WASHINGTON — Satellite operator Inmarsat of London said the launch of its third Global Xpress Ka-band broadband satellite, long delayed by reliability issues with the Russian-built Proton rocket, is now scheduled for Aug. 28 from the Baikonur Cosmodrome in Kazakhstan.

The satellite will round out Inmarsat’s billion-dollar Global Xpress constellation, designed to provide broadband services to mobile and fixed-site users around the world. The system, intended for both commercial and government markets, is compatible with the U.S. Air Force’s Ka- and X-band Wideband Global Satcom system.

Global Xpress, Inmarsat’s first foray into Ka-band services, is over a year behind schedule due largely to reliability issues in recent years with the Proton, which is built by Khrunichev State Research and Production Space Center of Moscow and marketed commercially by International Launch Services of Reston, Virginia. The rocket’s most recent failure occurred in May and destroyed a telecommunications satellite built for the Mexican government.

A failure review board led by the Russian space agency concluded that the failure was the result of a faulty bracket holding a third-stage steering engine turbopump that failed during flight, causing a loss of vehicle control. ILS announced Aug. 3 that it had signed off on the findings and would resume commercial missions, beginning with the third Global Xpress satellite, in late August or early September.

Inmarsat booked all three Global Xpress launches on Proton rockets. The first launched in December 2013 and the second followed this past February.

Warren Ferster is the Editor-in-Chief of SpaceNews and is responsible for all the news and editorial coverage in the weekly newspaper, the spacenews.com Web site and variety of specialty publications such as show dailies. He manages a staff of seven reporters...