****************************************************************************** dorismail 17-Apr-2009 07:19:43 Message No 0598 ****************************************************************************** Author: "H. Fagard" Subject: Antenna centering control and raising at Amsterdam Dear Colleagues, The antenna of the DORIS station at Amsterdam had to be replaced on December 4, 2008 because of a power loss on the 400 MHz channel (see DORISMail #0566). This change was carried out by the host agency, without supervision by a geodesist. The possible antenna offset was therefore unknown, until an IGN surveyor recently travelled to Amsterdam. The 2 GHz phase center of the new antenna was found 1 mm west, 2 mm north of the initial position. On the other hand, the antenna support was modified on this occasion, in the frame of a global action aiming at standardizing the antenna support models. The antenna is now supported by a 43 cm high stainless steel structure, set on the same concrete pillar as the three former antenna locations (AMSB, AMTB and AMUB). The transmissions from the former antenna location (AMUB) stopped on April 7, and resumed on April 8 after the antenna support change. The acronym for the new reference point is AMVB. The DOMES number for the new antenna reference point is 91401S005. The vector from AMUB (initial position between April 17, 2007 and December 4, 2008) to AMVB is: dE = -0.001 m ; dN = 0.002 m ; dh = 0.186 m. Hence the ITRF2005 @2000.0 coordinates for AMVB, derived from those published for AMTB in the DORISMail #0569: X = 1086063.069 m Y = 4927948.776 m Z = -3887840.197 m (sigma: 2 mm for each component) The ITRF2005 velocities for this site are: VX = -0.0109 m/y VY = 0.0039 m/y VZ = -0.0031 m/y SigVX = 0.0005 m/y SigVY = 0.0004 m/y SigVZ = 0.0004 m/y Here is a summary of the operation period for each antenna location: Code DOMES Start End Comment AMSA S001 1987-02-01 1997-04-21 AMSB S002 1997-04-21 2001-03-28 Progressive tilt (1) AMTB S003 2001-03-29 2005-11-24 Stable and centred AMTB S003 2005-11-24 2007-04-17 Antenna change, offset (2) AMUB S004 2007-04-17 2008-12-04 New position, raised by 15 cm AMUB S004 2008-12-04 2009-04-07 Antenna change, 2 mm offset AMVB S005 2009-04-08 - New support (1) 2 GHz phase center: 4 mm towards north, 64 mm towards west at the end of this time period, see DORISMail #0128 (2) 2 GHz phase center 7 mm towards south-east, see DORISMail #0497 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