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.

## 31 August 2011

### Target NEO Workshop Final Report

A recent space.com article on the final report from the Target: NEO workshop.

Selections from the article...

Developing the capability to launch human missions to asteroids would aid humanity's ability to foil a potentially devastating asteroid strike and help spur our march to Mars, a new report finds.

What's most needed to make manned asteroid missions possible, the report further concludes, is a comprehensive survey of the Near Earth Object (NEO) population, which would greatly aid planning efforts.

The new report, entitled "Target NEO: Open Global Community NEO Workshop," is anchored in views expressed by experts who gathered at George Washington University (GWU) in Washington in February. But this latest appraisal includes extensive peer review and refined findings from a number of follow-up meetings, both in the United States and abroad.

The key question posed by the GWU workshop: What information about NEOs is still needed to support a robust, sustainable human exploration program?

While this question prompted a variety of recommendations, a primary conclusion by the participants is the need for a space-based survey telescope to greatly expand the catalog of accessible asteroid targets for human exploration.

The space rock menace

There is a growing list of stakeholders supportive of NEO exploration, said Paul Abell, lead scientist for planetary small bodies at the Astromaterials Research and Exploration Science Directorate of NASA's Johnson Space Center in Houston.

"This report is timely," Abell told SPACE.com.

Small bodies have become a magnet for multiple interest groups in the U.S. and abroad, Abell said, be they space scientists, astrobiologists, planetary defense planners or NEO specialists who eye the rocky worlds as resource nodes.

For example, NASA recently selected an asteroid sample return mission called Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer, or OSIRIS-Rex. OSIRIS-Rex will be the first U.S. mission to carry samples from an asteroid back to Earth.

Japanese space officials are moving forward on their Hayabusa 2 asteroid explorer. Russia is readying its Phobos-Grunt spacecraft to explore a moon of Mars, and Canada is pressing forward on its dual-purpose microsatellite, NEOSSAT.

Then there’s the new, surprising data flooding in from NASA’s Dawn probe that’s taking a long look at Vesta, the second-largest object in the main asteroid belt between Mars and Jupiter.

"It shows you that, every time we go places, we’re always surprised and there’s so much to learn," Abell said. "That’s the fun part of science and exploration."

The "Target NEO" report points out that programs and planned missions to asteroids may be leveraged for mutual benefit in terms of data exchange. It also recommends coordination with the European Space Agency and other space agencies on a planetary defense demonstration mission.

Stepping stones to Mars

As for dispatching astronauts to asteroids, the report envisions that a target NEO will need to be discovered several years in advance to provide enough lead time to deliver robotic precursor missions, plan the human mission and deliver the crew to the chosen destination.

Abell also said that piloted flight to a NEO would hone techniques that could enable an exploration mission to the Red Planet.

"They provide good stepping stones out to Mars," Abell said.

Operating at an asteroid or Mars would be completely different than working at the moon, on the space shuttle or aboard the International Space Station.

Both asteroids and Mars, for example, would have much greater lags in communication times. So deep space missions would require the sharpening of true autonomy acumen, as well as a great deal of confidence in redundant hardware, deep space propulsion, life support gear and radiation shielding.

Link: Target: NEO workshop final report (PDF)

## 30 August 2011

### PR on Recent Workshop on Planetary Defense Policy Workshop with SWF/NASA/UN/ASE

From the press release from Secure World Foundation...

A workshop has brought together leading representatives from space agencies and international experts to discuss key issues related to global response and cooperation in the event of a Near Earth Object (NEO) impact threat to Earth.

The gathering of specialists took place August 25-26 in Pasadena, California. The meeting was co-organized and co-sponsored by Action Team-14, part of the United Nations Committee on the Peaceful Uses of Outer Space (UN COPUOS) Scientific and Technical Subcommittee, Secure World Foundation (SWF), and the Association of Space Explorers (ASE) that represents over 350 individuals from 35 nations who have flown in space.

The supporting agency host of the meeting was the National Aeronautics and Space Administration (NASA) Near Earth Object Observations Program Office.

This recent workshop is a follow-up to previous meetings that took place last year in Mexico City to discuss a NEO Information, Analysis, and Warning Network (IAWN) and in Darmstadt, Germany to confer about a NEO Mission Planning and Operations Group, or MPOG, to plan, organize, and conduct any necessary missions to threatening asteroids.

