Soyuz-2-1v launches a possible military inspector satellite

Russian military launched a Soyuz-2-1v/Volga rocket from Site 43 in Plesetsk, delivering a classified cargo into orbit on November 25, 2019. It was the sixth mission of the Soyuz-2-1v variant since its introduction in 2013.


Kosmos-2542 mission at a glance:

Kosmos-2542 (14F150 No. 2), Kosmos-2543
Launch date and time
2019 November 25, 20:52:03.401 Moscow Time
Launch vehicle
Upper stage
Payload fairing
98KS No. 78072004
Launch site



Preparations for the mission

On November 18, 2019, Russian authorities issued notifications for air traffic to avoid areas of the Arctic Ocean north of the Kola Peninsula and south of the Spitsbergen Archipelago. Another warning came for a large swath of the Pacific Ocean. The designated areas matched the impact sites used by previous launches of the Soyuz-2-1v rocket with the Volga upper stage from Plesetsk, in particular the delivery of the 14F150 payload in June 2017.

According to the notifications, the launch was expected on November 25, 2019, between 20:30 and 22:00 Moscow Time. The launch vehicle was expected to ascent along the following ground track to enter orbit:


Timeline of the Kosmos-2542 launch on November 25, 2019:

Moscow Time
12:52 p.m.
Stage I separation
12:54 p.m.
Payload section separation from the second stage
12:59 p.m.
Volga upper stage firing 1 to form transfer orbit
1:45 p.m.
Volga upper stage firing 2 to form spacecraft release orbit
3:35 p.m.
Spacecraft separation
4:04 p.m.
Volga upper stage deorbiting maneuver
12:35 a.m.*
Volga upper stage reenters the Earth's atmosphere
1:09 a.m.*

*November 26, 2019

Kosmos-2542 enters orbit

According to the official Russian media quoting the Ministry of Defense, the Soyuz-2-1v rocket lifted off on November 25, 2019, at 20:52 Moscow Time and ground assets of the Titov Chief Test Space Center, GIKTs, of the nation's Air and Space Forces began tracking the vehicle at 20:54 Moscow Time.

Around half an hour later, the official media announced that the payload section, including the Volga upper stage and the spacecraft, had separated from the second stage of the launch vehicle as planned at 21:00 Moscow Time.

Before the end of the day on November 25, the Ministry of Defense announced that the Volga upper stage had successfully delivered the military satellite in its planned orbit at the scheduled time. According to the Russian military, the newly launched satellite was based on a standard platform which can perform monitoring of the condition of Russian satellites. The optical equipment also allows the spacecraft to conduct imaging of the Earth's surface, the Interfax quoted the Ministry of Defense as saying.

The wording of the statement seemed to be hinting that the second mission in the 14F150 project had been underway, following the original launch in 2017, which was also officially described as having orbital inspection capabilities. Because the distinct feature of the 2017 launch was the subsequent release of additional satellites from the primary payload, the appearance of similar sub-satellites after the latest launch should provide more clues about the nature of the mission.

Several hours after the launch, the US Space Command, USSPACECOM, released orbital elements for three objects associated with the mission which likely represented the payload, the second stage of the Soyuz-2-1v rocket and the Volga upper stage:

Object ID
Orbital period
2019-079A 44797 (Kosmos-2542)
97.902 degrees
96.95 minutes
368 kilometers
858 kilometers
2019-079B 44798 (Volga stage)
97.902 degrees
96.93 minutes
367 kilometers
857 kilometers
2019-079C 44799 (Soyuz' second stage)
97.913 degrees
91.50 minutes
289 kilometers
364 kilometers

On the morning of November 26, the official TASS news agency reported quoting the Ministry of Defense that "specialists of the Titov Chief Space Center, GIKTs, completed the operations for removal of the Volga upper stage from the target orbit of the spacecraft of the Ministry of Defense and its sinking in the Pacific Ocean."

In reality, around 8.5 hours after releasing its payload, the Volga upper stage initiated a pre-programmed deorbiting maneuver which resulted in its decay at an altitude of around 100 kilometers over the Pacific Ocean at 09:09 Moscow Time (1:09 a.m. EST) on November 26, 2019.

Kosmos-2542 releases an orbital inspector

On December 6, 2019, the Russian Ministry of Defense announced that a small sub-satellite had separated from the multi-functional platform in orbit. In the course of the experiment, visual information is being transmitted to the ground processing facilities in order to assess the technical status of the spacecraft under observation, the Ministry of Defense said. According to the announcement, the experiment was conducted on December 6.

