Q&A with Steve Clarke, deputy associate administrator for exploration in NASA’s science division (members only)

Concerns over an unspecified part flying on the upper stages of United Launch Alliance’s rockets have delayed the launch of a GPS satellite on a Delta 4 booster from July 25 to no earlier than Aug. 22. The same issue has also delayed an Atlas 5 launch.

Technicians working at launch pad 0A at NASA’s Wallops Flight Facility in Virginia completed the final loading of cargo into Northrop Grumman’s Cygnus supply ship late Tuesday, and the Antares rocket was raised vertical again in preparation for Wednesday’s countdown.

Singed and blackened from three fiery trips to the edge of space and back, a Falcon 9 rocket returned to Cape Canaveral on Sunday after a mission last that week carried the Israeli Beresheet moon lander into orbit, ready for inspections before attempting a fourth — and likely final — launch this spring.