The payload section of the Soyuz rocket with 34 OneWeb satellites. Credit: Arianespace
Full assembled OneWeb satellites. Click to enlarge. Credit: OneWeb
The cluster of 34 OneWeb satellites is being integrated with a Fregat-M upper stage. Click to enlarge. Credit: Arianespace
Soyuz rocket shortly before liftoff on Feb. 7, 2020. Click to enlarge. Credit: Arianespace
Soyuz-2-1b lifts off from Baikonur with 34 OneWeb satellites on February 7, 2020. Click to enlarge. Credit: Arianespace
Rendering of Fregat upper stage with 34 OneWeb satellites during a passive flight in the initial orbit. Click to enlarge. Credit: Arianespace
Soyuz launches second OneWeb cluster
After the scrub of a Meridian mission from Plesetsk in January, Russia's first orbital launch attempt of 2020 fell on another Soyuz rocket, this time loaded with 34 satellites for the OneWeb constellation. The second mission to deploy the low-orbital Internet constellation lifted off from Baikonur Cosmodrome in Kazakhstan in early hours of February 7.
The second Soyuz mission with OneWeb satellites, ST27, at a glance:
Preparing the second OneWeb mission
While the original OneWeb mission from Kourou in 2019 delivered only six satellites, the second launch of a Soyuz rocket for the Internet constellation was to carry a load of 34 spacecraft from Baikonur for the first time, boosting the company's orbital assets to 40 satellites. (Up to 36 satellites maximum could be carried on such missions from Vostochny). It would be one of 21 Soyuz launches contracted by OneWeb to Arianespace for the first phase of the constellation's deployment. In February 2020, Arianespace said that up to eight Soyuz mission with OneWeb satellite clusters could fly from the Baikonur and Vostochny spaceports before the end of the year.
Arianespace designated the mission ST27 to denote the 27th commercial launch conducted by the company and its Starsem affiliate from Baikonur.
The launch was previously scheduled in November 2019, but by September of that year, it was postponed to December. According to the Russian media, the delays were associated with the post-production testing of the satellites.
On September 19, 2019, NPO Lavochkin announced the delivery of three Fregat-M upper stages to Baikonur in preparation for OneWeb missions. It would be the first Baikonur launches of the Fregat-M variant, which had previously flown only on missions originating from Kourou. By that time, the launch was re-scheduled for January 30, 2020. However, around the time when the first batch of OneWeb satellites was delivered to Baikonur from their manufacturing plant in Florida on December 16, 2019, the mission was postponed to February 8 and, was then set for February 7, 2020. The second batch of OneWeb satellites made it to Baikonur around January 17, 2020.
The initial processing of OneWeb spacecraft in Baikonur was conducted at a clean room facility completed in 1998 inside the former assembly building for the N1-L3 lunar complex and the Energia-Buran system at Site 112. Operated by Starsem, the clean room survived the roof collapse in the adjacent hall in 2002, which destroyed the historic Buran orbiter. Inside the Starsem facility, OneWeb satellites were attached to a custom-designed payload dispenser developed by RUAG Space AB of Linköping, Sweden, which in turn, was mounted on the Fregat-M.
On January 29, 2020, the payload section was transferred from Site 112 to Site 31 for integration with the launch vehicle. The rollout of the fully assembled vehicle to the launch pad took place on the morning of February 3, 2020.
The initial launch period was extending from February 7 to February 11, 2020, with daily 20-minute windows, which, in case of 24-hour delays would drift forward five minutes each day.
Soyuz-2-1b rocket with 34 OneWeb satellites is being erected on the launch pad on February 3, 2020.
Planned countdown milestones for the ST27 mission on Feb. 6, 2020, according to Arianespace:
Initial launch profile
After a few seconds of vertical ascent from the snow-covered pad, the launch vehicle began heading northward, across Russia to align its ascent trajectory with a near-polar orbit inclined 87.4 degrees toward the plane of the Equator.
The four boosters of the first stage separated 1 minute and 58 seconds after liftoff, but the core booster of the second stage continued firing until 4 minutes and 48 seconds into the flight. It separated moments after the ignition of the third stage. Two seconds later, the payload fairing, which protected the payload in the dense atmosphere, split in the two fragments and fell off.
The third stage fired until 9 minutes and 23 seconds into the flight, releasing the Fregat upper stage and its cargo on a ballistic trajectory with a highest point 191 kilometers above the Earth's surface, but just short of orbital velocity. It allowed the third stage to reenter and fall into a projected area of the Arctic Ocean, north of the Canadian coast.
Exactly one minute after the separation from the third stage, the Fregat fired its main engine for 4 minutes and 11 seconds to enter a transfer elliptical (egg-shaped) orbit with the lowest point (perigee) 140 kilometers above the Earth and the highest point (apogee) 425 kilometers above's the Earth's surface, which is near the target altitude for the release of OneWeb satellites.
Upper stage maneuvers
After its first maneuver, the Fregat climbed passively for nearly an hour. Upon reaching the apogee of the transfer trajectory, Fregat re-ignited its engine for 34 seconds to make its orbit circular at an altitude of around 450 kilometers.
Then, 1 hour 11 minutes and 40 seconds after launch, the first pair of OneWeb satellites was released in opposite directions from their dispenser.
In the following 15 minutes, Fregat made a 15-second burn with its small attitude control thrusters to get in position for another release around three minutes later, this time, of four satellites. The Fregat was then programmed to repeat its thruster firing and release routine seven more times, evenly distributing the quartets of satellites along their orbit. The final four of 34 passengers were scheduled to be off their space tug 3 hours and 45 minutes after their liftoff from Baikonur.
Around 1 hour and 20 minutes after the release of the final quartet, the Fregat was programmed to initiate a braking maneuver which was designed to push the stage on a disposal orbit, resulting in its quick destruction in the upper atmosphere nearly six hours after launch.
Following their release, the satellites were expected to maneuver to their operational positions 1,200 kilometers above the Earth's surface, using onboard electric thrusters.
The satellites initially climbed to altitudes ranging from 550 to 700 kilometers in April 2020, followed by another series of maneuvers starting in August 2020. Most members of the group arrived at the planned altitude range in early November 2020.
The ST27 mission timeline on February 7, 2020: