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

Weather forecasters expect a 70 percent chance of favorable conditions at Cape Canaveral for liftoff of a United Launch Alliance Delta 4 rocket Thursday with a GPS navigation satellite, marking the last flight of the Delta 4’s single-core variant after 29 flights since 2002.

Two small Chinese satellites designed to detect gamma-ray bursts associated with gravitational waves launched Wednesday on a Long March 11 rocket, beginning an astrophysics research mission to study black holes and neutron stars.

Two astronauts floated outside the International Space Station early Tuesday and replaced one of the grapple fixtures on the end of the lab’s robot arm, the first of two excursions over the next week to complete a complex overhaul that began with a pair of spacewalks last October.