****************************************************************************** dorismail 12-Jun-2006 09:31:09 Message No 0454 ****************************************************************************** Author: "H. Fagard" Subject: Tilted antenna at Djibouti Dear Colleagues, A new antenna tilt was just discovered by one of the IDS analysis centres, at Djibouti (DJIB). A comparison between the DORIS time series and those derived from the nearby permanent GPS shows a 17 mm/y slow motion toward north, starting shortly after the antenna installation in July 2000. Pictures taken following our request by the host agency show that, like at other places where such tilts happened, this is due to some corrosion at the base of the antenna. But unlike all other former cases, the corrosion doesn't seem to affect the antenna supporting plate - which is made of high quality stainless steel - but the material of the antenna itself. An IGN surveyor will travel to Djibouti at the end of the month, in order to measure the antenna phase centre offset, replace the antenna with a new one, and measure again the geodetic connection between DORIS and nearby control points, hence checking the stability of the DORIS antenna support. Of course all data from DJIB should be used with extreme caution by the analysis centres. Thanks and congratulations to Pascal Willis (IGN/JPL analysis centre) for pointing out this issue to us. 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 ====================================================================== Please do not reply directly to this message, but send comments and suggestions to IDS.central.bureau@cls.fr