Decisive step: set of recommendations

“As we now have the technological capacity, we should be able to prevent the threat of an asteroid impact on Earth or mitigate its consequences,” said Dr. Sergio Camacho, Secretary General of the Regional Centre for Space Science and Technology Education in Latin America and the Caribbean (CRECTEALC) in Mexico City. Camacho is a former Director of the United Nations Office for Outer Space Affairs, a post that he held from 2002 to 2007.

“I am very pleased with the progress made at this workshop towards establishing a space agency Mission Planning and Operations Group (MPOG) to plan, prepare and respond, if need be, to an asteroid threat,” Camacho said.

Preparing a draft Terms of Reference for such a group, with the participation of four space agencies, is a decisive step in this direction, Comacho added.

These results, together with those garnered from previous policy workshops -- also co-sponsored by Secure World Foundation -- on establishing an IAWN, an MPOG, and results to date from the multi-year work plan of the Action Team-14 on Near Earth Objects of the United Nations Committee on the Peaceful Uses of Outer Space, will result in February 2013 with a set of recommendations on which the Committee can act.

“I am also very pleased by the progress that we made in preparing these recommendations,” Comacho said. “By joining and coordinating efforts, the international community will be much better prepared to prevent the devastating consequences of an asteroid impact on Earth.”

Substantial progress

“This workshop made substantial progress toward an international interagency plan to mitigate the damaging effects of an asteroid strike against Earth. It also made headway in an effort to develop an overall international governance model for the response to a threatening Near Earth Object,” said Dr. Ray A. Williamson, Executive Director of Secure World Foundation.

The Association of Space Explorers has been promoting international efforts to plan for averting a future asteroid impact for more than five years, and last week’s Mission Planning and Operations Group meeting shows the world’s space agencies are moving closer to cooperative action, said Tom Jones, former NASA shuttle astronaut and current Chair of the ASE Committee on Near-Earth Objects.
Jones said that the “rules of the road” for the group should lead to joint technology development to deflect a rogue asteroid.

“What’s needed now is top-level agency endorsement of international planning and research, leading to a space demonstration of how we would change the course of an asteroid,” Jones said. “That’s the goal, so we can be ready for a hazardous asteroid down the road.”

### New Papers on low delta-V asteroids, asteroid mission measurement requirements, Human mission NEO targets, and detection of radiation pressure

Several new papers.

PAPER REFERENCE:

Physical characterisation of low delta-V asteroid (175706) 1996 FG3

Authors: Stephen D. Wolters, Ben Rozitis, Samuel R. Duddy, Stephen C. Lowry, Simon F. Green, Colin Snodgrass, Olivier R. Hainaut, Paul Weissman (Submitted on 08 Aug 2011)

Abstract: Asteroid (175706) 1996 FG3 is a binary asteroid and the baseline target for the proposed MarcoPolo-R sample-return mission. We present thermal IR photometry obtained with the ESO VLT+VISIR together with optical photometry obtained with the ESO NTT+EFOSC2 . An absolute visual magnitude H_V = 17.833 \pm 0.024 and phase parameter G = -0.041 \pm 0.005 is derived. The Near-Earth Asteroid Thermal Model (NEATM) has been fitted to the measured fluxes to derive a geometric visual albedo p_v = 0.046 \pm 0.014, effective diameter at the observed aspect D_eff = 1.68 \pm 0.25 km, and beaming parameter {\eta} = 1.15 for phase angle {\alpha} = 11.7{\deg}. The Advanced Thermophysical Model (ATPM) has been fitted to the measured fluxes to derive a more accurate effective diameter D_eff = 1.71 \pm 0.07 km and albedo p_v = 0.044 \pm 0.004. Based on the ATPM results, assuming the same albedo for primary and secondary, we derive a primary mean spherical diameter D_p = (1.69 +0.18/-0.12) km, secondary diameter D_s = 0.51 \pm 0.03 km, and a secondary orbital semi-major axis a = (2.8 +1.7/-0.7) km. A low surface thermal inertia {\Gamma} = 120 \pm 50 J m^-2 s^-1/2 K^-1 was also derived, suggesting a dusty surface and raising questions as to the binary formation mechanism of this asteroid. These physical properties are used to predict a Yarkovsky drift in semi-major axis of (-60 +31/-45) m yr-1.

