Tag: Apophis

Australian satellite startup to fly an instrument on private mission to Apophis

8:59 am

In March 2024 the orbital tug startup Exlab’s announced that it will use its orbital tug to deliver three cubesats to the asteroid Apophis when that object makes its next close fly-by of the Earth on April 13, 2029.

The California-based Exlab has now signed its first customer for that mission. An Australian satellite startup, Fleet Space Technologies, has agreed to fly an instrument on this private commercial mission.

Under the ApophisExL mission, Fleet will provide geophysical sensing technologies for ExLabs’ mothership to collect targeted data and characterize the asteroid. The datasets should enable new avenues for data sharing and commercial use, set criteria for prioritizing asteroids for prospecting and feed critical intelligence into planetary‑defence planning.

Fleet already has a contract to fly another instrument, a seismometer, on Firefly’s second Blue Ghost lander mission to the Moon. It has also developed and flown satellite instruments used to detect minerals on Earth.

Both companies are clearly aiming to enhance their brand name with this mission, set to launch in 2028.

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More missions to Apophis when it flies past Earth in 2029?

11:45 am

Apophis' path past the Earth in 2029
A cartoon (not to scale) showing Apophis’s
path in 2029

There were two stories today that heralded the addition of one real and two potential new spacecraft to rendezvous with the potentially dangerous asteroid Apophis when it flies past the Earth on April 13, 2029.

First, the European Space Agency (ESA) awarded a 1.5 million euro contract to the Spanish company Emxys to build a small cubesat that will fly on ESA’s Ramses mission to Apophis. This is the second cubesat now to fly attached to Ramses, with the first designed to use radar to study Apophis’ interior.

The second CubeSat, led by Emxys, will be deployed from the main spacecraft just a few kilometres from Apophis. It will study the asteroid’s shape and geological properties and will carry out an autonomous approach manoeuvre before attempting to land on the surface. If the landing is successful, it will also measure the asteroid’s seismic activity.

Second, American planetary scientists have been lobbying NASA to repurpose the two small Janus spacecraft for a mission to Apophis. These probes were originally built to go to an asteroid as a secondary payload when the Pysche asteroid mission was launched, but when Pysche was delayed they could no longer go that that asteroid on the new launch date. Since then both Janus spacecraft have been in storage, with no place to go.

The scientists say they could easily be repurposed to go to Apophis, but NASA will have to commit to spending the cost for launch, approximately $100 million. NASA officials were not hostile to this idea, but they were also non-committal. I suspect no decision can be made until the new administrator, Jared Isaacman, is confirmed by the Senate and takes office.

Time however is a factor. The longer it takes to make a decision the fewer options there will be to get it to Apophis on time.

At the moment there is only one spacecraft in space and on its way to Apophis, and that is the repurposed Osiris-Rex mission, now called Osiris-Apex. Japan might also send a craft past Apophis as part of its mission to another asteroid.

Learning as much as we can about Apophis is critical, as there is a chance it will impact the Earth sometime in the next two hundred years.

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Engineers confirm OSIRIS-APEX successfully completed its second of six close fly-bys of the Sun

10:19 am

Engineers have now confirmed that the asteroid probe OSIRIS-APEX successfully completed its second of six close fly-bys of the Sun in September, using its solar panels to shield its instruments from the Sun’s heat and light.

On Jan. 23 the mission team completed its review of all the data recorded by the spacecraft and its instruments during the solar pass [about 46 million miles from the Sun]. “There were no surprises, and the spacecraft is operating well,” said Mike Moreau, OSIRIS-APEX deputy project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

As planned, on Sept. 2, 2024, OSIRIS-APEX passed through perihelion — the phase of its orbit closest to the Sun. The trajectory to Apophis takes the spacecraft much closer to the Sun than it was originally designed for. Between Aug. 1 and Oct. 13, the spacecraft was configured in a special orientation that uses one of the solar arrays to shade the most heat-sensitive components, keeping them within safe operating temperatures.

Because of the improvised orientation during the close approach, full data communications was not possible until months afterward. Only now have engineers completed their analysis.

OSIRIS-APEX original mission was to visit the asteroid Bennu and return samples from it to Earth. Once that mission was successfully completed, the probe was repurposed to go to the potentially dangerous asteroid Apophis when it makes its next close approach to the Earth in April 2029.

