This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

27 November 2007

"Return of the Falcon," a new animation of the Hayabusa mission

From Planetary Society Blog:

"JAXA has released a 30-minute video of the Hayabusa mission, "Return of the Falcon," combining computer animation with actual footage of the construction and launch as well as images from the spacecraft of Itokawa. It takes a while to download but is worth a watch. The video is set to the smooth jazz sounds of Emiko Kai, composed before the launch of Hayabusa (then named MUSES-C) to express "people's interest, hope, and support for a successful flight. The music represents the hopes of all people supporting the mission as though it represented a Muse gently watching over the challenges of a boy named 'Hayabusa.'"

Link: Planetary Society Blog Post

Link: JAXA Movie Link

20 November 2007

NASA Article: "Hubble Zooms in on Heart of Mystery Comet"

Image above: Images of Comet 17P/Holmes as seen from the ground (left) and the Hubble Space Telescope (right). Click image for enlargement. Credit: A. Dyer, Alberta, Canada (left); NASA/ESA/H. Weaver/The Johns Hopkins University Applied Physics Laboratory (right)

From the new release:

NASA's Hubble Space Telescope has probed the bright core of Comet 17P/Holmes, which, to the delight of sky watchers, mysteriously brightened by nearly a millionfold in a 24-hour period beginning Oct. 23, 2007.

Astronomers used Hubble's powerful resolution to study Comet Holmes' core for clues about how the comet brightened. The orbiting observatory's Wide Field Planetary Camera 2 (WFPC2) monitored the comet for several days, snapping images on Oct. 29, Oct. 31, and Nov. 4. Hubble's crisp "eye" can see objects as small as 33 miles (54 kilometers) across, providing the sharpest most detailed view yet of the source of the spectacular brightening.

The Hubble image at right, taken Nov. 4, shows the heart of the comet. The central portion of the image has been specially processed to highlight variations in the dust distribution near the nucleus. About twice as much dust along lies along the east-west direction (the horizontal direction) as along the north-south direction (the vertical direction), giving the comet a "bow tie" appearance.

The composite color image at left, taken Nov. 1 by an amateur astronomer, shows the complex structure of the entire coma, consisting of concentric shells of dust and a faint tail emanating from the comet's right side.

Link: NASA Press Release

Link: HubbelSite

Presentations from Recent Space Resources Space Resources Roundtable IX on Asteroids

The Ninth Space Resources Roundtable was held at the Colorado School of Mines from 24-27 October 2007. Many of the presentations dealt with In-Situ Resource Utilization (ISRU) on the moon and Mars. A few paper dealt with non-lunar ISRU (with some relation to asteroids). Here are some of the papers:

"Meteoric Steel as a Construction Resource on Mars"
G.A. Landis
Link: Presentation (zip file download, 5.9 MB)

"The Effective Bullet Shape for Impact Asteroid Sampling"
T. Makabe, H.Yano
Link: Presentation (zip file download, 6.5 MB)

"Defining Intercept Orbits for NEO 2004 GU0 in Support of Potential Long-Duration Manned or Sample-Return Missions"
J.G. Rodriguez
Link: Presentation (zip file download, 0.6 MB)

"ISRU Mission Recommendations to the SELENE-2 Project"
H. Kanamori
Link: Presentation (zip file download, 5.2 MB)

Link: Agenda (with Presentations)

NYTimes Article on Arecibo: "A Hazy Future for a ‘Jewel’ of Space Instruments"

From the article...

With a quarter of its annual budget slashed, to $8 million from $10.5 million, Arecibo will be listening to the universe less often in the coming years. For researchers like Dr. Lovell, a professor of astronomy at Agnes Scott College in Georgia, that may mean her work — detecting radio waves emitted by ions from busted-up water molecules — will take years longer to complete.

More alarming would be the closing of Arecibo in four years, a possibility that has been raised by the National Science Foundation, which pays for the operation of the telescope.

In an era of tight and tightening budgets, a review panel for the foundation’s astronomy division two years ago looked for places where money could be freed up for new facilities. It recommended a 25 percent cut in Arecibo’s foundation financing by 2011 and then another 50 percent cut, to $4 million, in 2011.

The panel said Arecibo should look to other institutions and agencies to make up for the 2011 cut; if it could not find the money, the panel said, the foundation should consider closing it.

A quarter of its staff was laid off last year. The telescope is now on hiatus for repainting, but when it resumes operation, the number of observing hours will be cut, and nearly half of its receivers will be furloughed. Its emphasis will shift to large, continuing surveys, and smaller projects like Dr. Lovell’s may be much more squeezed than in the past.

An outcry followed the review panel’s decision, particularly from planetary scientists who thought that the group had overlooked Arecibo’s role in cataloging potential dangers from asteroids. Its radar can precisely plot the orbit of an asteroid to determine if it could be on course for a collision with Earth.

Two weeks ago, scientists and officials testified before a Congressional committee about the asteroid issue and touched on Arecibo’s fate. “The planetary science community is in danger of losing one of its instrumental crown jewels,” Donald K. Yeomans, a scientist at NASA’s Jet Propulsion Laboratory, told the House subcommittee on space and aeronautics.

NASA is a candidate to pick up some of the financing, particularly the $1 million to $2 million annual cost of the planetary radar. The agency has contributed to the radar operations in the past, as much as $500,000, but NASA officials say their focus should be on instruments in space, not on the ground.

"A Hazy Future for a ‘Jewel’ of Space Instruments"
Kenneth Chang
New York Times
20 November 2007

Link: Article

19 November 2007

Interesting Asteroid/Comet Abstracts from Seventh IAA International Conference on Low-Cost Planetary Missions

Here are some interesting abstracts from the recent Seventh IAA International Conference on Low-Cost Planetary Missions (12-14 September, 2007, Pasadena, California USA).

