A new Russian weather observatory and the first prototype for Telesat’s planned network of 100-plus broadband communications satellites in low Earth orbit were among 19 spacecraft feared lost after a Fregat rocket stage ran into trouble soon after liftoff aboard a Soyuz booster Tuesday.

Three space station fliers — the outgoing NASA commander and two Russian cosmonauts — undocked and returned to Earth Wednesday, ending a 167-day stay in space with a communications blackout that left the crew out of contact with flight controllers during much of the trip home.

Six satellites are set to ride a light-class European Vega rocket into orbit from French Guiana on Wednesday night, the first Vega launch since a failure last year that officials attributed to human error.