Cite as: 1108.1831v1 [astro-ph.IM]

Link: Paper (PDF format)

PAPER REFERENCE:

Measurement requirements for a near-Earth asteroid impact mitigation demonstration mission

Authors: Stephen D. Wolters, Andrew J. Ball, Nigel Wells, Christopher Saunders, Neil McBride (Submitted on 21 Jul 2011)

Abstract: A concept for an Impact Mitigation Preparation Mission, called Don Quijote, is to send two spacecraft to a Near-Earth Asteroid (NEA): an Orbiter and an Impactor. The Impactor collides with the asteroid while the Orbiter measures the resulting change in the asteroid's orbit, by means of a Radio Science Experiment (RSE) carried out before and after impact. Three parallel Phase A studies on Don Quijote were carried out for the European Space Agency: the research presented here reflects outcomes of the study by QinetiQ. We discuss the mission objectives with regards to the prioritisation of payload instruments, with emphasis on the interpretation of the impact. The Radio Science Experiment is described and it is examined how solar radiation pressure may increase the uncertainty in measuring the orbit of the target asteroid. It is determined that to measure the change in orbit accurately a thermal IR spectrometer is mandatory, to measure the Yarkovsky effect. The advantages of having a laser altimeter are discussed. The advantages of a dedicated wide-angle impact camera are discussed and the field-of-view is initially sized through a simple model of the impact.

Cite as: 1107.4229v1 [astro-ph.IM]

Link: Paper (PDF format)

PAPER REFERENCE:

Ultra-Low Delta-v Objects and the Human Exploration of Asteroids

Authors: Martin Elvis, Jonathan McDowell, Jeffrey A. Hoffman, Richard P. Binzel (Submitted on 20 May 2011 (v1), last revised 15 Jun 2011 (this version, v2))

Abstract: Missions to near-Earth objects (NEOs) are key destinations in NASA's new "Flexible Path" approach. NEOs are also of interest for science, for the hazards they pose, and for their resources. We emphasize the importance of ultra-low delta-v from LEO to NEO rendezvous as a target selection criterion, as this choice can greatly increase the payload to the NEO. Few such ultra-low delta-v NEOs are currently known; only 65 of the 6699 known NEOs (March2010) have delta-v <4.5 km/s, 2/3 of typical LEO-NEO delta-v. Even these are small and hard to recover. Other criteria - short transit times, long launch windows, a robust abort capability, and a safe environment for proximity operations - will further limit the list of accessible objects. Potentially there are at least an order of magnitude more ultra-low delta v NEOs but, to find them all on a short enough timescale (before 2025) requires a dedicated survey in the optical or mid-IR, optimally from a Venus-like orbit because of the short synodic period for NEOs in that orbit, plus long arc determination of their orbits.

Cite as: 1105.4152v2 [astro-ph.IM]

Link: Paper (PDF format)

PAPER REFERENCE:

Detection of radiation pressure acting on 2009 BD

Authors: Marco Micheli, David J. Tholen, Garrett T. Elliott (Submitted on 03 Jun 2011)

Abstract: We report the direct detection of radiation pressure on the asteroid 2009 BD, one of the smallest multi-opposition near-Earth objects currently known, with H ~ 28.4. Under the purely gravitational model of NEODyS the object is currently considered a possible future impactor, with impact solutions starting in 2071. The detection of a radiation-related acceleration allows us to estimate an Area to Mass Ratio (AMR) for the object, that can be converted (under some assumptions) into a range of possible values for its average density. Our result AMR = (2.97 \pm 0.33) x 10^(-4) m^2 kg^(-1) is compatible with the object being of natural origin, and it is narrow enough to exclude a man-made nature. The possible origin of this object, its future observability, and the importance of radiation pressure in the impact monitoring process, are also discussed.

Cite as: 1106.0564v1 [astro-ph.IM]

Link: Paper (PDF format)

## 29 August 2011

### Paper: Capturing Near Earth Objects

From the MIT Technology Review article of a new paper from Baoyin, et al called "Capturing Near Earth Objects"...