- An Approach To Minimum Cost NEO Characterization. R. Reinert , R. Dissly, and Scott Mitchell, Ball Aerospace & Technologies Corp.
Link: Abstract

This abstract details a few mission concepts including (from the abstract):

- NEO Scout Low-Cost Spacecraft Concept. The NEO Scout mission concept is designed to minimize mission cost by using a very low-cost spacecraft. The NEO Scout approach uses a basic single-string architecture and a simple hydrazine monopropellant propulsion approach to rendezvous with a single NEO after a launch to a C3 of 5-10 by a Taurus, Falcon-5, or Minotaur-V medium-cost LV.

- NEO Sentry Minimum Launch Cost Mission Concept. The NEO Sentry mission is aimed at minimizing mission cost by using the lowest cost launch vehicle. It uses a high performance dual-mode bipropellant propulsion approach and ultra-low mass to rendezvous with a single NEO after launch to a 185-km LEO by a bargain-basement Falcon-1 LV.

- NEO Explorer (NEOX) Solar Electric Propelled Spacecraft Concept. The NEOX mission concept minimizes mission cost by enabling a single spacecraft to rendezvous with multiple NEO’s and by allowing multiple S/C to be launched by a single LV. The NEOX mission profile takes advantage of the low-thrust mission designs described below to rendezvous with up to three separate NEO's, or to perform a single rendezvous with a NEO inaccessible to chemically propelled vehicles. SEP efficiency lowers the NEOX S/C mass sufficiently to allow 2 such S/C to be launched on a single Delta-II, or four to be launched on the smallest Delta

- Deep Interior: Radar Exploration of Asteroid Interiors. A. Safaeinili (1), E. Asphaug (2), Y. Gim (1), E. Heggy (2), 1.Jet Propulsion Laboratory, 2. UC Santa Cruz, 3. Lunar and Planetary Institute
Link: Abstract

From the abstract...

Our nominal mission design for a radar investigation at a typical km-sized asteroid utilizes a polar orbit, with a period of weeks, while the asteroid spins underneath with a period of hours. The result is to "peel the apple" with thousands of unique radar returns providing global coverage at the spatial requirements of tomographic reconstruction. Another alternative, appealing at small (sub-km) asteroids where orbiting can be a challenge (solar wind pressure becomes comparable to the asteroid gravity), or at binary asteroid systems, is to utilize a hovering mission approach (as was done by the Japanese Hayabusa mission) while, as before, the asteroid spins underneath. Optical imaging is sufficient for the a posteriori reconstruction of spacecraft position at the time of data acquisition, so the only instruments required for this mission is the radar hardware, the antenna, and a simple camera. At present, this mission fits inside of the Discovery cost parameters even if one flies to two or more asteroids. With further radar flight heritage, this radar reflection imaging technology can evolve into a very low cost mission that could be flown routinely to near-Earth objects and other small bodies.

- Triple F: A comet nucleus sample return mission for ESA’s Cosmic Vision program. M. KÜPPERS1, H. U. KELLER1, E. KÜHRT2, P. EHRENFREUND3 AND THE TRIPLE F TEAM, 1 Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany, 2 Institut für Planetenforschung, DLR, Germany, 3 Leiden Institute of Chemistry, Leiden, The Netherlands
Link: Abstract

From the abstract...

A relatively small spacecraft will be launched into its interplanetary trajectory to a short period comet. After a short monitoring period near the cometary nucleus, needed to find suitable sampling spots, the spacecraft will touch down on the surface of the nucleus to collect samples. The sampling depth will be several decimeters. Finally the cooled samples will be returned to Earth. The mission is proposed to ESA’s Cosmic Vision and exploration programs, in co-operation with the Russian space agency.

- Hayabusa-2, The Next Asteroid Sample Return Mission of Japan. Makoto Yoshikawa, Hajime Yano, Junichiro Kawaguchi, Post-Hayabusa Mission WG, Japan Aerospace Exploration Agency.
Link: Abstract

From the abstract...

We have been considering post Hayabusa missions much before Hayabusa's arrival to the asteroid. This is because we think that asteroid is the key object to understand the origin and evolution of the solar system. Since the results of Hayabusa were very impressive and important from the point of the planetary science, we are now attempting to start next mission as soon as possible. We call the next mission as Hayabusa-2. The spacecraft is basically the same as Hayabusa. Of course we modify several points where there were problems. But the model is almost same, so we can save time to manufacture it, and we are hoping that we can launch it in 2011 or 2012. The target is again small near earth asteroid but C-type. So we are looking forward to seeing how the small C-type asteroid looks like. The current target of Hayabusa-2 is 1999 JU3.

Also, we are considering another sample return mission, which we call "Hayabusa-Mark2" tentatively. Hayabusa-Mark2 is not the copy of Hayabusa, but it is much-advanced mission both in the sampling and the remote sensing. For example, we want to challenge sampling with preserving depth profile and to get much more detailed data of the sampling sight. Hayabusa-Mark2 is also considered in the scheme of Cosmic Vision of ESA.

- Stand-off Estimation of Binary Asteroid Mass Distributions. D.J. Scheeres1,2 and E.G. Fahnestock1, 1The University of Michigan, Ann Arbor.
Link: Abstract

From the abstract...

