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<p class="MsoNormal">Author: Hans van der Marel<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">Dear Colleagues,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Today 7 December, 2023 (between 10 and 13 UTC) the old Dorne Margolin T antenna at the IGS station WSRT00NLD was replaced by a modern LEICA AR25-R4 :<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">Antenna type : LEIAR25.R4 LEIT<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">Serial number: 726840<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">Antenna height: 0.3754 (changed)<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:35.4pt"><span lang="EN-US">Radome serial number: 765734<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The Dorne Margolin T was installed more than 25 years ago, in 1997. As expected, it was impossible to separate the old antenna from the monument without some reconstruction work. The latter involved replacing a metal
adapter with a newly fabricated adapter. As a consequence the antenna height changed.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">We are fairly confident that the new adapter did not introduce noticeable changes in the horizontal position: any differences, if they exist, should be below the millimeter level. In the vertical, the ARP of the new
antenna is 13.4 mm below the old ARP, but this is absorbed in the modified antenna height.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The old and new antenna positions have been checked by a local survey and a local GNSS monitoring network. The local GNSS monitoring network consists of two receiver at distances of several hundreds of meters, that started
observing two weeks before the change and continue observing for some time after the change. Results from the local survey and GNSS monitoring, which is ongoing, are not available yet. These will be an independent verification of the work that was done. <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">A new station logfile will be submitted soon.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Finally, I would like to thank my colleagues from the Dutch Kadaster who took it upon them to prepare, and monitor the antenna change.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Hans van der Marel <o:p></o:p></span></p>
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