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.

28 February 2006

B612 Foundation's Preferred Mitigation Concept: Gravity Tractor

Here are some comments from B612 Foundation Chairman Russell Schweickart, it seems the gravity tractor is now their preferred mitigation concept (in place of the VASIMR plasma rocket with nuclear reactors):

- "Clearly the gravity tractor concept, with no new technology needed and no detailed knowledge needed re asteroid characteristics, can be accomplished in relatively short order, provided the money and motivation (or authorization, in the case of NASA) is available."

- "This mission, however, is far simpler than most Discovery class missions since it need carry virtually no scientific payloads, and Discovery missions fall in the $300M realm. At the moment we’re looking at what options for getting this mission underway make most sense."

- "Yes, the gravity tractor can be built and tested now, and by coincidence should we actually need an Apophis deflection (unlikely but possible) the gravity tractor is capable of doing the deflection job."

Link: Article

27 February 2006

Cumulative Impact Probability of Top 98 Near Earth Asteroids (as of Feb. 27, 2006) = 1 in 206 (with qualifications)

An interesting question related to the NEO threat is sa follows: "What is the actual risk of an object hitting the earth?" This should be a simple number the general public can easily understand. However, there are many qualifications experts want to include for such a number.

In response to that question, here is quick and dirty way to obtain a number representative of the risk using the most recent data.

I took Near Earth Asteroid (NEA) impact risk statistics for the top 98 NEAs from JPL (Source: updated February 27, 2006 and generated a cumulative impact probability for the top NEAs from this list.

So, taking the cumulative impact probability (if it is accurate now and in the future) for the top 98 NEAs from this list of this date, one obtains a chance of an impact of approximately 1 in 206.

Most of this risk comes from the top 10-20 objects in the 98 (ranked in terms of impact probability, from highest to lowest). This data should be coupled to potential damage since these objects are not all the same in composition and size. In addition, normally the chance of impact is lowered as more observations are made. As others have stated, it is the asteroid we do not know about that may most likely hit us.

Link: Recently Observed Objects Risk Scale from JPL

Article on European Space Agency’s Don Quijote Asteroid Deflection Mission

"Despite its playful name, taken from Miguel de Cervantes’s classic novel, the European Space Agency’s Don Quijote mission is deadly serious. Slated for 2012, the $180-million mission will attempt to move one of two target asteroids, just identified this fall, by rear-ending it with a speeding spacecraft. Quijote is the first venture of its kind, although the B612 Foundation, a privately-funded nonprofit based in Tiburon, California, intends to launch a similar effort by 2015."

"Rear-ending Rocks in Space"
Gregory Mone
Popular Science
January 2006

ESA's Don Quijote mission consiss of 2 spacecraft: one spacecraft (Hidalgo) will impact an asteroid of approximately 500 m diameter at a relative speed of at least 10 km/s, the other spacecraft (Sancho) will rendezvous and remain in orbit around the asteroid for several months before and after the impact. Public information indicates that the Don Quijote spacecraft set would have a total payload launch mass of around 1 MT. Public sources also indicate a launch using a Soyuz-Fregat launch vehicle (now most likely a Soyuz/ST launch vehicle that has a payload of 2 MT at a c3 = 0).

Link: Article

Updated Space Studies Insitute (SSI) Website Includes Asteroid Mitigation Section

The newly revised Space Studies Institute (SSI), founded by Dr. Gerard K. O’Neill, website includes section on asteroid deflection and mitigation.

Quotations include:

" For a long while, the conventional wisdom on this issue was that one would use nuclear explosives for this purpose. But according to a paper published in the June 4th, 1998 issue of Nature, this may not be as easy as previously thought. It points out that many asteroids are multi-lobed. A nuclear detonation might be largely absorbed by one lobe, with little course deflection resulting in the whole. The paper theorizes that the average asteroid may not be so much like a solid rock as an aggregate of fragments loosely held together by fine dust. If this “flying gravel pile” theory is correct, a nuclear detonation might pulverize an approaching asteroid, converting one big problem into many little ones...A mass driver engine, by contrast, could provide the low, steady, continuous thrust needed to change an asteroid’s course gradually, using the asteroid’s own material for reaction mass."

