Mark Bailey's report from the IMPACT meeting, Turin 1-4 June
ASTRONOMY & GEOPHYSICS: The Journal of the Royal Astronomical Society, Vol 40 Issue 4, August 1999, pp. 25-26
Astronomers representing space agencies and other groups with interests in the international Spaceguard programme met in Turin from 1-4 June 1999 for the meeting "International Monitoring Programs for Asteroid and Comet Threat (IMPACT)". Plenary sessions reviewed current survey programmes and associated scientific and policy issues thrown up by the recent greatly enhanced discovery rate of Near-Earth Objects (NEOs); sub-groups hammered out recommendations and procedures for future implementation. The agreed resolutions will be taken forward with governments and funding agencies, and international bodies such as the International Astronomical Union. [Note: These recommendations are listed in the article below by Don Yeomans]
The IMPACT workshop to review progress towards establishing an international programme to detect - and if necessary deflect - any incoming asteroid or comet with the potential to destroy civilization or threaten life on Earth, was not the first such meeting. It followed a meeting on the Mediterranean island of Vulcano in September 1995. The IMPACT meeting, sponsored by bodies including the International Astronomical Union (IAU), the Planetary Society, the Spaceguard Foundation, the Italian Space Agency (ASI), and both NASA and ESA, included representatives from virtually all the organisations currently carrying out major work in this area. Six of the seven principal observational groups were represented, as too were all the teams presently involved in handling the vast increase in orbital data and other information for astronomers worldwide.
The rapid progress in this area is best illustrated by the success of the Massachussetts Institute of Technology/Lincoln Laboratory programme LINEAR (Lincoln Near Earth Asteroid Research), at the experimental test site on the White Sands Missile Range in Socorro, New Mexico. The Lincoln survey, largely funded by the United States Air Force, uses a wide-field, rapid read-out CCD on a military GEODSS (Ground-based Electro-Optical Deep Space Surveillance) 1-metre telescope, capable of reaching a limiting magnitude of ~22 on a 2 square degree field of view in less than 100 seconds integration time. The system has been operating with the wide-field CCD since March 1998, in which time it has already discovered more than 200 of the 700 or so known NEOs, and has produced - in that time alone - more than a five-fold increase in the workload of the IAU Minor Planet Center (MPC), representing more than a million astrometric observations. The programme will shortly be joined by a second GEODSS telescope, operating at the same site, and is expected to produce a second step-increase in the rate of discovery.
One of the main themes of the meeting concerned the question how to handle the vastly increased number of asteroid detections, and how to ensure that the asteroids, once found, are not subsequently lost due to lack of suitable follow-up. The MPC, originally set up to coordinate a moderate rate of discovery of comets and minor planets, needs additional resources to cope with the extra demands of an order of magnitude increase in data throughput. A further factor is the increasing demands of users of the MPC service, who sometimes require essentially instantaneous access to new discoveries, rapid computation of orbital data and projections, and information on where other survey telescopes are looking, both to maximize the overall survey efficiency and the chance that an asteroid, once detected, will not be lost.
Increasingly, it is clear that wide-field survey programmes able to discover many so-called "small" solar system objects should support the desired central facilities, such as the Spaceguard Central Node and the Minor Planet Center. A proper survey should also incorporate the relatively low cost of follow-up facilities to ensure that initial detections are not lost.
The second broad area of discussion focused on the programmes necessary to achieve complete physical characterization of the NEO ensemble, both comets and asteroids. Only by this means can a full understanding of the origin of NEOs be achieved (e.g. the respective proportions originating via collisions in the main asteroid belt or through the evolution and possible break-up of comets). Such information would also be necessary in order to deflect such objects prior to possible impact with the Earth, should our generation be both u n l u c k y enough to be alive when a major impact is due and l u c k y enough to discover the projectile before it discovers us.