Most of the discussion about near Earth asteroids focuses on whether they represent a threat to Earth and what to do take if they turn out to be heading our way. But today, Hexi Baoyin and pals at Tsinghua University in Beijing offer a different take. The question they ask is how to place an asteroid in orbit around the Earth. Their conclusion is a little surprising. They say it's relatively straightforward to nudge a small asteroid in our direction. They've even discovered a number of candidates nearby that we might want to bring as little closer. Their inspiration is a phenomenon that astronomers have noticed with Jupiter. Every now and again, the gas giant captures a nearby object, which hangs around for a few years and then wanders off into space. A good example is the comet Oterma which went into orbit about Jupiter in1936 before heading off into the Solar System two years later. Could a similar thing happen to Earth, ask Baoyin and co. Having studied the orbits of the 6000 known near Earth objects (NEO), they say the short answer is no. None of them will come close enough for Earth to capture. However, a few of these objects will come maddeningly close. So near, in fact, that a small nudge would send them into Earth orbit. "When such an NEO approaches Earth, it is possible to change its orbit energy...to make the NEO become a small satellite of the Earth," they say. A particularly good candidate is a 10-meter object called 2008EA9 which will pass within a million kilometres or so of Earth in 2049. 2008EA9 has a very similar orbital velocity as Earth's. Baoyin and co calculate that it could be fired into Earth orbit by changing its velocity by 410 metres per second. That's tiny. This nudge should place the asteroid in an orbit at about twice the distance of the Moon. From there it can be studied and mined, they say. Just like Oterma's, this orbit is likely to be temporary so 2008EA9 will probably wander off into the heavens after a few years.

PAPER REFERENCE:

Capturing Near Earth Objects

Authors: Hexi Baoyin, Yang Chen, Junfeng Li (Submitted on 24 Aug 2011)

Abstract: Recently, Near Earth Objects (NEOs) have been attracting great attention, and thousands of NEOs have been found to date. This paper examines the NEOs' orbital dynamics using the framework of an accurate solar system model and a Sun-Earth-NEO three-body system when the NEOs are close to Earth to search for NEOs with low-energy orbits. It is possible for such an NEO to be temporarily captured by Earth; its orbit would thereby be changed and it would become an Earth-orbiting object after a small increase in its velocity. From the point of view of the Sun-Earth-NEO restricted three-body system, it is possible for an NEO whose Jacobian constant is slightly lower than C1 and higher than C3 to be temporarily captured by Earth. When such an NEO approaches Earth, it is possible to change its orbit energy to close up the zero velocity surface of the three-body system at point L1 and make the NEO become a small satellite of the Earth. Some such NEOs were found; the best example only required a 410m/s increase in velocity.

Cite as: 1108.4767v1 [astro-ph.IM]

Link: MIT Technology Review Article

Link: Paper (PDF format)

## 28 August 2011

### Job Posting in Planetary Defense: Minor Planet Center (MPC) looking for IT Specialist

An IT specialist job announcement from the Minor Planet Center (MPC).

From Wikipedia: "Under the auspices of the International Astronomical Union, the MPC is the official organization in charge of collecting observational data for minor planets (asteroids) and comets, calculating their orbits and publishing this information via the Minor Planet Circulars." The MPC is part of the Smithsonian Astrophysical Observatory (SAO) at the Harvard-Smithsonian Center for Astrophysics.

Here is the MPC link as well as the USAJOBS link. Here is the listing:

SMITHSONIAN ASTROPHYSICAL OBSERVATORY

HR: Employment Opportunities
Job posting 11-59
Opening date: August 26, 2011
Closing date: September 16, 2011

TITLE: IT Specialist, IS-2210 (SYSADMIN/APPSW), Grade 13, $89,449 to$116,282/yr

TYPE OF POSITION: Trust Fund (non-federal) Indefinite

DIVISION: - Minor Planet Center, Solar, Stellar and Planetary Sciences Division

LOCATION: Cambridge, Massachusetts

AREA OF CONSIDERATION: All qualified candidates First consideration may be made 14 days after the opening date.

