Technicians around Cape Canaveral spent the last four weeks assembling a United Launch Alliance Atlas 5 rocket and preparing a Lockheed Martin-built NOAA weather satellite for liftoff March 1.

The fourth modernized Global Positioning System satellite launched this year has completed in-orbit testing and joined the constellation.

A troublesome liquid oxygen valve on the Space Launch System’s first flight-rated core stage will keep NASA from performing a second test-firing of the rocket’s four main engines this week.