What are the trapped radiation belts or the Van Allen belts (altitudes, structur

Question

What are the trapped radiation belts or the Van Allen belts (altitudes, structure, type of trapped particles, etc.)? Two identical satellites are launched on different orbits: The first one remains on a circular orbit below 1,400 km; and the second one is injected on a geo transfer orbit, i.e., an elliptical orbit that goes from 600 to 36,000 km then back to 600 km, etc. Which satellite is more likely to experience more failures and why? What types of failures do you think it will experience? Based on, Book: Interactive aerospace engineering and design Chapter: 8 The Space Environment-An Engineering Perspective

Explanation / Answer

The term Van Allen belts refers specifically to the radiation belts surrounding Earth. The Van Allen radiation belt is a torus of energetic charged particles (plasma) around Earth, which is held in place by Earth's magnetic field. This Van Allen radiation belt field is not uniformly distributed around the Earth. On the exterme outward (sunward) side, it is compressed because of the solar wind, while on the other side it is elongated to around three earth radii. This creates a cavity called the Chapman-Ferraro Cavity, in which the Van Allen radiation belt resides. It is split into two distinct belts, with energetic electrons forming the outer belt and a combination of protons and electrons creating the inner belt. In addition, the belts contain lesser amounts of other nuclei, such as alpha particles. The Van Allen belts are closely related to the polar aurora where particles strike the upper atmosphere and fluoresce. Effect on space voyages: Solar cells, integrated circuits, and sensors can be damaged by radiation. Geomagnetic storms occasionally damage electronic components on spacecraft. Miniaturization and digitization of electronics and logic circuits have made satellites more vulnerable to radiation, as incoming ions may be as large as the circuit's charge. Electronics on satellites must be hardened against radiation to operate reliably. The Hubble Space Telescope, among other satellites, often has its sensors turned off when passing through regions of intense radiation. Missions beyond low earth orbit leave the protection of the geomagnetic field, and transit the Van Allen belts. Thus they may need to be shielded against exposure to cosmic rays, Van Allen radiation, or solar flares. The region between two to four earth radii lies between the two radiation belts and is sometimes referred to as the safe zone. A satellite shielded by 3 mm of aluminium in an elliptic orbit (200 by 20,000 miles) passing through the radiation belts will receive about 2,500 rem (25 Sv) per year. Almost all radiation will be received while passing the inner belt. [12]

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