Asteroid 2011 AG5 Earth Impact Threat Should Be Studied More

by Leonard David, SPACE.com’s Space Insider Columnist
Date: 12 March 2012 Time: 05:47 PM ET

An artist’s illustration of asteroids, or near-Earth objects, that highlight the need for a complete Space Situational Awareness system. CREDIT: ESA – P.Carril

A massive asteroid that may be on a collision course with Earth should be studied in more detail, according to a former Apollo astronaut who specializes in monitoring potentially hazardous space rocks.

Asteroid 2011 AG5 has been the object of attention because scientists say it may swing close to our planet in the year 2040.

The big space rock is on NASA’s impact hazards list, but more definitive tracking of the object is still needed, scientists say. In fact, some near-Earth object (NEO) experts say it’s time to start hammering out a plan in case the asteroid needs to be deflected.

Former Apollo astronaut Russell Schweickart is calling upon NASA to undertake a detailed engineering and mission planning analysis of 2011 AG5.

In a March 3 open letter to NASA administrator Charles Bolden, Schweickart spotlighted what he sees as the potential deflection challenges posed by asteroid 2011 AG5, should the object happen to be headed for a so-called keyhole in 2023, setting up a possible impact with Earth in 2040.

Keyholes are small regions in space near Earth through which a passing NEO may be perturbed — due to gravitational forces — placing it onto a path that would strike Earth.

In this most recent communiqué, Schweickart questioned a view held by Bolden from an earlier exchange of letters between the two that a Deep Impact-like intercept of asteroid 2011 AG5 could be staged in enough time to derail a space rock from hitting Earth.

NASA’s Deep Impact probe was purposely crashed into comet Tempel 1 on July 4, 2005.

A more daunting challenge

While Deep Impact was a very successful mission, it is a poor analogy for the potential deflection challenges presented by 2011 AG5, Schweickart noted. To depend on such an impact mission to justify waiting until after the next tracking opportunities — before doing any further engineering analysis — is ill advised, he said.

Schweickart contends that a 2011 AG5 deflection campaign requires two missions, not one, as was used on Deep Impact. In addition, intercepting and impacting 2011 AG5 presents far more daunting challenges than was posed by comet Tempel 1.

In his open letter, Schweickart told Bolden that, “neither you nor I would have risked our lives without solid engineering having gone into our respective missions. In this instance again, there are potentially lives at stake, and I know you take that responsibility seriously, as do I.”

“To be clear, what I am asking for is specific engineering and mission planning analysis to be performed now in order to insure that we fully understand the timeline requirements, in the unlikely event that AG5 should be headed for the 2023 keyhole,” Schweickart wrote.

“We all realize it is highly likely that AG5 is not headed for an impact. But we must also hedge against the possibility that this will not be the case by being prepared to act, and not find ourselves awkwardly beyond the point where deflection remains an option,” Schweickart concluded in his open letter to the NASA chief.

NASA’s response

In response to the letter, Schweickart told SPACE.com that a NASA-organized teleconference was held on March 8 involving himself, as well as John Grunsfeld, NASA’s Associate Administrator for the Science Mission Directorate, Jim Green, Director of Planetary Science, and Lindley Johnson, NEO Observations Program Executive.

“It was a very constructive discussion and as a result we will be getting together in the next few weeks to discuss the various issues and options which would apply to a variety of future scenarios regarding 2011 AG5,” Schweickart said. “I’m looking forward to these substantive discussions and I commend John Grunsfeld and NASA for this positive response.”

Schweickart’s new letter to Bolden, “presents points we at NASA have considered in looking at the 2011 AG5 scenario,” Lindley Johnson told SPACE.com.

“A big concern with any mission analysis is that they are only as good the initial input conditions. The results you obtain are always dependent on those conditions,” he said.

Johnson said that if 2011 AG5’s orbit model in hand now turns out to be a good representation of where the NEO will be in the future, then a mission analysis could be done now, and such work would be worthwhile.

But, if the asteroid’s orbit isn’t that well defined, then a mission analysis would need to be mostly re-done after a better orbit is ascertained, he said.

“We are certain we will have a higher confidence model after observations are collected in another orbit of AG5,” Johnson said, “and we are confident we will have more than sufficient time to do both the mission analysis and undertake any response still necessary after that observation opportunity.”

“However, we will continue to study the AG5 situation, as we do continuously for all objects on the impact hazards list,” Johnson concluded.

Tools to monitor 2011 AG5

“There are logical reasons to start really planning to do something really soon … and analyzing AG5 really soon,” said Clark Chapman, a noted specialist in asteroids and a planetary scientist at the Southwest Research Institute in Boulder, Colo.

It has been generally thought that 2011 AG5 can’t be observed again until September of 2013, Chapman told SPACE.com. “That’s not true. We can see it again in August of this year.”

