SpaceX launched its sixth mission of the year Wednesday, with a Falcon 9 rocket carrying a pair of communications satellites – Eutelsat 117 West B and ABS-2A – into orbit. Liftoff from SLC-40 at Cape Canaveral occurred at the start of a 44-minute window that opened at 10:29 local time (14:29 UTC).



SpaceX Launch:

Wednesday’s launch was the twenty-sixth launch of SpaceX’s Falcon 9 vehicle; coming less than three weeks after the previous mission, which deployed the Thaicom 8 satellite in late May.

As with the Thaicom launch, Falcon was again targeting a geosynchronous transfer orbit; this time carrying a pair of smaller satellites instead of one larger one.

The two satellites on Wednesday’s launch were Eutelsat 117 West B and ABS-2A, which are to be operated by France’s Eutelsat and Bermuda-based Asia Broadcast Satellite Limited respectively.

Both satellites were constructed by Boeing and are based on the BSS-702SP bus – a lightweight modification of the Boeing 702 platform – designed to be launched in pairs to bring down launch costs.

Eutelsat 117 West B was originally ordered as SATMEX-9 by Satélites Mexicanos, or SATMEX, a Mexican operator which merged with Eutelsat in January 2014.

SATMEX and ABS were Boeing’s launch customers for the BSS-702SP, signing a contract in March 2012 for two spacecraft each, plus launch services via SpaceX’s Falcon 9 rocket. The first two satellites, Eutelsat 115 West B and ABS-3A, were launched aboard a Falcon in March 2015.

Continuing Eutelsat’s recent pattern of naming satellites after their orbital location, Eutelsat 117 West B will be stationed at a longitude of 117 degrees West alongside Eutelsat 117 West A – another spacecraft it acquired in the SATMEX merger.

Formerly known as SATMEX-8, 117 West A was launched by a Proton-M in March 2013 and is expected to remain in service until 2028.

The communications payload aboard Eutelsat 117 West A consists of 48 Ku-band transponders which will be used to provide data and video distribution and direct-to-home broadcasting to Central and South America, the Caribbean and southern parts of the United States.

With a design life of at least 15 years, the spacecraft will be expected to remain operational until 2031 at the earliest. The satellite also carries a Wide Area Augmentation System (WAAS) payload, GEO-5, which was developed by Raytheon on behalf of the US Federal Aviation Administration (FAA).

WAAS is used to monitor and correct timing signals from GPS navigation satellites, providing more accurate data to compatible receivers. The FAA funded the program to improve aerial navigation, allowing GPS to be used by pilots in situations calling for precise navigation, such as instrument approaches and landings.

Two first-generation WAAS payloads were carried aboard the Inmarsat-3 F3 and F4 satellites, launched by Atlas IIA and Ariane 44L rockets in December 1996 and June 1997 respectively. Neither of these payloads remains in service.

Further WAAS payloads have been launched aboard Telesat’s Anik F1R and PanAmSat’s (later Intelsat) Galaxy 15 satellites in 2005 and Inmarsat-4 F3 in 2008.

All of these remain in service – the Galaxy 15 satellite having recovered from a malfunction in 2010 that saw it spend almost nine months drifting uncontrollably East from its orbital station.

Although their host satellites still have at least four years of service remaining, their WAAS payloads were only designed to operate for ten years so GEO-5 will begin the process of replacing the current-generation system.

GEO-5 will replace one of the WAAS payloads launched in 2005 – likely the one aboard Anik F1R – with the GEO-6 payload currently scheduled for launch late next year aboard the SES-15 satellite to replace the other. A replacement for the unit aboard Inmarsat-4 F3 has not yet been announced.

ABS-2A will join Asia Broadcast Satellite’s fleet at a longitude of 75 degrees East, where it will be co-located with the existing ABS-2 which was launched in February 2014.

ABS-2A carries 48 Ku-band transponders which will be used to provide communications to Russia, India, Africa, the Middle East and South and South-East Asia.

The Falcon 9 was selected to launch the Eutelsat and ABS satellites as part of the original contract to develop the spacecraft. Following last year’s launch of the first two satellites Wednesday’s mission will complete the contract.

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The previous launch used a Falcon 9 v1.1 rocket, flying without first stage landing legs in order to maximise its payload capacity and ensure mission success.

Upgrades to the rocket since then have resulted in a version of the rocket known as the “Full Thrust” configuration, which offers increased performance. As a result, the rocket can now reach a geosynchronous transfer orbit without sacrificing the ability to attempt to land the first stage.

Although SpaceX continues to characterise the attempts to recover the rocket’s first stage to be experimental – particularly when flying to higher orbits – four of the last six recovery attempts have succeeded including two geosynchronous missions.

Depending on mission requirements the first stage can either return to Cape Canaveral where the former Launch Complex 13 has been converted to a landing facility, or an Autonomous Spaceport Drone Ship (ASDS) – a converted barge – can be deployed downrange to receive the descending stage.

For geosynchronous launches the ship is used as the rocket would not have sufficient fuel to return to the Cape.

During this mission’s landing attempt, one of the three engines used for the landing burn suffered issues, resulting in the stage hitting the ASDS’ deck hard and was subsequently classed as lost.

The Falcon 9 is a two-stage rocket, fuelled by RP-1 propellant which is oxidised by liquid oxygen. The first stage is powered by nine Merlin-1D engines, which ignite three seconds before liftoff providing a short opportunity for onboard computers to stop the launch if an anomaly is detected.

Following ignition, the rocket lifted off once the countdown reached zero, beginning an ascent East from Cape Canaveral. Seventy-seven seconds after liftoff the vehicle encountered the point of maximum dynamic pressure, or Max-Q, when stresses on the rocket are at their greatest.

First stage flight lasted two minutes and 36 seconds before the engines cut off; stage separation then took place three seconds later followed after another eight seconds by ignition of the second stage’s single Merlin Vacuum engine – a Merlin-1D optimised for operation outside the atmosphere.

The second stage was called upon to make two burns during Wednesday’s launch. The first of these lasted six minutes and 35 seconds, with separation of the rocket’s payload fairing coming 47 seconds after ignition.

Following this burn the rocket coasted for sixteen minutes and 32 seconds before restarting for a 64-second burn to achieve the proper deployment orbit for the two satellites.

The two satellites were mated together at the nose of the rocket; as the BSS-702SP platform is designed for dual-launch the satellites do not require a separate adaptor and can instead be directly attached to one another.

The Eutelsat spacecraft was stacked atop ABS-2A and thus separated first, about three and a half minutes after the second burn concluded. ABS-2A separated five minutes later, concluding a thirty-five-minute, 29-second mission for the Falcon 9.

The Falcon flew from Space Launch Complex 40 (SLC-40) at Cape Canaveral – a former Titan launch pad which was rebuilt for the Falcon between 2008 and 2009.

It is currently SpaceX’s sole East Coast launch facility, however later this year the company is expected to start launching from Launch Complex 39A – a facility previously used by Saturn rockets and the Space Shuttle – at the nearby Kennedy Space Center.

Wednesday’s launch was the sixth of the year for SpaceX and the tenth for the United States. The next Falcon is currently scheduled to fly in mid-July, carrying a Dragon spacecraft for the CRS-9 resupply mission to the International Space Station.

Eutelsat’s next satellite, Eutelsat 172B, is currently scheduled for launch on an Ariane 5 in the first half of next year, while the next launch for ABS is expected to be of ABS-8 by another Falcon 9, no earlier than the end of next year.

(Images: SpaceX, NSF member Marek Cyzio L2)

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