These astronomical programmes require spectrophotometric observations of asteroids and cometary nuclei with the objective of identifying bulk properties of the solid body such as mineralogical composition (e.g. in comparison with interplanetary dust particles, meteorites or main-belt asteroids), shape, spin axis, rate of rotation, density, and whether the structure is monolithic, or (possibly more likely) rubble-pile. These types of observations provide ground truth for the size distribution of NEOs, their relationship to the planetary building blocks called planetesimals, and their respective interrelationships with other members of the Sun's extended family of small bodies. Such information is also essential if any NEO is to be deflected.
Access to a wide range of astronomical telescopes in the 2-10 m class will be required over the next decade to carry out these visual/infrared programmes, as too will data from planned space missions over the next few years. As was pointed out by Don Yeomans (Director of the NASA/JPL NEO Program Office), solar system astronomy is now entering a new golden age, with spacecraft going to 13 separate comet or asteroid targets in as many years. Within this time-frame it is likely that our knowledge of such small bodies will go through a revolution as profound as that of the first phase of solar system exploration, which resulted, in the late 1960s, in recognition of the extraterrestrial impact hazard in the first place.
The third, and possibly the most contentious, focus of the meeting attempted to deal with the responsibility of astronomers, as professional scientists and citizens, regarding the collision hazard. For example, what procedures should be in place prior to the announcement of a possible impact (e.g. enhanced peer-review), and then who should be informed, how quickly, and at what stage should the information be placed in the public domain and the media involved? It is obvious that as the present survey programmes get fully into their stride, the so-called "announcement dilemma" will become an increasing problem.
Several objects have non-zero probabilities of impact with the Earth within the next 50-100 years. The values (all low) will likely be revised downwards in the light of further observations, but the number of such cases is bound to increase.
The difficulty is that whereas premature announcement might lead to a culture of false alarms and the accusation of "crying wolf" (not to mention possible panic amongst vulnerable members of the public), the lack of an early announcement might lead to a situation where the warning of a real impact was not made early enough for effective mitigation.
The media, of course, love this. Headlines can almost always be guaranteed announcing the (possible) end of the world, while on the back of this genuine public interest, a serious programme of public understanding of science - spanning the whole range of Spaceguard-related topics - could be developed.
A recent example shows how difficult it is to control the monster. Earlier this year, everyone agreed that the asteroid 1999 AN10 could not possibly hit the Earth in 2027, despite the likelihood of an exceptionally close approach. (Caveats, for example, included whether the object might be a comet and could suddenly start outgassing, or might hit an interplanetary boulder that changed its path, or any number of possible low-probability scenarios.) The splash in a UK newspaper The Sunday People, however, reported: "At 7.42 a.m. on August 7, 2027 the world will come to an end ... that's if the boffins have got it wrong by 9 minutes!"
Scientists are caught - almost literally - between a rock and a hard place. The announcements have to be made, else they are accused of censorship or - worse - a cover up, leading to loss of trust in so-called experts. But the issue is also potentially serious, involving issues of national concern (which could diverge for different nations), even the future of civilization. Such discussions should not occur entirely in the rarefied atmosphere generated by self-selected experts.
One problem, succinctly expressed by David Morrison (NASA Ames, and Chair of the IAU Working Group on NEOs), is that "people just don't understand probability". In particular, people do not understand how to respond to the aired possibility of low-probability, high-consequence events, and it was therefore suggested that the information should be presented in a simpler way.
One proposal, presented by Rick Binzel (MIT), was to use an impact hazard index, in which events occuring with a probability comparable to the annual background rate for a similar-size object would receive a hazard index of 0 or 1, implying that they are "down in the noise" and therefore not worth getting concerned about. Higher impact probabilities for the same size object would receive a higher index, on a scale 2-10, with 10 denoting the virtually certain impact of thecanonical 10 km diameter dinosaur-killer.
A possible difficulty with this approach is that it demotes the background impact rate to a level of insignificance, when in fact it is the s i g n i f i c a n c e of background impacts, in comparison with other possible environmental disasters, that makes the asteroid impact hazard unique.