I have embedded below a short video showing the spacecraft’s journey to get to Apophis.
» Read more

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ESA and JAXA sign agreement to increase cooperation and accelerate development of Ramses mission to Apophis

10:18 am

The new colonial movement: The European Space Agency (ESA) and Japan’s own space agency JAXA on November 20, 2024 signed a new cooperative agreement to increase their joint work on several missions, the most important of which is the proposed Ramses mission to the potentially dangerous asteroid Apophis during its 2029 close fly-by of Earth.

Two agencies agreed to accelerate to study potential cooperation for ESA’s Rapid Apophis Mission for Space Safety (RAMSES) which aims to explore the asteroid Apophis that will pass close to our planet on 13 April 2029, including but not limited to provision of thermal infrared imager and solar array wings as well as possible launch opportunities.

The two countries are already working together on two different planetary missions, the BepiColombo mission to Mercury and the Hera mission to the asteroid Dymorphos. Both are on their way to their targets. This new agreement solidifies the commitment of both to make sure Ramses is funded, built, and launched in the relatively short time left before that 2029 Earth fly-by. At the moment the ESA has still not officially funded it fully.

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ESA awards OHB Italia a preliminary contract to build Ramses probe to Apophis

9:22 am

The European Space Agency (ESA) yesterday awarded the company OHB Italia a €63 million preliminary contract to begin work on mission dubbed Ramses that will launch in 2028 and rendezvous with the potentially dangerous asteroid Apophis when it flies past the Earth on April 13, 2029 at a distance of less than 20,000 miles.

The contract award is preliminary because the entire project still has to be approved by the ESA ministral council of nations, meeting in 2025. Because of the short development time, however, ESA’s management found funds from its existing budget to begin work.

To speed work, the project is also using as its design basis the Hera asteroid spacecraft, which was recently launched to study the binary asteroids Didymos-Dimorphos. That mission was also built remarkably fast for a European space project, going from contract to launch in just four years.

NASA has already re-tasked its OSIRIS-REx asteroid mission to head for Apophis, renaming it OSIRIS-APEX for reasons that baffle me. The mission had successfully delivered samples from the asteroid Bennu, but after completing that mission had sufficient fuel and was well placed to do this additional rendezvous as well.

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NASA asks space industry for proposals on using the shelved Janus probes on mission to Apophis

9:23 am

NASA has now put out a request for proposals from the space industry for refitting the two Janus planetary probes, whose asteroid mission was shelved when its launch as a secondary payload was delayed due to problems with the Psyche primary payload, as a mission to the asteroid Apophis in connection with its April 13, 2029 close approach to the Earth.

NASA has been studying this new mission goal since early 2023, but apparently had failed to come up with a plan. It is now asking the private sector for suggestions on getting it done, including finding the funding for any plans.

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ESA announces asteroid mission to Apophis

9:06 am

Apophis' path past the Earth in 2029
A cartoon showing Apophis’s path in 2029

The European Space Agency (ESA) today announced that is beginning work on an asteroid mission, dubbed Ramses, to the potentially dangerous asteroid Apophis when it makes its next close-fly of the Earth in 2029.

Ramses needs to launch in April 2028 to allow for an arrival at Apophis in February 2029, two months before the close approach. In order to meet this deadline, ESA requested permission to begin preparatory work on the mission as soon as possible using existing resources. This permission has been granted by the Space Safety programme board. The decision whether to commit to the mission in full will take place at ESA’s Ministerial Council Meeting in November 2025.

Using a suite of scientific instruments, the spacecraft will conduct a thorough before-and-after survey of the asteroid’s shape, surface, orbit, rotation and orientation. By analysing how Apophis changes during the flyby, scientists will learn a lot about the response of an asteroid to external forces as well as asteroid composition, interior structure, cohesion, mass, density, and porosity.

Based on the track record of European space projects, which appear to always proceed at a glacial pace with late problems that cause the missions to miss their launch window (with the launch of the Franklin Mars rover as the poster child), the project is getting started far too late to meet its launch date of April 2028. We shall see if Europe surprises us this time and gets the project off the ground as planned.

Right now the only confirmed mission to Apophis is OSIRIS-APEX, which was redirected to the asteroid after it delivered its samples from Bennu to Earth. Many others have been proposed, including a commercial mission, but none appear to be confirmed or under construction.

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Several new missions to the asteroid Apophis proposed by commercial and governments

9:39 am

Apophis' path past the Earth in 2029
A cartoon showing Apophis’s path in 2029

At a conference this week several new missions to the asteroid Apophis during its close Earth fly-by in 2029 were proposed by both private companies and government entities.

