«Towards Solving the Asteroid/Comet Impact Hazard Problem: Necessity of Implementation in the (Inter)National Space Situation Awareness Boris Shustov ...»
The 9-th US Russia Space Surveillance Workshop
26-29 August 2012
Towards Solving the Asteroid/Comet Impact Hazard Problem:
Necessity of Implementation in the (Inter)National Space Situation
Institute of Astronomy, Moscow, Russia
A brief review of the current state of studies on the asteroid/comet hazard (ACH) problem in Russia is presented. Instruments and techniques for detection and monitoring the threatening bodies are discussed in more detail. Differences and similarities of the methods used for space debris observation and those proposed for the detection of threatening asteroids and comets are analyzed. Special attention is drawn to the necessity of the implementation of the ACH technical and organizational approaches in the (inter)national space situation awareness (SSA) system.
1. INTRODUCTION Life and the human civilization on the Earth exist in the environment of cosmic threats. Some threats are of a natural origin. These are relatively rare dangerous events of space weather anomalies (one event in a few decades of years), asteroid/comet impact hazard (typical time interval - centuries), and much more rare astrophysical catastrophes in the vicinity of the Solar system (e.g. stellar explosions), as well as possible biological invasions. The space debris problem and the menace of contamination by the return of biological species (dangerously changed by poorly known space factors) are problems that are considered as an inevitable consequence of human propagation in space. In various circumstances various threats attract public attention and become most “popular”.
The Asteroid-Comet Impact Hazard (ACH) problem has become, in recent years, a very topical subject. This is due to the fact that the specialized programs of observations have resulted in a sharp increase in the efficiency of discovering such bodies, and new information compels one to have a new look at the ACH problem. Along with specialized scientific conferences, public discussions on the ACH problem are led by the UN, governments and parliaments of some countries and nongovernmental organizations. The leading countries began to invest considerable funds in the technology of discovery and monitoring the object approaching the Earth, as well as to counteracting the hazard of collisions of such bodies with our planet.
The asteroid/comet hazard is a risk for mankind to have serious damage, due to collisions of natural celestial bodies (i.e., asteroids and comets) with the Earth. Usually, the lower boundary of dimensions of a hazardous body is determined as 50–100 m. The average estimate of the energy released at a collision of a body of 60–70 m diameter is comparable to the energy of the most powerful explosion ever fulfilled by man on the Earth. Accordingly, a collision with a 300 m asteroid, Apophis, would result in an explosion exceeding in its destruction capability the entire explosive arsenal of mankind. The total destruction on areas of tens of thousand square kilometers, and the heavy consequences on continental scales should be a consequence of such a collision.
Another frequently used abbreviation for the ACH problem is the NEO problem, where NEO stands for Near-Earth Objects. NEOs are natural bodies (asteroids and comets), and do not include working satellites (spacecrafts) and space debris. One can remark either that the typically considered scope of the NEO problem includes mostly issues related to the detection and characterization of threatening bodies, while the ACH is somewhat broader and includes complex issues related to prevention and mitigation.
For obvious and everyday practical reasons, space debris remains a space threat, attracting major attention of nations during the last fifty years (i.e. cosmic era). As a result we have substantial progress in the construction of specialized instruments and networks aimed to detect and monitor space debris. Radar and optical detectors, including lasers, are the main tools used for tracking space debris. Radars are most efficient for LEO objects. Optical instruments are more efficient for the observation of space debris fragments at distances larger than 5000 km. About 20 000 objects are catalogued at the moment. Nevertheless, the majority of debris objects remain unobserved. There are more than 600,000 objects larger than 1 cm (0.4 in) in orbit (according to the ESA Meteoroid and Space Debris Terrestrial Environment Reference, the MASTER-2005 model).
NEO have been detected with optical and infrared instruments. Most of the NEO observations were performed with optical telescopes. Recently, the infrared 40-cm space telescope WISE has demonstrated the high effectiveness of infrared instruments. Radars are powerful for characterization of large and close asteroids and comets, but they cannot be used for detection.
Up to now only a few hundreds of the objects were observed. Contemporary completeness of our awareness about threatening NEOs is approximately at same level as for space debris. The total number of potentially hazardous NEOs larger than 50 m is estimated as some hundreds of thousands. Only about 1% of them have been detected! Thus, the first task both for space debris and NEO is a massive detection of the objects.
As far as it concerns detection and monitoring of threatening objects with optical instruments, the solution of space debris and NEO problems require similar approaches. Therefore, it seems to be logical to consider both problems in a consistent way.
In this paper we briefly review of the current state of studies on the asteroid/comet hazard problem in Russia (section 2). Special attention is drawn to the necessity of implementation of the ACH technical and organizational approaches in the (inter)national space situation awareness system. Differences and similarities of methods, used for space debris observation and those proposed for the detection of threatening asteroids and comets, are very briefly analyzed (section 3). Conclusions are given in section 4.
Let me remind that this brief review mostly refers to the state of the art of the ACH problem in Russia, so numerous important papers and documents by the researchers of the international NEO community are not mentioned here.
2. STATE OF ART OF THE ACH PROBLEM IN RUSSIAAn increasing activity of studying the ACH problem is noted in the scientific and industrial communities of Russia. In order to coordinate investigations in the field, the “Expert Working Group on the problem of asteroid/comet hazard problem” was established in February 2007 by the Space Council of the Russian Academy of Sciences. In 2011 the group was transformed into “Expert Working Group on Space Threats”. Coordination of the fundamental research on the ACH and space debris issues is considered as a primary task of the group. This group includes representatives of the Russian Academy of Sciences (RAS), major universities, Federal Space Agency of Russia, Emergency Committee, Rosatom, Ministry of Defense, and other concerned ministries and organizations. Some materials about the activities of the Expert Group are presented at its website http://www.inasan.ru/eng/asteroid_hazard/. The main practical task of the group is to elaborate a project of a dedicated national (federal) program. Good examples of national programs were provided by NASA’s NEO program and European SSA program.
