On February 26, 2011, the hatches between the International Space Station and Discovery were opened. The STS-133 crew members joined the members of the Expedition 26 on the station.
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Archive for February, 2011
Space Shuttle Discovery docks to the International Space Station at the Pressurized Mating Adapter 2 of the Harmony node.
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Space Shuttle Discovery performs the Rendezvous Pitch Maneuver. During this maneuver, the crew on the ISS inspects the shuttle\’s outer surface for possible damage.
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On February 24, 2011, the Automated Transfer Vehicle “Johannes Kepler” docked to the International Space Station. ATV-2 delivers more than seven tons of supplies to the station.
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On February 14, 2011, two of the Mars 500 crew members performed the first \’Marswalk\’ at the IBMP facilities in Moscow. The walk lasted one hour and twelve minutes.
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| Credits: NASA |
As mentioned in a previous post, only a small fraction of the existing space debris population is detectable and tracked by ground systems. A smaller fraction is catalogued by special programs and/or departments of national space agencies. This is where statistics comes into play. Numerous models have been created in order to assess present collision risks associated with certain orbits and to predict future evolution of the debris environment around Earth.
The National Aeronautics and Space Administration (NASA) has developed two categories of applications for modeling of space debris environment and risk analysis. The first category, based on evolutionary models such as NASA’s long term debris environment evolutionary model (LEO-to-GEO Environment Debris model or LEGEND), are designed to predict the evolution of the debris environment.
These models cover the near-Earth space between 200 km and 50,000 km, provide space debris characteristics for a debris population consisting of particles as small as 1 mm, and have a typical projection period of 100 years. The second category, which consists of engineering models like ORDEM2000, is used for debris impact risk assessment for spacecraft and satellites, and also as benchmarks for ground-based debris measurements and observations.
The European Space Agency (ESA) has a different set of tools used for modeling the space debris environment and assessing risk associated with collisions in Earth orbit. The DISCOS database (the Database and Information System Characterizing Objects in Space) consolidates the knowledge on all known objects tracked since Sputnik-1, and it is recognized as a reliable and dependable source of information on space objects in Earth orbit. MASTER (Meteoroid and Space Debris Terrestrial Environment Reference) is the agency’s most prominent debris risk assessment tool, which uses statistical methods to determine the impact flux information from all recorded historic debris generation events. ESA also uses DELTA (Debris Environment Long-Term Analysis) to conduct analysis of the effectiveness of debris mitigation measures on the stability of the debris population. Such analysis can cover 100 to 200 year time spans.
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