Permanent Monitoring Panel -
Defence Against Cosmic Objects

Members of the Panel:

Chairman:
J. Mayo Greenberg (Netherlands)

Members:
Alberto Cellino (Italy); Walter F. Huebner (USA)

Associate Members:
Michael F. A'Hearn (USA); Andrew F. Cheng (USA); Alan W. Harris (Germany); Thomas G. Müller (Germany/Spain); Paolo Paolicchi (Italy); John Remo (USA); Roberto Somma (Italy); Edward F. Tedesco (USA)

Summary of the Emergency

It has been recognized that the continuing impacts of cosmic objects (asteroids and comets) on Earth present a very low probability threat but with devastating consequences. Objects that are larger than about 200 meters in effective size will cause local, regional, or global catastrophes if they collide with Earth. Objects that come close to the Earth's orbit are also known as Near-Earth-Objects (NEOs) or, if they pass the Earth within 0.05 astronomical units (AU), as Potentially Hazardous Objects (PHOs). It appears that for the first time in man's history we have the capability to avert such collision by destroying or deflecting NEOs with Earth. Four main objectives are considered in this program:

Find the objects (there are an estimated 1000 objects larger than 1 km and about 25'000 objects larger than about 200 m in effective size).
Follow the objects in their orbits, determine their orbital parameters, and catalog them
Determine their physical properties, such as their mass, material strength, and internal structure.
Based on these properties, develop Earth collision mitigation technologies.

It is generally agreed that the first step is to survey and catalogue the approximately 1000 near-Earth asteroids (NEAs) larger than about 1 km and find 90% of them by 2008. While objectives (1) and (2) are actively pursued (although only for objects larger than 1 km in effective size), objectives (3) and (4) lag behind. The permanent monitoring panel will focus its attention on those objectives were progress is most constructive for reaching the final goal: Collision mitigation. One of the first intermediate goals is to acquire the geological and geophysical data of NEOs. As the most dangerous known example of natural disasters, the NEO impact hazard calls for the must careful consideration and planning by the international community.

Priorities in dealing with the Emergency

The priorities of the NEO program are as follows:

Find NEOs and follow them up with observations to determine and catalog their orbits.
Physically characterize them. This includes remote sensing to determine the effective size of the objects and their albedo independently.
Determine their geophysical and geological properties such as mass and mass distribution, moments of inertia, material strengths, internal structure, and relationship of global properties to surface properties.
Develop techniques for Earth-collision mitigation based on geological and geophysical properties.

Comments of priorities:

Significant progress has been made in finding NEOs with effective diameter larger than 1 km. Many objects have been found that are in the range of 200 m to 1 km in effective diameter. Howewer, this effort must be expanded. Telescopes are needed that can find these smaller but much fainter objects.
The rate of discovery of NEOs is so large that the rate of physical characterization by remote sensing cannot keep space. More telescope time with simultaneous infrared observations is needed to determine the size and albedo of NEOs as separate quantities.
Several fully instrumented missions are needed to measure globally geophysical properties including the material strengths and internal structure of NEOs.
Detailed methods for collision avoidance must be worked out depending on the geological and geophysical properties of NEOs.

Workshop and Meeting Reports

Hazards from Cosmic Objects: International Seminars on Nuclear War and Planetary Emergencies, 23rd Session, p. 370-371, 1999.

Physical and Chemical Properties of Comet Nuclei: International Seminars on Nuclear War and Planetary Emergencies, 23rd Session, p. 169-179, 1999

The Physical Properties of Asteroids and the Effects of Shock Waves: International Seminars on Nuclear War and Planetary Emergencies, 23rd Session, p.180-191, 1999.

Asteroids as Rubble Piles: International Seminars on Nuclear War and Planetary Emergencies, 23rd Session, p.192-202, 1999

NEOs: Physical Properties.International Seminars on Nuclear War and Planetary Emergencies, 25th Session, 2001

Summary of the Workshop on Geophysical and Geological Properties of NEOs: "Know Your Enemy," 17-25 June, 2001, Erice

Special Recommendations

A database of geophysical and related properties should be established. The database should consist of four parts: An observational database, a material properties database, a database for missions and instrument development, and a database for dissemination and public outreach. The database will act like a vector defining direction and magnitude of efforts needed to accomplish the goals of geological and geophysical data on NEOs. It will also serve as a metric to measure the progress and success of scientific research and technology developments to divert cosmic objects from colliding with Earth.