Ariane 5 to send a duo of communications satellites into orbit
Arianespace is all set to conduct its eighth mission of the year, which will send two communications satellites into space atop the company’s workhorse Ariane 5 booster. Liftoff is slated to take place from the Ariane Launch Complex № 3 (ELA-3) in Kourou, French Guiana. The 45-minute launch window starts at 5:30 p.m. local time (4:30 p.m. EDT; 20:30 GMT) on
Tuesday, Oct. 4 Wednesday, Oct. 5.*
The mission, designated VA231, is being conducted to deliver GSAT-18 and Sky Muster II (also known as NBN-Co 1B) commsats into a geostationary orbit. The flight will last one hour and 22 minutes, with the Sky Munster II being released at 28-and-a-half minutes after launch and GSAT-18 being deployed some four minutes later.
The mission campaign started on May 18, 2016, with the unpacking of the rocket’s cryogenic main stage, called EPC. Two days later, a pair of solid rocket boosters was attached to this stage. The GSAT-18 satellite arrived first at French Guiana, on May 30. On the next day, the rocket’s cryogenic upper stage (ESC-A) was erected with the vehicle equipment bay (VEB).
On June 1, the fit checks and initial preparations of GSAT-18 began in the S5C payload processing facility. The Sky Muster II spacecraft arrived in French Guiana two months later, on Aug. 30, and the teams immediately commenced initial checks in the S5C building.
In September, both satellites were transported to nearby S5A and S5B halls where, on Sept. 13, the fueling operations of the spacecraft started. On the same day, the launch vehicle was moved from the Launcher Integration Building (BIL) to the Final Assembly Building (BAF).
During the second half of September, engineers at the spaceport were busy integrating the satellites on the payload adaptor and encapsulating them in the payload fairing. The spacecraft were finally installed on the launcher on Sept. 27 and then final inspection of the upper stage’s engine was performed.
Next, the teams carried out final payload checks and conducted the launch rehearsal on Sept. 28. The launch readiness review took place on Sept. 30, signaling that Ariane 5 is ready for its rollout to the launch site one day ahead of the planned liftoff. Countdown for the launch will commence some 11 hours and 43 minutes before liftoff.
During the countdown campaign, the engineers will have enough time to perform final checks of electrical systems and to fill both rocket stages with liquid oxygen and hydrogen. About one hour and 15 minutes ahead of rocket ignition, the pre-launch checks of telemetry, tracking, and command systems will be carried out. Some seven minutes before the start of the mission, all the systems should be reported as ready for launch, commencing a synchronized sequence that will lead to the ignition of the rocket’s main stage engine.
GSAT-18 is India’s latest communications satellite. It was built by the Indian Space Research Organization (ISRO) and will be operated by the Indian National Satellite System (INSAT). The spacecraft weighs about 3.4 metric tons, and its dimensions are 10.17 by 5.57 by 6.56 feet (3.1 m × 1.7 m × 2.0 m). The satellite is based on ISRO’s I-3K platform and is fitted with two solar arrays and batteries that will generate up to 5.600 kW of power for a designed lifetime of about 15 years.
GSAT-18 will carry 24 C-band, 12 extended C-band, and 12 Ku-band transponders to provide telecommunications services for India. The satellite will be positioned at 74 degrees East longitude and co-located with other operational INSAT satellites.
“GSAT-18 is designed to provide continuity of services on operational satellites in C-band, Extended C-band and Ku-bands,” ISRO wrote on its website.
Commissioned in 1983, INSAT is the largest domestic communication system in the Asia Pacific Region. The system consists of a series of multipurpose geostationary satellites launched by ISRO to satisfy the telecommunications, broadcasting, meteorology, and search and rescue operations. Eleven out of 24 INSAT satellites launched to date are still operational.
Manufactured by Space Systems Loral (SSL), Sky Muster II is based on the SSL 1300 bus. The satellite has a mass of about 6.4 metric tons, and its dimensions are 27.9 by 9.84 by 11.5 feet (8.5 m × 3.0 m × 3.5 m). The spacecraft’s two deployable solar arrays and batteries will generate up to 16.4 kW of onboard power for more than 15 years of its operational lifetime.
Sky Muster II will be operated by NBN Co Limited – an Australian government-owned corporation that manages the country’s National Broadband Network (NBN). Carrying 202 Ka-band transponders, the satellite will occupy a geostationary position between 135 and 150 degrees East. It is expected to extend high-speed internet to Australia, including the Norfolk, Christmas, Macquarie, and Cocos islands, in conjunction with the services already delivered by Sky Muster I spacecraft that was launched on Oct. 1, 2015.
The company hopes that Sky Muster satellites will bring them closer to their goal of connecting all Australians to the NBN network. The firm aims to provide everyone in the country with access to fast broadband by 2020.
“This is an enormous project and we are doing our best to deliver the NBN Sky Muster service as fast as we can, but reaching all corners of the country will take some time,” said Julia Dickinson, NBN’s Satellite Architect.
The Ariane 5 in ECA configuration, which will be employed for Tuesday’s launch, is the heavy-lift rocket Arianespace uses for missions to geostationary transfer orbit (GTO) and usually carries two telecommunications satellite payloads.
The flight is powered during the initial flight phase by a cryogenic core stage and two solid rocket boosters, followed by the use of a cryogenic upper stage for orbital injection of the payload.
The 180-foot (54.8-meter) tall ECA is an improved version of the Ariane 5 launcher and is designed to deliver payloads, mainly communications satellites, weighing up to 10 metric tons.
Although it has the same general architecture, some significant changes were made to the basic structure of the generic version to increase thrust and enable it to carry heavier payloads. ECA is also used by institutional customers for non-GTO missions; for example, launching ESA’s Herschel and Planck scientific missions in 2008.
Tuesday’s mission will be the 233rd liftoff of an Ariane vehicle from the Kourou Spaceport. It will be the fifth Ariane 5 launch of 2016 (the 88th Ariane 5 launch overall) and the eighth of 12 flights planned this year by Arianespace, utilizing its family of the heavy-lift Ariane 5, the medium-lift Soyuz, and the lightweight Vega. GSAT-18 and Sky Muster II are the 542nd and 543rd satellites to be launched by Arianespace.
Arianespace’s next launch is scheduled for Nov. 17 when it is expected to deliver into space four Galileo navigation satellites for the European Space Agency (ESA). That mission will also be performed by the Ariane 5 launcher, lifting off from Kourou.
*This article was updated at 17:50 EDT on Oct. 4 to reflect a recent change of launch schedule.
Tomasz Nowakowski is the owner of Astro Watch, one of the premier astronomy and science-related blogs on the internet. Nowakowski reached out to SpaceFlight Insider in an effort to have the two space-related websites collaborate. Nowakowski's generous offer was gratefully received with the two organizations now working to better relay important developments as they pertain to space exploration.