Context : The ESO 3.6 m Telescope is an optical reflecting telescope run by the European Southern Observatory at La Silla Observatory, Chile since 1977, with a clear aperture of about 3.6 metres (140 in) and 8.6 m2 (93 sq ft) area. 
Question : In which year was the service entry date for ESO 3.6 m Telescope?
1977