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Spacecraft flew hundreds of thousands to hundreds of millions of kilometers from the earth, injecting speed when the size and direction of a slight error, arrived at target planets will appear large deviation error, for example, when Mars probe injecting speed 1 m/s speed (about one over ten thousand), arrived at Mars, about 100000 km distance deviation. Therefore, precise control and navigation must be carried out during the long flight. Flying to the moon is usually controlled by the orbital control system of the ground and space probe (see orbit control). Interplanetary flight distances, radio signal transmission time is long, the real-time remote control, can't so planets and interplanetary spacecraft orbit control system shall have the ability of autonomous navigation (see interstellar travel navigation and control). The United States, for example, "pirates" spacecraft in space flight of more than eight hundred million km, for 11 months of 2000 times of autonomous orbit adjustment, the final surface to achieve a soft landing on Mars, placement accuracy up to 50 km. In addition, in order to ensure the accuracy of the orbit control engine, the communication antenna is always aimed at the earth, and other systems work normally, and the detector has the autonomous attitude control ability
The people's governments of various cities and counties are directly affiliated to each unit:
A hand-held metal detector is designed to detect metal objects or objects carried by people or objects. It can be ground
From the viewpoint of traffic safety, it is important to have both winter as summer tyres using the proper groove depth and properties to match the weather conditions. When there is excess water or slush on the highway as well as the driving speed exceeds a specific limit, the tread pattern in the tyre no longer pushes aside the lake or slush from beneath the tyre. The feel between the tyre along with the road is going to be lost, therefore will the grip.
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