From The Editors Science

SpaceX Launches 5 Iridium Next and 2 GRACE-FO Satellites

Powered by a pre-flown first stage booster, a SpaceX Falcon 9 rocket lifted off from the Vandenberg Air Force Base in California at 3:47 p.m. EDT, on Tuesday (May 22), carrying a payload of seven satellites, including five Iridium Next and two NASA GRACE-FO (Gravity Recovery and Climate Experiment Follow-On) satellites.

“Liftoff for GRACE Follow-On, continuing the legacy of the GRACE mission of tracking the movement of water across our planet,” NASA TV’s launch commentator Gay Yee Hill announced, as the rocket climbed into orbit on the ride-share mission between Elon Musk’s SpaceX, Iridium, and German Research Center for Geosciences (GFZ).

The GRACE-FO project – a joint NASA-GFZ endeavor – saw the space agency spending some $430 million, while GFZ’s share of the cost totaled up to around €77 million (about $91 million).

The previously used first stage booster powering the Tuesday launch was none other than the one deployed for the hush-hush Zuma mission for the United States Air Force, in January this year, which was, incidentally, SpaceX’s first launch in 2018.

While the first stage of the brand new Falcon 9 rocket did make a safe return back to Earth, the top-secret payload, probably worth billions, did not make it to its intended orbit, crashing into the ocean instead.

However, SpaceX got a clean chit from investigators who determined that it was spacecraft contractor Northrop Grumman and not the Musk-owned company that was responsible for the failed Zuma mission.

SpaceX is under a $536 million contract with Iridium Communications Inc. to launch 75 Iridium Next satellites over eight Falcon 9 mission.

With six Iridium missions already in the SpaceX bag, including Tuesday’s launch, Musk’s company is now left with 20 more satellites to launch over the two remaining missions – Iridium-7 and Iridium-8; which can be achieved by mid-2018, provided SpaceX is able to maintain the blistering pace it has set, thus far.

The two GRACE-FO craft that were part of Tuesday’s payload is a continuation – or follow-on, as they like to call it – of the Gravity Recovery and Climate Experiment, the original GRACE mission that started back in 2002, involving similar satellites.

“GRACE was really a revolutionary mission for understanding the water cycle, how the climate behaves and the trends taking place over the last 10 or 15 years, and it did this in a very unique way by making measurements of how the mass gets redistributed on the surface of the earth,” GRACE-FO project scientist, Frank Webb said at the news conference.

“We’re able to see how water has moved from different parts of the earth by actually measuring its mass, which is not something you see with your eyes. It’s something you have to feel with the satellite system,” he said.

A few seconds after the recycled first stage booster was jettisoned, the Falcon 9’s second stage fired its Merlin, accelerating ahead for the actual release of the payload sitting inside the nose cone.

Some 12 minutes into the launch, the NASA GRACE-FO satellites were successfully deployed into a near-polar orbit, after which the Merlin re-ignited and shot farther away to release the Iridium Next satellites, launching them in quick succession through a dispenser at the forward end of the second stage.

Contact with the two GRACE-FO satellites was confirmed, soon after, by the ground controllers in Oberpfaffenhofen, Germany, near Munich, based on radio signals received via a tracking station at McMurdo, Antarctica.

Nor too long after that, SpaceX also confirmed the successful deployment of the Falcon 9’s entire payload of seven satellites, calling it “a clean sweep again for deployments.”

“It’s been a great Falcon 9 day here in Hawthorne and at Vandenberg Air Force Base,” declared John Insprucker, Falcon 9 lead engineer at SpaceX and host of the company’s live webcast of the mission.

Iridium boss, Matt Desch also confirmed receiving “good telemetry from all 5 Iridium NEXT satellites,” not forgetting to thank SpaceX for the “complete success” of the mission.

SpaceX did not make any attempts to recover the first stage of the rocket, as it usually does with pre-flown boosters, allowing it to crash into the Pacific Ocean.