  • Blue Origin is considering sending its Blue Ring orbital tug, launched in 2027 on a Falcon 9.
  • JPL proposes sending two cubesats on the orbital tug mission previously announced by the startup ExLabs.
  • NASA continues to study sending the two Janus spacecraft, since its original asteroid mission was lost when the Psyche asteroid mission was delayed.
  • The European Space Agency has two different missions under study.

With all of these missions, the big obstacle is funding. Most are either only partly funded, or not at all.

At the moment the only mission actually on its way to Apophis is OSIRIS-APEX, which having completed its sample return mission to Bennu was then sent to Apophis.

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Orbital tug startup ExLabs plans mission to asteroid Apophis in 2028

9:03 am

The orbital tug startup Exploration Labs (ExLabs) has announced it is planning to use its tug to deliver three cubesats on a rendezvous mission to asteroid Apophis in 2028, shortly before the asteroid does a close fly-by of Earth in April 2029.

The article at the link provides no other information about this mission. In searching the web I was unable to find anything further. It seems this mission is at present nothing more than a proposal, issued at this time mostly for public relations purposes to showcase the abilities of its proposed orbital tug, presently under development.

This conclusion does not mean the mission won’t happen, only that it is very far from a reality.

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OSIRIS-REx Sample from Bennu successfully recovered

10:18 am

Engineers today successfully recovered the asteroid sample capsule from the probe OSIRIS-REx, carrying several grams of material from the potentially dangerous asteroid Bennu.

The samples will be shipped to special facilities to protect the material from being exposed to Earth’s environment when the capsule is opened. It will take several months at least before the first research results are announced.

OSIRIS-REx, now renamed OSIRIS-APEX, now heads for the potentially dangeous asteroid Apophis, where it will orbit that asteroid beginning in 2029, shortly after Apophis makes its next close fly-by of Earth.

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The twin asteroid Janus probes, stranded by Psyche delay, might go to Apophis

9:20 am

Apophis' path past the Earth in 2029
A cartoon showing Apophis’s path in 2029

The science team that built the twin Janus spacecraft, designed to fly past an asteroid but stranded when its launch got canceled, are now considering the potentially dangerous asteroid Apophis as a new target.

If the Janus spacecraft can find a ride by early 2028, scientists could use one or both of the spacecraft to scout out the large asteroid Apophis before its super-close approach to Earth in April 2029. (If only one spacecraft visits Apophis, scientists would see only about half of the asteroid but could send the second spacecraft elsewhere; if both spacecraft fly past the same object they can be arranged to reveal the whole surface.)

Initially the entire Janus mission had been designed on the assumption it would launch as a secondary payload when the Psyche mission to the asteroid Psyche launched last fall. When that launch had to be canceled because Psyche was not ready, Janus lost its mission. The science team has since been struggling to find a replacement, handicapped by the fact that it must go as a secondary payload.

There is a serious issue however with arriving ahead of Apophis’s close approach in 2029. The science community has discouraged such missions, because they fear a spacecraft arriving then could shift Apophis’s trajectory and actually increase the chance it will hit the Earth during a later close approach. Instead, all planetary probes presently going to Apophis in 2029 are planning to arrive after the flyby.

The risk is extremely small, but it must be considered before sending Janus to Apophis.

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South Korea cancels probe to asteroid Apophis

8:57 am

The South Korea government has canceled its proposed unmanned probe to asteroid Apophis that had been designed to reach the asteroid during its ’29 close approach of Earth and fly in formation with it.

The science ministry, which manages state-funded space programs, recently ruled the mission “unfeasible” and decided not to request the $307.7 million budget it initially sought for the mission. … “We’ve decided not to pursue Apophis probe mission because there were various issues making it difficult for the mission to be successful,” Shin Won-sik, a science ministry official, told SpaceNews. “To probe Apophis, we have to launch a spacecraft by 2027 at the latest. But with the rocket and spacecraft-making capabilities we have, it’s unrealistic to launch in time.”

South Korean officials insisted they are not abandoning all future asteroid missions, but merely shifting this effort to other asteroids in which there is less time pressure to launch. Right now they are considering a mission in the mid-2030s, which could also be an asteroid sample return mission.

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New OSIRIS-REx photos of Bennu sample site after sample grab

1:40 pm

Nightingale before and after sample grab
Click here and here for original images.