"Critical mass driver subsystems have been developed to technology readiness level 6 by SSI at Princeton University under contract NASA and private funding...A concept that has received relatively little attention in the literature is the employment of a mass driver to apply a steady acceleration to the asteroid which, given sufficient time, will develop lateral movements that can convert a strike on earth into a miss. The major advantage of this approach is that all the energy comes from the sun and all the reaction mass is obtained from the mass of the asteroid itself. The only mass that needs to be transported to the asteroid is that of the solar collectors, power supplies and acceleration coils which convert electrical energy to kinetic energy."

Link: Asteroid Deflection at SSI

Link: Asteroid Mitigation at SSI

Confirmation of Threat: 2004 VD17 Gets a Torino Rating of 2 (1 in 1,850 chance of hitting the Earth)

Object 2004 VD17 was given a Torino scale rating of 2, apparently only the second time in risk monitoring history this has happened. Thus currently only two objects have a Torino scale rating above 0: the well known 99942 Apophis (2004 MN4) and now 2004 VD17. However, whereas Apophis has close approaches within the next few decades, 2004 VD17 projections reveal close approaches in 2096, 2102, and 2104. 2004 VD17 has a 1 in 1,850 chance of hitting the Earth whereas Apophis has a 1 in 5,880 chance of Earth impact.

Here are some estimated parameters for 2004 VD17 from the most recent observations by JPL on Feb. 23, 2006:

Diameter: 0.580 km
Mass: 2.7e+11 kg
Torino Scale (maximum): 2
Palermo Scale (maximum): -0.40
Palermo Scale (cumulative): -0.40
Impact Probability (cumulative): 5.4e-04
Number of Potential Impacts: 4

Torino Scale 2 Definition: "A discovery, which may become routine with expanded searches, of an object making a somewhat close but not highly unusual pass near the Earth. While meriting attention by astronomers, there is no cause for public attention or public concern as an actual collision is very unlikely. New telescopic observations very likely will lead to re-assignment to Level 0."

- More detail from

Notes: 2004 VD17 was discovered by LINEAR on 7 Nov. 2004 and was announced the next day. It was posted with impact solutions at JPL and NEODyS on 9 Nov. when further observations became available. JPL elevated 2004 VD17 to Torino Scale 1 (a routine alert that an object "merits special monitoring") on 22 Nov., and NEODyS put it at TS-1 on the 23rd.

2004 VD17 had been noted to go out of view on 5 Feb. 2005 and wasn't observed after 28 Jan. until David Tholen's team picked it up from Mauna Kea on March 4th, which was published 13 days later.

On 15 Nov. 2005 it was reported that Tholen's team had recovered 2004 VD17 on the 4th, 11th, and 13th of that month using the University of Hawaii 2.2m telescope on Mauna Kea. This more than tripled the object's observation arc, from 117 to 371 days.

2004 VD17 brightened into view in early Feb. 2006 and was picked up with the Spacewatch 1.8m telescope on 6 Feb. It remains in view until around June 22nd, then comes back again in late July for the rest of the year. NEODyS notes "Very accurate observations necessary in March."

On 6 Feb. 2006, for only the second time in risk monitoring history, 2004 VD17 was raised to a Torino Scale rating of 2 (for "a somewhat close but not highly unusual pass near the Earth ... an actual collision is very unlikely"). JPL raised it to TS-2 after the next observation became available on Feb. 23rd.

Link Wikipedia Entry on 2004 WD17

Link: hohmanntransfer website

Link: 2004 VD17 Earth Impact Risk Summary from JPL

Link: Recently Observed Objects Risk Scale from JPL

26 February 2006

Image of Gravitational Tractor Concept by Dan Durda

Astronomy Picture of the Day: Gravitational Tractor
November 10, 2006

"How would you change the course of an Earth-threatening asteroid? One idea - a massive spacecraft that uses gravity as a towline - is illustrated in this dramatic artist's view of a gravitational tractor in action. In the hypothetical scenario worked out by Edward Lu and Stanley Love at NASA's Johnson Space Center, a 20 ton nuclear-electric spacecraft tows a 200 meter diameter asteroid by simply hovering near the asteroid. The spacecraft's ion drive thrusters are canted away from the surface. The steady thrust would gradually and predictably alter the course of the tug and asteroid, coupled by their mutual gravitational attraction. While it sounds like the stuff of science fiction, ion drives do power existing spacecraft and a gravitational tractor would work regardless of the asteroid's structure or surface properties."

