[IGSSTATION-8288] GOPE, GOP6, GOP7: Change of external frequency source

[Jakub Kostelecky]

Author: Jakub Kostelecky

Due to a failure in the passive hydrogen maser the external frequency source
for the stations GOPE00CZE, GOP600CZE and GOP700CZE was changed to the 
cesium atomic clock. Effective date: 2021-09-01 16:40 UT. The site logs 
were changed in the SLM system and they wait for validation.

Best Regards,
Jakub Kostelecky
GOP operation center
Geodetic Observatory Pecny
Research Institute of Geodesy, Topography and Cartography
www.pecny.cz,www.vugtk.cz