Russia's Proton Returns to Flight on Friday – UPDATE 2

UPDATE, August 28, 2015, 11:25 pm EDT:  the upper stage firings were successful and Inmarsat-5 F3 has been successfully delivered into geostationary orbit.

UPDATE, August 28, 2015, 8:00 am EDT:   Liftoff took place as planned and the three-stage Proton-M rocket appears to have performed flawlessly. The Briz-M upper stage is now making the first of five firings to place the satellite into geostationary orbit.  It will take 15 hours and 31 minutes for the satellite to reach its destination.

ORIGINAL STORY, August 27, 2015: Russia plans to launch an Inmarsat satellite using its Proton-M rocket on Friday, August 28.  It is the first Proton-M launch since a May 2015 failure destroyed a Mexican communications satellite.  The once reliable Proton, the largest of Russia’s current fleet, has suffered a number of failures in recent years, but typically returns to flight after a few months, as is true this time.

U.S.-based International Launch Services (ILS) markets the Proton globally and will broadcast Friday’s launch of Inmarsat-5 F3 on its website.   The launch of the Proton-M with a Briz-M upper stage is scheduled for 14:44 Moscow Time, which is 12:44 British Summer Time (in London where Inmarsat is headquartered), which is 11:44 GMT, which is 7:44 am EDT.  (Note that ILS incorrectly tweeted today, Thursday, that the launch is at 12:44 GMT. As Inmarsat’s website attests, it is at 12:44 BST, or 11:44 GMT).

The May 16, 2015 Proton failure 497 seconds after launch was attributed to an old design flaw that affects the turbopump for the rocket’s third stage steering engine.  In investigating this accident, Russia engineers determined that the same flaw caused a failure almost three decades ago, in 1988, that previously was thought to have been caused by a manufacturing defect. This year’s failure doomed Mexico’s MexSat-1 (Centenario) communications satellite, the second of three in that series.  The third is scheduled for launch on a Lockheed Martin Atlas V rocket in October 2015.

At the time of the MexSat-1 failure, the President of Inmarsat, Rupert Pearce, issued a statement sounding highly displeased since it was the third time the company’s Global Xpress system was encountering delays because of Proton failures.  Ironically, Pearce expressed relief that the company had another satellite under construction and a “potential” SpaceX launch in the second half of 2016 in case Proton was delayed for a long time or this return-to-flight failed.   A month later, SpaceX suffered its own launch failure and has not announced when it will resume launches.

Russia is developing a new series of rockets, Angara, to replace Proton and other Soviet-era launch vehicles, several of which have failed in recent years.  The May 16 Proton failure came on the heels of a Soyuz failure that placed the Progress M-27M spacecraft in the wrong orbit from which it quickly reentered.  SpacePolicyOnline.com’s fact sheet on Russian launch failures since December 2010 lists them.

Assuming all goes well, the Inmarsat-5 F3 satellite will reach geostationary orbit 15 hours and 31 minutes after liftoff, Inmarsat explains.  Once operational, it will join two previously launched satellites in providing Ka-band global high speed broadband network connectivity — the Global Xpress service.  This satellite will cover the Pacific Ocean region.  Inmarsat-5 F1 covers the Indian Ocean region, while Inmarsat-5 F2 covers the Americas and Atlantic Ocean region.  Both were launched by Proton rockets, in December 2013 and February 2015 respectively.