Recent investigations of the dynamics and morphology of the binary asteroid system 1999 KW4 have revealed a complex and dynamic system that should be typical of binary asteroids. While investigation of the KW4 system is of intrinsic interest, methods we have developed to understand and characterize this system are also applicable to other NEA binaries with similar morphology. In this presentation we will detail an underlying dynamical theory we have developed and an accompanying procedure which allows one to estimate the mass distribution properties of a binary system without having to fly a spacecraft within the gravitational field of the system. Specifically, we show that in a system such as KW4 there is sufficient information in the dynamical oscillation of its components to estimate the second degree and order gravity field coefficients and moments of inertia of both bodies based on stand-off observations alone. This is significant when compared to the situation for solitary asteroids where the gravity field can only be determined by tracking the motion of a spacecraft perturbed by the higher order gravity coefficients. Also, the moments of inertia cannot be estimated for solitary asteroids, except if the body is in non-uniform rotation. For a binary system with an excitation level similar to KW4’s, it is possible to determine the total mass, mass fraction of the system, the J2 gravity coefficient of the primary, the principal moments of inertia of the secondary, and potentially the principal moments of inertia of the primary if it has a significant equatorial ellipticity. The moments of inertia contain significant information on how the mass is distributed within a body not available from the gravity coefficients alone. The placement of passive probes on the surface of the binary components with radio transmitters can yield significantly improved precision for these estimated quantities. The estimation of these quantities do not require the spacecraft to orbit the system closely, which can reduce a mission’s operational costs significantly.

Link: 7th Low-Cost Planetary Missions Conference Website

Link: 7th Low-Cost Planetary Missions Conference Website: Agenda

ESPA Ring as Foundation for Future Spacecraft Design

I have been recently interested in the use of the ESPA ring for planetary missions (potentially including asteroid missions). The most recent NASA Small Business Innovation Research (SBIR) grants included one to CSA engineering for examination of the ESPA ring for future planetary missions (see below).

NASA 2007 Phase I SBIR: "ESPA for Lunar and Science Missions"

NASA mission planning in the next decade includes small spacecraft and secondary flight opportunities on Evolved Expendable Launch Vehicles (EELVs), specifically Atlas V and Delta IV. NASA's use of EELVs is accelerated because of the impending termination of the Delta II launcher. Nearly all EELVs slated for launch have significant excess payload capacity. The EELV Secondary Payload Adapter (ESPA) Ring was developed by CSA Engineering under an Air Force SBIR to utilize excess lift capability by providing a secondary mission capability.

ESPA, as built, can provide access to space for NASA lunar and science missions. However, to ensure that diverse NASA mission objectives can be achieved with the best possible mission configurations, structural tailoring of the ESPA will be required. The proposed effort will develop modular features of ESPA that are required for optimal NASA mission configurations targeting, but not necessarily limited to, the following:
(1) Separable ESPA: Separation capability built into the ESPA Ring.
(2) Hierarchical ESPA: Scaling of the ESPA design for larger EELV payloads and for small launch vehicles.
(3) ESPA Mounts: Interior and exterior mounting for spacecraft and auxiliary structures.

Phase 1 will establish feasibility for the modular ESPA designs. Plans will be presented for flight qualification of all designs. Phase 2 will produce flight qualified hardware to at least TRL 6 for a design determined to be the most desirable for near-term NASA implementation.

Link: NASA 2007 Phase I SBIR Announcement for CSA Engineering Inc.

Link: ESPA ring paper - "Designing for ESPA: The Challenges of Designing a Spacecraft for a Launch Accommodation Still in Development"

Link: AeroAstro ESPA-class concepts

Link: ESPA ring brochure from CSA Engineering (PDF)

Link: NASA Lunar CRater Observation and Sensing Satellite (LCROSS) spacecraft (based upon ESPA ring), part of the Lunar Reconnaissance Orbiter (LRO)

18 November 2007

Asteroid 2007 VF189: Son of ROSETTA

Selection from the Planetary Society blog entry...

On the heels of the news last week that the Rosetta spacecraft was spotted by sky surveys and briefly named among the minor planets as 2007 VN84 came another close approach by a newly discovered near-Earth object, designated 2007 VF189, which had an orbit surprisingly similar to the Rosetta spacecraft, making a close approach to Earth (closer than the Moon, about 250,000 kilometers away) roughly six hours after Rosetta, on November 14. This is a story that has been unfolding on the Minor Planets Mailing List, and I've been watching it with interest. (A big thanks to all of the various MPML participants whose comments I'm paraphrasing below, in particular Richard Kowalski -- whose Catalina Sky Survey discovered both 2007 VN84 and 2007 VF189 -- as well as Steven Chesley and Alan Harris.)

In brief: the probability for there to be a random object so close in the sky to Rosetta is 1 in 70; the probability for Rosetta and this object to come close to Earth within 6 hours of each other is 1 in 10; and the probability that they would have velocities within 2.1 km/sec of each other is 1 in 10. Multiplying those together, you get a 1 in 7000 chance for Rosetta and another object to pass so close to each other, at nearly the same speed, near Earth. That's an interesting number, because it's not too likely, but neither is it vanishingly unlikely. Plenty of people bet lots of money on worse odds.

In the end, then, 2007 VF189 is a small, unremarkable Apollo-class object (meaning it's an Earth-orbit-crossing asteroid with an orbital period of longer than one year), and nobody would have paid much attention to it if not for last week's mixup.

"Son of Rosetta"
The Planetary Society Weblog
By Emily Lakdawalla
16 November 2007

Link: Article

Link: JPL Small-Body Database Browser for 2007 VF189

Link: Minor Planet Center data for 2007 VF189

Link: Article from Der Spiegel, Thorsten Dambeck, 15 November 2007, "Unknown flying object pursues space probe "Rosetta"

Link: Translation of Above Der Spiegel Article

16 November 2007

Interesting Article on Modern Perception of Global Natural Risks

Selections from the article...

In recent years, humankind has become aware of a number of global and existential risks that potentially threaten our survival.

