Following are three informal reports from the IMPACT Workshop (International Monitoring Programs for Asteroid and Comet Threat) held in Torino, Italy, on June 1-4, 1999. This workshop was attended by a substantial fraction of active researchers on NEOs, especially those involved in discovery and orbit computation. The meeting was a follow-up to the workshop on the island of Vulcano (Italy) in September 1995, entitled "Beginning the Spaceguard Survey". The aim of the Torino workshop was to assess the current state of NEO searches, to emphasize the need for a co-ordinated effort, and to establish the basis for effective international co-operation on the subject. Workshop sponsors included the International Astronomical Union (IAU), NASA, and ESA.
Some Highlights from the Impact Workshop by David Morrison Back from the Torino Workshop by Benny J. Peiser A "Hot Debrief" on the Workshop held in Torino by Jonathan Tate
By David Morrison
- Nature of the Impact Hazard: For any given size (energy) of potential impactor, there is a "background probability" of impact from unknown objects. As more NEOs are discovered, this background probability decreases. However, occasionally a newly discovered NEO is found to be on an orbit that repeatedly brings it close to the Earth, and that has a non-zero chance of impact at one or more discrete times in the future. As the orbit is refined, these discrete moments of risk will generally disappear. There are no more than a handful of truly threatening NEOs (D >1 km) in any century, and perhaps none. The progress of Spaceguard can then be thought of as a replacement of a general background risk with discretely identified risks from a very small number of NEOs, which will of course be carefully tracked to determine their future orbits with high precision.
- Appreciation of the Risk: Although the public is broadly aware of the impact hazard, and there has recently been evidence of increased interest in the U.S. Congress and the UK Parliament, it appears that the reality of the impact hazard has still not been accepted by many decision-makers, including most professionals in the risk assessment profession. Geof Sommer of RAND provided the workshop a provocative discussion of how we might formulate some of our issues in terms that can communicate better with policy makers and perhaps enhance the credibility of NEO impacts as a risk issue.
- Search and Discovery: The rate of discovery of NEAs has greatly accelerated, with the bulk of the recent discoveries coming from the MIT LINEAR program using a single 1-m telescope. Grant Stokes reported that a second identical LINEAR telescope is about to begin regular operations, and other systems are also working, as described in previous NEO News notes. However, to meet the Spaceguard objective of discovering 90% of NEAs >1 km in diameter by 2009, it will be necessary to extend the search down to visual magnitude 20.5, which has not been demonstrated for LINEAR or other systems that use 1-m telescopes. Thus it is not yet clear whether an expanded network of 1-m telescopes can do the full job.
- Follow-up Observations: NEA discoveries must be rapidly followed up to determine orbits. Many groups, including amateur astronomers, now contribute to follow-up observing programs. This work is quite effective, but most of the present observers do not have large enough telescopes to observe discoveries that reach to magnitude 20.5. Thus as the discovery rate of faint NEAs increases, there may be a crises in follow-up. We also lack follow-up capability in the Southern Hemisphere, which could lead to the loss of many NEAs that are moving south at the time of discovery.
- Availability of data: As the number of NEA observers increases, and as more people have the capability to calculate orbits and impact probabilities, it is essential to move toward more rapid dissemination of data on NEA positions. Probably a system can be developed soon to provide automatic, essentially instantaneous posting of observational data on the Internet.
- Cooperation and Coordination: A successful Spaceguard program requires detailed coordination of observations to avoid redundancy and make full use of the available resources. Some observers are already posting their observing plans on the Internet. Better coordination will be required, however, as the rate of discovery continues to increase.
- Physical Characterization: There is a continuing need for physical characterization of NEOs, primarily using ground-based telescopes and radar. In addition, a number of spacecraft missions to comets and asteroids are planned or underway, which should greatly increase our knowledge of the nature of these objects.
- Impact Hazard Scale: A new Torino Impact Hazard Scale, developed by Rick Binzel, was endorsed by attendees at the workshop. This scale, ranging from 0 (risk well below background level) to 10 (certain catastrophic impact) will be described in detail in a future message.
- Verification of Threatening NEOs: The workshop attendees recommended that the International Astronomical Union take responsibility for establishing a system for voluntary rapid peer review of predictions or announcements of any NEO with significant impact risk (level 1 or higher on the Torino risk scale). This review will also be described when the IAU works out the details.
From Benny J. Peiser
After four days of presentations, deliberations and decisions, the IMPACT workshop in Turin ended last Friday on a very positive note. Despite a number of minor disagreements, there is a general perception that international research on the impact hazard and NEO searches are gearing up and moving in the same direction. With additional search programmes planned in a number of countries in the next couple of years, the sky coverage is soon approaching saturation. Obviously, achieving such a comprehensive coverage would be a major breakthrough. Yet it remains questionable whether it would actually guarantee the Spaceguard Survey's goal of detecting 90% of all NEOs >1km within the next 10 years. Other problems will also have to be addressed: the search for fainter objects (< 1 km) requires access to sufficiently large telescopes; how will we deal in the event of an undetected (or, indeed, detected/predicted) Tunguska-type impact? Follow-up searches will remain important for any calculation of potential impact hazards.