A second possible difficulty is that in practice most discussions are likely to revolve around whether a particular object is a "one" or a "two", making largely redundant the precise and detailed definition ofan impact hazard scale extending, for public consumption, over the full range 0-10. Although there was general agreement that a way has to be found to communicate results to the public in an accurate and effective way, it would appear that the proposed "Turin [sic] Impact Scale" is at once too simple-minded and too complicated.
An alternative solution, namely better education of the general public in the finer points of impact probabilities at the ~10^-5 per annum level (i.e. comparable to the annual probability of the Earth being struck by a kilometre-sized body with attendant global consequences involving billions of deaths), has many attractions, not least its application to other spheres of public policy. For example, low-probability events killing "only" a few hundred people at the ~10^-5 per annum level, are already assessed - and mitigated - by government agencies across a wide range of health and environmental areas, because they are deemed intolerable. At the other extreme, governments are occasionally forced into making unplanned expenditure and policy shifts, simply because the public has failed to appreciate that a much lower annual risk of disaster (e.g. at the 10^-9 level) is normally regarded as tolerable. Examples such as BSE or GM foods are no doubt debatable, but a vigorous programme of public understanding of science in this area could be beneficial.
The workshop was notable for the spirited, sometimes heated debates on these issues, and some memorable contributions from the floor. The participants agreed several resolutions for consideration by government departments and funding agencies. In particular, given that a vigorous start to the Spaceguard programme has now been made by one nation, namely the USA, contributions by other nations with relevant expertise, especially those in Europe or with access to the southern sky, would be particularly welcome.
In fact, the meeting recognized that only in this way will a genuine international programme be generated, allowing the full objectives of the Spaceguard survey, namely to identify and characterise any large asteroid or comet due to impact the Earth within the next century, to be achieved within the next twenty years. European astronomers have an important role to play.
Mark E. Bailey, Armagh
Observatory Copyright 1999, Astronomy & Geophysics
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) is described in the final part of this edition of NEO News.
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). The IAU proposal is included as an Appendix in the following report from Don Yeomans.
From: Don Yeomans, JPL, IMPACT Meeting Co-Chair
Date: August 5, 1999
GENERAL STATEMENT of the participants at the Torino Meeting "International Monitoring Programs for Asteroid and Comet Threat" (IMPACT) 1-4 June 1999
that cosmic impact is a significant low-probability, high-consequence mphenomenon that could affect civilization or life on Earth:
the existence of considerable world expertise in the subject, and of national centers of excellence in minor body research:
the requirement of implementing an effective monitoring system for Near-Earth Objects (NEOs), including their discovery, astrometry, physical characteristics and dynamical behavior;
that a start has been made towards establishing an international Spaceguard program;
Recommends that governments should:
establish national Spaceguard centres to advise their governments on the assessment of the impact hazard and to act as foci for NEO research:
support these centres financially to facilitate international collaboration in the international Spaceguard program.
RECOMMENDATIONS FOR GROUND-BASED DISCOVERY AND FOLLOW-UP OBSERVATIONS FOR NEAR-EARTH OBJECTS
Noting that the world has inadequate facilities for any one group to complete the Spaceguard Survey and noting the complexity of optimizing the use of a wide variety of systems, the Torino workshop participants strongly urge that the requisite effort be applied to optimize the entire set of search and follow-up systems. In particular, the recommendations for NEO search, discovery, follow-up and recovery areas follows:
Search: Now that current NEO sky searches each month are approaching saturation for northern hemisphere observing sites, an effort should be made to extend the search efforts to fainter limiting magnitudes.
Follow-up: Steps should be taken to examine additional incentives for the follow-up observations necessary to compute orbits.
Southern Hemisphere Observing: It is desirable to have southern hemisphere NEO search facilities, and important to have southern hemisphere NEO follow-up facilities, both professional and amateur. Recognizing the difficult economic situation of most southern hemisphere countries, we encourage the appropriate agencies to support national and regional efforts to make these facilities available.
Critical observations: Access should be improved to sufficiently large telescopes in both the northern and southern hemispheres to ensure that NEOs are observed at subsequent (recovery) opportunities after the discovery itself.