These natural and man-made risks comprise cosmic disasters, volcanic super-eruptions and climatic disruption on the one hand, and nuclear warfare, technological catastrophes and fully-fledged bioterrorism on the other.

In order to secure the future of civilisation, we are challenged to recognise and ward off these low-probability, but potentially destructive hazards.

A new debate is gaining momentum about how best to achieve a secure future for our planetary civilisation.

A recent study confirms that the annual percentage of people killed by natural disasters has decreased tenfold in the last 40 years, in spite of the fact that the average annual number of recorded disasters increased fivefold. Evidently, open and technological societies are becoming increasingly resilient to the effects of natural disasters.

The more people see, hear or read about the risks of Near Earth Object (NEO) impacts, nuclear terrorism or global climate catastrophes, the more concerned they have become. The mere mention of catastrophic risks, regardless of its low probability, is enough to make the danger more urgent, thus increasing public estimates of danger.

Scientists who evaluate risks are often torn between employing level-headed risk communication and the temptation to overstate potential danger.

In recent years, leading scientists in the UK, such as Brandon Carter, Stephen Hawking and Sir Martin Rees, have advanced the so-called Doomsday Argument, a cosmological theory in which global catastrophes due to low-probability mega-disasters play a considerable role.

This speculative theory maintains that scientific risk assessments have systematically underestimated existential hazards. Hence the probability is growing that humankind will be wiped out in the near future.

Nevertheless, there are many good and compelling reasons why human extinction is not predetermined or unavoidable.

According to a more optimistic view of the future, all existential risks can be tackled, eliminated or significantly reduced through the application of human ingenuity, hyper-technologies and global democratisation.

Current advances in developing an effective planetary defence system, for example, will eventually lead to a protective shield that can safeguard life on the Earth from disastrous NEO impacts.

"Existential risk and democratic peace"
BBC Viewpoint
Benny Peiser, Liverpool John Moores University, UK
15 November 2007

Link: Article

15 November 2007

Articles on Mistaken Identification of ESA Rosetta Spacecraft as Asteroid

Image description: Rosetta’s navigation camera (NAVCAM) took this shot of Earth right after Rosetta’s closest approach to our planet. The picture was taken at 22:56 CET on 13 November, as Rosetta’s second Earth swing-by concluded, while the spacecraft was flying at a height of about 6250 km from the surface. Credits: ESA.

Image description: An artist's rendition of Rosetta's second close approach to Earth on Nov. 13, 2007. The swing-by is Rosetta's third major step on its 10-year journey to comet 67/P-Churyumov-Gerasimenko. Credit: C. Carreau/ESA.

From one of the articles...

The Minor Planet Center, the world clearinghouse for information about newly discovered asteroids, raised the alarm last week. In an email to professional observatories, they announced that a previously unknown asteroid would miss the Earth by just 5,600 kilometers.

The newly discovered space rock was given an official label by the MPC, which is run by the Smithsonian Astrophysical Observatory, Massachusetts, for the International Astronomical Union. Observations for 2007 VN84 were collected from astronomers around the world, to track the threatening celestial body. This would be one of the closest approaches ever by a sizable asteroid – its distance away being less than half the diameter of the Earth.

Then Denis Denisenko, of Moscow's Space Research Institute (IKI), made an interesting discovery. He noticed that the incoming asteroid's track matched that of the European space probe Rosetta on a scheduled flyby of Earth.

The Rosetta craft was launched from Europe's Guiana Space Center in early March of 2004; the purpose of the space probe is to place itself in low orbit around the comet Churyumov-Gerasimenko at a distance of 675 million kilometers from the sun. To get there, the billion-dollar craft will spend ten years boosting its velocity (using the gravity assist technique) with no fewer than three flybys of Earth and one of Mars.

Denisenko's discovery came none too soon; Britain's Royal Astronomical Society was preparing a bulletin for the media that would have been released on Monday.

"Near-Miss Asteroid Found to be Artificial"
Bill Christensen
12 November 2007

Link: Article

From another article...

But the incident raises questions about how well the warning system works. The Minor Planet Center complains that, "this incident highlights the deplorable state of availability of positional information on distant artificial objects". This lack of a centralised database makes checking incoming objects against known space probes difficult.

"Astronomers defend asteroid warning mix-up"
Justin Mullins
13 November 2007

Link: Article

Article: "Incredible Comet [Comet 17P Holmes] Bigger than the Sun"

From the article...

A comet that has delighted backyard astronomers in recent weeks after an unexpected eruption has now grown larger than the sun...The sun remains by far the most massive object in the solar system, with an extended influence of particles that reaches all the planets. But the comparatively tiny Comet Holmes has released so much gas and dust that its extended atmosphere, or coma, appears larger than the diameter of the sun in a new image..."It continues to expand and is now the largest single object in the solar system," according to astronomers at the University of Hawaii.

"The coma's diameter on Nov. 9 was 869,900 miles (1.4 million kilometers), based on measurements by Rachel Stevenson, Jan Kleyna and Pedro Lacerda of the University of Hawaii Institute for Astronomy. They used observations from the Canada-France-Hawaii Telescope. The sun's diameter, stated differently by various sources and usually rounded to the nearest 100, is about 864,900 miles (1.392 million kilometers)."

Incredible Comet Bigger than the Sun
Robert Roy Britt
15 November 2007

Link: Article

12 November 2007

NEO News (11/12/07) More on Congress NEO Hearings

Note: The following is the 10/12/07 Edition of NEO News, an email newsletter distributed by David Morrison.