The OSIRIS-REx science team today released the photos the spacecraft obtained in its last fly-by of the asteroid Bennu on April 7th of the Nightngale sample site, showing how it changed after the sample grab in October 2020.

The two photos to the right compare that site, with the top image taken before the sample grab and the bottom image taken on April 7th.

Comparing the two images reveals obvious signs of surface disturbance. At the sample collection point, there appears to be a depression, with several large boulders evident at the bottom, suggesting that they were exposed by sampling. There is a noticeable increase in the amount of highly reflective material near the TAG [touch-and-go] point against the generally dark background of the surface, and many rocks were moved around.

Where thrusters fired against the surface, substantial mass movement is apparent. Multiple sub-meter boulders were mobilized by the plumes into a campfire ring–like shape — similar to rings of boulders seen around small craters pocking the surface.

Jason Dworkin, the mission’s project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, noticed that one boulder measuring 4 feet (1.25 meters) across on the edge of the sampling site seemed to appear only in the post-TAG image. “The rock probably weighs around a ton, with a mass somewhere between a cow and a car.”

Dante Lauretta, of the University of Arizona and the mission’s principal investigator, later pointed out that this boulder is likely one of those present in the pre-TAG image, but much nearer the sampling location, and estimates it was thrown a distance of 40 feet (about 12 meters) by the sample collection event.

The sample grab arm penetrated the surface by more than a foot, and that event is marked by that dark depression at the center of the site.

OSIRIS-REX will now prepare for its May 10th engine firing that will send it on its route back to Earth to return that sample in September 24, 2023. After that the spacecraft could be sent on another mission, this time to the potentially dangerous asteroid Apophis.

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South Korea’s leader announces his nation’s goals in space

2:53 pm

The new colonial movement: Moon Jae-in, South Korea’s president since 2017, on March 25th gave his first speech focused on his nation’s goals in space, outlining plans to encourage private enterprise as well as achieving an unmanned mission to the Moon by 2030.

His speech listed three main programs. First, they are developing their own home-built rocket, dubbed the KSLV-2, which they hope to launch on its first orbital test flight by October of this year.

Second, he touted a project to send a probe to the asteroid Apophis in 2029. I described this probe in my November 2020 report on a science conference focused entirely on Apophis. If all goes well, they hope to have the probe fly in formation with the asteroid as it makes its close approach that year.

Third, he committed his nation to landing an unmanned lander on the Moon by the end of this decade. (Sound familiar?)

While much of this was the typical photo-op stuff that politicians love, designed mostly to enhance their public image, Moon did make it clear their goals are also to foster a new private aerospace industry that would compete in the emerging new space market.

Moon underscored the role of the private sector in enhancing Korea’s space development capabilities. To that end, he said, the government will step up efforts to build an “innovative industrial ecosystem that nurtures global space companies such as SpaceX.”

Another issue he put forth was strengthening international competitiveness of made-in-Korea satellite systems, in the lead-up to the introduction of 6G wireless networks, self-driving vehicles, and other products and services enabled or enhanced by satellites.

All-in-all, it is actually surprising that up to now South Korea has not made its presence felt in space. This announcement suggests they now intend to change that.

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Radar images of Apophis during its March close approach of Earth

9:45 am

Apophis as seen by radar March 9, 2021
Click for full image.

Using two radar dishes, Green Bank in West Virginia and Goldstone in California, astronomers were able to produce radar images of the asteroid Apophis during its most recent close fly-by of Earth on March 10th.

The image to the right, cropped and reduced to post here, shows Apophis on March 9th. If you go to the full image you can also see the March 10th and 11th images, which appear to show the asteroid in different orientations as it rotated.

These images represent radar observations of asteroid 99942 Apophis on March 8, 9, and 10, 2021, as it made its last close approach before its 2029 Earth encounter that will see the object pass our planet by less than 20,000 miles (32,000 kilometers). The 70-meter radio antenna at the Deep Space Network’s Goldstone Deep Space Communications Complex near Barstow, California, and the 100-meter Green Bank Telescope in West Virginia used radar to precisely track Apophis’ motion. At the time of these observations, Apophis was about 10.6 million miles (17 million kilometers) from Earth, and each pixel has a resolution of 127 feet (38.75 meters).

The data obtained has firmly removed any chance Apophis will impact the Earth in the next 100 years. However, it still could hit us late in the 22nd century.

These observations were originally planned to also include data from the Arecibo Observatory, but that telescope was destroyed in December when its instrument platform collapsed. If it had been operational, these radar images would have had much better resolution.

