The final launch of an Ariane 5 ES rocket will loft another four Galileo satellites from the European Spaceport in Kourou, French Guiana on Wednesday – with the launch expected at 11:25 UTC. The launch of satellites will complete the first construction cycle for the constellation. The launch is scheduled to take place just 14 minutes prior to the Falcon 9 launch with Iridium NEXT-7 out of Vandenberg.
The Ariane 5 ES – which has also been used to loft Automated Transfer Vehicles (ATV) to the International Space Station – has an estimated LEO launch capacity of 21,000 kg (46,000 lb).
It includes all the performance improvements of Ariane 5 ECA core and boosters but replaces the ESC-A second stage with the restartable EPS used on Ariane 5 GS variants.
Arianespace mainly relies on its Ariane 5 ECA variant. However, the ES found a role with the Galileo launches, although this launch was its last – a finale to numerous elements involved with this mission.
Many Lasts for this launch #VA244:
1. Last Ariane 5 ES model
2. Last Medium fairing
3. Last EPS upper stage
4. Last launch without the use of the cryo arms from #ELA3 #ZL3
5. Last Ariane 5 launch with #Galileo
6. Last time we will launch 4x Galileo S/C in one launch #ESA pic.twitter.com/k0vZ5inMhH
— DutchSpace (@DutchSpace) July 24, 2018
For this final mission, the launcher (L596) was the 99th Ariane 5 launched (although this was the 100th Ariane 5 built). All future Galileo launches – mainly to update the constellation with advanced phases and spares – will be conducted on Arianespace’s upcoming Ariane 6 launches.
The Ariane 6’s A62 version will take over with two launches used to orbit another four satellites during a timeframe between December 2020 and June 2021.
The Galileo System began Initial Services on 15 December 2016, and a growing number of commercial devices are using Galileo today. Completion of the constellation improves Galileo’s positioning accuracy further still.
A steady stream of orbital spares, ready to replace satellites reaching the end of their operational lives, is essential to ensure Galileo continues operating seamlessly.
With tomorrow's launch of 4 more #Galileo satellites, Europe's satellite #navigation constellation will reach 26 satellites in space, completing the project's first construction cycle.
🎥 https://t.co/mHJbkKNFzd pic.twitter.com/Ff77gNNOzE
— ESA (@esa) July 24, 2018
The Galileo constellation consists of 26 operational satellites along three orbital planes in medium Earth orbit. Two satellites are on orbit as spares to cover any issues with the primary spacecraft. This is Europe’s largest ever fleet of satellites, operating in the new environment of medium-Earth orbit.
Europe’s own GPS constellation was deemed to be a major requirement, so as to ensure it wasn’t stuck with having to rely on US or Russian systems.
This decision is deemed to be a wise one, given the increasingly uncertain geopolitical climate that has followed since Galileo’s inception. A plot twist also involves the UK, which has been a major financial and technical contributor to the system but has been threatened with a lockout due to the UK population’s decision to leave the European Union.
The launch campaign began with the launch of the first two experimental satellites, Giove-A, and Giove-B, orbited by Arianespace’s Starsem affiliate on Soyuz launchers from Baikonur Cosmodrome in 2005 and 2008.
The deployment of the system has utilized an element of international cooperation, with the Russian Soyuz rocket – albeit under the operation of Arianespace, taking the system to Full Operation Capability (FOC), followed by the first with the Ariane ES, which was the eighth Galileo mission – bringing the number of satellites in space up to 18 at that time.
Issues during previous launches with Soyuz rockets caused some replanning of the full deployment schedule. However, the Ariane 5 ES’s final – and successful – launches have improved the pace allowing for the system to be in full use with an acceptable timescale.
The latest four satellites (23 to 26 – FOC-M8) are named Anna, Ellen, Samuel and Tara. Each of the satellites is named after children that won the European Commission’s Galileo drawing competition.
These satellites – which weigh between 715 kg and 717 kg – were built by OHB System in Germany with U.K.-based Surrey Satellite Technology supplying the navigation payloads.
The A5 dispenser system will keep the quartet of Galileo satellites in place during ascent, before deploying them in rapid sequence at a targeted release altitude of 23,222 km.
The 447 kg dispenser, designed by Airbus Defence and Space, is made from a combination of metal and composite materials for maximum stiffness, the dispenser has undergone very comprehensive testing at Airbus Defence and Space near Bordeaux, France, and the IABG testing centre in Ottobrunn, Germany – using both Galileo engineering models and an actual flight satellite, including fit, shock and separation testing.
The target orbit was actually 300 km below the Galileo constellation’s final working altitude: this leaves the Ariane’s EPS upper stage in a stable ‘graveyard orbit’, while the quartet of Galileos maneuver themselves up to their final set height.
The test campaign met all objectives, confirming the behavior performs as predicted, after which the dispenser was shipped to Europe’s Spaceport in French Guiana. It performed well during the previous mission during which it debuted.
This mission was performed on behalf of the European Commission under a contract with the European Space Agency (ESA).
The birds sport two Passive Hydrogen Maser atomic clocks; two Rubidium atomic clocks; Clock monitoring and control unit; Navigation signal generator unit; L-band antenna for navigation signal transmission, C-band antenna for uplink signal detection, two S-band antennas for telemetry and telecommands and a search and rescue antenna.
Galileo’s highly-accurate atomic clocks will provide the accuracy of the system. Each satellite emits a signal containing the time it was transmitted and the satellite’s orbital position.
The Galileo program is Europe’s initiative for satellite navigation, providing a highly accurate global positioning system under civilian control, along with European control centers and a worldwide network of sensor and uplink stations.
Flight VA244 mission was Arianespace’s 49th performed for ESA. Arianespace has seven more ESA missions in its launch manifest including EDRS-C, Bepi-Colombo, the James Webb Space Telescope, CHEOPS and ADM-Aeolus.