NEO News (11/12/07) More on Congress NEO Hearings

This edition of NEO News contains some additional material on the hearings held last week by the House Subcommittee on Space and Aeronautics dealing with advanced NEO searches and related topics. I have (1) posted a news story on the hearing from, (2) selected several very nice summary comments taken from the testimony, and (3) also added a few comments of my own on some misunderstandings that can arise in these discussions, misunderstandings that apparently caused the NASA NEO study to limit itself to technologies for deflecting NEAs between 140m and 1km in diameter, neglecting both the most dangerous (>1km) and the most common (<140m) cases. Also, unrelated to the hearings, there is (4) a post on the strange story off how the Rosetta spacecraft was mistaken for a NEA.

David Morrison



AFP, 8 November 2007

NASA penny-pinching risks exposing humankind to a planetary catastrophe if a big enough asteroid evades detection and slams into Earth, US lawmakers argued Thursday. But the US space agency said the chances of a new "Near-Earth Object" (NEO) like the one that wiped out the dinosaurs were too remote to divert scarce resources.

Scott Pace, head of program analysis and evaluation at NASA, said the agency could not do more to detect NEOs "given the constrained resources and the strategic objectives NASA already has been tasked with."

Pace and other NASA officials were grilled at a congressional hearing on the existing NEO program, which seized the public imagination in the late 1990s through the movies "Armageddon" and "Deep Impact." Lawmakers decried the threatened closure of a giant radio telescope in Puerto Rico run with NASA's assistance that is the world's foremost facility for tracking space objects.

"We're talking about minimal expense compared to the cost of having to absorb this type of damage," Republican Congressman Dana Rohrabacher said. "After all, it may be the entire planet that is destroyed!"

Puerto Rico delegate Luis Fortuno fretted over the economic impact on his impoverished US territory, but also warned of the broader consequences for the entire planet. The National Science Foundation has earmarked the Arecibo Observatory, which featured in science-fiction movie "Contact" and the James Bond installment "Goldeneye," for closure after 2011 if new private-sector money is not found.

NASA officials said they would get by with new monitoring systems, including a network of four telescopes being built in Hawaii by the US Air Force.

Critics say NASA has imposed big cuts on many research programs in a bid to meet President George W. Bush's goal of returning astronauts to the Moon by 2020 and use it as a stepping stone for manned missions to Mars and beyond.

The hearing of the House of Representatives space and aeronautics subcommittee highlighted one small asteroid named Apophis, about 250 meters (273 yards) wide, which some scientists say could swing by Earth on Friday, April 13, 2029. NASA says there is a one in 45,000 chance that Apophis could pass through a "gravitational keyhole" and return to hit the planet in 2036. "It's a very unlikely situation and one we can drive to zero, probably," said Donald Yeomans, who manages the NEO program at NASA's Jet Propulsion Laboratory.

NASA now only tracks NEOs larger than one kilometer (0.62 miles) in diameter, which come near Earth only once every few hundred thousand years. Objects of that size can cause global disaster through their immediate surface impact and by triggering rapid climate change. "Extinction-class" objects measuring at least 10 kilometers, such as the object that crashed into Mexico's Yucatan peninsula about 65 million years ago, would be rarer still.

Lawmakers complained that NASA had failed to come up with a budget in line with a 2005 act of Congress that mandated an expanded search for NEOs that are at least 140 meters in diameter. The agency's annual NEO budget of 4.1 million dollars was attacked as being too meager to cover this goal.

There are about 20,000 smaller objects with the potential to hit home, according to NASA, and Republican Representative Tom Feeney said "they could still inflict large regional impacts if they struck the Earth."

Options to divert space rocks on a collision course with Earth include slamming nuclear missiles into them, although scientists believe that in most cases involving smaller debris, conventional rockets would do the job.

Yeomans said also that while the European and Japanese space agencies are stepping up their own NEO programs, more than 98 percent of the work is now done by NASA.

© 2007 AFP



From testimony of J. Anthony Tyson, LSST

Until recently, the discussion of risk associated with an impact of a NEO has been statistical; what is the probability? This is similar to considerations of risk in many other areas such as weather and traffic accidents. What if it were feasible to deploy a system that would alert me of an impending traffic accident well in advance? That would change the very nature of that risk from a probabilistic worry to a deterministic actionable situation. The ability to detect virtually every potentially hazardous Near-Earth object and determine its orbit with precision transforms that statistical threat into a deterministic prediction. We face many threats, and virtually all of them are either so complex or unpredictable that they are treated probabilistically even though the social and financial consequences are legion. With a comparatively small investment the NEO risk can be transformed from a probabilistic one to a deterministic one, enabling mitigation.

From testimony of Donald Yeomans, JPL

What should be done in the event of an identified NEO Threat? A number of existing technologies can deflect an Earth threatening asteroid -- if there is time. The primary goal of the PHA survey programs is to discover them early and provide the necessary time. An asteroid that is predicted to hit Earth might require a change in its velocity of only 3 millimeters per second if this impulse were applied twenty years in advance of the impact. The key to a successful deflection is having sufficient time to carry it out, whether it is the slow, gentle drag of a gravity tractor or a more impulsive shove from an impacting spacecraft or explosive device. In either case, a verification process would be required to ensure the deflection maneuver was successful and to ensure the object's subsequent motion would not put it on yet another Earth impacting trajectory. While suitable deflection technologies exist, none of them can be effective if we are taken by surprise. It is the aggressive survey efforts and robust planetary radars that must ensure that the vast majority of potentially hazardous objects are discovered and tracked well in advance of any Earth threatening encounters. The first three steps in any asteroid mitigation process are: Find them early, find them early, and find them early!

From testimony of Russell Schweickart, B612 Foundation

In closing I would suggest a personal perspective based on having spent the last 6 years of my life studying this issue. NEOs are part of nature. A NEO impact is a natural hazard in much the same way as are hurricanes, tsunamis, floods, etc. NEO impacts are deceptively infrequent, yet devastating at potentially unimaginable levels. NEOs are however not our enemies. We do not need to "defend" against NEOs, we need to protect ourselves from their occasional impact, as we do with other natural hazards.

