OneWeb will resume the deployment of its satellite constellation with the launch of 36 satellites aboard India’s GSLV Mk.III rocket. The mission – which marks the first commercial launch for the GSLV – is due to lift off from the Satish Dhawan Space Centre at 12:07 AM local time on Sunday, Oct. 23 (18:37 UTC on Saturday, Oct. 22).
The Geosynchronous Satellite Launch Vehicle Mk.III (GSLV Mk.III), also known as LVM3, is India’s largest and most powerful rocket. It will be making its fifth flight and fourth orbital launch with this mission, having first flown in 2014. The payload, a cluster of 36 OneWeb communications satellites, is bound for low Earth orbit (LEO) – a new destination for the GSLV Mk.III rocket.
The OneWeb launch will be conducted by the Indian Space Research Organisation (ISRO) through its commercial arm, NewSpace India Limited (NSIL). OneWeb signed an initial letter of intent with NSIL last October, covering launches on both GSLV Mk.III and the smaller Polar Satellite Launch Vehicle (PSLV). A firm contract for two launches was announced in April – with this first launch going from contract signing to the launch pad in barely six months.
OneWeb was founded in 2012 by Greg Wyler, an American businessman who had previously founded O3b Networks, who planned to use a large constellation of low-orbiting satellites to provide high-speed internet access around the world. OneWeb sees businesses and government users as its target customers, unlike similar offerings from other companies – such as SpaceX’s Starlink – which target the consumer market.
Once complete, OneWeb’s initial constellation will consist of 648 satellites: 12 planes with 49 satellites in each, plus on-orbit spares. The satellites are being built in a dedicated facility set up in partnership between OneWeb and Airbus Defence and Space, located near Cape Canaveral, Florida.
Each OneWeb satellite has a mass of 147 kilograms and an anticipated operational lifespan of at least seven years. The first six satellites were launched in February 2019 to perform initial on-orbit testing and validation. Two operational launches – with 34 satellites apiece – followed in February and March 2020, before OneWeb filed for bankruptcy at the end of March. It was later acquired by a consortium led by the British government and India’s Bharti Enterprises Ltd., allowing OneWeb to emerge from bankruptcy in November 2020 and resume launches in December.
Earlier this year, OneWeb and French telecommunications operator Eutelsat announced that they would merge. Subject to approval, the merger is expected to be completed next year and will see OneWeb’s LEO fleet operate alongside Eutelsat’s extensive network of geostationary communications satellites.
The GSLV Mk.III launch is the 14th mission to build OneWeb’s constellation. OneWeb had previously been using Russia’s Soyuz rocket, contracted through Arianespace and its subsidiary Starsem, to launch its satellites. These had been gathering pace since resuming after OneWeb’s bankruptcy, passing the halfway point in deploying the initial constellation last October.
This year, however, OneWeb’s constellation deployment has been severely disrupted by Russia’s war against Ukraine and the knock-on effects to the international partnerships that Russia had formerly been engaged in with OneWeb.
When Russia invaded Ukraine in late February, preparations were well underway for a Soyuz launch from Baikonur, then scheduled for March 5, which was to have deployed another 36 OneWeb satellites. This became an early flashpoint in tensions between Russia and the West, with Russia demanding that the British government give up its stake in OneWeb and that OneWeb itself provide a guarantee that the satellites would not be used for military purposes. When their ultimatum was not met, Russia announced the launch’s cancellation.
The rocket, already at the launch pad, was rolled back to the assembly building and destacked, with the satellites being secured in a cleanroom at Baikonur. OneWeb’s deployment – previously averaging a launch every one to two months – came to a halt as the company looked for new launch partners. In addition to the two GSLV Mk.III launches it has signed with ISRO and NSIL, OneWeb has also agreed to a three-launch deal with SpaceX on its Falcon 9 rocket, with these five missions expected to deploy enough satellites to finish the initial constellation.
When launching aboard GSLV Mk.III, the 36 OneWeb satellites will be deployed using a lightly modified version of the 36-satellite dispenser previously used on Soyuz. This was developed by Beyond Gravity – a subsidiary of the Swiss RUAG group – and provided by Arianespace, who are supporting the mission.
This OneWeb launch campaign began with the arrival of its satellites at the Satish Dhawan Space Centre in India in mid-September. The end of the month saw work begin to mate the spacecraft with their dispenser, and this was completed by early October. ISRO, meanwhile, was at work building up the GSLV rocket atop its mobile launch platform. After encapsulation within the payload fairing, the satellites were transported to the assembly building and integrated atop the rocket.
Rollout to the Second Launch Pad (SLP) took place on Oct. 15, with the vehicle moving a short distance from the assembly building to the launch pad. SLP is one of two pads used for orbital launches at the Satish Dhawan Space Centre, located on Sriharikota Island off India’s east coast. Formerly known as the Sriharikota High Altitude Range, the site was renamed following the death of former ISRO chairman Satish Dhawan in 2002 and has been the site of all of India’s orbital launches.
LVM-3 M2/OneWeb India-1 mission: The vehicle is moved to the launch pad in the early hours today. pic.twitter.com/zF3JZgE26S
— ISRO (@isro) October 15, 2022
The SLP was built in the early 2000s in an effort to allow India to increase its launch cadence and saw its first use in 2005. It and the nearby First Launch Pad (FLP) are both used for PSLV launches, but SLP is the only pad that can be used for GSLV Mk.III launches. SLP has also hosted all launches of the GSLV Mk.I and Mk.II since it completed construction – the Mk.I having previously flown from the FLP.