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Apophis: the asteroid that may someday hit the Earth

8:40 am

Apophis' path past the Earth in 2029
From the conference’s logo.

Last week planetary scientists held a three-day virtual conference focused on the asteroid Apophis, whose orbit regularly places it close to the Earth with a real possibility that it might someday hit the Earth.

When Apophis was originally discovered early in 2004, it wasn’t at first seen as an out-of-the-ordinary asteroid. Not much was known about it other than its albedo and that it was not trivial in size, probably around 1,000 feet in diameter. All this changed in December 2004, when further observations suggested that it had a 2.7% chance of impacting the Earth in 2029, making it the most dangerous asteroid ever discovered.

Fortunately, all subsequent observations of the asteroid have since eliminated any possibility of an impact, at least through the year 2068. Depending on what happens during the 2029 and 2036 fly-bys of Earth, there is a very small chance that it could hit the Earth in 2068, though the data says the chances of that happening are quite small (1 in 150,000).

On April 13, 2029 however Apophis will still zip past the Earth less than 20,000 miles above its surface, well within the orbit of all geosynchronous satellites. For viewers in Europe and Africa it will be a naked eye object, with a magnitude of -3.

Because the date of that close fly-by is so well known, and because this asteroid still poses a threat to the Earth, the planetary science community is very much interested in taking advantage of that close approach. From the conference’s webpage:

Knowledge is the first line of planetary defense, and the 2029 Apophis encounter is a once-per-thousand-year opportunity for investigating an asteroid as large as 350 meters passing within 6 Earth-radii. Time is of the essence as we have less than a decade to plan Earth-based and possible in-situ missions whose measurements can deliver unprecedented detailed knowledge on the physical nature of Apophis as the prototype example (poster child) of potentially hazardous asteroids.

I attended that conference, and am here now to give a summary.
» Read more

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Avalanches on an asteroid

9:12 am

A new analysis predicts that when the asteroid Apophis flies past the Earth in 2029, the close fly-by will cause avalanches on the asteroid.

If asteroids pass close to Earth, they begin to experience the effects of our planet’s gravity. Just like the moon pushes and pulls the oceans, creating the tides, asteroids are susceptible to tidal forces from our planet. To judge what effect this will have on Apophis, scientists need to know what it’s made of. Their best guess is based on photos taken by a Japanese spacecraft named Hayabusa, which took detailed pictures of an Apophis-sized asteroid named Itokawa. Those images revealed that the asteroid wasn’t a solid mass of rock spinning through space, but rather a giant clump of debris held together loosely by gravity. “You look at the [Hayabusa] pictures and you’re like, ‘Uh, that’s a pile of rocks, dude.’ It’s very likely that Apophis is similar,” says astrophysicist Derek Richardson of the University of Maryland, College Park.

To show that Earth’s gravity could cause some of these rocks to tumble, Richardson and his colleagues developed a computer model that allowed them to place virtual sand piles across the surface of a model asteroid with roughly the same dimensions as Apophis. By factoring in the gravity from the asteroid, the tidal force from Earth, centrifugal force caused by the asteroid’s rotation, inertial forces, and other effects, the team was able to predict how the particles on the surface of the asteroid would behave on approach. The results confirm that Earth’s tidal forces would be strong enough to cause tiny avalanches on the asteroid, the team reported online ahead of print in Icarus.

Need I note that there are a lot of uncertainties here? Because they are using what is known about a different asteroid, all of their assumptions about Apophis’s properties in their computer model could be very wrong.

Still, this is interesting, because it does demonstrate that an asteroid could be significantly disturbed simply by flying past a planet.

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An detailed analysis of the tumbling of the asteroid Apophis, detected by radar observations in January, suggests it will be easier to predict the asteroid’s orbit in the future.

10:15 am

The sky isn’t falling: A detailed analysis of the tumbling of the asteroid Apophis, detected by radar observations in January, suggests it will be easier to predict the asteroid’s orbit in the future.

The gentle but persistent nudging [of the Yarkovsky effect] arises when sunlight is absorbed by a rotating object and then reradiated as heat in some other direction. In particular, if Apophis were spinning retrograde (opposite the way Earth does), then over time its orbit would change in a way that increases the chance of impact in 2036. But now we can rest easy, because Apophis appears to be tumbling as it orbits the Sun. That’s the conclusion reached by a team of telescopic observers who monitored the asteroid’s light curve as it passed near Earth in January. Apophis is spinning around two axes at the same time, implying that any Sun-warmed surfaces are radiating heat in all directions, not just one in particular.