Unlike other natural hazards, however, NEO impacts can be predicted well ahead of time and actually prevented from occurring. If we live up to our responsibility, if we wisely use our amazing technology, and if we are mature enough, as a nation and as a community of nations, there may never again be a substantially damaging asteroid impact on the Earth. We have the ability to make ourselves safe from cosmic extinction. If we cannot manage to meet this challenge, we will, in my opinion, have failed to meet our evolutionary responsibility.



David Morrison

Some of the often misunderstood concepts behind NEO surveys concern the meaning of a specified 90% target size, 1km diameter in the case of the current Spaceguard Survey, and 140m for the proposed Spaceguard deep survey. An example from the news story above is this statement: "NASA now only tracks NEOs larger than one kilometer (0.62 miles) in diameter." But the fact is, in Al Harris's often-quoted words, "we don't throw back the small ones." The majority of NEAs found by Spaceguard are less than 1km in diameter. By the time we reach 90% completeness at 1km, we will have found almost ten times more NEAs smaller than this limit, and certainly these smaller NEAs are tracked and cataloged. The best known example is Apophis, the most dangerous NEA found yet, which is only about half the 1km Spaceguard target size. In any such survey, most of the NEAs will be below the index size, but these will be less complete than the index size used for the 90% metric.

Similarly, any survey scaled for 140m NEAs will predominantly find NEAs smaller than this size. In fact, the discoveries from this deep survey will extend down below the atmospheric cut-off at about 30m diameter. Rusty Schweickart in his testimony estimates that when we reach 90% completeness at 140m, we will be 40% complete for Tunguska-size objects. The most likely object to require deflection is actually below the 140m index size.

There are implications of these facts that need to be considered. For example, the data handling must be scaled for nearly 10 times the number of NEAs at 140m size, since again, we won't throw back the small ones. Further, any plans for deflection should recognize that the most likely challenges will come from NEAs less than 140m in diameter. The NASA study apparently focused only on deflecting NEAs between 140m and 1km in diameter, neglecting both the most dangerous (those larger than 1km, of which 10% will remain undiscovered at the nominal end of the current Spaceguard survey) and the most common (those under 140m diameter).

None of the prepared testimony explicitly mentioned uncertainties in the population of small NEAs or in the ability to model the efficiency of survey telescopes. This in understandable, given the limited time available, but it does over-emphasize specific dates and sizes that enter into models of the new deep surveys. It is not unreasonable that both the number of NEAs larger than 140m and the ability of new telescopes (both ground-based and space based) to detect and identify them could be off by as much as a factor of two. We won't know when we are likely to achieve 90% completeness at 140m until the telescopes are built and the new survey is well underway. Therefore I don't worry too much about small differences in the estimated dates of completion. I am more interested in the start date than the completion date for Spaceguard-2.



The Planetary Society Weblog, 9 November 2007
By Emily Lakdawalla

Whenever I am out at night with my husband and I point to the sky and say, "that's Venus" or "look, that's Saturn, see how yellow it is," he likes to burst my bubble by saying "no, it's just a plane." Every great once in a while, I'm sad to say, he's right.

Well, a similar scenario has just unfolded within the near-Earth asteroid community. On November 8 the Minor Planet Center issued a routine Minor Planet Electronic Circular, reporting on observations of a newly discovered object, newly designated 2007 VN84. Several observatories had spotted the faint object, and, based upon those observations, an orbital trajectory was calculated, which placed the object on a very close path by Earth, "0.000081 AU (1.89 Earth radii) on Nov 13.844 UT." Now, that 1.89 Earth radii is measured relative to Earth's center, meaning that the thing was going to fly within 6,000 kilometers of Earth on November 13 at 20:15 UTC. That's pretty close! This is a truly near-Earth object.

Rosetta's second Earth flyby is due to take place Closest approach will take place on 13 November 2007 at 20:57 UTC, at which time Rosetta will speed past at 45,000 km/h (about 12.5 km/s) relative to Earth. At this time, Rosetta will be 5,301 km above the Pacific Ocean, south-west of Chile, at 63° 46' south and 74° 35' west. But a sharp-eyed reader of the MPECs, Denis Denisenko, realized that there was something going on. I'm not sure what tipped him off; whether he noticed that specific date and time and remembered another significant event to happen on that day, or whether he has a habit of checking near-Earth object trajectories against catalogs of manmade objects. However the discovery happened, he realized that 2007 VN84 had a trajectory that was awfully similar to Rosetta, which is due to swing by Earth on November 13 at 20:57 UTC. He posted as much to the Minor Planet Mailing List.

Indeed, today, the Minor Planet Center issued an Editorial Notice stating that further investigation has shown that the object briefly designated 2007 VN84 is, in fact, the Rosetta spacecraft, and that the designation "2007 VN84" will be retired. The editorial notice goes on to say, with notable asperity, "This incident, along with previous NEOCP postings of the WMAP spacecraft, highlights the deplorable state of availability of positional information on distant artificial objects.... A single source for information on all distant artificial objects would be very desirable."

I think it's pretty funny that a very big spacecraft designed to study minor planets in the solar system has itself, however briefly, been named among the minor planets. This episode also goes to show how sensitive our detection capability is. Rosetta is a pretty reflective object, but it's also quite small when compared to near-Earth objects that could do us any damage. And here we had at least several days' warning of this small object's approach. It's actually comforting to me, in a way; it seems that there is now no way we can have less than a few weeks' warning of the approach of an object large enough to do us some harm. Bad things may happen if such an object hits, but that's enough time to get a lot of people out of harm's way.

