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Collision risk assessment
Abstract
Avoidance of near misses or collisions is required for almost all
satellites on orbit, but it is of particular interest for manned
missions and spacecraft at densely populated regions. In order to avoid
these possible collisions, it is needed to determine a possible
conjunction and its associated uncertainty. Two main constraints must be
taken into account when a tool to forecast the collision risk of an
object is being developed: the high number of objects in space and the
accuracy of the catalogued object data. The number of objects on Earth
orbit makes impossible to propagate all the catalogued objects, thus
filtering and parallel processing techniques are presented. The accuracy
of the catalogued object data and the propagation of the error over the
time identify a position ellipsoid of error, whose behaviour has an
important influence on some parameters on the filtering techniques and
the way the collision probability is computed. Some collision
probability methods are presented.
Korea has been operating multi-purpose low-earth orbit (LEO) satellites such as the Korea multi-purpose satellite (KOMPSAT) since 1999 and the Communication, Ocean, and Meteorological Satellite (COMS), which was launched into geostationary orbit in 2006. The Korea Aerospace Research Institute (KARI) consequently became concerned about the deteriorating space debris environment. This led to the instigation, in 2011, of a project to develop the KARI space debris collision risk management system (KARISMA). In 2014, KARISMA was adopted as an official tool at the KARI ground station and is operated to mitigate collision risks while being continuously upgraded with input from satellite operators. The characteristics and architecture of KARISMA are described with detailed operational views. The user-friendly user interfaces including 2D and 3D displays of the results, conjunction geometries, and so on, are described in detail. The results of our analysis of the space collision risk faced by the KOMPSAT satellites as determined using KARISMA are presented, as well as optimized collision avoidance maneuver planning with maneuvering strategies for several conjunction events. Consequently, the development of KARISMA to provide detailed descriptions is expected to contribute significantly to satellite operators and owners who require tools with many useful functions to mitigate collision risk.
Since 1957, more than 4500 satellites have been launched and over 1000 active satellites are in orbit. The intensive use of the space environment created a large amount of man-made objects in orbit around the Earth, which no longer serve a useful purpose. These objects are commonly referred to as space debris
. Approximately 20,000 objects larger than 10 cm are known to exist; 500,000 particles between 1–10 cm in diameter and about 10 million debris smaller than 1 cm have been estimated to exist.
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