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Sixth GLONASS-K satellite lifts off Russia has launched a fresh satellite to replenish its orbital navigation network along with small experimental spacecraft. The GLONASS-K No. 18 and Mozhaets-6 satellites lifted off on a Soyuz rocket from the Plesetsk launch site in the morning of Sept. 13, 2025.
GLONASS-K No. 18L mission at a glance:
Fourth GLONASS-K mission In early September 2025, Russian authorities announced flight and sea navigation restrictions in the Western Pacific, which matched the deorbiting zone for a Fregat upper stage after delivering GLONASS satellites launched from Plesetsk on a Soyuz-2 rocket. The danger areas were timed for the early hours on Sept. 13 and Sept. 14, 2025. At the time, the GLONASS-K No. 18L satellite was known to be in the pipeline for launch in the second half of 2025. GLONASS-K No. 18L became the sixth satellite in this particular line of upgrades of Russian navigation satellites, designed to replace the GLONASS-M variant. Within days after the first restrictions in the international waters were announced, the authorities in the Tyumen Region of Russia warned about the planned impact of rocket debris in the Uvatsky District on September 13. Repeating a pattern from launches of GLONASS-K No 13 and 14, the local government statement confirmed that the GLONASS-K No. 18L would be the payload of the launch in question, even though there were no such confirmations from the Ministry of Defense Another warning on the same date was issued for a remote area of the Pacific, south of Auckland, New Zealand, which was appropriate for the impact of the third stage of a Soyuz rocket reentering the atmosphere after a suborbital hop just short of orbital velocity. Finally, the emergency service in the Komi Republic of Russia declared danger areas for a period from September 12 to 14 at the routinely used Vashka and Zheleznodorozhny impact sites, which covered Udorsky, Knyazhpogostsky and Kortkerossky districts. The same sites were used in the previous GLONASS launch. Flight profile The liftoff of the Soyuz 2-1b/Fregat rocket with the sixth GLONASS-K satellite took place as scheduled on Sept. 13, 2025, from Site 43 in Plesetsk. The launch likely emulated the flight profile of the previous missions. Under that scenario, after several seconds of vertical ascent, the launch vehicle heads southeast to align its ground track with an orbit inclined 64.77 degrees toward the Equator. The four boosters of the first stage separate around two minutes into the flight and then fall in the Komi Republic. Around 45 seconds later, the payload fairing protecting the satellite is commanded to split into two halves and drops off right after the vehicle exits the discernible atmosphere. The second (core) stage of the rocket continues 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 splits into three segments and separates as well. All the fragments resulting from the separation of the second and third stage then fall in the Tobolsk and Uvatsk districts of the Tyumen Oblast (region). The third stage of the rocket completes its powered ascent and separates from the payload section nine minutes and 22 seconds after liftoff. Flying just short of orbital velocity, the nearly empty booster naturally reenters 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. Within 20 minutes after the liftoff, the official Russian media posted a statement from the Russian military confirming the launch carrying a "spacecraft for the Ministry of Defense and the Mozhaets-6 educational research satellite." The latter spacecraft was intended for testing algorithms of celestial navigation, the Ministry of Defense said. The Mozhaets series had been traditionally developed at the Mozhaisky Military Academy. Space tug maneuvers During a typical GLONASS mission, the Fregat 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 at the newly reached altitude and it should be followed by the separation of the satellite around 30 seconds after the completion of the maneuver. Upon the release of the satellite, Fregat is usually programmed to conduct two maneuvers with its attitude-control thrusters, SOZ, to enter a burial orbit above its former satellite passenger or to reenter the Earth's atmosphere. Around five hours after the launch, the Ministry of Defense reported that both payloads had been delivered into their orbits on time. Roskosmos also reported that the spacecraft were designated Kosmos-2595 and Kosmos-2596.
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