Through many dangers, toils and snares.... SpaceX to send amazing GRACE to spaaaaace

Rocket boffins to dump second-hand Falcon 9 in the sea

Falcon 9 on the launchpad (pic: NASA/Bill Ingalls)
Falcon 9 on the launchpad (pic: NASA/Bill Ingalls)

Because ride-sharing is caring, SpaceX will send the next batch of Iridium NEXT satellites into orbit along with a pair of NASA gravity monitoring orbiters, GRACE-FO.

The launch, scheduled for 1947 UTC (1247 PT) from California’s Vandenberg Air Force Base today, will reuse the outdated Falcon block 4 rocket that flung mystery-sat Zuma into orbit. Or didn’t, depending on which version of events you choose to accept.

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Sadly for fans of the Falcon 9 party trick of landing fiery-end down, SpaceX does not intend to attempt to recover the rocket for a second time.

At 2 minutes and 49 seconds into the flight, the first stage will separate and head for a watery grave and 23 seconds later the aluminium and carbon fiber fairing protecting the payload will peel off and head back to Earth for a hoped-for recovery.

SpaceX’s recovery ship, Mr Steven is heading out into the ocean to attempt to catch at least one half of the expensive shell used to protect spacecraft during the early phases of launch. The plan is part of SpaceX's drive to reuse as much of the launch system as possible.

Meanwhile the SpaceX second-stage booster will fire until 11 minutes and 33 seconds into the flight, when NASA’s GRACE-FO spacecraft will be deployed. The second stage rocket will then shut down and coast until a little under an hour after liftoff, when the engine will be restarted for a quick burn prior to the five NEXT communications satellites being ejected, as Iridium continues upgrading its constellation.

The return of GRACE

NASA’s Gravity Recovery and Climate Experiment Follow-on (GRACE-FO) is a follow up to the original GRACE mission, which launched on 17 March, 2002 and lasted far longer than the projected five year lifespan. Consisting of twin satellites, the mission finally ended on 27 October, 2017.

GRACE-FO similarly consists of twin satellites, orbiting 220km (137 miles) apart at an altitude of 490km (304 miles). The pair measure Earth’s gravity field by detecting minute changes (down to a micron level) in the distance between the spacecraft caused by anomalies in gravity. The result is a monthly map of the Earth’s gravity field and gives clues as to how mass (normally water) is moving around the planet.

Scientists are keen to keep collecting this data even after the original 15 years of GRACE. While sea-level rises have been tracked very accurately over the years, the additional data allows the boffins to separate rises due to melting ice flowing into the ocean from land versus expansion of seawater as it warms.

On Monday pre-launch briefing saw Capt. Jennifer Haden of the 30th Space Wing, forecast a greater than 90 per cent chance that the weather would co-operate for tonight's launch, SpaceX's tenth from Space Launch Complex 4E. ®

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