****************************************************************************** DORIS Electronic Mail Mon Jan 4 9:28:38 WET 1999 Message Number 0062 ****************************************************************************** Author: Herve Fagard (IGN) Subject: Antenna falls, moving and change at Ottawa Dear Colleagues, I will try to sum up hereafter the numerous antenna position changes that took place at Ottawa since the initial installation of the antenna. - The antenna was installed in November 1988, and started transmitting when SPOT-2 was launched, i.e. in January 1990. - This antenna fell down for the first time at the end of April 1991. It was reinstalled in the same location a few days later. - The second fall took place sometime between September and December 1993 (the exact date is unknown). The antenna was reinstalled at a slightly different position around the end of January '94. - At the end of January '98 the antenna support was found loose (see DORIS mail # 30). The Alcatel antenna was then replaced with a Starec one, on the same vertical line, and a mark was set below the antenna. In March the antenna support was reinforced to avoid a new fall or dammage. All the different positions of the antenna phase centers have been assigned a DOMES number as follows : DOMES # Installed Removed Code Antenna Position 40102S005 15-NOV-1988 24-APR-1991 OTTA Alcatel original location 40102S006 25-APR-1991 28-MAY-1991 OTTA Alcatel dubious position (1st fall) 40102S007 29-MAY-1991 31-AUG-1993 OTTA Alcatel between 1st and 2nd fall 40102S008 01-SEP-1993 31-JAN-1994 OTTA Alcatel dubious position (2nd fall) 40102S009 01-FEB-1994 03-JAN-1998 OTTA Alcatel between 2nd and 2rd fall 40102S010 04-JAN-1998 28-JAN-1998 OTTA Alcatel dubious position (3rd fall) 40102S011 29-JAN-1998 OTTB Starec current location The vectors between the stable positions are (sigma = 1 cm) : S005 ---> S007 : dX = 0 dY = 0 dZ = 0 (assuming the antenna was put back to the same position) S007 ---> S009 : dX = 0.01 m dY = 0.10 m dZ = -0.23 m (this values were derived from the shift between the holes in the wall) S009 ---> S011 : dX = 0.04 m dY = -0.16 m dZ = 0.17 m Many thanks to Robert Duval (NRCan) who helped me a lot to put the jigsaw together. With my best wishes for 1999, 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 ====================================================================== [Mailed From: Pascal Willis ]