Soyuz launches on a military mission

A Soyuz-2-1b rocket launched a classified payload from the Plesetsk, north of Moscow, on Nov. 25, 2023, seemingly after a two-day delay.

Previous military launch: 2023 Dec. 21


Soyuz rocket mission on Nov. 25, 2023, at a glance:

Spacecraft designation
Launch date and time
2023 Nov. 25, 23:58:07 Moscow Time (3:58 p.m. EST)
Launch vehicle
Payload fairing
Launch site
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In mid-November 2023, Russian authorities issued a warning to air and sea traffic about an upcoming rocket launch between Nov. 23 and Nov. 27, 2023. It restricted several areas off the Russian Northern coast for impact of rocket components, which matched the ascent trajectory to an orbit with an inclination around 97 degrees toward the Equator.

On Nov. 25, 2023, or two days after the opening of the launch window, the Russian Ministry of Defense and Roskosmos announced that a Soyuz-2-1b rocket had lifted off from Plesetsk at 23:58:07 Moscow Time (3:58 p.m. EST) and successfully delivered a military satellite.

The official statement from the Ministry of Defense said that the spacecraft had been successfully inserted into its planned orbit and that it had been taken under control by ground assets of the Russian Air and Space Forces, VKS. The spacecraft maintained stable communications with ground control and its systems functioned nominally, the military said.


The expected ground track of the ascent trajectory for Soyuz rocket during launch on Nov. 25, 2023.

Although the ascent trajectory of the flight seemingly resembled the launches of the Bars-M military cartography satellites, subsequent developments hinted a different mission.

The US Space Force cataloged two objects in a 302 by 318-kilometer with an inclination 96.6 degrees toward the Equator, which were identified as Kosmos-2572 and the rocket stage (even though the Russian authorities had not yet released the official designation of the payload at the time):

Orbital period
2023-182A (COSMOS 2572)
90.75 minutes
96.63 degrees
322 kilometers
301 kilometers
2023-182B (SL-4 R/B)
90.72 minutes
96.63 degrees
318 kilometers
301 kilometers

The satellite was in a Sun synchronous orbit passing the ascending node (a point where the ground track of the orbit crosses the Equator from the Southern to Northern hemisphere) at 12:30 local time. (The Sun-synchronous orbit is often chosen to provide imaging satellites with consistent lighting conditions of photographed areas below their flight path.)

In the days following the launch, the tracking data indicated that the newly launched spacecraft had been losing altitude faster than the spent stage that delivered it into orbit. Barring the US Space Force mixing up the spacecraft and the rocket, it looked counterintuitive because the large empty booster would presumably encounter more friction from the rarified air at that altitude than would its more compact cargo. In the meantime, there were no signs of the orbit-raising maneuver typically performed by Bars-M satellites within a few days after the launch.

However, in early December 2023, there were signs that the orbit of the spacecraft (identified by the US Space Force as Object A) started decaying slower than before. The descent rate of more than one kilometer per day fell to just around half a kilometer per day by Dec. 4, 2023, possibly hinting the activation of the some kind of low-thrust propulsion system aboard the satellite such as ion engine, counteracting the decay, or the placement of the satellite into an attitude that help reduce the atmospheric drag. In the meantime, the presumed empty stage (Object B) from the mission continued spiraling down slightly more than half a kilometer per day.

The fact that the new satellite was launched on a more powerful Soyuz-2-1b rocket variant than the 2-1a version used in Bars-M missions pointed toward a heavier payload in a similar class as the seven-ton civilian Resurs-P imaging satellite. The payload fairing used in the Nov. 25, 2023, launch appeared to be common for both Bars-M and Resurs-P missions.

Starting on Dec. 6, 2023, tracking data indicated that the spacecraft had initiated a climb to a higher orbit. Within next three days, a perigee of its orbit increased from 293 to 299.6 kilometers and an apogee lifted from 312 to 322 kilometers.

By Dec. 22, 2023, after some decay of the orbit, the satellite boosted its apogee, entering the 286 by 317-kilometer orbit.


The article, graphics and illustrations by Anatoly Zak; Last update: May 20, 2024

Page editor: Alain Chabot; Last edit: December 2, 2023

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A Soyuz-2-1b rocket lifts off from Plesetsk on Nov. 25, 2023. Click to enlarge.