ISRO has designated the launch mission GSLV MK.III M2, or LVM3-M2, indicating that it is the second operational flight for the GSLV Mk.III. ISRO has used the GSLV and LVM3 names interchangeably throughout the rocket’s service so far, with the LVM3 name being used more often than GSLV Mk.III in the agency’s updates related to the OneWeb mission – although the rocket is still more widely known by its GSLV designation.
GSLV Mk.III is one of four rockets currently in service with ISRO, alongside the Polar Satellite Launch Vehicle (PSLV), the GSLV Mk.II, and the newly introduced Small Satellite Launch Vehicle (SSLV). Compared to GSLV MK.II, the Mk.III is a completely new design intended to give India the ability to carry out indigenous launches of far heavier payloads than its previous-generation rockets could support.
The first GSLV Mk.III lifted off in December 2014 on a successful suborbital test flight with an inert upper stage. The next two missions were termed developmental launches, but they carried live payloads bound for geostationary orbit. The first of these development flights placed the GSAT-19 spacecraft into a marginally-lower-than-planned orbit in June 2017, with the second deploying the GSAT-29 spacecraft successfully the following November. These flights paved the way for the rocket’s first operational launch, conducted in July 2019 to send the Chandrayaan-2 spacecraft on its journey to the Moon.
The OneWeb mission marks the first time GSLV Mk.III will carry a commercial payload, as opposed to an ISRO or Indian government mission, and it is also the first time GSLV Mk.III will launch to LEO. ISRO has previously flown commercial missions with its PSLV rocket, beginning with the launch of the Italian AGILE astronomy satellite in 2007, but these launches have typically consisted of smaller satellites and rideshares. Combined, the 36 OneWeb spacecraft are a much heavier payload requiring the services of ISRO’s most powerful launcher.
The GSLV Mk.III is a three-stage rocket, with the first stage consisting of a pair of S200 solid rocket motors that will ignite at T0 and power the GSLV’s initial climb away from the launch pad. The solids are attached to either side of an L110 liquid-fueled core which serves as the vehicle’s second stage. To reach its planned near-polar orbit, the rocket will fly a dog-leg trajectory, heading first to the southeast before turning onto a more southerly track once it is far enough east to ensure it will not drop debris over Sri Lanka.
Powered by a pair of High Thrust Vikas Engines (HTVEs), the L110 will ignite at approximately 106 seconds after liftoff, burning alongside the S200s for the last 26 seconds of the first stage burn. Two minutes and 10 seconds into the flight, with the rocket at an altitude of about 73 kilometers, the solid motors will burn out and separate. The second stage will continue burning as it continues to propel the OneWeb satellites toward orbit.
The HTVE engines are uprated derivatives of the Vikas-4B engine, which was used on the first two GSLV Mk.III missions. Vikas, which has also flown on the PSLV, GSLV Mk.I, and GSLV Mk.II, is an Indian license-built version of the French Viking engine, previously used by the Ariane family of rockets. These engines use a hypergolic propellant called UH-25, a mixture of unsymmetrical dimethylhydrazine and hydrazine hydrate, which is oxidized by dinitrogen tetroxide.
Separation of the rocket’s payload fairing will take place at two minutes and 49 seconds mission elapsed time. The ogive-shaped fairing at the top of GSLV protects the satellites during the rocket’s ascent through Earth’s atmosphere. After reaching space, the protection provided by the fairing is no longer needed, and the fairing is discarded to save weight.
The L110 stage’s burn is expected to last three minutes and 17 seconds, shutting down and separating at five minutes and three seconds mission elapsed time. About two and a half seconds after separation, the rocket’s third stage will ignite.
The third stage of GSLV Mk.III is a C25, a cryogenic-propellant stage fueled by liquid hydrogen and liquid oxygen, and it is powered by a single CE20 engine. It will make a single burn, lasting 10 minutes and 39 seconds, to push the OneWeb satellites’ deployment orbit to an altitude of 601 kilometers and an inclination of 87.4 degrees. Once released into this orbit, the satellites will use their onboard electric propulsion systems to raise themselves into their operational 1,200-kilometer orbits.
The deployment sequence itself involves a series of maneuvers across five phases and nine separation events to ensure the satellites are adequately spaced to avoid any potential collisions. With the upper stage turning perpendicular to its direction of flight, separations will begin four minutes after the end of the C25 stage’s burn when the first four spacecraft are released. A second group of four satellites will also be released at this orientation before the stage turns back to the direction of flight for a small “velocity addition” using its thrusters.
The upper stage will repeat this sequence for phases two, three, and four. The fifth phase will only include one separation event with the last four satellites being deployed to begin their missions. With its final payloads separated, the C25 stage will reorient itself again before downlinking telemetry and passivating itself. The spent stage will remain in orbit, with passivation serving to reduce the risk of residual propellant causing it to explode.
The OneWeb launch is India’s fourth launch of 2022 and the first since ISRO’s new SSLV rocket failed on its maiden flight in August. It is expected to be the only GSLV Mk.III launch this year, with the rocket’s next mission currently slated for early 2023 with another 36 OneWeb satellites.
ISRO is believed to have at least one more launch scheduled before the end of the year, with a PSLV rocket due to carry the EOS-06 – or OceanSat-3 – environmental research satellite into orbit. As of September, this was on track for an October launch date, however, no further updates have been given since – meaning it is now unlikely to fly this month.
(Lead image: GSLV Mk.III M2 at the launch pad. Credit: ISRO)
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