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|Proton launches the final Blagovest satellite
The third mission of the Proton rocket in 2019 delivered the fourth and final satellite for the Blagovest constellation of military communications spacecraft in geostationary orbit 36,000 kilometers above the Earth's surface. The liftoff took place in the early hours of August 6 (Moscow Time) and the orbital insertion was successfully completed in around nine hours, according to Roskosmos.
Blagovest No. 14L mission at a glance:
Preparing the fourth Blagovest mission
As of August 2018, the launch of the fourth Blagovest satellite was expected in the first quarter of 2019, but by the end of 2018, the mission slipped to May or June 2019. A May 17 launch date was initially reported but by the end of March 2019, the mission was postponed until a period between May 24 and 25.
By the middle of April 2019, the launch was postponed to July 16 and by the end of June, it slipped to August 6 of the same year.
On August 1, Head of Roskosmos Dmitry Rogozin announced that the State Commission had approved the rollout of the Proton vehicle with the Blagovest satellite to the launch pad on the morning of the following day. Based on reports in the Kazakh press on August 2, the rocket arrived at the launch as planned.
How Blagovest was launched
A Proton-M rocket with a Briz-M upper stage carrying Blagovest No. 14L lifted off from Pad 24 at Site 81 in Baikonur Cosmodrome on August 6, 2019, at 00:56:00.008 Moscow Time (5:56 p.m. EDT on August 5). According to the flight plan, the first stage operated for two minutes before separating and the second stage separated five minutes and 27 seconds into the flight. The third stage then took over the powered ascent and 16 seconds later, the payload fairing protecting the Blagovest satellite split into two segments and fall off the rocket.
The third stage was programmed to continue firing until nine minutes and 40 seconds into the flight, releasing the payload section, including the upper stage and the satellite, into a ballistic trajectory just short of orbital velocity and matching an inclination of 51.55 degrees toward the Equator.
Around 15 minutes after the scheduled launch, the official Interfax news agency reported that the rocket had lifted off with a military spacecraft. The agency quoted military officials as saying that all pre-launch operations and the liftoff of the launch vehicle had gone as scheduled. According to the Ministry of Defense, the overall control of the mission was conducted by ground assets of the Titov Chief Test Space Center of the VKS, whose ground assets began tracking the vehicle at 01:01 Moscow Time. The military also confirmed that the payload section successfully separated from the third stage at 01:06 Moscow Time on August 6, 2019.
Upper stage maneuvers
Just 94 seconds after the separation from the third stage, the Briz-M was programmed to fire its own engine for 4.1 minutes to reach an initial parking orbit with an altitude of 180 kilometers and an inclination of 51.56 degrees. It then made a 52-minute swing around the Earth before firing again, this time for 17.7 minutes. The maneuver was designed to push the stack into a highly elliptical 272 by 5,007-kilometer orbit and reduce the inclination to 50.3 degrees. The vehicle then passively climbed the new transfer orbit for more than two hours.
When the stack reached the point where the transfer orbit crosses the equatorial plane from Northern to Southern Hemisphere (known as ascending node), the Briz-M's engine was to fire again for 17.9 minutes, this time, stretching the orbit so that its apogee (the highest point) ended up at the altitude of the geostationary orbit 35,808.5 kilometers above the Earth's surface. The same maneuver was also designed to live the perigee at an altitude of 390 kilometers, while the inclination was to be reduced to 48.7 degrees. Around 1.4 minutes after the third maneuver, the space tug was to jettison its nearly empty external tank.
The remaining stack then climbed passively for five hours, before Briz-M had to initiate its fourth and final engine firing lasting 13.3 minutes.
The fourth maneuver was designed to circularize the orbit and tilt the orbital inclination to match the plane of the Equator, getting the spacecraft ready for separation from Briz slightly more than a minute after the fourth Briz firing and 9 hours and 3 minutes after launch. The satellite was expected to end up in the orbit with a period of 86,164 seconds (or nearly 24 hours), which would make it appear fixed in the sky for an observer on Earth. At the time of separation, Blagovest was programmed to maintain its attitude in space along all three axis in the position acquired at the completion of the Briz M's firing.
Around 2.2 hours after parting with the satellite, the upper stage would perform 15- and 100-second maneuvers with an interval of around 1.1 hours to enter a burial orbit before its onboard batteries expire 12.7 hours into the flight.
At 10:15 Moscow Time on August 6, 2019, Roskosmos posted a statement that the Proton rocket successfully delivered a spacecraft for the Ministry of Defense into planned orbit at scheduled time. "The launch of the vehicle and the orbital insertion of the satellite went as schedule," the announcement said, "The spacecraft was taken under control by the ground assets of the Titov Chief Test Space Center of the Space Forces within the Air and Space Forces."
Upon reaching orbit, the spacecraft received an official name – Kosmos-2539.
Blagovest No. 14L's planned launch timeline on August 6, 2019:
Blagovest satellite. Credit: ISS Reshetnev