Of course, all this hubbub is occasioned by Rosetta's upcoming flyby. The Rosetta Blog has some updates, including the nice detail that no further trajectory correction maneuvers are necessary, which bodes well for them accomplishing the acquisition of science data during the flyby.

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NEO News (now in its thirteenth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, Ames Research Center, the International Astronomical Union, or any other organization. To subscribe (or unsubscribe) contact For additional information, please see the website If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.

08 November 2007

U.S. House Comm. Hearing on 08 November 2007: Near-Earth Objects (NEOs)—Status of the Survey Program and Review of NASA’s 2007 Report to Congress


Near-Earth Objects (NEOs)—Status of the Survey Program and Review of NASA’s 2007 Report to Congress

Thursday, November 8, 2007
10:00 a.m. – 12:00 p.m.
2318 Rayburn House Office Building
Washington, D.C. USA

Purpose: On Thursday, November 8, 2007 at 10:00 a.m., the House Committee on Science and Technology’s Subcommittee on Space and Aeronautics will hold a hearing to examine the status of NASA’s Near-Earth Object survey program, review the findings and recommendations of NASA’s report to Congress, Near-Earth Object Survey and Deflection Analysis of Alternatives, and to assess NASA’s plans for complying with the requirements of Section 321 of the NASA Authorization Act of 2005.

Panel 1
- The Honorable Luis G. Fortuño, Resident Commissioner, Puerto Rico

Panel 2
- Dr. James Green, Science Mission Directorate, NASA
- Dr. Scott Pace, Program Analysis and Evaluation, NASA
- Dr. Donald K.Yeomans, Jet Propulsion Laboratory
- Dr. Donald B.Campbell, Cornell University
- Mr. Russell Schweickart, B612 Foundation
- Dr. J. Anthony Tyson, University of California, Davis

Link: Article - 08 November 2007 (NASA pressed to avert catastrophic Deep Impact)

Link: U.S. House Science Comm. Hearing Information

Link: Hearing Charter (PDF)

Link: Testimony of Chairman Mark Udall, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress

Link: Testimony of Rep. Luis G. Fortuno, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress

Link: Testimony of James Green, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress

Link: Testimony of Scott Pace, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress

Link: Testimony of Donald Yeomans, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress

Link: Testimony of Russell Schweickart, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress

Link: Testimony of J. Anthony Tyson, Hearing on Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress

Journal Article: "A possible impact crater for the 1908 Tunguska Event"

Summary from

"A team of scientists from the Marine Science Institute in Bologna [Italy] claims to have found the crater left by the aerial blast of a comet or asteroid in 1908 in the Tunguska region of Siberia. The blast flattened 770 square miles (2,000 square kilometers) of forest, but to date no remains or crater have been found. This has left open the question of what kind of object made the impact. The team believes that, contrary to previous studies, nearby Lake Cheko is only one century old and 'If the body was an asteroid, a surviving fragment may be buried beneath the lake. If it was a comet, its chemical signature should be found in the deepest layers of sediments.' The team's findings are based on a 1999 expedition to Tunguska and appeared in the August issue of the journal Terra Nova."

Journal Reference:

Terra Nova, 00, 1–7
Volume 19 Issue 4 Page 245-251, August 2007
"A possible impact crater for the 1908 Tunguska Event"
Luca Gasperini, Geologia Marina, Istituto di Scienze Marine, CNR, Via Gobetti 101, Bologna 40129, Italy. Tel.: +39 051 639 8901; fax: +39 051 639 8901; e-mail:

The so-called ‘Tunguska Event’ refers to a major explosion that occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2000 km2 of taiga, globally detected pressure and seismic waves, and bright luminescence in the night skies of Europe and Central Asia, combined with other unusual phenomena. The ‘Tunguska Event’ may be related to the impact with the Earth of a cosmic body that exploded about 5–10 km above ground, releasing in the atmosphere 10–15 Mton of energy. Fragments of the impacting body have never been found, and its nature (comet or asteroid) is still a matter of debate. We report results from the investigation of Lake Cheko, located ~8 km NNW of the inferred explosion epicenter. Its funnel-like bottom morphology and the structure of its sedimentary deposits, revealed by acoustic imagery and direct sampling, all suggest that the lake fills an impact crater. Lake Cheko may have formed due to a secondary impact onto alluvial swampy ground; the size and shape of the crater may have been affected by the nature of the ground and by impact-related melting and degassing of a permafrost layer.

Link: National Geographic Article

Link: Terra Nova Journal (August 2007)

Link: Terra Nova Journal Article

Link: Terra Nova Journal Article PDF

Planetary Society Statement on Arecibo Radio Telescope

Selections from the Planetary Society Statement:

Arecibo is caught in a bureaucratic argument. The Arecibo Observatory is a National Science Foundation (NSF) operation, but they consider the subject of NEOs and planetary radar to be in NASA’s bailiwick. NASA supports ground-based astronomy, and supported the Arecibo radar for many years, but the agency now objects to picking up the funding of what is currently an NSF program.

The House Science and Technology Committee has been the leading government advocate for understanding the nature and possible treat from objects (NEOs) that might impact the Earth. In the past, the committee has had to direct NASA to provide increased support to this area. The Planetary Society has no position on whether this should be a NSF program or a NASA program; but, we strongly feel that it should be an American program with congressional support. We urge you to provide such support to keep the Arecibo planetary radar operating.

The Planetary Society recently conducted a privately funded, international competition to design a mission to tag the asteroid Apophis, in case its Earth approach is close enough to require higher accuracy tracking. The competition attracted thirty-seven proposals and has generated much public interest.