DUTIES: Duties may include but are not limited to: implementing all aspects of the software development lifecycle, including requirements generation, design, code, verification and test, and maintenance; interfacing with science staff at the highest project levels to obtain information regarding their needs as the user of the system; designing software following the Minor Planet Center (MPC) software design standards, applicable vendor's literature, and established practices; overseeing the translation of design into code within the MPC programming team and coordinating software development activities between subsystem teams to ensure design consistency; designing software subsystems and components, coding and debugging complex programs to support mission planning, scientific data analysis and reduction, and data archiving and retrieval on workstation computer and image display systems; verifying and testing all generated software and maintaining code as part of an overall system and overseeing these activities within the team.

QUALIFICATIONS : For all positions individuals must have IT-related experience demonstrating each of the four competencies listed below.

1. Attention to Detail - Is thorough when performing work and conscientious about attending to detail.

2. Customer Service - Works with clients and customers (that is, any individuals who use or receive the services or products that your work unit produces, including the general public, individuals who work in the agency, other agencies, or organizations outside the Government) to assess their needs, provide information or assistance, resolve their problems, or satisfy their expectations; knows about available products and services; is committed to providing quality products and services.

3. Oral Communication - Expresses information (for example, ideas or facts) to individuals or groups effectively, taking into account the audience and nature of the information (for example, technical, sensitive, controversial); makes clear and convincing oral presentations; listens to others, attends to nonverbal cues, and responds appropriately.

4. Problem Solving - Identifies problems; determines accuracy and relevance of information; uses sound judgment to generate and evaluate alternatives, and to make recommendations. In addition to the basic requirements listed above applicants must possess a minimum of one year of specialized experience equivalent to at least the grade 12 in the normal line of progression for this occupation which should demonstrate mastery of and skill in applying the various phases of the system software development lifecycles, including requirements generation, design, code, verification and test, systems integration, and maintenance; knowledge of the physical systems for which software is being developed to be able to define scientific requirements and develop software requirements; knowledge of FORTRAN, C, scripting languages, Unix and Linux; knowledge of the current state of system software technology and related computer equipment in the assigned area; knowledge of mathematics, sufficient to be able to communicate with scientists and engineers concerning calculations and algorithms; knowledge of image handling, graphics, display systems, and database management systems; ability to develop software at the subsystem level while conforming to standards; ability to assess emerging technologies as alternatives to current practices; ability to provide expert technical guidance to management and other staff; ability to present findings to management and staff on complex issues; and the ability to communicate both orally and in writing.

APPLICATION PROCEDURE: We will only accept applications on line for this position.

For a copy of the complete vacancy announcement and how to apply, visit: USAJOBS

The Smithsonian Astrophysical Observatory is an equal opportunity employer committed to diversity in our workplace.

Link: MPC Job Posting

## 26 August 2011

### Applications for the GSA Planetary Science Division’s Eugene M. Shoemaker Impact Cratering Award are due September 9, 2011

From Dr. David A. Kring, Ph.D. at the Center for Lunar Science &amp; Exploration at the USRA – Lunar and Planetary Institute...

Applications for the GSA Planetary Science Division’s Eugene M. Shoemaker Impact Cratering Award are due September 9, 2011.

The Eugene M. Shoemaker Impact Cratering Award is for undergraduate or graduate students, of any nationality, working in any country, in the disciplines of geology, geophysics, geochemistry, astronomy, or biology. The award, which will include \$2500, is to be applied for the study of impact craters, either on Earth or on the other solid bodies in the solar system. Areas of study may include but shall not necessarily be limited to impact cratering processes; the bodies (asteroidal or cometary) that make the impacts; or the geological, chemical, or biological results of impact cratering. Details about the award as well as an application form for interested students can be found here.

Link: Shoemaker Award Page

## 22 August 2011

### Next Pixar Film in 2013: Earth if K-T Extinction Event Did Not Happen

The next Pixar film will involve a scenario where the K-T extinction event did not happen, and the resulting consequences for evolution on planet Earth. From the article...

Pixar films with explore two new worlds in two upcoming films - the land of dinosaurs and the world inside the human mind - filmmakers announced at the D23 Expo 2011 Saturday.

The fan exposition in Anaheim, Calif., featured the announcement of the two yet untitled movies as executives promoted the entire Disney/Pixar slate.

