Soyuz-2 rocket launches the 60th GLONASS mission
The Russian military personnel launched a fresh satellite to replenish the nation's orbital navigation network. The 60th mission to deploy the GLONASS constellation lifted off from Plesetsk Cosmodrome on a Soyuz-2-1b/Fregat rocket on March 16, 2020. Slightly more than three and a half hours later, the GLONASS M-60 satellite was released into its circular orbit about 19,000 kilometers above the Earth's surface.
GLONASS-M No. 60 mission at a glance:
Preparing the mission
On January 29, 2020, ISS Reshetnev announced that the spacecraft for the 60th GLONASS-M mission had been delivered to the launch site. According to the company, the GLONASS-M satellite was placed into the processing building, where specialists from ISS Reshetnev would test the vehicle, install its solar panels and dock it to the adapter, which serves as an interface with the upper stage.
At the time, one more GLONASS-M satellite, manufactured around five years earlier, remained in storage at ISS Reshetnev and it would be the final spacecraft in the series to be launched before the transition to the new-generation GLONASS-K and GLONASS-K2 satellites, the company said.
The GLONASS M-60 mission reportedly used the oldest rocket available in storage.
GLONASS-M No. 60 launch profile
The mission followed the routine ascent profile of the GLONASS launches. After several seconds of vertical ascent, the launch vehicle headed southeast to reach an orbit with an inclination of 64.77 degrees toward the Equator. The four boosters of the first stage separated around two minutes into the flight and were expected to fall at drop zone S-19 in the eastern section of the Arkhangelsk Region. Around 45 seconds later, as the vehicle left the dense atmosphere, the payload fairing protecting the satellite was commanded to split into two halves and its fragments probably targeted the S-20 drop zone in the Komi Republic of Russia.
The second (core) stage of the rocket continued firing until around 4.7 minutes into the flight, separating moments after the ignition of the RD-0124 engine on the third stage. Seconds later, the cylindrical aft section of the third stage split into three segments and separated as well. The core stage and the fragments of the aft section likely fell at the S-21 drop zone in the Omsk Region.
The third stage of the rocket completed its powered ascent and separated from the payload section nine minutes and 22 seconds after liftoff. Just short of orbital velocity, the third stage was intended to naturally reenter the Earth's atmosphere near the opposite side of the Earth from the launch site, with its flaming remnants projected to fall into the southern section of the Pacific Ocean.
Shortly after planned liftoff time, the Russian media confirmed the fact of the launch. Quoting a Ministry of Defense announcement, the reports said that all pre-launch operations and the liftoff of the Soyuz-2-1b rocket at 21:28 Moscow Time had gone as planned and the assets of the ground control complex had began monitoring the liftoff and the flight of the rocket at 21:30 Moscow Time. Shortly thereafter, the normal separation of the Fregat upper stage with the GLONASS-M satellite was confimed as taken place at 21:38 Moscow Time.
Space tug maneuvers
During GLONASS missions, the Fregat-M upper stage conducts three orbital maneuvers to deliver the spacecraft to its operational circular orbit more than 19,000 kilometers above the Earth's surface.
The first firing of the Fregat's main engine, lasting around 20 seconds, is initiated around a minute after the separation from the third stage. The maneuver inserts the stack into an initial parking orbit and, after a less-than-half-an-hour passive flight, the Fregat fires its main engine again, this time for around 9.5 minutes. The second maneuver stretches the original near-circular orbit, boosting its apogee (highest point) to a target altitude of more than 19,000 kilometers. The Fregat/GLONASS stack then climbs that trajectory for more than 2.5 hours before firing again. The third Fregat maneuver at apogee, lasting just under four minutes, makes the orbit circular, and should be followed by the separation of the satellite around 30 seconds after the completion of the maneuver.
Shortly after planned separation of the GLONASS-M No. 60 satellite, the Russian Ministry of Defense declared the launch a success. According to the military, ground control established and maintained reliable telemetry communications with the satellite and all its systems functioned nominally.
Upon the release of the satellite, Fregat is programmed to conduct two maneuvers with its attitude-control thrusters, SOZ, to enter a burial orbit above its former satellite passenger.
Roskosmos declared the GLONASS-M No. 760 spacecraft operational on April 14, 2020.
An artist rendering of the Uragan-M (GLONASS-M) satellite in deployed configuration. Credit: ISS Reshetnev
Fregat upper stage boosts Uragan (GLONASS-M) satellite into an initial orbit. Click to enlarge. Copyright © 2017 Anatoly Zak
Fregat and GLONASS-M satellite approach the release orbit. Click to enlarge. Copyright © 2017 Anatoly Zak
GLONASS-M satellite separates from the Fregat upper stage. Click to enlarge. Copyright © 2017 Anatoly Zak