KVN antenna positions are measured by using GPS antennas (see Figure 9). Two GPS antennas were installed at both sides of elevation gears and measured their positions for a day. Locations of receiver were determined, and then the invariant point (IVP) was calculated using those two GPS antenna positions and their offsets from the IVP. The accuracy of GPS measurement is approximately about 5 cm.
In order to improve and maintain accurate antenna positions, KVN antenna positions are regularly monitored using GPS and geodetic VLBI observations. The K band geodesy VLBI program between KVN and VERA has been started in 2011 (see Table 8). The typical 1-sigma errors of geodetic solutions are about 0.4 cm in X, Y, and Z directions for a successful measurement. However, the geodetic VLBI solutions were not applied to KVN antenna positions until more measurements are obtained.
|Obs. Code||Obs. Date||Antenna||Note|
|r11333k||2011 Nov. 29||Ky Ku Kt Vm Vr Vs Vo||VERA+Yonsei solution was obtained|
|r11361k||2011 Dec. 27||Ky Kt Vm Vr Vs Vo||Observation failed|
|r12271k||2012 Sep. 27||Ky Ku Kt Vm Vr Vs Vo||All solutions were obtained|
|r13088k||2013 Mar. 29||Ky Ku Kt Vm Vr Vs Vo||All solutions were obtained|
|r13140k||2013 May 20||Ky Ku Kt Vm Vr Vs Vo||All solutions were obtained|
|r13251k||2013 Sep. 9||Ky Ku Kt Vm Vr Vs Vo||in progress|
|r13313k||2013 Nov. 9||Ky Ku Kt Vm Vr Vs Vo||in progress|
|r14028k||2014 Jan. 28||Ky Ku Kt Vm Vr Vs Vo||in progress|
|r14095k||2014 Apr. 5||Ky Ku Kt Vm Vr Vs Vo||in progress|
|Ky, Ku, and Kt stand for Yonsei, Ulsan, and Tamna antennas in KVN, respectively.|
|Vm, Vr, Vs, and Vo represent Mizusawa, Iriki, Ishigakijima, and Ogasawara antennas in VERA, respectively.|