The untitled dinosaur film will be released in the holiday season of 2013. Bob Peterson, who co-directed and voiced Dug the dog in the monster Pixar hit Up, will direct the new movie. He said he was inspired by a childhood visit to the World's Fair in New York where he saw animatronic dinosaurs created by Walt Disney. "It made a big impression on me," he said.

Peterson said the premise of the film will take aim at the notion that dinosaurs were made instinct by a giant asteroid hitting the Earth. "In this film, the asteroid missed the Earth and dinosaurs continued to live," he says.

Link: USA Today article

## 21 August 2011

### Masters Thesis: Design of a Surface Albedo Modification Payload for Near Earth Asteroid (NEA) Mitigation

A new Masters thesis paper from student Shen Ge at Texas A&M University called "Design of a Surface Albedo Modification Payload for Near Earth Asteroid (NEA) Mitigation".

PAPER REFERENCE:

Design of a Surface Albedo Modification Payload for Near Earth Asteroid (NEA) Mitigation

Authors: Shen Ge
Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Aerospace Engineering (August 2011)

Abstract: The development of the Surface Albedo Treatment System (SATS) onboard a spacecraft mission to the near earth asteroid (NEA) Apophis in 2012 is an innovative concept of deflecting NEAs from possible impact with the Earth through altering the Yarkovsky effect, a non-secular force in the solar system due to uneven surface thermal emission most profoundly affecting small rotating bodies subjected to sunlight. Though this force is small, its magnitude can be dramatic if extended over a period of time and if it uses the close approach of an asteroid near Earth to magnify the perturbation. The payload dispenses colored powder called albedo changing particles (ACPs) onto the surface changing its albedo and indirectly the surface temperature which changes the Yarkovsky effect. This study gives an in-depth description of both computational and experimental parts of the design of this system with primary focus on initial ground test setup. The initial experiments proposed to design the SATS is outlined in detail and justified by the mission criterion of interest as well as modeling the actual dispersal on the surface.

### Paper: Orbital dispersion and Earth-impact probability analysis for fragmented asteroids

A new paper from Lee, et al called "Orbital dispersion and Earth-impact probability analysis for fragmented asteroids".

PAPER REFERENCE:

Orbital dispersion and Earth-impact probability analysis for fragmented asteroids

Authors: Daero Lee(a), John E. Cochran Jr.(b), and Tas Soo No(c)
a. Wind Power Grid-Adaptive Technology Research Center, Chonbuk National University, Jeonju 560-756, Republic of Korea
b. Department of Aerospace Engineering, Auburn University, Auburn, AL 36849, USA
c. Department of Aerospace Engineering, Chonbuk National University, Jeonju 560-756, Republic of Korea
Received 10 November 2010; revised 21 March 2011; accepted 25 May 2011. Available online 1 June 2011.

Abstract:This paper describes the orbital dispersion problem for a fragmented asteroid in an elliptical orbit. The use of a state transition matrix derived from the general relative equation of motion for an elliptical orbit is emphasized in this paper. The state transition matrix is used to propagate the orbital dispersion. The Earth-impact probability is then computed to obtain a measure of the likelihood of impact with the Earth after the asteroid is fragmented with a high-energy fragmentation method. The state transition matrix approach is also compared with numerical integration approaches that use the two-body equation and the general relative equations of motion. The computational efficiency of such a state transition matrix approach is verified with accuracy equal to the numerical integration approaches. The employed state transition matrix, known as the Cochran, Lee and Jo (CLJ) state transition matrix, is also evaluated for the numerous fragments with data from the burst.

### Paper: Optimal impact strategies for asteroid deflection

A new paper from Vasile, et al called "Optimal impact strategies for asteroid deflection".

PAPER REFERENCE:

Optimal impact strategies for asteroid deflection

Authors: Massimiliano Vasile, Camilla Colombo (Submitted on 25 Apr 2011)

Abstract:This paper presents an analysis of optimal impact strategies to deflect potentially dangerous asteroids. To compute the increase in the minimum orbit intersection distance of the asteroid due to an impact with a spacecraft, simple analytical formulas are derived from proximal motion equations. The proposed analytical formulation allows for an analysis of the optimal direction of the deviating impulse transferred to the asteroid. This ideal optimal direction cannot be achieved for every asteroid at any time; therefore, an analysis of the optimal launch opportunities for deviating a number of selected asteroids was performed through the use of a global optimization procedure. The results in this paper demonstrate that the proximal motion formulation has very good accuracy in predicting the actual deviation and can be used with any deviation method because it has general validity. Furthermore, the characterization of optimal launch opportunities shows that a significant deviation can be obtained even with a small spacecraft.