We believe that for the effective participation of Russia in the international cooperation on the NEO problem, we have to develop a comprehensive national (federal) program. The arguments
pro national (federal) program are simple:
1. The NEO problem is a multi-problem. Various organizations are to be involved (coordinated);
2. The capabilities of research centers are not sufficient for implementation and support of the modern service of detection and monitoring of NEO, in particular those requiring space facilities;
3. The expensive technologies of preventing collisions and mitigation can be proposed, but not be implemented under the responsibility of research institutions;
4. Cooperation of countries on the NEO problem implies the involvement of the Russia Government (or authorized body);
5. National program means regular funding. This is absolutely necessary for the realization of a real program.
The major elements of a concept of the long-term federal NEO program, that was prepared by the Expert Working Group, were described in [1, 2]. In June 2010 a special joint meeting of the heads of the Federal Space Agency (Roscosmos) and the Space Council of the Russian Academy of Sciences was held. The draft concept was presented at the meeting and positively considered.
Roscosmos and RAS expressed their wish to integrate issues of NEO and space debris in the Federal Program. By the way, this decision demonstrates that the approach used to establish, in the last three years, the European Space Situational Awareness System  was considered with attention. Recently, considerable efforts were made in Russia to elaborate a National Program of counteraction to space threats.
There are three basic aspects to be recognized in the ACH problem:
• Detecting, determining the properties of, and assessing the risk from hazardous celestial objects.
• Protection and damage reduction.
• Having a cooperative approach.
We briefly describe the suggested blocks of the national program, “responsible” for these issues of the ACH problem.
2.1. Detection and monitoring Detection.
The major requirement for the system that ensures massive detection of potentially hazardous
bodies can be formulated in simple words as follows:
A given share (typically not less than 90%) of NEOs, that are large enough to make a serious harm for humankind as whole or for individual countries (typical size of such a body exceeds 50 m), should be detected timely (typically required warning time must be not less than 30 days).
Having in mind that observed and estimated rapprochement velocities for NEOs do not exceed 40 km/s, and the extra time (typically about 7 days) required for the reliable classification of the object as a dangerous one since the first observation, we get that the detection system should massively discover NEOs with absolute (asteroid) magnitude H 24.
There are a lot of astronomical instruments over the world. Some of them are huge, some are wide field, but very few of them (at the moment PS1 only !) are capable to solve the detection task.
In the draft concept of the national Program, we consider practical things (for detection) to be primarily done as follows: Construction of new optical instruments for massive discovery of the NEOs. First of all we need to complete construction of the wide field 1.6 m telescope at the Institute of Solar-Terrestrial Physics, Siberian Branch of the RAS  ( see Fig. 1.)
Fig. 1. The project of 1.6 m wide field telescope: designer view and major parameters.
Space based telescopes are powerful instruments for detecting and characterization of hazardous bodies. We have presented a project of a space system for the detection of NEOs in . In the paper we proposed a low cost space project with 75-cm aperture wide field (7° FOV) telescope of original design by V.Terebish. The general view of the satellite, scheme of the telescope, as well as matrix of detectors (basic unit – CCD detector “Kvadro” manufactured by Electron company) are shown in Fig.2.
Fig.2. The general view of the satellite, scheme of the wide field (7° FOV) moderate size (75 cm) telescope, a 4×4 matrix of detectors and basic unit – CCD detector “Kvadro”.
The telescope seems to be efficient both for detection of potentially hazardous objects (PHO) and space debris.
The monitoring (follow up observations) is a key factor for the proper characterization of the hazardous object. The national program includes as one of the first tasks, the plan to establish a network for the follow-up observations of the discovered NEOs and especially of the potentially hazardous objects (PHOs). There exist premises for this. To mention some: programs of observations of NEOs are being performed at Pulkovo Observatory (RAS), in the Institute of Solar-Terrestrial Physics (RAS), Special Astrophysical Observatory (RAS), Kazan University (with 150-cm telescope elevated in Turkey), and Institute of astronomy (RAS) with 2m telescope at Terskol observatory, etc. For observational networks, the ISON (Institute of Applied Mathematics of the RAS) is developing and internationally demonstrating its efficiency for space debris studies. It expands the observational program to NEOs. The system of robotic telescopes, MASTER (of 40 – 50 cm aperture), established by Moscow University, mostly for gamma bursts monitoring, turned out to make an essential contribution to NEO studies. These facilities, as well as specially designed ones, are suggested to constitute the national network. The task is not easy, mostly because of organizational difficulties, but again we are encouraged by the good examples of organizations of effective (inter)national observational programs in the US and Europe.
3. Data handling:
The processing of information on the observed positions of NEOs is currently being carried out by the Minor Planet Center operating at the Smithsonian Astrophysical Observatory in Cambridge, MA, USA, which also identifies and assigns preliminary names to them, provides first preliminary and then more refined calculated results on their orbits, and publishes information on those objects for which additional observations are needed to confirm their discovery and to refine their orbits and other characteristics. The prediction of motion of potentially hazardous objects, the search for their close approaches to Earth, and the estimation of impact probabilities within the next few decades will be (and indeed are being) made at the Jet Propulsion Laboratory, Pasadena, CA, USA, and the University of Pisa, Italy.