Live coverage: Rosetta’s final hours

Blaming a slew of technical snags and “avoidable errors,” NASA officials said Tuesday that the launch of the James Webb Space Telescope, already years behind schedule, will be delayed to 2020, potentially pushing the mission’s development cost above an $8 billion cap mandated by Congress.

A Proton rocket blasted off from the Baikonur Cosmodrome in Kazakhstan at 2040 GMT (4:40 p.m. EDT) Friday with Turkey’s Turksat 4B communications satellite.

After months of delays caused by the coronavirus pandemic, Arianespace scrubbed back-to-back Vega launch attempts Saturday and Sunday due to unfavorable high-altitude winds over the European-run Guiana Space Center in South America. The Vega rocket is awaiting launch on a rideshare mission carrying 53 small satellites into orbit for 21 customers in 13 countries.