Cite as: arXiv:1104.4670v1 [astro-ph.IM]

Link: Paper (PDF format)

## 19 August 2011

### Ed Lu at TEDxNASA@SiliconValley 2011 on asteroid detection

From ZDNet Smart Planet....At TEDxNASA in San Francisco, former astronaut and physicist Ed Lu discusses the need to develop an early-warning and precision tracking/guidance system to prevent asteroids from hitting the planet.

## 18 August 2011

### Media Confusion on ESA Don Quijote Mission

A recent spate of news articles over the last 1-2 days needed some clarification regarding the ESA asteroid mission Don Quijote. I have noticed an inordinate amount of web articles on this mission yesterday and today (August 16-17), several years after it was analyzed as a potential mission concept study.

From some preliminary investigating it seems as if some of the articles/blogs that have carried this new item across the planet have indicated that the asteroid Apophis is a mission target (which it was not) and suggesting that the mission is more truly funded than it is (indicating a launch in 2015). One of the referenced articles is the London Daily Mail article. Another article is from Gizmodo and another article is from RedOrbit. These articles/posts seem to have been picked up and referenced by other news sources.

This FoxNews article attempts to correct the interpretation, the following comes from the article: "If an asteroid were ever detected, we'd want to do something -- and deflection is definitely one of the options," an ESA source told FoxNews.com. But despite a Daily Mail story touting the program as current, Don Quijote has long been shuttered. "The Don Quijote mission has been a study only. ESA is not working on this mission anymore," ESA spokesman Andreas Schepers told FoxNews.com.

My current perception is that this was a mission study that was never picked up by ESA for an actual mission (such as a NASA Discovery Class mission) since it was developed in a slightly different administrative area of ESA. UPDATE: The mission was initiated and performed by the ESA General Studies Programme in ESA's Future and Strategic Studies Office (with the technical support of the Concurrent Design Facility - CDF). The "missions" part of ESA did not pick up this concept study for an actual mission (my own estimate of ESA's organizational structure may be slightly off, but the general concept is probably correct). There may be attempts in the next 2-3 years to market this mission concept by ESA to its management within the EU but my opinion is that there is no actual funded mission as such as indicated in these articles (unfortunately for those with an interest in this area).

Generally, I think one would want to be very careful of any asteroid mitigation demonstration mission on the asteroid Apophis. That would probably be a test target of last resort. Given the uncertainty of effect of any impact mitigation mission, one would want to choose a relatively benign target (which Apophis is not given potential for disruption in its orbit during certain keyhole passes at a minimum). This comment is not mean to be any negative comment on any one specific news source but an attempt to clarify the general media record.

Here is some accurate information from the European Space Agency (ESA) on the mission: Don Quijote mission page.

Update: Video Report from Australia that also potentially adds confusion to the story in terms of the current status of the Don Quijote mission.

### Paper: Measurement requirements for a near-Earth asteroid impact mitigation demonstration mission

From the MIT Technology Review article of a new paper from Wolters, et al called "Measurement requirements for a near-Earth asteroid impact mitigation demonstration mission"...

In 2002, the European Space Agency began a program called Don Quijote to find out how best to perform such a deflection. Don Quijote involves sending two spacecraft to a near Earth asteroid; one to smash into it and the other to watch while in orbit above the impact crater. The goal is to change the asteroid's semimajor axis by more than 100 metres and to measure the change with an accuracy greater than 1 per cent. But the question is how best to monitor what's going on in a way that is relevant to other asteroids. After all, the ultimate plan is to use the information from this mission to move some other asteroid with our name on it. Now, Stephen Wolters at the Open University in the UK and a few friends have published a new analysis of the mission saying that measuring the change in orbit is not enough. Instead, the spacecraft needs to characterise the impact in detail, determining the density of the material near the asteroid's surface, the size of the surface grains as well as the mass and speed distribution of the impact ejecta. Only with this information will it be possible to work out exactly how the momentum from the impactor was transferred to the asteroid. That significantly changes the mission. In addition to an on-board radio transmitter that will allow space scientists back on Earth to work out its distance exactly, the spacecraft will need a sophisticated imaging suite capable of photographing the damage and carrying out infrared spectroscopy to determine the asteroid's mineral content.