What’s needed is one of the largest ground-based telescopes on Earth, or the Hubble Space Telescope, Chapman advised. Doing so wouldn’t be too easy, “but in all probability could be done.”

For one, the asteroid is very faint and ground-based telescopes would need to slew toward the horizon in a really dark sky.

“Telescopes are sort of designed to look more or less up … rather than over,” Chapman noted. In the case of the Hubble Space Telescope, caution is the rule as it would be necessary to point the scope 42 degrees away from the sun to observe 2011 AG5, “but exceptions have been made in the past.”

Odds of an impact

Still, whether using these tools to eye the asteroid will improve our understanding of the asteroid’s track isn’t a given.

“We simply don’t know whether observations in August can make that much of a difference … but that’s another arena in which studies should be done in the very near term,” Chapman said.

In the meantime, more information about 2011 AG5 is needed, Chapman said.

“We don’t know how big this thing is,” he said. “And if it’s on the big side, it would be hard to move it away from the keyhole with only a few years planning. And if it’s really big, it’s hard to move it away from the Earth if it goes through the keyhole.”

Chapman stressed that the most probable result of more tracking of the asteroid is that the 2040 impact of Earth probability will drop to zero.

“I’m of the view that you can’t say, ‘let’s just wait and the odds are likely to go to zero.’ Yes, the odds are likely to go to zero…but suppose they don’t,” Chapman said.

Leonard David has been reporting on the space industry for more than five decades. He is a winner of last year’s National Space Club Press Award and a past editor-in-chief of the National Space Society’s Ad Astra and Space World magazines. He has written for SPACE.com since 1999.

Asteroid 2011 AG5 Earth Impact Threat Should Be Studied More | Near-Earth Objects | Space.com.

Big Asteroid’s Chances of Hitting Earth in 2040 Overblown, NASA Says

SPACE.com Staff
Date: 05 March 2012
Time: 10:57 AM ET

The orbit of asteroid 2011 AG5 carries it beyond the orbit of Mars and as close to the sun as halfway between Earth and Venus. CREDIT: NASA/JPL/Caltech/NEOPO

An asteroid discovered last year has been gaining notoriety because of a chance that it could hit Earth in 28 years, but NASA scientists say the odds are extremely remote that it will pose any danger to us.

The huge space rock, called asteroid 2011 AG5, is about 460 feet (140 meters) wide and circles the sun on a path between the orbits of Mars and Venus. Astronomers spotted it on Jan. 8, 2011 using the 60-inch Cassegrain reflector telescope on Mount Lemmon north of Tucson, Ariz., with some projections suggesting the odds of an Earth impact are 1 in 625.

Yet currently, the asteroid is rated a 1 on the 1-10 Torino Impact Hazard Scale that denotes potentially dangerous asteroids (1 is the least hazardous rating), NASA scientists say. So while there is a slight chance that asteroid 2011 AG5 could impact our planet in 2040, astronomers still need much better observations to define its orbit.

“Because of the extreme rarity of an impact by a near-Earth asteroid of this size, I fully expect we will be able to significantly reduce or rule out entirely any impact probability for the foreseeable future,” said Don Yeomans, manager of NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif., in a statement.

The space rock is currently located in the daytime sky, so astronomers cannot make more observations from Earth until its orbit swings into the nighttime sky. That will occur in a next year, Yeomans said.

“In September 2013, we have the opportunity to make additional observations of 2011 AG5 when it comes within 91 million miles (147 million kilometers) of Earth,” Yeomans said. “It will be an opportunity to observe this space rock and further refine its orbit.”

The asteroid is also expected to come near Earth in February 2023, but it will pass no closer than about 1 million miles (1.6 million kilometers). Then again in 2028, 2011 AG5 will be in the area, but it won’t come within about 10.4 million miles (16.7 million kilometers) of our planet.

The pull of Earth’s gravity during this pass, however, will have the chance of setting the rock on a more direct collision course that could target the asteroid to slam into our planet on Feb. 5, 2040.

Still, the odds of this occurring are remote, scientists say. The asteroid’s 1-in-625 chance of posing a threat to Earth is not expected to last.

“It is important to note that with additional observations next year the odds will change and we expect them to change in Earth’s favor,” Yeomans said.

This asteroid is just one of 8,744 near-Earth objects that have been discovered. NASA’s Near-Earth Object Observations Program detects and studies these rocks to keep a vigilant lookout for any that might pose a threat to us.

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via Big Asteroid’s Chances of Hitting Earth in 2040 Overblown, NASA Says | Asteroid 2011 AG5 | Space.com.

It’s called Apophis. It’s 390m wide. And it could hit Earth in 24 years’ time.

Scientists call for plans to change asteroid’s path.
Developing technology could take decades.

