Intelsat-31, communication satellite delivered to SSTO yesterday on atop of Proton-M, was deployed successfully by Briz-M upper stage.
After five burns of S5.98 engine and 15 hours in space, Briz-M deployed Intelsat-31 on altitude of 65000 km at T+15h31′ over New Guinea. Roscosmos confirmed that satellite was deployed on correct orbit and is operating correctly; spokesman of State Corporation Roscosmos told in official announcement:
“The separation of the satellite from the booster took place on time,”
It was second launch of the Proton-M in 2016 and next success of International Launch Services which is operating Proton-M from Baikonur cosmodrome. Mission duration was extremely long not without reason. Impressive range of Briz-M and its independent guidance, navigation, control system and ability of multiple restarting its engine were utilized to reduce fuel necessary for apogee kick motor. It results in extended life of satellite which is limited by fuel load. Deploying satellite was performed around ten minutes after last fifth burn at 22:40 GMT.
Spotted during launch prolonged time of first burn of Briz-M was result of anomaly in the second stage of the Proton. According to telemetry data from Khrunichev State Research and Production Space Center, manufacturer of the Proton-M, Briz-M had lower than planned insertion speed (for 28.2 m/s). To deliver weighing 6320 kg satellite to 173 km parking orbit it was necessary to extend first burn of Briz-M for about 33 seconds. Briz-M was able to extend its burn time using own telemetry and control system without intervention from ground control center. Anomaly was confirmed by Roscosmos to interview given to Russian Interfax news agency. Spotted issues with second stage will be investigated by special State commission.
UPDATE: It was confirmed by Roscosmos that only one from four engines in second stage of Proton-M stopped operating earlier.