PAPER REFERENCE:

Measurement requirements for a near-Earth asteroid impact mitigation demonstration mission

Authors: Stephen D. Wolters, Andrew J. Ball, Nigel Wells, Christopher Saunders, Neil McBride (Submitted on 21 Jul 2011)

Abstract: A concept for an Impact Mitigation Preparation Mission, called Don Quijote, is to send two spacecraft to a Near-Earth Asteroid (NEA): an Orbiter and an Impactor. The Impactor collides with the asteroid while the Orbiter measures the resulting change in the asteroid's orbit, by means of a Radio Science Experiment (RSE) carried out before and after impact. Three parallel Phase A studies on Don Quijote were carried out for the European Space Agency: the research presented here reflects outcomes of the study by QinetiQ. We discuss the mission objectives with regards to the prioritisation of payload instruments, with emphasis on the interpretation of the impact. The Radio Science Experiment is described and it is examined how solar radiation pressure may increase the uncertainty in measuring the orbit of the target asteroid. It is determined that to measure the change in orbit accurately a thermal IR spectrometer is mandatory, to measure the Yarkovsky effect. The advantages of having a laser altimeter are discussed. The advantages of a dedicated wide-angle impact camera are discussed and the field-of-view is initially sized through a simple model of the impact.

Cite as: arXiv:1107.4229v1 [astro-ph.IM]

Link: MIT Technology Review Article

Link: Paper (PDF format)

### Paper: Utilization of H-reversal Trajectory of Solar Sail for Asteroid Deflection

From the MIT Technology Review article of a new paper from Gong, et al called "Utilization of H-reversal Trajectory of Solar Sail for Asteroid Deflection"...

Apophis is a 46 million tonne asteroid that will pass within a hair's breath of Earth in 2029. However, Apophis's trajectory is likely to take it through a region of space near Earth known as a keyhole that will ensure the asteroid returns in 2036. Nobody knows how close Apophis will come on that pass. But if there's a chance of a collision, we'll have only 7 years to work out how to avoid catastrophe. Today, Shengping Gong and pals at Tsinghua University in Beijing say they've come up with a plan that will ensure Apophis never returns to Earth on this timescale . They point out that keyholes are tiny, in this case just 600 metres wide. So deflecting Apophis by only a small amount in the near future will ensure it misses the keyhole and so cannot return to Earth. There are various ways to deflect an asteroid. Gong and pals say their preference is to use a solar sail to place a small spacecraft into a retrograde orbit and on collision course with Apophis. The retrograde orbit will give it an impact velocity of 90km/s which, if they do this well enough in advance, should lead to a collision large enough to do the trick.

PAPER REFERENCE:

Utilization of H-reversal Trajectory of Solar Sail for Asteroid Deflection

Authors: Shengping Gong, Junfeng Li, Xiangyuan Zeng (Submitted on 16 Aug 2011)

Abstract: Near Earth Asteroids have a possibility of impacting with the Earth and always have a thread on the Earth. This paper proposes a way of changing the trajectory of the asteroid to avoid the impaction. Solar sail evolving in a H-reversal trajectory is utilized for asteroid deflection. Firstly, the dynamics of solar sail and the characteristics of the H-reversal trajectory are analyzed. Then, the attitude of the solar sail is optimized to guide the sail to impact with the object asteroid along a H-reversal trajectory. The impact velocity depends on two important parameters: the minimum solar distance along the trajectory and lightness number. A larger lightness number and a smaller solar distance lead to a higher impact velocity. Finally, the deflection capability of a solar sail impacting with the asteroid along the H-reversal is discussed. The results show that a 10 kg solar sail with a lead-time of one year can move Apophis out of a 600-m keyhole area in 2029 to eliminate the possibility of its resonant return in 2036.

Cite as: arXiv:1108.3183v1 [astro-ph.IM]

Link: MIT Technology Review Article

Link: Paper (PDF format)
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