RECOMMENDATIONS FOR PHYSICAL CHARACTERIZATION AND SPACE-BASED OBSERVATIONS OF NEAR-EARTH OBJECTS
In view of the importance of knowing the sizes, albedos, compositions, spin rates, shapes and bulk material properties of Near-Earth Objects, the following recommendations are made:
More observing time should be allocated at ground-based facilities of the appropriate type for NEO visual and near infrared spectroscopy, infrared radiometry, photometry for light curve analyses and international radar observations.
A study should be conducted to determine the design and characteristics of an infrared-visual space telescope to determine the sizes, albedos, and compositions of near-Earth objects. This study should consider large format thermal infrared and visual arrays, infrared thermal spectrometers as well as the efficiency of searching for Atens and asteroids whose orbits lie entirely interior to the Earth's orbit. The cost-effectiveness of space-based measurements versus ground-based measurements should also be investigated.
Additional space missions to NEOs should be undertaken to characterize this diverse group of objects and to determine their material properties, in particular their material strengths and moments of inertia.
A web-based database should be developed to provide information on the physical characteristics of NEOs including the physical parameters (and corresponding references) obtained from photometry, polarimetry, radiometry, spectroscopy, radar techniques and from space-based measurements.
RECOMMENDATIONS FOR THE COMPUTATIONS AND DATA PROCESSING NECESSARY FOR NEO RESEARCH
Recognizing the importance of the free exchange of data for NEO research but acknowledging the need for suitable funding and a smooth transition from the current situation, the Minor Planet Center (MPC) should move rapidly toward the following goal: All data sets of the MPC should be generated, updated and freely distributed in near real time (i.e. within minutes of data receipt at the MPC) unless an observer has requested that the MPC validate that observer's data before making these data public.
Pre-Discovery Data: The development of one or more plate archive search engines is needed. It may be necessary to offer financial incentives to expedite the necessary measuring of these plates.
Radar Data We stress the importance of timely NEO radar observations for the purpose of orbit improvement. The possibility of impact could be confirmed or ruled out with radar observations. Therefore we urge that radar observing capabilities be maintained and, if possible, upgraded and extended into the southern hemisphere.
Observational Scheduling: Development and maintenance of a service for optimizing the scheduling of observations is desirable to maximize orbit improvement and to establish priorities for observational targets.
Orbit Computation: It is recommended that the various orbit computation groups inter-compare their orbit solutions and uncertainty estimates.
Orbital Nonlinearity: The importance of nonlinearity in orbital uncertainty computations and propagation is difficult to quantify. Further research on this topic is needed.
Analysis of Potential Threats: A computational "filter" should be applied when a NEO orbit is established or changed. A typical sequence might consist of the following steps.
Compute the MOID and its uncertainty as a function of time
Compute all close approaches that appear to threaten the Earth and that are consistent with the observations. This analysis should cover a reasonable time frame, such as the next 50 years, and allow for the detection of cases to a probability of the order of the background rate of undiscovered NEO impacting the Earth.
Carefully analyze potential impacting cases
We urge that these computations always be performed by at least two independent groups.
Initial Orbit Computation: We encourage research on the computation of initial orbits and their uncertainties.
Comet and Asteroid Orbits: We strongly urge that additional groups compute orbits and impact probabilities for comets. We further recommend that cometary nongravitational (outgassing) force models be revisited in the light of much expanded observational data sets and improved computational capabilities. In addition, efforts should continue to examine the sensitivity of asteroid orbital evolution to asteroid nongravitational perturbations such as the Yarkovsky effect.
RECOMMENDATIONS FOR INTERNATIONAL COOPERATION IN NEO HAZARD MANAGEMENT
The Torino IMPACT Workshop recommends that a voluntary process be developed under the aegis of the IAU Working Group on Near-Earth Objects (WGNEO) whereby researchers will be encouraged to meet their professional obligation by obtaining a rapid peer review of any prediction they may make of a possible impact by a sizable NEO, prior to public announcement.