It is very difficult to measure the Yarkovsky effect, thus making it very difficult to precisely calculate the orbits of many near Earth asteroids. In the case of Apophis, however, it appears the astronomers have gotten a good handle on the problem.

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New data has allowed scientists to lower the chance that the asteroid Apophis will hit the Earth in a future orbit.

10:32 pm

New data has allowed scientists to lower the chance that the asteroid Apophis will hit the Earth in a future orbit.

Recent observations from Pan-STARRS PS1 telescope at Haleakala, Hawaii have reduced the current orbital uncertainty by a factor of 5, and radar observations in early 2013 from Goldstone and Arecibo will further improve the knowledge of Apophis’ current position. However, the current knowledge is now precise enough that the uncertainty in predicting the position in 2029 is completely dominated by the so-called Yarkovsky effect, a subtle nongravitational perturbation due to thermal re-radiation of solar energy absorbed by the asteroid. The Yarkovsky effect depends on the asteroid’s size, mass, thermal properties, and critically on the orientation of the asteroid’s spin axis, which is currently unknown. This means that predictions for the 2029 Earth encounter will not improve significantly until these physical and spin characteristics are better determined.

The new report, which does not make use of the 2013 radar measurements, identifies over a dozen keyholes that fall within the range of possible 2029 encounter distances. Notably, the potential impact in 2036 that had previously held the highest probability has been effectively ruled out since its probability has fallen to well below one chance in one million. Indeed only one of the potential impacts has a probability of impact greater than 1-in-a-million; there is a 2-meter wide keyhole that leads to an impact in 2068, with impact odds of about 2.3 in a million.

The second paragraph basically says that the keyholes that might bring Apophis back to Earth are very small, making it unlikely that the asteroid will fly through any one of them in 2029. The first paragraph however notes that it will be impossible to chart the asteroid’s course accurately enough to rule out this possibility until we have more data on the asteroid itself.

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New data from the Herschel Space Telescope suggests that the asteroid Apophis is bigger and less reflective than previous believed.

11:04 am

More Apophis news: New data from the Herschel Space Telescope suggests that the asteroid is bigger and less reflective than previous believed.

Instead of 900 feet across, they now estimate it has a diameter of about 1070 feet. And knowing that the asteroid has a lower albedo means that astronomers will be better able to gauge the effect of solar radiation on Apophis’s orbit.

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On Wednesday Apophis will pass the Earth at a distance of 9 million miles, allowing astronomers to gather more data about this asteroid’s orbit and composition.

9:01 am

On Wednesday Apophis will pass the Earth at a distance of 9 million miles, allowing astronomers to gather more data about this asteroid’s orbit and composition.

Having crossed outside Earth’s orbit, Apophis will appear briefly in the night-time sky. Wednesday 9 January will afford astronomers the rare opportunity to bring a battery of telescopes to bear: from optical telescopes to radio telescopes to the European Space Agency’s Infrared Space Observatory Herschel. Two of the biggest unknowns that remain to be established are the asteroid’s mass and the way it is spinning. Both of these affect the asteroid’s orbit and without them, precise calculations cannot be made.

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Using a solar sail to deflect an earth-destroying asteroid

10:35 am

solar sail mission to Apophis

In a paper published today on the Los Alamos astro-ph preprint website, two Chinese scientists have proposed using a solar sail for deflecting any asteroid that happens to be aimed at the earth. The diagram to the right is their simulated mission to impact the asteroid Apophis, which will pass close to the earth in 2029 and — depending on whether that flyby puts it through a very small 600 meter-wide mathematical “keyhole” — could then return in 2036 on a collision course.

The idea is to use the sail to slow the spacecraft down enough so that it starts to fall towards the sun. The sail is then used to maneuver it into a retrograde orbit. When it impacts the asteroid the impact will therefore be similar to a head-on collision, thereby imputing the most energy in the least amount of time with the least amount of rocket fuel. In their Apophis simulation, a mission, weighing only 10 kilograms (about 22 pounds), launched around 2025, and hitting the asteroid in this manner in 2026, would deflect its flyby in 2029 enough to guarantee it will not fly through the “keyhole” and therefore eliminate any chance of it hitting the earth in 2036.

Obviously many questions must be answered before such a mission should fly.
» Read more

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