Live coverage: Vega rocket launches with LISA Pathfinder

United Launch Alliance called off the planned liftoff of a Delta 4-Heavy rocket and a classified National Reconnaissance Office spy satellite from Vandenberg Air Force Base in California on Wednesday after indications of elevated hydrogen concentrations around one of the launcher’s main engines. Three previous launch attempts were scrubbed by technical concerns and bad weather.

A Russian Soyuz rocket topped with two European Galileo navigation satellites soared into orbit before dawn Tuesday, vaulting through low clouds hanging over its jungle launch base in French Guiana.

A powerful Russian Proton booster launched from Kazakhstan at 0931:42 GMT (5:31:42 a.m. EDT) Monday with the first part of a multibillion-dollar Mars mission led by the European Space Agency. An upper stage engine fired four times over 10 hours to send the Mars orbiter and lander away from Earth.