****************************************************************************** dorismail 25-Apr-2008 09:29:18 Message No 0536 ****************************************************************************** Author: "H. Fagard" Subject: Antenna raising at Rio Grande (Argentina) Dear Colleagues, The antenna of the DORIS station at Rio Grande has been raised in order to remove the N-type bent adapters at the base of the antenna. The signal obstructions were significantly reduced thanks to this support change, the removal of a nearby enclosure, and the modification of the roof of the building which hosts the beacon. The antenna is now supported by the same device recently tested at Monument Peak: a 45 cm high stainless steel structure. It is installed on a 55 cm diameter, 1.8 m high* concrete pillar, anchored 7 m deep into the ground. *these values differ slightly from those given in the DORISmail No 0117, but they are more accurate. The transmissions from the former antenna location (RIPB) stopped on April 15, and resumed on April 17 after the antenna raising. The acronym for the new reference point is RIQB. The DOMES number for the new antenna reference point is 41507S006. The geodetic connection to the permanent GPS receiver, already measured in 2001, was measured again through GPS observations and spirit levelling. All the measurements from the 1995, 2001 and 2008 surveys were processed in a global adjustment. The resulting ITRF2000, 1997.0 coordinates for RIQB are: X= 1429899.226 m Y= -3495323.806 m Z= -5122723.846 m SigX = 0.002 m SigY = 0.003 m SigZ = 0.004 m The ITRF2000 velocities for this site are : VX = 0.0079 m/y VY = -0.0102 m/y VZ = 0.0028 m/y SigVX = 0.0007 m/y SigVY = 0.0009 m/y SigVZ = 0.0011 m/y For those who may be interested, here are also the ITRF2005, 2000.0 values: X= 1429899.248 m Y= -3495323.780 m Z= -5122723.862 m SigX = 0.002 m SigY = 0.002 m SigZ = 0.002 m VX = 0.0082 m/y VY = -0.0100 m/y VZ = 0.0035 m/y SigVX = 0.0001 m/y SigVY = 0.0001 m/y SigVZ = 0.0001 m/y On the other hand, please note that the former antenna (RIPB) was changed following a failure on June 4, 2005, but the antenna verticality was not adjusted at that time. The exact location of the "second" RIPB antenna was therefore not known exactly, but it was measured before its recent removal. The 2 GHz phase center was 1 mm south, 3 mm west of the mark. The following summary of the different antenna occupations at this site may be useful to the analysis centres: Code DOMES Model Start End Comment RIOA S003 Alcatel 1987-12-02 1995-01-17 RIOB S004 Starec 1995-01-20 2001-01-08 RIPB S005 Starec 2001-01-10 2005-06-04 Presumably centred (1) RIPB S005 Starec 2005-06-04 2008-04-15 Slight offset (2) RIQB S006 Starec 2008-04-17 (current) Centred (1) At this time, we were not aware of the geometry defect that affects some Starec antennas (end tube of the antenna not parallel to the main tube), so the accurate centring of the 2 GHz PC is only within a few mm (2) 2 GHz phase centre: 1 mm towards south, 3 mm towards west Please note that all antenna positions at this site were _stable_ ones. There has been no antenna tilt at all, the high quality stainless steel plate that has supported RIPB for seven years was still in pristine condition. 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