The issues and guidelines outlined in Appendix A should form a basis for consideration by the IAU WGNEO subject to consideration of the following points;
The general procedures and guidelines (Appendix A) should be reviewed at the next IAU General Assembly in 2000 August.
The suggested time period required for the WGNEO review committee to complete their analyses and report to the WGNEO chair needs to be defined (i.e., this time period is currently given as 72 hours in Appendix A).
The recommendation is made that the NEO community of researchers adopt the use of the "Torino Scale" as a common communication tool for describing the hazards posed by NEOs. The Torino Scale has been released to the public and a description can be found here: http://web.mit.edu/newsoffice/www (also see article by Binzel below)
Planning and coordination for impact hazard mitigation should be conducted in large part to minimize the adverse social consequences of impact warnings.
Procedures should be developed for the rapid characterization of Tunguska-like detonation events which are likely to occur without warning.
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APPENDIX: DRAFT IAU VOLUNTARY PEER-REVIEW PLAN
The following guidelines for voluntary IAU review of reports of possible future NEO impacts that exceed the Torino Scale level 1 has been discussed among the Organizing Committee of the Working Group on NEOs. These guidelines have been submitted to the IAU Executive Committee for their consideration.
Proposed IAU procedural guidelines in the event that a potentially Earth threatening object is discovered.
The IAU Working Group on Near-Earth Objects (David Morrison, Chair)
that the International Astronomical Union (IAU) has charged its Working Group on Near-Earth Objects (WGNEO), in consultation with astronomers worldwide, to draft a set of recommended procedures to be followed in case asteroids or comets are discovered that lead to predictions of potential impacts on Earth;
that the recent cases of asteroids 1997 XF11 and 1999 AN10 have provided, at an early stage after their discovery, real examples of such predictions;
that NEO scientists have a professional obligation to seek peer review of their results before any public announcement of impact risk or threat;
that there is a need to identify the successive steps to be adopted by the astronomical community in order to provide the authorities, the media and the public with reliable information on the discovery of potentially threatening objects;
RECOMMENDS the following procedures to be available to the members of the astronomical community in any future case of discovery and/or theoretical analysis leading to the prediction of impacts that fall at level 1 or higher on the Torino Impact Hazard Scale at any apparition in the next century).
The IAU establishes the following review procedure available on a voluntary basic to all scientists involved in any prediction of possible NEO impacts. The information leading to such a prediction, consisting of an evaluation of the case and all data and computational details necessary to understand and reproduce the studies carried out by the authors, shall be transmitted for confidential review to the chair of the WGNEO, the General Secretary of the IAU, and the members of the WGNEO Review Team, before any announcement and/or written document on the subject be made public on any information media, including the World Wide Web. The membership of the standing Review Team will be selected by the Chair of the WGNEO with the concurrence of the IAU Division 3 President and the General Secretary, with names and e-mail addresses posted on the IAU NEO webpage. The individual members of the NEO Review Committee members shall review the work for technical accuracy and shall communicate within 72 hours the results of their reviews to the chair of the WGNEO and directly to the authors of the report or manuscript.
If the consensus of the above review supports the conclusion that there is a significant impact risk, the results of this analysis will be posted on the IAU webpage for public access. If the review disagrees with the original analysis or if there is not a consensus among the reviewers, the confidential results of the review will be given to the authors so they can revise or improve their work, as they see fit. The news posted on the WGNEO webpage shall represent the official position of the IAU; no further information will be provided by the WGNEO, unless important updates become necessary.
The authors of the work are encouraged to refer the media to this IAU position if they choose to make a public release of their conclusions. If so requested by various agencies (e.g., NASA or ESA), the IAU will also inform the responsible officials of these agencies of the results of the WGNEO review.
THE TORINO SCALE FOR IMPACT HAZARDS
by Richard Binzel, MIT
What is it for?
The Torino Scale is a "Richter Scale" for categorizing the Earth impact hazard associated with newly discovered asteroids and comets. It is intended to serve as a communication tool for astronomers and the public to assess the seriousness of predictions of close encounters by asteroids and comets during the 21st century.