Link: Astronomy Picture of the Day

Christian Science Monitor: Online Poll Results from 2005 on Apophis Mission

Poll results from the last year on a mission to asteroid Apophis.

- Question: "Should NASA launch a mission soon to tag the Apophis asteroid?"

- Result: Yes 78.27%, No 21.73% (out of 925 votes)

Link: Poll results

Link: Original Christian Science Monitor Article

"Pat Robertson Vaporized By Apophis Asteroid" and "Tom DeLay: Tax Cuts, Faith to Prevent Apophis Asteroid Collision"

I had noticed these "spoof" articles from last year using the asteroid Apophis. These fake articles are set in the future. Note: I post this for reference purposes only, making no political claims.

"Pat Robertson Vaporized By Apophis Asteroid"
Ion Zwitter
Avant News Editor
Avant News
November 15, 2005

Link: Article

"Tom DeLay: Tax Cuts, Faith to Prevent Apophis Asteroid Collision"
Ion Zwitter
Avant News Editor
Avant News
November 10, 2005

Link: Article

10 February 2006

ESA Advanced Concepts Meeting Paper on Asteroid Deflection

Dr. Roger Walker, Research Fellow over at European Space Agency (ESA) Advanced Concepts Team (ACT), has a presentation on asteroid deflection at the upcoming Workshop on Innovative Systems Concepts (21 February 2006) at the European Space Research and Technology Centre (ESTEC) in Noordwijk (The Netherlands). The presentation is entitled: "Advanced Solar and Nuclear Electric Propulsion Systems for Asteroid Deflection."

Link: Workshop

Link: Workshop Program

Link: ESA ACT mission analysis page on asteroid deflection

Link: ESA ACT paper on asteroid deflection

06 February 2006

United Nations Office for Outer Space Affairs Meeting (20 Feb. - 03 March) Considers NEO Threat

The forty-third session of the Scientific and Technical Subcommittee of the Committee on the Peaceful Uses of Outer Space will be held from 20 February - 03 March 2006 at the United Nation Office at Vienna, Vienna International Center, Vienna, Austria. This session will consider multiple issues including the NEO threat. I believe B612 Foundation Representatve Rusty Schweikert will be there.

The following is from the agenda (related to the NEO threat):

In paragraph 10 (b) of its resolution 60/99, the General Assembly endorsed the recommendation of the Committee that the Subcommittee, at its forty-third session, consider this item in accordance with the workplan adopted by the Subcommittee at its forty-first session (A/AC.105/823, annex II, para. 18) and amended at its forty-second session (A/AC.105/848, annex I, para. 20).

According to the workplan, the Subcommittee, at its forty-third session, would:

(a) Consider reports from Member States and international organizations on their near-Earth object activities, including missions, search and follow-up, as well as plans for future activity;
(b) Consider the need for a working group in 2007;
(c) Update the work programme for the third year as necessary and consider the need for intersessional work.

The reports mentioned in subparagraph (a) above will be contained in document A/AC.105/C.1/L.284.

Additionally, the Action Team on Near-Earth Objects will consider the way forward and, specifically, the possible need for further activity to be carried out nationally, regionally or through international cooperation. Such cooperation should be considered together with the prospects for harmonization and avenues for broader collaboration.

Link: Provisional agenda for the Forty-third Session of the Scientific and Technical Subcommittee 2006 (20 February-3 March 2005)

Link: United Nations Office for Outer Space Affairs

Article on Current Apophis Situation

"Can NASA learn enough about an approaching asteroid to rule out a collision in 2036?"
Bruce Lieberman
San Diego Union-Tribune
February 1, 2006

Link: Article

Planetary Society Funds for Asteroid Research

The Planetary Society is asking for funds related to two project: the Gene Shoemaker NEO Grant Fund anda new joint project to analyze asteroid threats with the B612 Foundation.

The Shoemaker Fund grants are to support asteroid tracking worldwide. The project with the B612 Foundation is to create a system of computerized "automated" maps that "will visually depict the specific narrow corridor across the face of the planet within which any given asteroid would strike."

Link: Release from the Planetary Society

Link: To support NEO research
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