In a politically important statement, directed at national governments and funding agencies, the participants of the IMPACT workshop strongly recommend that governments should establish national Spaceguard centres and to support these centres financially in order to facilitate international collaboration in the global Spaceguard programme.
One of the more practical results of the IMPACT workshop was the general agreement on a much improved hazard scale in conjunction with the question of how to deal with future predictions of possible impacts by a sizeable near-Earth object. While the exact details will be finalized by the IAU in the next four weeks or so, there is now a generally accepted tool on which future cases such as XF11 and AN10 can be handled in a better way. The final results and recommendations of the workshop will be published in July/August.
And finally - can I just say that it was a pleasure to meet almost 20% of CCNet subscribers at Turin - most of whom I had never met before. Putting a face to a name and meeting individuals on a one-to-one basis has certainly helped to improve the communication and discussion among many participants. I am particularly glad that some of the mistakes and misunderstandings regarding the recent AN10 debate were sorted out in an amicable manner.
From Jonathan Tate
The Sponsors of the workshop were the IAU, ASI, NASA, ESA, Spaceguard Foundation, IACG, The Planetary Society, Alenia Aerospazio - Divisione Spazio and the Provincia di Torino.
This meeting was a follow up to the IAU WGNEO sponsored workshop on the island of Vulcano (Italy) in September 1995, entitled "Beginning the Spaceguard Survey". The aim of that workshop was to emphasize the need for a co-ordinated effort, and to establish the basis for effective international co-operation on the subject.
Participation at the Turin workshop included a high proportion of the world expertise in NEO studies, and high ranking members of NASA, the IAU and other sponsoring organizations. The objectives of the workshop were:
- To encourage scientists in all nations and their sponsoring agencies to increase NEO search and follow-up efforts.
- To improve communications among observers worldwide and to use these improved communications to foster co-ordination of search and follow-up activities.
- To assess the actual potential and limitations of ground-based observing facilities, and to discuss the possible role of space-based segments in NEO search.
- To develop procedures for assuring a rapid communication of accurate information about Extremely Hazardous Objects which may be detected in the future.
- To draft and discuss Recommendations to be distributed to the scientific and political bodies able to support and fund NEO researches.
The structure of meeting was to hold an initial plenary session during which the conference was briefed on a number of topics, to bring everyone fully up to date with recent developments. After the briefings the conference split up into four sub-groups to discuss specific issues, and to produce recommendations to be passed to the IAU. These recommendations, once agreed by the sub-groups were then discussed at another plenary session where they were agreed by the floor, or not.
While it is not yet possible to detail the recommendations that will be passed to the IAU, as they have yet to be "word-smithed" by the sub-group chairmen and agreed in their final forms, it is possible to list a few of the significant statements made, discussions had and recommendations made. So, below are some bullet points, to be followed by a full report as soon as the results are published.
- Actual impacts are likely to be preceded by prior close approaches.
- Comets pose a much smaller risk than asteroids.
- Issues of funding and national interest need to be addressed.
- The issue of whether asteroids are rubble piles or solid bodies is still unresolved. This information is very necessary for any mitigation strategies. We need 4m-10m class telescopes to do compositional studies on NEOs.
- Alan Harris of JPL estimated that about 18% of 1 km and above sized NEOs have been discovered, but there are large population uncertainties. However, we are still discovering asteroids at too slow a rate (8-20 times).
- There are currently a number of space missions to asteroids and comets. This is a "Golden Age" for studying comets and asteroids according to Don Yeomans.
- NASA is increasing funds for NEO research, and has set up its own US JPL program office.
- UK efforts need increased government interest. Recent events have shown that there is official acceptance of seriousness of problem. In the UK we have a wealth of experience, even in (eg) 4m class telescopes. VISTA could be a wonderful tool.
- Japan is pressing ahead with its new NEO detection programme...
- There is an urgent need for some follow up programmes, and more funding (staff) for the MPC. Ted Bowell proposed changes to the MPC that were highly controversial, raising questions of control and IAU international control. No consensus was reached.
- European possibilities were discussed eg DLR, ODAS, including the use of ESO facilities.
- The number of inner Earth objects is thought to be similar to the number of Atens. Both can be easy to find, provided that you look at smaller solar elongations.
- Group 1 discussions emphasized the need for S. Hemisphere telescopes (economic and political).
- Group 2 discussions emphasized the need for research into NEO physical characteristics.
- In Group 3 the importance of precoveries and plate log searches was stressed. There was some emphasis on UKST archive.. This would also be an obvious role for the NSC. There was a strong recommendation that analysis of PHAs should always be performed by at least two independent groups.
- Group 4 developed a protocol, primarily for IAU purposes, dealing with the announcement of PHOs. In the plenary session there was some confused discussion, and eventually a shorter agreed document was approved. This emphasized the need for individual nations to discuss the issue; what do public, politicians and decision makers require? The need for a National Spaceguard Centre is obvious.
- R. Binzel discussed his new hazard scale, but J. Tate has already produced something broadly acceptable for UK purposes. This scale is designed for use when talking to the general public or the media. D. Morrison observed that "people just don't understand probability". S. Isobe reckoned that the index was a good lecturing tool, but not good for communicating with the mass media.
Please be aware that this is a far from complete report, but I hope that something of the workshop's flavour comes through.