Alok Jha
The Guardian, Tuesday 6 December 2005

In Egyptian myth, Apophis was the ancient spirit of evil and destruction, a demon that was determined to plunge the world into eternal darkness.

A fitting name, astronomers reasoned, for a menace now hurtling towards Earth from outerspace. Scientists are monitoring the progress of a 390-metre wide asteroid discovered last year that is potentially on a collision course with the planet, and are imploring governments to decide on a strategy for dealing with it.

Nasa has estimated that an impact from Apophis, which has an outside chance of hitting the Earth in 2036, would release more than 100,000 times the energy released in the nuclear blast over Hiroshima. Thousands of square kilometres would be directly affected by the blast but the whole of the Earth would see the effects of the dust released into the atmosphere.

And, scientists insist, there is actually very little time left to decide. At a recent meeting of experts in near-Earth objects (NEOs) in London, scientists said it could take decades to design, test and build the required technology to deflect the asteroid. Monica Grady, an expert in meteorites at the Open University, said: “It’s a question of when, not if, a near Earth object collides with Earth. Many of the smaller objects break up when they reach the Earth’s atmosphere and have no impact. However, a NEO larger than 1km [wide] will collide with Earth every few hundred thousand years and a NEO larger than 6km, which could cause mass extinction, will collide with Earth every hundred million years. We are overdue for a big one.”

Apophis had been intermittently tracked since its discovery in June last year but, in December, it started causing serious concern. Projecting the orbit of the asteroid into the future, astronomers had calculated that the odds of it hitting the Earth in 2029 were alarming. As more observations came in, the odds got higher.

Having more than 20 years warning of potential impact might seem plenty of time. But, at last week’s meeting, Andrea Carusi, president of the Spaceguard Foundation, said that the time for governments to make decisions on what to do was now, to give scientists time to prepare mitigation missions. At the peak of concern, Apophis asteroid was placed at four out of 10 on the Torino scale – a measure of the threat posed by an NEO where 10 is a certain collision which could cause a global catastrophe. This was the highest of any asteroid in recorded history and it had a 1 in 37 chance of hitting the Earth. The threat of a collision in 2029 was eventually ruled out at the end of last year.

Alan Fitzsimmons, an astronomer from Queen’s University Belfast, said: “When it does pass close to us on April 13 2029, the Earth will deflect it and change its orbit. There’s a small possibility that if it passes through a particular point in space, the so-called keyhole, … the Earth’s gravity will change things so that when it comes back around again in 2036, it will collide with us.” The chance of Apophis passing through the keyhole, a 600-metre patch of space, is 1 in 5,500 based on current information.

There are no shortage of ideas on how to deflect asteroids. The Advanced Concepts Team at the European Space Agency have led the effort in designing a range of satellites and rockets to nudge asteroids on a collision course for Earth into a different orbit.

No technology has been left unconsidered, even potentially dangerous ideas such as nuclear powered spacecraft. “The advantage of nuclear propulsion is a lot of power,” said Prof Fitzsimmons. “The negative thing is that … we haven’t done it yet. Whereas with solar electric propulsion, there are several spacecraft now that do use this technology so we’re fairly confident it would work.”

The favoured method is also potentially the easiest – throwing a spacecraft at an asteroid to change its direction. Esa plans to test this idea with its Don Quixote mission, where two satellites will be sent to an asteroid. One of them, Hidalgo, will collide with the asteroid at high speed while the other, Sancho, will measure the change in the object’s orbit. Decisions on the actual design of these probes will be made in the coming months, with launch expected some time in the next decade. One idea that seems to have no support from astronomers is the use of explosives.

Prof Fitzsimmons. “If you explode too close to impact, perhaps you’ll get hit by several fragments rather than one, so you spread out the area of damage.”

In September, scientists at Strathclyde and Glasgow universities began computer simulations to work out the feasibility of changing the directions of asteroids on a collision course for Earth. In spring next year, there will be another opportunity for radar observations of Apophis that will help astronomers work out possible future orbits of the asteroid more accurately.

If, at that stage, they cannot rule out an impact with Earth in 2036, the next chance to make better observations will not be until 2013. Nasa has argued that a final decision on what to do about Apophis will have to be made at that stage.

“It may be a decision in 2013 whether or not to go ahead with a full-blown mitigation mission, but we need to start planning it before 2013,” said Prof Fitzsimmons. In 2029, astronomers will know for sure if Apophis will pose a threat in 2036. If the worst-case scenarios turn out to be true and the Earth is not prepared, it will be too late. “If we wait until 2029, it would seem unlikely that you’d be able to do anything about 2036,” said Mr Yates.

It’s called Apophis. It’s 390m wide. And it could hit Earth in 31 years’ time | Science | The Guardian.