At the time, the newly released vehicle was tracked in a 368 by 858-kilometer orbit with an inclination 97.895 degrees toward the Equator and a period of 96.95 minutes.

By December 9, the US radar detected the first maneuver of the new satellite, designated 2019-079D in the US and Kosmos-2543 in Russia, which boosted its perigee by four kilometers. By mid-December 2019, the sub-satellite boosted its perigee by 55 kilometers. Because the mother vehicle entered orbit within one degree of inclination from the USA-245 classified satellite launched by the United States, observers immediately suspected an attempt by the Russian pair to intercept and inspect the American spacecraft. Interestingly, according to a satellite observer Nico Janssen, between December 9 and December 10, USA-245 left its 272 by 985-kilometer orbit and maneuvered somewhere else, possibly attempting to prevent a close encounter with the newly released Kosmos-2543, which climbed to a 590 by 859-kilometer orbit.

On January 29, 2020, Janssen wrote on SeeSat mailing list that while Kosmos-2543 had remained in its practically unchanged 586 by 861-kilometer orbit, Kosmos-2542 climbed to a 369 by 915-kilometer orbit. At the time (around January 23), the USA-245 satellite was tracked in a 283 by 1,002-kilometer orbit. Janssen concluded that the orbital planes of the Russian and American spacecraft differed by just 0.55 degrees and their orbital periods had only a one-second difference.

According to Janssen, by February 19, 2020, the USA-245 made a couple of small maneuvers resulting in a 269 by 1,018-kilometer orbit. At the same time, Kosmos-2542 was in a 371 by 915-kilometer orbit, still synchronized with that of USA-245, Janssen wrote. The inclination difference between the two satellites was around 0.3 degrees and the physical separation between them varied from 655 to 1,341 kilometers, according to Janssen's observations. He predicted that the distance would increase in several days, before decreasing again to between 539 and 1,210 kilometers by the end of the month.

In the meantime, Janssen also tracked Kosmos-2543 in the 588 by 861-kilometer orbit, mostly matching its parameters nearly a month earlier. Its inclination difference with USA-245 was around 2.4 degrees apart and the distance between the two satellites varied from 10,160 and 11,241 kilometers, Janssen said. According to his predictions, on February 22, the two spacecraft were to fly within 221 and 421 kilometers from each other and on February 26, they would pass as close as 153 and 790 kilometers.

Russian journalist Igor Lissov compared observations of USA-245 by Janssen with orbital parameters of Kosmos-2542 published by the US Space Command, USSPACECOM. Writing on the Novosti Kosmonavtiki web forum, Lissov noted that radio-tracking used by Janssen provides accurate measurement of the orbital period, but that method is ill-suited for determining the shape of the orbit. Lissov argued that the accuracy of observations afforded by radio-tracking had allowed to confirm with certainty only one maneuver of the American satellite since December 2019, which Lissov approximated as taking place between January 31 and February 8, 2020. Lissov doubted the probability of a significant maneuver by USA-245 in January 2020, excluding a possible minor orbit adjustment to counteract atmospheric drag.

Given the uncertainty with timing of each maneuver, Lissov questioned which satellite was an actual hunter and which one was being followed.

According to Janssen, the USA-245 satellite raised its orbit by a few kilometers on March 5, 2020, resulting in desynchronization of its path with that of Kosmos-2542 and an ever-increasing distance between the two spacecraft. In the meantime, Kosmos-2542 was slowly lowering its orbit, transitioning from 372 by 913- to 331 by 911-kilometer orbit, according to Janssen. He predicted that without further maneuvers, the distance between the two satellites would temporarily decrease to 139 kilometers on May 1, 2020.

At the same time, Kosmos-2543 remained in its 589 by 859-kilometer orbit making minimal passes by USA-245 every four days, Janssen said. He expected that on May 27, 2020, the two satellites would pass within 30 kilometers from each other.

However, according to orbital tracking, between April 21 and April 26, 2020, Object-A (Kosmos-2542) lowered its perigee to 300 kilometers and, therefore, no longer had synchronization with USA-254. The spacecraft was in the 303 by 903-kilometer orbit.

Inspector meets a Russian target

In the middle of June 2020, independent observers saw Kosmos-2543 making another rendezvous, this time, with Kosmos-2535, launched on July 10, 2019.

