Space Situational Awareness - Near Earth Objects

Near-Earth Objects (NEOs) are asteroids or comets with sizes ranging from meters to tens of kilometres that orbit the Sun and whose orbits come close to that of Earth's. Currently, there are over 400 000 asteroids known in our Solar System; more than 6500 of these are NEOs, i.e. their orbits come close to that of Earth's.

An example of a Near-Earth Object is 25143 Itokawa, an object about 300 m in diameter that was recently visited by the Japanese spacecraft Hayabusa.

About NEOs

NEOs could potentially hit our planet and, depending on their size, produce considerable damage. While the chance of a large object hitting the Earth is very small, it would produce a great deal of destruction; thus NEOs merit active detection and tracking efforts.

The goal of SSA's Near-Earth Object Segment (SSA-NEO) is to:

• Be aware of the current and future position of NEOs relative to our planet
• Estimate the likelihood of Earth impacts
• Assess the consequences of any possible impact
• Develop NEO deflection methods

The NEO Segment will observe NEOs, predict their orbits, produce impact warnings when necessary and be involved in possible mitigation measures.

The NEO Segment

Optical Ground Station, Tenerife

The SSA-NEO system is based on syndicating and federating observation and tracking data provided by a large number of European and international sources.

The key components include:

• Observatories and astronomers with telescopes of various sizes, both professional and amateur
• A central SSA-NEO data centre, the 'Small Bodies Data Centre', which uses astrometric measurements collected by the Minor Planet Center (USA)
• An analysis capability to predict possible impact locations and assess dangers
• Analyses related to risk mitigation, including the possible deflection of an asteroid
• A system for issuing warnings and alerts to civil authorities in Europe

Data on NEOs are collected from telescopes and radar systems worldwide. Each of these submit observations to the Minor Planet Center (MPC), operated by the International Astronomical Union (IAU) at Cambridge, Massachusetts, USA, which acts as a central clearing house for asteroid and comet observations.

The measurements collected there are retrieved by the European Small Bodies Data Centre; orbits and miss distances are computed. In case of high-risk impact predictions, the data will be cross-checked with NASA's SENTRY system, operated by the Jet Propulsion Laboratory (JPL), California, before issuing alerts.

The NEO team

The NEO team is based at ESA's Small Bodies Data Centre at ESA/ESRIN and at ESA/ESTEC under the leadership of Dr Detlef Koschny, an experienced planetary scientist. He has worked on numerous ESA missions, including Smart-1, Venus Express and the Agency's comet chaser, Rosetta, as well as the asteroid sample return mission Marco Polo. He is supported by Gerhard Drolshagen, an expert in the space environment and its effects who has studied meteoroids and space debris and performed impact risk assessments for numerous ESA missions.

The SSA-NEO team also includes ESA scientists having expertise in space debris studies, NEO mission analysis, planetary and asteroid science, astronomy and astrometry. These are supported by experts in scientific institutes and European industry, which are helping to create a functional and effective NEO warning system.

"Within Europe, we have developed world-class capabilities and expertise in observing, discovering and assessing NEOs. Our goal now is to coordinate and support local experts and make their observations available in a consistent system that offers benefits to all citizens - including those outside Europe" says Dr Koschny.

Precursor services overview

The necessary elements for providing NEO survey services to Europeans are already in place. However, they are operated by diverse scientific institutions having limited resources. During 2009-2012, the SSA-NEO Segment will implement precursor services, provided via the Small Bodies Data Centre at ESA/ESRIN, Italy.

Impact crater near Carancas, Peru, 2007

These precursor services will integrate existing NEO information and ensure they are available 24 hrs/day. Activities include:

• Establish the required infrastructure at ESA/ESRIN - mainly computer hardware and an expert coordination team
• In collaboration with European scientific and research institutes: develop a new central database for Europe's NEO information (while maintaining current services)
• Assess capabilities of existing European resources, including infrastructure (observatories, catalogues, networks) and expertise
• Integrate and federate these resources into SSA-NEO with guaranteed service and performance agreements
• Study and assess, in cooperation with relevant international scientific and political bodies (IAU, UN, etc.), the best way to coordinate warnings if a potential Earth impactor is detected

Facilities and infrastructure

The Small Bodies Data Centre (SBDC) will be located at ESA/ESRIN in Frascati, Italy. The SBDC will be built up during the time period 2010 - 2011. It will support the integration and initial operation of the NEO services. The centre's activities will focus on the operation of the services. It will support the experts in the field in upgrading the systems and performing the scientific studies needed to improve the services.

2006 VA passed about 14 000 km from Earth on 6 November 2009

The SBDC will be established during 2010-11 timeframe. It will support the integration and initial operation of the NEO services.

The centre's activities will focus on the operation of the services, and it will support the experts in the field in upgrading the systems and performing the scientific studies needed to improve the services.