****************************************************************************** dorismail 17-Apr-2007 14:06:09 Message No 0492 ****************************************************************************** Author: "H. Fagard" Subject: Antenna tilt at Ascension Island (South Atlantic Ocean) Dear Colleagues, The DORIS antenna at Ascension Island (South Atlantic Ocean, acronym ASDB) has been found to be slightly tilted because of some corrosion of the antenna base plate. The current offset of the 2 GHz phase centre, kindly measured by the host agency (Ariane tracking station) is: dE = -21 mm dN = 1 mm dH < 1 mm (FROM the original position TO the shifted one). The starting date of the antenna movement is unknown, but we think that this has been a very slow process. Although this antenna is installed in a very corrosive environment (probably the worst in the whole DORIS network, because of sea spray from a nearby blowhole), the marine aluminium base plate (not anodised aluminium like at the other sites where such antenna skews were experienced) had resisted very well so far. The antenna, installed in 1997, was still well centred when checked in 2003. A new monument, including a more corrosion-proof base plate, will be built in the next few months, in a slightly different location allowing to reduce signal obstructions and multipaths caused by two nearby satellite dishes. Best regards, Herve Fagard -- ====================================================================== Herve FAGARD e-mail : herve.fagard@ign.fr Institut Geographique National 94165 SAINT-MANDE CEDEX PHONE : + 33 1 43 98 81 48 FRANCE FAX : + 33 1 43 98 84 50 ====================================================================== Cliquez sur l'url suivante https://www.mailcontrol.com/sr/5IP5kefcVFgava4311zko4wBUItmTKMi7ZrxPXY4bj!v0ZR5U0pLmkFV3QZMdzU8QZmlBb0lyDOnOmzev0kkAgbg4QEhGdxud6hkDFbLc+oy42Du4IqZSj4ODN+!p3Z7vPEYo9ZzPj6xOcaWvtkzflslIrjmWfXAwMskf9D2PwlPzs4a7FGXrTxdDzbUR1qyxgwO8nWVGfRkdbrwqxYP3cVf9cNpu7OS si ce message est indésirable (pourriel). Please do not reply directly to this message, but send comments and suggestions to IDS.central.bureau@cls.fr