According to tracking data, Kosmos-2543 made at least six maneuvers between June 4 and June 10, descending to a 591 by 631-kilometer orbit, which alternated the chaser's position from being ahead to trailing its rendezvous target. The orbital plane of Kosmos-2543, which drifted from December 16, 2019, pushed the local time of its descending node from 09:41 to 09:08 UTC and, by June 8, 2020, it got finally synchronized with the orbital plane of Kosmos-2535, a Russian space historian Igor Lissov wrote. According to Lissov by June 15, 2020, Kosmos-2543 and Kosmos-2535 were around 60 kilometers apart and were in orbits with the following parameters:

Kosmos-2543 (inspector)
590.8 kilometers
630.7 kilometers
Kosmos-2535 (target)
605.3 kilometers
616.1 kilometers

On the same day (June 15), Kosmos-2543 maneuvered again to match its apogee and perigee with those of Kosmos-2535. Then, on June 21, the inspector slightly boosted its perigee. According the publicly available two-line elements, TLEs, analyzed by Igor Lissov, on June 17, 2020, the two satellites were less than 100 meters from each other and their minimum relative speed was less than 10 centimeters per second as of 13:00 UTC on that day. Although, the known accuracy of the tracking data is lower than possible differences in orbital parameters between the two satellites, the fact of a very close rendezvous (between the inspector and its target) could hardly be doubted, Lissov wrote. As of June 22, 2020, there were no noticeable changes in the the orbital motion of the two objects following their rendezvous, according to Lissov.

On July 15, 2020, the Russian Ministry of Defense officially confirmed that its small inspector satellite had conducted a close-proximity evaluation of another Russian satellite in orbit. The inspection produced valuable information and images of the target vehicle and the resulting information had been transmitted to ground stations, the Russian military said. The statement clearly referred to the rendezvous between Kosmos-2543 and Kosmos-2535.

Soon after the Russian announcement, the US Space Command published orbital data for Object 45915, which separated from Kosmos-2543 on July 15, 2020, around 07:50 UTC at a considerable velocity relative to its host satellite, according to space historian Jonathan McDowell. The newly discovered object was tracked in the 784 by 505-kilometer orbit with an inclination 97.87 degrees toward the Equator and identified as Object E, which linked its origin to Kosmos-2543. As of July 18, te US Space Command classified the type of object as "to be determined."

Following its proximity operations near Kosmos-2535, the alleged inspector satellite -- Kosmos-2543 -- was seen drifting away in September 2020, Nico Janssen wrote on September 19, 2020.

Russian "inspector" makes new close encounters with US milsat

Continuing its mysterious activities in Earth's orbit, the presumed Russian "Inspector" satellite – Kosmos-2542 – made another rendezvous with its favorite American target.

During the Summer 2021, Kosmos-2542 had maneuvered to re-synchronize its orbit with that of the USA-245 military satellite, Nico Janssen, independent satellite observer, said on August 25. The maneuvers resulted in multiple close encounters between the Russian and US spacecraft. According to Janssen, on August 2, Kosmos-2542 passed as close as 34 kilometers from USA-245, and on Aug. 13, 2021, it was within 53 kilometer from its purported target.

Kosmos-2542 and -2543 remained in orbit until the end of 2023, but during that year their orbits were naturally decaying without signs of maneuvers:

Orbit, Jan. 1, 2023
Orbit, Oct. 7, 2023
295 x 522 kilometers
302 x 307 kilometers
416 x 531 kilometer
394 x 480 kilometers
Object E
503 x 777 kilometers
502 x 768 kilometers

By Oct. 23, 2023, Kosmos-2542 descended to a 189 by 201-kilometer orbit and was losing between 20 and 25 kilometer per day, and, finally reentered the next day around 10:07 UTC over Samara, Russia.


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This page is maintained by Anatoly Zak; Last update: October 25, 2023

Page editor: Alain Chabot; Last edit: November 26, 2019

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A Soyuz-2-1v rocket is being prepared for rollout from the vehicle assembly building in Plesetsk in November 2019. Click to enlarge. Credit: Russian Ministry of Defense


Click to enlarge. Credit: Russian Ministry of Defense


A Soyuz-2-1v rocket arrives at launch pad in Plesetsk in November 2019. Click to enlarge. Credit: Russian Ministry of Defense


A Soyuz-2-1v rocket is being erected on the launch pad in Plesetsk in November 2019. Click to enlarge. Credit: Russian Ministry of Defense


A Soyuz-2-1v rocket moments before liftoff on November 25, 2019. Click to enlarge. Credit: Russian Ministry of Defense