The company did, however, send Mr. Steven to retrieve the $6 million fairing – a part of the rocket’s nosecone that, basically, protects the payload during the ever so stressful ascent.

Mr. Steven, by the way, is a SpaceX-customized fairing recovery boat, fitted with a massive net, held in place by giant metal arms extending out of the vessel – which Musk fondly refers to as the “giant catcher’s mitt.”

However, the fairing narrowly missed Mr. Steven’s “mitt” and landed in the Pacific, instead – a failure that SpaceX is familiar with, as Mr. Steven had missed the fairing after the previous Iridium Next launch on March 30, as well.

“The payload fairings both successfully deployed parachutes, but they landed in the Pacific Ocean,” Insprucker said. “The fairing recovery ship ‘Mr. Steven’ came very close, but not quite. We’re going to keep working on that, but meanwhile, the second stage went into a great orbit.”

While no major damage was reported, seawater is likely to affect the sensitive components of the fairing, making it more difficult and certainly more expensive to refurbish for future use.

On Monday, Iridium became the second company after Inmarsat to be recognized by the International Maritime Organization as having a network that conforms to the safety and performance criteria for providing Global Maritime Distress and Safety System.

“Our strong presence in the world of safety services is a testament to the unique benefits our network can enable,” Desch said after the Tuesday launch.

“With every successful launch, we are one step closer to Iridium Next being fully operational, which officially starts a new age of satellite connectivity,” said the Iridium chief.

“When it comes to safety communications, especially for those operating in the skies or out at sea, having built-in network redundancy and resiliency enabled by our satellite’s cross-links is paramount, especially during times of distress,” Desch said.

“We recognize this and feel that as the only network covering the entire planet, we have an inherent responsibility to constantly innovate for this critical arena,” he added.

In a conference call with reporters, last week, Desch had said that Iridium customers will now be able to benefit from the new satellites “well over 80 percent of the time since we are biasing our Next satellite beams to carry more of the traffic, particularly in the Northern Hemisphere.”

He said that the “Next satellites are faster, voice calls sound better, and we want our customers to get service through them as soon as possible,” he said.

In the coming weeks, the new satellites are expected to reach a height of 484 miles above Earth where they’ll join the other Iridium spacecraft, taking the total fleet strength to 55, with 20 more to go, before the conclusion of its contract with SpaceX.

Desch also confirmed that testing of ground terminals for a brand new broadband service called Iridium Certus is well underway and should be able for commercial operations in a matter of months.

As for the GRACE-FO mission, Michael Watkins, GRACE-Follow On science lead and director of NASA’s Jet Propulsion Laboratory, said, “GRACE and GRACE-Follow On are some of NASA’s most unique missions.”

“What GRACE has done, and what GRACE-Follow On will do shortly after its launch, is map the Earth’s water in motion,” he said.

“What’s fascinating about GRACE is it does it not by looking the surface of Earth — not by looking at water or by bouncing a radar off the water — but by actually measuring the weight of the water,” Watkins added.

“So it actually is able to tell how much water is in a given location on the Earth and how that’s changing over time,” he said.

The Airbus Defense and Space-developed GRACE-FO craft are equipped with microwave ranging instruments that calculate the distance separating the satellites as they orbit Earth 137 miles or so apart from each other.

“Think of the actual satellite size as about the size of a sports car, one in Los Angeles and one in San Diego,” said Phil Morton, NASA’s GRACE-Follow On project manager. “That’s about how far apart they’re flying typically.”

The GRACE-FO satellites have been developed along the lines of the original GRACE spacecraft so that they are able to gather similar data, with upgrades like laser ranging devices expected to measure the distance between the two satellites with a precision that’s 10 times more accurate than baseline microwave instruments, says Frank Flechtner, who’s the GRACE-FO project manager at GFZ in Potsdam, Germany.

However, the mission’s primary objective is dedicated to gravity measurements and Earth’s water cycle.

“The satellites are sensitive to all mass change around the globe,” says Webb. “We make measurements every 30 days, so we see atmospheric, ocean tides, solid earth changes, water ice moving around.”

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