NASA’s GRACE-FO, Five Iridium Satellites Share A Ride to Space

NASA’s GRACE-FO, Five Iridium Satellites Share A Ride to Space

NASA and the communications satellite company Iridium shared a ride to orbit today on a SpaceX Falcon 9 rocket.  Liftoff of the “ride-share” launch was on time at 3:47 pm ET from Vandenberg Air Force Base, CA.  NASA’s GRACE-FO twin Earth science satellites and Iridium’s five Iridium-NEXT communications satellites were all successfully deployed after launch.

Artist’s illustration of the twin GRACE-FO satellites (one in the foreground, one in the upper right) with their connecting microwave links shown in red. Credit: NASA

While cubesats routinely share rides to orbit with other customers, it is less common for NASA and a commercial company to pair up.

Gravity Recovery and Climate Experiment – Follow On (GRACE-FO) is a cooperative climate science mission between NASA and the German Research Center for Geosciences (GFZ).   The twin GRACE-FO satellites follow each other around in Earth orbit, 220 kilometers apart (about the distance from Los Angeles to San Diego), and measure minute changes in gravity as they pass over the globe by tracking the changes in their relative positions using microwave signals.  The satellites are also equipped with an experimental laser ranging system.  GRACE-FO is the successor to the GRACE mission which operated for 15 years (2002-2017) and provided a wealth of data about the movement of Earth’s water masses in a liquid, solid or gaseous (water vapor) form.

At a pre-launch press conference yesterday, NASA and GFZ officials said the cost of the mission was $430 million for NASA and 77 million Euros (about $90 million) for Germany.  Germany was responsible for the launch and arranged the ride-share with SpaceX and Iridium according to GFZ’s Frank Flechtner.

NASA TV showed a videotaped message from Administrator Jim Bridenstine during launch coverage today, which he later tweeted.

One of the reasons Bridenstine’s nomination was controversial was because of remarks he made on the floor of the House in 2013 when he was a Congressman representing the first district of Oklahoma.  He expressed skepticism about climate change and the role humans play in it.  Critics worried what it would mean for NASA’s Earth science portfolio if he became Administrator.  He moderated his views during his confirmation hearing last November, saying he accepts that humans contribute to climate change, but would not go so far as to agree that humans are the primary factor.

He reiterated that at a “town hall” meeting with NASA employees last week in response to a question, explaining how his views have evolved.  He recounted part of what he said in 2013, concluding that now “I don’t deny the consensus that the climate is changing … and we humans are contributing to it in a major way.  … NASA is the one agency on the face of the planet that has the most credibility to do the science necessary so we can understand it better than ever before.”  He also said climate science should be “free from partisan or political … rhetoric.”

On the other hand, he added that President Trump’s budget request for NASA’s Earth science budget for FY2019 is higher than three of the budgets under the Obama Administration.  And in retelling what he said in 2013, he omitted mention of the biting partisan ending of that floor speech.

Whatever may have happened in the past, he now appears knowledgeable about and supportive of NASA’s Earth science portfolio and of implementing the guidance of the National Academies’ Earth Science and Applications from Space Decadal Surveys.  GRACE-FO was one of the recommended missions from the 2007 Survey.

Artist’s illustration of an Iridium-NEXT satellite. Credit: Iridium.

As for Iridium’s part of today’s launch, Iridium CEO Matt Desch said during a May 14 press conference that the ride-share was fortuitous for the company, which had been planning to use Russia’s Dnepr rocket which is no longer available.

The Iridium system requires 66 operational satellites and the company is in the process of replacing its entire original system.  It has been launching the new generation Iridium-NEXT satellites 10 at a time on SpaceX Falcon 9 rockets. With today’s launch, 55 are now in orbit.  Two more 10-satellite launches are planned to complete the new constellation and have nine on-orbit spares.

Iridium is best known as essentially a satellite-based cell phone system, meaning that it provides voice and data connectivity though handsets, but without terrestrial cell towers.  That makes them invaluable in natural disasters and remote areas of the globe.  The satellites are interconnected so signals go from the transmitting handset to the receiving handset through only satellite links, making communications very secure.  DOD is a significant user of the Iridium system.

Iridium-NEXT also carries the Aireon space-based air traffic surveillance system for real-time tracking of aircraft equipped with Automatic Dependent Surveillance-Broadcast (ADS-B) transmitters.  Aireon receivers on Iridium-NEXT satellites can receive data from ADS-B equipped aircraft anywhere on the globe and transmit it to air traffic controllers and airline operations centers in seconds.

The original Iridium satellites create a visible “flare” when the setting or rising Sun glints off their main antennas.  The flares are a thing of beauty to some and an irritation to others.  Desch said the new generation satellites will not cause the flare and joked that as the older satellites are deorbited, the company is having a “flarewell campaign.”

Iridium deliberately deorbits its old satellites so they do not add to the space debris population.  The company is a “poster child for what can go wrong,” Desch said because one of its satellites collided with a defunct Russian satellite in 2009, creating a cloud of debris.  He worries about the debris situation, especially with regard to cubesats and megaconstellations like those planned by OneWeb and SpaceX’s Starlink.  His concern focuses on how to deal with satellites that completely fail once in orbit, meaning they cannot be moved out of the way.  “Having some oversight and plans in place” is needed, “but few are talking about it now.”

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