This conference was the second on Space Protection of the Earth (SPE), following by two years the first such meeting (SPE-94) organized at the same location by staff of the Russian Federal Nuclear Center. Alternatively this could be considered the fifth in a sequence of meetings organized to examine defense issues associated with the asteroid and comet impact hazard. The previous meetings in this series were the NEO Interception Workshop at Los Alamos, USA (1992), the International Workshop on Planetary Emergencies at Erice, Italy (1993), SPE-94 at Snezhinsk, Russia (1994), the Planetary Defense Workshop at Livermore, USA (1995), and now SPE-96. Non-Russian attendees came from China, Japan, Kazakistan, Ukraine, and the United States, but the Russians at the meeting (more than 100) greatly outnumbered the foreign contingent (about 10 people). Official languages at the meeting were Russian and English, and simultaneous translation of all papers was provided. The quality of the facilities and hospitality were excellent. Snezhinsk itself remains as isolated as ever behind its well-guarded double fence, and there are still no map listings or road signs pointing to it. Living up to its name (which means "snowy"), we had snow flurries on several days during the meeting.
To my surprise I was the only American scientist who attended. All the people from Livermore and Los Alamos who had been involved in the planning decided, in some cases at the last minute, not to come. Edward Teller did send a video presentation, in which he chose to emphasize the research value of NEOs rather than defense issues: "the questions of what actually happened, and by implication what is apt to happen in the future." Specifically, he dealt with the question whether large impacts had been important for the course of biological evolution. He emphasized that "scientific knowledge is what brings all of us together". He also called for launching space platforms to search near-Earth space for incoming NEOs, as well as performing experiments on objects that come as close as the Moon. Acknowledging the fact that nuclear explosives are "very frightening", Teller stated that "most important asteroids can be deflected without nuclear explosives" and urged that emphasis be placed on "conventional means". He added that "The use of nuclear explosives in the proper place will come as an obvious consequence. I don't want to urge that; I want to urge knowledge and I want to urge everything that follows from knowledge". Many of those at the conference, held here in this nuclear center, where not exactly pleased that Teller was advocating non-nuclear options for planetary defense.
I was generously allocated time for two major talks, one on the NASA perspective toward protecting the Earth from impacts (emphasizing the nature of the risk from different size impactors, comparing the hazard qualitatively and quantitatively, and discussing the Spaceguard approach to inventorying potentially threatening NEOs), and one talk on NASA space missions to asteroids (Galileo, NEAR, and the ground-based radar imaging). These were generally well received, and especially effective were the video simulations from Ostro and Hudson of the shape and rotation of Toutatis and Castalia and of the kinds of spacecraft orbits that are possible near them. To a group that had mostly been thinking of asteroids as simple solid non-rotating spheres, it was a revelation to see what real NEOs look like, and those videos were a powerful tool for bringing the conference into touch with the real worlds of NEOs. I also spoke briefly in the final discussions on the issue of long-term NEO surveys vs. short-range defense approaches.
My general impression was that the conference was better informed and held at a more advanced level than the SPE-94 two years ago, but that most of the participants still had not really come to grips with the complexities of the NEO defense issues. Fortunately Vadim Simonenko, the SPE-96 organizer, was active in providing comments and critiques after nearly every talk, in an effort to educate and introduce a greater level of realism. In this he was often supported or complemented by Andrei Sokolsky of the Institute of Theoretical Astronomy in St. Petersburg. Simonenko and Sokolsky are both experts in the field, and their presence and active leadership was important to keep the meeting on track. It was also encouraging to see more integration and communication between the defense scientists and astronomers within the Russian community.
Many of the papers concentrated on destruction rather than deflection of NEOs. The most interesting to me were those that provided information on the relative efficiencies of stand-off, surface, and buried nuclear explosions, including quantitative estimates of the yield and warhead masses that might be required to deal with NEOs of different size. One of the more interesting discussions included the status of possible NEO defense programs from the perspective of international law, a very appropriate topic in the same week as the signing by the USA and Russia of the new Comprehensive Nuclear Test Ban Treaty at the UN. (The bottom line here is no prospect of nuclear testing in space for the foreseeable future, in contrast to the arguments made by Teller and Lowell Wood at the SPE-94 meeting that nuclear experiments for "peaceful" purposes were permitted under international law). Very little was said about long-term programs, however, and I believe I was the only speaker to address Spaceguard issues in any detail.
There were some interesting but confusing (to me) discussions of the fragmentation of NEOs. The objective of disruption, of course, is to ensure than all fragments are so small they will explode harmlessly in the upper atmosphere even if they hit the Earth. I think the problem of calculating the size of the largest fragment is a difficult one, but several of the Russians considered this a solved problem based on the results of underground nuclear tests. They asserted that the observed size distribution of the fractured materials in the cavity surrounding an underground test would be the same as that produced by an explosion on or in an asteroid, and I have trouble believing that. Maybe I am just confused, but asteroid breakup and spallation seems very different to me from the conditions that apply in an underground nuclear test on the Earth.
