From Switzerland - the most voluminous contribution to the XMM programme
20 July 1999What is bigger than ESA's largest science satellite? Answer: the spacecraft transport container in which XMM will leave for French Guiana in two months' time. On Monday 19 July, after a four-day trip down the Rhine on a barge, this Swiss-made very large container arrived at Katwijk, a few kilometres from ESTEC.
The container, 16 metres long, 4.5-m wide and 4.5-m high, was built by APCO Technologies in Vevey on the shores of Lake Geneva. Given its dimensions, the first overland leg of its journey needed a special convoy and police escort for the first 230 km to Basel. The 26 m articulated lorry, with a clearance over the roads of only 10-cm had driven at a snail's pace. It followed a tortuous itinerary, avoiding bridges and other obstacles under which its exceptional load could not pass.
On the evening of 14 July, the convoy arrived at Birsfelden on the Rhine, just outside Basel. There at the Ultra-Brag AG handling and shipping terminal, a 76-m long Rhine barge was waiting. The 'Sempachersee' is one of a hundred ships that ply each week between the Swiss city and the ports of Antwerp and Rotterdam.
More accustomed to bulk cargoes (grain or cobblestones) and heavy manufactured goods, the employees at Ultra-Brag were intrigued by this special space consignment. No doubt because they also regularly handle the containers carrying the Ariane launcher fairings on their way to Rotterdam. Switzerland's Contraves Space produces the fairings.
The XMM spacecraft container is the biggest APCO Technologies has ever designed and built. Half of the company's activity is for Europe's space industry. Over the years APCO has contributed to the Ariane-4 and Ariane-5 ground installations in French Guiana where it has a permanent office; it has regularly provided mechanical ground support equipment (dollies, lifting devices, tests stands and transport containers) for ESA programmes such as ISO, Envisat, Integral, ATV, Rosetta, Metop; and it produces spaceflight hardware.
The X-ray telescope's transport container may be APCO's largest item produced for the XMM programme, but not its most significant. This undoubtedly is the Mirror Interface Structures (MIS) and the so-called 'spiders' for the spacecraft's X-ray telescopes. On the MIS of each telescope, interfacing the Mirror Support Platform of the spacecraft, the spider is the very critical spokewheel-like component upon which the mirror shells are glued. Both these 800-mm diameter high precision structures had to be machined to a flatness better than 5 microns! Another important contribution from APCO: it has delivered the clampband, part of the satellite release system that will set XMM free in orbit and the transport containers for the X-ray telescopes (five in total).
Other flight hardware produced in Vevey for the European Space Agency include the outer vessel of ISO's 'thermos flask', the metallic structure of the Huygens probe thermal shield, one of the science experiments to fly on Rosetta (RTOF spectrometer), and major parts of the MERIS instrument on Envisat.
The XMM transport container was well hidden under a protective cover as a 300-tonne travelling crane on the Rhine quayside hoisted it from the lorry and into the hold of the 'Sempachersee'. Weighing 23.5 tonnes empty, the container is no ordinary stainless steel box. Double-walled and shockproof, it has a special internal 'L-shaped' fully suspended structure using massive coil springs and to which XMM will be attached horizontally at its launcher interface. The container will be flushed with nitrogen, ventilated and maintained at a constant temperature during the journey to Kourou. In fact the container is practically a travelling class-100 clean room!
APCO Technologies is not the sole Swiss contributor to the XMM mission. Other industrial companies have delivered equipment for the spacecraft: Contraves Space (Zurich) has provided the thermal control system of the upper half of the spacecraft, the Mirror Support Platform (MSP), support structures for the propellant tanks, the entrance baffles on the X-ray telescopes and the outgassing baffle of the Telescope Tube. For its part, Clemessy AG (Pratteln) designed, manufactured, and tested the all the ground power sub-systems for the spacecraft including the launch power supply. Finally, the Paul Sherrer Institut (PSI), based in Villigen, is one of the four partners in the Reflection Grating Spectrometers (RGS) consortium. It was responsible for the structure and thermal design of the RGS camera heads including their cooling system. Following development and testing Contraves Space built the cameras.
After having passed through Rotterdam and a final detour through Gouda and Alphen-aan der Rhijn, the container finally arrived early on 19 July at the port of Katwijk. It was welcomed by several members of the XMM team. By midday, the container had been hoisted by a 30 metre high crane and transferred to a semi-articulated vehicle with its long trailor and steerable rear wheels.
Waiting until the evening for clearer roads, the special convoy set off on the final leg of the journey to ESTEC. Sharp corners and small roundabouts were among the obstables that the outsize convoy had to negotitate, and even with its police escort, it took over an hour to cover the three kilometres! So night was falling when it arrived at the Technical Centre and was unloaded on a parking area - not far from the integration area and the clean rooms in which XMM is undergoing final tests.