Crucial first steps in ATV’s orbital journey

What’s shaping up to be a spectacular night launch actually involves two missions: Ariane 5 boosting the third Automated Transfer Vehicle into orbit, and that of ATV-3 itself, which starts on separation from the launcher’s upper stage.

Ariane 5 flight VA205 is set to loft ATV-3 and its cargo into an initial circular orbit at an altitude of 260 km.

From there, ATV-3 will conduct a series of engine burns to match, or ‘phase,’ its altitude and speed gradually with those of the International Space Station.

Weighing in at 19 714 kg, including 6596kg of fuel, air, oxygen, scientific equipment, spare parts and crew supplies, ATV-3 is the heaviest payload ever lofted by Ariane 5. Including the launcher itself, 777 tonnes will be pushed off the pad.

Ariane mission

The Ariane 5 mission begins with the ignition of the main stage liquid-propellant engine, followed by ignition of the two solid-propellant boosters.

Liftoff occurs a few seconds later, and 17 seconds into flight the majestic vehicle starts a roll manoeuvre as it soars into the sky.

Next, two minutes later, the depleted solid boosters are jettisoned, and Ariane continues climbing. Several minutes later, the aerodynamic fairing is jettisoned, as the vehicle is now above much of the atmosphere.

Nine minutes into flight, the second stage separates from the main stage, which falls back into the Atlantic Ocean off the coast of Portugal.

The upper stage then makes two engine burns separated by a coast phase, delivering ATV into its target orbit.

Almost 64 minutes after ignition, ATV separates from the upper stage high over the Pacific Ocean between Australia and New Zealand.

The upper stage will later deorbit itself over a deserted area of the South Pacific, as ATV continues its mission.

ATV’s early orbits

Once in free flight, ATV’s computers begin a critical automated sequence to bring the vessel smoothly to life.

Initially operating on battery power, ATV starts sending telemetry to ground controllers at the ATV Control Centre in Toulouse, France, and prepares its propulsion system. Reception of the first signals will indicate that all is well with the vessel.

Some 20 minutes after separation, ATV slews into the required attitude to deploy its solar wings, which unfold to generate power from sunlight.

Within about 60 minutes, its navigation system starts receiving GPS signals to help fix its position.

At the two-hour point, the vessel’s proximity link antenna deploys, allowing later communications directly with the Station.

The launch and early orbit phase ends after five hours.

Docking is planned five days later, on 29 March.

Highlight timeline

Note: Times shown as planned with respect to the H0 ignition time. Actual times may vary. Watch the launch webcast live via esa.int<> or blogs.esa.int/atv.

• –11 hr 30 mn Start of final countdown
• –4 hr 50 mn Start of filling of main cryogenic stage with liquid oxygen and hydrogen
• –1 hr 10 mn Check of connections between launcher and telemetry, tracking and command systems
• –7 min 00 sec ‘All systems go’ report at Launch Control Centre, allowing start of synchronised sequence
• –1 min 00 sec Switch to onboard power
• –04 sec Onboard systems take over
• –03 sec Unlocking of guidance systems to flight mode

• +7.0 sec Ignition of solid boosters
• +7.3 sec Liftoff
• +17.1 sec Beginning of roll manoeuvre
• +2 min 22 sec Booster separation
• +3 min 26 sec Fairing jettison
• +8 min 54 sec End of main engine firing
• +9 min 00 sec Upper stage separation
• +9 min 07 sec Beginning of upper stage first burn
• +17 min 18 sec End of upper stage first burn
• +59 min 23 sec Beginning of upper stage second burn
• +59 min 51 sec End of upper stage second burn
• +1 hr 3 min 50 sec ATV separation
• +1 hr 35 min 30 sec ATV solar array deployment complete