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Space Debris Passage
In the first days of space exploration, oneconcern was the possibility that astronauts orspacecraft might be hit by meteoroids. Scientistscalculated that this possibility was extremely small,05because meteoroids are rare, but that the astronautsor spacecraft would almost certainly encounter themore common micrometeorites, which are aboutthe size of grains of dust and much more common.However, in the 60 years since the beginning of10space exploration, large quantities of human-madeorbital debris have accumulated. Much of thedebris consists of satellites that have stopped func-tioning, or rocket booster sections that separatedfrom the main spacecraft during a mission. Some of15the debris consists of items lost by astronauts, suchas tools or space suit parts. Still more of the debrisis the result of collisions, such as when a satellitecollides with another or with a large piece of debris.NASA estimates there are millions of debris20particles that are too small to be tracked. Thesecircle Earth at speeds up to 17,500 miles per hour,making even the smallest particles dangerous. Onescientist calculated that a chip of paint hitting thewindow of a spacecraft at orbital speeds will hit25with the same amount of force as a bowling balltraveling at 60 mph. Such an impact occurred onthe space shuttle Challenger's second flight, chip-ping the windows and causing minor damage to theprotective tiles on the spacecraft. While the damage30was not immediately dangerous, it led to the fearthat any craft in orbit for long periods of time couldaccumulate enough damage to cease functioning.Larger objects are even more dangerous, butthey can be monitored and avoided. NASA tracks35about 500,000 pieces of debris larger than a marble,about 20,000 of which are larger than a softball.When NASA was still flying shuttle missions, itwould often have to direct the shuttle to maneuverto avoid collisions with the larger debris. This could40usually be planned and accomplished in a fewhours, but moving the International Space Stationto avoid a collision takes up to 30 hours of advancenotice.Many satellites have the ability to adjust their45course slightly and can be remotely directed to avoidcollisions with larger objects that would damage ordestroy the satellites. NASA and the European SpaceAgency (ESA) have departments of scientists andengineers dedicated to cataloging, modeling, and50predicting the movements of space debris.Some debris falls back to Earth, and most of itis burned up in the atmosphere. However, a largepiece will survive long enough to get through theatmosphere and crash. In 1979, the obsolete Skylab55fell out of orbit, and much of it withstood the tripthrough the atmosphere, crashing in the Australianoutback. Space agencies also monitor debris topredict if any particular piece might fall and when.Although they can issue warnings, there is currently60nothing that can be done about pieces that mightget through the atmosphere.To avoid adding to the aggregation of debris,future satellites may need to be able to takethemselves out of orbit as their usefulness comes65to an end. Until a way to remove these remains isimplemented, however, those 500,000 pieces oflarge fragments, along with the millions of smallerpieces, will continue to orbit Earth.
1. The central idea of the passage is primarily concerned with the
2. Which choice provides the best evidence for the answer to the previous question?
3. Paragraph 2 helps support the central idea of the passage by providing
4. According to the passage, why does space debris created by humans pose a greater threat than meteoroids?
5. Which of the following pieces of evidence strengthens the author's line of reasoning?
6. As used in line 54, "obsolete" most nearly means
7. Based on information in the passage, which of the following conclusions can be reached?
8. Which choice provides the best evidence for the answer to the previous question?
9. As used in line 66, "implemented" most nearly means
10. Based on the passage and the graphic, if NASA were to place a new satellite into orbit, which would be an altitude range to avoid?
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