The most remarkable and disturbing presentations, from my perspective, came on the final day when representatives of Russian aerospace industry (Lavochkin, Khrunichev, and Makeyav) described comprehensive proposals to deal with the impact hazard, programs that were collectively called "Space Shield". All of these elaborate proposals were exclusively designed for the short-range interception of incoming NEOs. Each advocated development of a space-based optical detection system with a range of 10-20 million kilometers to provide 4-7 days warning, together with multi-layered space-launched and ground-based interceptor missiles with kinetic-energy or nuclear warheads. These proposals implicitly or explicitly rejected many of what I consider to be the basics of NEO defense: the importance of carrying out a Spaceguard type search, the advantages of ground-based over space-based searches, the expectation of long warning times, the advantages of intercepting at very great range from the Earth, the advantages of deflection over disruption, the dangers of maintaining a large fleet of rocket interceptors on the pad, etc. At the least, this was a throw-back to the early US discussions such as those held at Los Alamos in 1992, and I had hoped that we were beyond that stage today, especially when dealing with the representatives of large, experienced technical organizations such as Lovochkin or Krunichev. A.V Zaitzev of Lavochkin assured our attention by beginning his talk with the assertion that he could now reveal for the first time the secret development in the USSR of the elements of a Space Shield defense system. The system is based on the Zenit Rocket which can be readied for launch in 90 minutes, the VEGA/Phobos/Mars-96 spacecraft which has the capacity to carry multi-megaton nuclear explosives and operate in a deep-space environment, and the ASTRON space telescope which can form the basis of a NEO surveillance system. The objectives of the surveillance system are to pick up incoming NEOs with 5 days warning (about 15 million km range), using 3-5 spacecraft in deep space, several million km from Earth. The system would be deployed between 1999 and 2002. Most remarkable of all, Zaitsov argued several times that we have the capability to use "cosmic billiards" to deflect nearby NEOs and use them to shoot down more distant objects. This is the Lavochkin plan for dealing with long period comets: to deflect a NEO into the comet path and destroy it. Amazing!
A pervasive fallacy at the meeting was the emphasis on discovery and interception of incoming NEOs in the last few days before impact. Not only did the Russian aerospace representatives focus their attention on near-Earth surveillance systems; this was also one of the points made by Syuzo Isobe in arguing for a NEO detection experiment on the proposed Japanese lunar lander to search for incoming projectiles from directions near the Sun. Isobe calculates that 30% of the close approaches come from within 30 degrees of the Sun, and that these will be missed by ground-based Spaceguard detection systems. All of these arguments implicitly reject the concept of long-term advance warning based on a Spaceguard Survey. The idea of Spaceguard is to find the objects when their orbits bring them within the range of our telescopes; we do not need to pick up each NEO on each pass. Those that are too close to the Sun this year will be picked up next year or the year after when conditions are more favorable. But I was alone in making these points. One participant even disputed my arguments on the following grounds: we need a short-term space surveillance system since even if Spaceguard finds and catalogues all the dangerous NEOs, we never know when one of these known NEOs will suffer a collision and change course so as to hit the Earth without warning. The infinitesimal probability of such a thing happening did not dampen his enthusiasm for building a multi-billion dollar Space Shield to protect us against this eventuality.
In the final session several people urged the group make more of an effort to move beyond vu-graph studies and try to achieve some real results. The problem is lack of funding, in Russia and internationally. Because there is no funding, the proposals remain at a conceptual level only, without any detailed analysis. I also think there is a problem of limited technical feedback. Because there is no well-defined science community and no obvious journals in which to publish, people working on space defense issues do not have the benefit of peer review and feedback. We need some way to get rid of the high noise level and focus on those ideas that have the greatest value. There will be another SPE meeting in 1998, but I wonder how much progress will actually have been made, and whether there will be an increase in international participation. I hope the answer is yes on both counts.
In conclusion I would like to mention some other events that happened in association with the SPE-96 meeting. There were two well-attended public lectures. Canadian-American filmmaker Paul Almond presented a fascinating review of a possible scenario for dealing with the discovery today of a large asteroid that will hit the Earth with only one year of warning. Based on his discussions with many US officials, Almond presented a very specific description of both the scientific discovery process and of who in the US government and defense communities would do what, when, and where. In a place like Snezhinsk with limited contacts with the rest of the world, his detailed scenario had the audience on the edge of their seats. I gave the other public lecture, covering two different topics, the search for life in the universe and defending the planet against NEO impacts. The Russian media have given little or no publicity to the discovery of planets around other stars or the recent analysis of ALH84001, so most of this material was new to the audience. And once again the Ostro/Hudson/JPL videos of Toutatis and Castalia were a big hit. The other activity associated with the SPE-96 conference was a summer-school for junior high or intermediate school students, who had worked on projects associated with NEO defense. I served as one of the judges for this work, and it was extraordinary to hear articulate 7th and 8th graders expounding on the impact hazard and on techniques for exploring NEOs. Judging by this experience, the next generation has no trouble with these concepts, in spite of continuing confusion on the part of some of their elders.