Image: Shady side of ATV

A rare view from behind of the solar wings built for ESA’s Automated Transfer Vehicle – the side that does not point at the Sun and is not covered in solar cells, a bright white to help proof it against corrosive atomic oxygen.

While the fourth ATV is being prepared for launch on 5 June from Kourou, French Guiana, the various elements of ESA’s next space ferry are taking shape at locations across Europe.

Here, an engineer at Dutch Space – down the road from ESA’s ESTEC technical centre in Noordwijk, the Netherlands, in nearby Leiden – is seen checking the hinges used to deploy ATV’s solar wings.
As these panels are not meant to be opened in Earth gravity, a special rig hanging from the ceiling is needed to spread them out, with weights at the bottom to keep everything in place.

The panel’s whiteness is due to a painted layer protecting it against the highly erosive atomic oxygen encountered at the International Space Station’s altitude. Scant oxygen molecules at the top of the atmosphere are split into individual atoms by ultraviolet radiation.

On early Shuttle missions thermal blankets were entirely eroded by atomic oxygen (ATOX). After that, the ATOX sensitivity of various materials used in space was quantified and protective measures were developed. ESTEC’s labs are equipped with atomic oxygen simulators to check space materials are proofed against it.

The various electrical cables on the back of the panels do not need added ATOX protection for the ATV mission. They are fixed in wavy lines to help withstand physical thermo-elastic induced in orbit stress due to the difference in the coefficient of thermal expansion between the solar panels and the copper wires.

Once inspected, these panels were refolded to be prepared for transport, destined to fly next year on the last ATV.