interest in missions to Apophis, with a variety of concepts being put forward by space agencies and companies.

One of the most intriguing was a proposal from Blue Origin using its Blue Ring spacecraft. The company publicly announced Blue Ring last October, pitching it as a platform for “in-space logistics and delivery” in Earth orbit and cislunar space.

“I’ve been wanting to give this talk for years now,” Steve Squyres, chief scientist of Blue Origin, said at the workshop. A former Cornell University professor who led the Spirit and Opportunity Mars rover missions, he joined Blue Origin four and a half years ago but had heard about plans for Blue Ring even before that. “I realized what a powerful tool it could be for planetary exploration.”

He described a spacecraft that offered ample mass, power and propulsion capabilities for missions like one to Apophis. One mission architecture he showed in his talk had Blue Ring arriving at Apophis three months before the flyby and remaining in the vicinity until long after the Earth flyby. It could carry two tons of payload in the form of instruments or deployable spacecraft, like the Janus smallsats. “It’s a big honking spacecraft.”

Blue Ring has not yet flown but the first spacecraft is scheduled to launch later this year. An Apophis mission would likely be the fifth Blue Ring, Squyres said, reducing risk. However, he did not describe how much the mission would cost our how it would be financed, other than stating that Blue Origin would sell space on it for an undisclosed fee.

At the other end of the spectrum was a concept called Rapid Apophis Characterization with Two Satellites, or RA’s CATS (Apophis, named after an Egyptian god of darkness, led to an Egyptian theme among some mission concepts.) It would place two smallsats into elliptical Earth orbits, allowing them to perform high-speed flybys of Apophis around the time of closest approach.

Nathan Golovich of Lawrence Livermore National Lab, which developed the RA’s CATS mission concept, said it could be built and launched for less than $50 million, making use of rideshare launches on missions to GEO.

There is interest in Apophis missions in Europe as well, with ESA considering two concepts. Rapid Apophis Mission for Space Safety (RAMSES) would use a spacecraft based on Hera, the mission ESA is launching later this year to the asteroid Didymos, whose moon Dimorphos was hit by NASA’s DART spacecraft in 2022. RAMSES would arrive at Apophis a few months before closest approach and operate for at least six months.

“The spacecraft concept is based on what we have ready and available at ESA,” said Paolo Martino, one of the people working on RAMSES at the agency. “This has proven to be highly cost effective and highly schedule effective.”

Another option is Satis, a 12U XL cubesat that would arrive a few weeks before closest approach, performing a basic reconnaissance of the asteroid. ESA’s Moissl said it could be done for a “super low budget” of less for 50 million euros. “It’s a barebones solution. It gets the job done.”

“There is a consensus among the member states that RAMSES is the better mission concept, but there is still work needed on the financing,” he said.

“We need to start yesterday”

Financing, rather than scientific merit or technology, emerged as the biggest obstacle for an Apophis mission other than OSIRIS-APEX. Project officials did not disclose the estimated cost of RAMSES, but it’s expected to be no more than Hera, which has an overall budget of 350 million euros.

Such missions normally win formal approval at ESA ministerial meetings, held every three years, with the next scheduled for late 2025. “This is not compatible with the timeline for the implementation of a mission to Apophis,” said Martino. The project is trying to find some interim funding to allow for initial development before the next ministerial. “We need to start yesterday.”

NASA officials, meanwhile, have said there’s no room in current planetary budgets, squeezed by challenges with missions like Mars Sample Return as well as broader fiscal pressures, to start any Apophis mission, no matter how little it costs.

“The international community is very busy coming up with ideas for going to Apophis,” said Lori Glaze, director of NASA’s planetary science division, during a meeting of a Mars exploration committee a day after the Apophis workshop. “But we can’t sponsor a mission without money, and right now that’s a real challenge.”

NASA, though, is at least considering how it could support missions to Apophis. The agency’s Office of Technology, Policy and Strategy held a “listening workshop” in February, collecting input on ideas for Apophis missions, but has not provided any updates since then.

Lindley Johnson, NASA’s planetary defense officer, said that a workshop summary was being developed for public release. “I would hope there would be some public results made available in the next few weeks.”

One proposed mission is not counting on NASA or other government funding. The Jet Propulsion Laboratory had been working on a concept called Distributed Radar Observations of Interior Distributions (DROID), which would send a spacecraft to rendezvous with Apophis and deploy two cubesats to perform a “CAT scan” of the asteroid’s interior, but had yet to secure funding.

“We have a new life,” said JPL’s Lorraine Fesq. The lab is now working with Exploration Laboratories, or ExLabs, a startup with long-term ambitions for asteroid mining. “We got very creative and came up with this new business model.”

The partnership, between ExLabs and Caltech, which operates JPL for NASA, will have ExLabs fund a Phase A design study for DROID using the company’s Space Exploration and Resource Vehicle (SERV) spacecraft. Caltech will then work to raise money for later development of the mission, going out to donors much like it would for a new campus building.

“We saw this opportunity with JPL as a fantastic opportunity for tech transfer and for us to be able to truly understand what it takes to get to an asteroid,” said Tom Cooley, former chief scientist for the Space Vehicles Directorate at the Air Force Research Lab and now senior vice president of ExLabs, adding that there would be room on SERV for additional payloads beyond DROID.

The mood at the workshop oscillated between excitement and dismay: excitement about the potential missions and the science they could provide from a once-in-a-millennium flyby, but dismay about the challenges getting any of them funded on such a short timeline.

“The most likely scenario is that zero things go besides APEX,” concluded Golovich. “That might be a little bit pessimistic. Maybe one goes.”

Squyres was more optimistic, suggesting space agencies work together to cobble together a mission using whatever they have. “The question is, how on earth do you get all these space agencies to work together to make something happen? I don’t know the answer to that.”

Such efforts need to come together quickly to get a spacecraft built and launched in time to reach Apophis before its 2029 flyby. “Decisions have to be made here in the next six months as to what we are going to do,” Johnson said, “because we are out of time.”

This article first appeared in the May 2024 issue of SpaceNews Magazine.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...