The cost of a tagging mission to Apophis would be at least $100 million – and the only way to know if such a mission is necessary is to refine the current estimate of Apophis’ orbit with the powerful adar tracking of a telescope like Arecibo. Avoiding one unnecessary tagging mission would more than pay back any investment of funds to keep Arecibo open. And if some object out there really is on a collision course with Earth and we don’t have the means to track it properly, the price we would pay would be astronomical.

Link: Planetary Society Press Release

Link: Planetary Society Arecibo Statement

Link: Planetary Society PDF Document

06 November 2007

New SEI Image of Solar Ablation Asteroid Mitigation Concept

SpaceWorks Engineering, Inc. (SEI) has posted an image of a potential asteroid movement technology. The image shows a solar ablation asteroid mitigation concept wherein a series of mirrors and lenses focus sunlight onto the NEO, causing material on the NEO’s surface to be expelled.

Link: Image

Link: SEI Planetary Defense website

Link: PowerPoint (in PDF format) from H. J. Melosh (University of Arizona) on Mirror Ablation Process (from the 2004 Planetary Defense Conference)

Link: Video (Windows Media) from H. J. Melosh (University of Arizona) on Mirror Ablation Process (from the 2004 Planetary Defense Conference)

NyTimes Article: "Rethinking What Caused the Last Mass Extinction"

NYTimes article on evidence (or alternatives) to the K-T impact. Selections from the article...

Scientists associate the iridium anomaly with the asteroid impact or impacts thought to have set off the extinctions. The thin layer, which has been detected worldwide, is also considered the marker for the end of the Cretaceous and beginning of the Tertiary period, known as the K-T boundary.

The discovery of thriving communities of survivors at the end of the Cretaceous is giving some scientists second thoughts about the extinction’s causes and effects. Some question the conventional explanation of a single large impact that enveloped Earth in a cloud of dust and almost instantaneously brought on a deadly global winter. They contend that this may be an oversimplification, and that the real story behind the dinosaur-ending disaster is more complicated and as yet unclear.

In other words, the world’s ecosystem was under widespread stress for an extended time. The extinctions might have had multiple causes, not the single asteroid impact and almost instant death as hypothesized in 1980 after the detection of the global iridium layer.

A few other paleontologists have also cast doubt on the timing and single-impact suddenness of the mass extinction. The idea of a killer impact that became the standard theory was proposed in 1980 on the basis of iridium traces; it gained wide acceptance after the discovery in 1991 of the impact crater in Mexico. But in some places, the fossil record for dinosaurs seems to disappear a little before the iridium is deposited. Geologists have found several other crater remnants that could have been gouged out by asteroids and also the suspect volcanoes of India.

"Rethinking What Caused the Last Mass Extinction"
John Noble Wilford
November 6, 2007
New York Times

Link: NYTimes Article

05 November 2007

Concept from Yesterday: Colonies from Nickel-Iron Asteroids

From a NASASpaceflightnow forum post:

"Back in the early 1960's, when Men were Men and Aerospace Engineers dreamed BIG, Dandridge Cole of Martin Co. suggested making arti-g colonies from nickel-iron astorids. Process was simple: drill a hole to the center of the asteroid, pumo a boatload of water in, then seal up. Then, using truly huge mirrors, refelct sunlight onto the asteroid until it nearly melted. The water inside would boil, and what with the nickel-iron alloy being soft and malleable, it'd blow up like a balloon."

Link: Images - 1

Link: Images - 2

Link: NASASpaceflightnow forum on "asteroid habitat with gravity"

Link: Article on Dandridge M. Cole's work -"Islands in Space: The Challenge of the Planetoids"

1. Levitt, I. M., and Cole, Dandridge M. Exploring the Secrets of Space: Astronautics for the Layman. Englewood Cliffs, N.J., Prentice Hall, Inc., 1963, pp. 277-278.

2. Cole, Dandrige M., and Cox, Donald, W. Islands in Space: The Challenge of the Planetoids. Philadelphia, Chilton Books, 1964.

3. Cole, Dandrige M., and Scarfo, Roy G. Beyond Tomorrow: The Next 50 Years in Space. Amherst, Wis., Amherst Press, 1965.

01 November 2007

Article: What to Do Before The Asteroid Strikes

Good summary article, selections from the article...

Because Apophis was discovered during one of the world’s greatest natural disasters, the worries about the impact went largely unnoticed. But that tense day, December 26, 2004, stunned the small group of astronomers who dutifully detect and plot trajectories of hundreds of thousands of the millions of chunks of rock whizzing around the solar system. Though too small to end civilization—unlike the asteroid that may have doomed the dinosaurs—Apophis could pack a punch comparable to a large nuclear weapon. Traveling at 28,000 miles per hour, it would heat up as it passed through Earth’s atmosphere, turning the dark rock into a fiery sun as it arced across the sky. Then it would either explode just aboveground—as one most likely did in 1908, leveling a vast forest in the Tunguska region of Siberia—or gouge a crater 20 times its size. “If it hit London, there would be no London,” says Apollo 9 astronaut Rusty Schweickart, who had closely followed the discussion of the potential 2029 impact. Slamming into the ocean, Apophis could create a tsunami dwarfing the one that killed more than 200,000 people around Indonesia.

Schweickart was deeply shaken by the Apophis experience. “I don’t know how to transmit to you the emotion, the level of intensity of a group of people you could name on two hands during those days in December 2004,” he says. His interest in the asteroid threat extended back to 2001, when he and a few colleagues sat down at NASA’s Johnson Space Center in Houston just six weeks after the terrorist attacks on New York and Washington to discuss ways to deflect an incoming asteroid.

"What to Do Before The Asteroid Strikes: The doomsday rock is out there. It’s just a matter of time..."
Andrew Lawler
01 November 2007
Discover Magazine

Link: Article (Discover Magazine)
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