Q&A with Keith Gendreau, principal investigator of the first X-ray space communications experiment (members only)

The Ariane 5 rocket’s fifth flight of the year launched at 2030 GMT (4:30 p.m. EDT) with the Sky Muster and Arsat 2 communications satellites, designed to deliver broadband Internet to far-flung Australian citizens and broadcast television and networking services to Argentina and nearby countries.

SpaceX’s launch director halted a countdown Tuesday to replace a sensor on the upper stage of a Falcon 9 rocket set to blast off with the GovSat 1 communications craft, the product of a joint venture between the commercial satellite operator SES and the government of Luxembourg.

The first six broadband satellites for OneWeb, which envisions a constellation of hundreds of orbiting relay stations beaming Internet signals down to Earth, lifted off Wednesday aboard a Soyuz rocket from French Guiana. Launch occurred at 2137 GMT (4:37 p.m. EST).