Why is the Torino Scale needed?
When a new asteroid or comet is discovered, predictions for where the object will be months or decades in the future are naturally uncertain. These uncertainties arise because the discovery observations typically involve measurements over only a short orbital track and because all measurements have some limit in their precision.
Fortunately, for the majority of objects, even the initial calculations are sufficient to show that they will not make any close passes by the Earth within the next century. However, for some objects, 21st century close approaches and possible collisions with the Earth cannot be completely ruled out.
How does the Torino Scale Work?
The Torino Scale utilizes numbers that range from 0 to 10, where 0 indicates an object has a zero or negligibly small chance of collision with the Earth. (Zero is also used to categorize any object that is too small to penetrate the Earth's atmosphere intact, in the event that a collision does occur.) A 10 indicates that a collision is certain, and the impacting object is so large that it is capable of precipitating a global climatic disaster.
The Torino Scale is color coded from white to yellow to orange to red. Each color code has an overall meaning:
White - "Events having no practical consequences," meaning they are virtually certain to miss Earth or are so small that any impact would almost certainly dissipate in the atmosphere. White corresponds to category 0.
Green - "Events meriting careful monitoring" refers to objects that have predictable close approaches with some very small, but not seriously concerning, chance of a collision. Nonetheless, prudence dictates their orbits should be tracked closely so that the collision chance becomes refined, and probably in all cases, will ultimately be reclassified within Torino Scale category zero. Green corresponds to category 1.
Yellow - "Events meriting concern" are close approaches by objects that have higher collision chances than the Earth typically experiences over a few decades. These are object for which refinement of the orbit is of high priority. Yellow corresponds to categories 2, 3, 4.
Orange - "Threatening events" refers to close encounters with objects that are large enough to cause regional or global devastation, where the chance of collision greatly exceeds the level that typically occurs within a given century. These are objects for which refinement of the orbits are an extreme priority. Orange corresponds to categories 5, 6,7.
Red - "Certain collisions" refers to objects that are certain to collide with Earth having sufficient size to likely penetrate the atmosphere with the capability to cause either local damage, regional devastation, or a global climatic catastrophe. Red corresponds to categories 8, 9, 10.
How does an object get its Torino Scale number?
An object is assigned a 0 to 10 value on the Torino Scale based on its collision probability and its kinetic energy (proportional to its mass times the square of its encounter velocity). Categorization on the Torino Scale is based on the placement of a close approach event within a graphical representation of kinetic energy and collision probability . An object that is capable of making multiple close approaches to the Earth will have a separate Torino Scale value associated with each approach. (An object may be summarized by the single highest value that it attains on the Torino Scale.) There are no fractional values or decimal values used in the Torino Scale.
Can the Torino Scale value for an object change?
Yes! It is important to note that the Torino Scale value for any object initially categorized as 1 or greater _will_ change with time. The change will result from improved measurements of the object's orbit showing, most likely in all cases, that the object will indeed miss the Earth. Thus, the most likely outcome for a newly discovered object is that it will ultimately be re-assigned to category 0. Any object initially placed in category 0 is unlikely to have its Torino Scale value change with time.
How did the Torino Scale get its name?
The Torino Scale was created by Professor Richard P. Binzel in the Department of Earth, Atmospheric, and Planetary Sciences, at the Massachusetts Institute of Technology (MIT). The first version, called "A Near-Earth Object Hazard Index", was presented at a United Nations conference in 1995 and was published by Binzel in the subsequent conference proceedings (Annals of the New York Academy of Sciences, volume 822, 1997.)
A revised version of the "Hazard Index" was presented at a June 1999 international conference on near-Earth objects held in Torino (Turin) Italy. The conference participants voted to adopt the revised version, where the bestowed name "Torino Scale" recognizes the spirit of international cooperation displayed at that conference toward research efforts to understand the hazards posed by near-Earth objects. ("Torino Scale" is the proper usage, not "Turin Scale.)