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| | ESA Science & Technology: SOHO Keyhole Operations |
 | | For SOHO, now into its ninth year of operations, this is a relatively new event, and a direct result of the difficulties experienced with the High Gain Antenna (HGA) during the summer of 2003. |
 | | The term "keyhole", in antenna terminology, stems from a characteristic feature of aerial navigation maps showing the coverage of, for example, a radar antenna: A circular area near the antenna is shaded due to too-short range. |
 | | Over time, many types of CCDs (Charge-Coupled Devices) used to detect EUV radiation are degraded by contamination of heavy ions from cosmic/solar particle radiation (interfering with the doping of the chip), deposits and polymerisation of deposits on the surface and, finally, trapped charges (again interfering with the doping of the substrate). |
| sci.esa.int /science-e/www/object/index.cfm?fobjectid=34471 (1058 words) |
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