The Air Force Space and Missile Systems Center told Bloomberg News in a statement that the launch date "has slipped due to ongoing SpaceX qualification testing and final engineering reviews by both SpaceX and the Air Force of Falcon 9 design changes". The Falcon 9 Block 5 is expected to change that.
The U.S. Air Force has delayed the launch of its first Global Positioning System III satellite from this month to October at the earliest as it reviews the upgraded rocket that Elon Musk's SpaceX plans to use to boost it into orbit.
The GRACE-FO satellites are also joined by five Iridium satellites on the Falcon 9.
While SpaceX often recovers the first-stage of its rockets so they can be reused in future missions, SpaceX did not attempt such a recovery this time. Iridium shares rose more than 8 percent earlier Tuesday for the biggest intraday gain in nearly seven months. In reality, the deployment of the two payloads will be separated not just by time but also by a burn of the Falcon 9's second stage engine to push it even farther away from Earth. The stream will spring to life shortly before the scheduled launch opportunity and SpaceX will provide commentary and additional details as the event unfolds. The May 22 launch grows the constellation to 55 Iridium Next satellites in orbit. SpaceX appears to have been absolved from blame for this mishap, and certainly the first stage booster performed nominally during that mission. He billed it as one of the "largest tech upgrades in history", telling investors he expects the rest of the satellites to go up this year, "completing our Iridium NEXT constellation and starting on a well deserved [capital expenditures] holiday".More news: Brandon Marshall says President Trump's anthem comments were 'disgusting'
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For the first few days after launch, the lower, faster satellite will pull slowly ahead of the other until the two satellites are approximately 137 miles (220 kilometers) apart - the optimal separation distance for science operations. SpaceX's Falcon 9 rocket will tote two satellites that are part of NASA's Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, as well as five more Iridium Next communications satellites, when it takes off from Vandenberg Air Force Base in California at 3:47 p.m. EDT (1947 GMT).
NASA contributed $430 million to the new mission and the German contribution was 77 million euros, officials said.
The science provided by this pair of satellites is really interesting. They'll measure the distribution of the Earth's mass and can monitor changes in ice sheets, glaciers and sea level, according to NASA.
Once the Earth-facing satellite has put a safe distance between itself and its sibling, it will thrust back up into a higher orbit, so that one follows the other on the same trajectory.