© Fraunhofer FHR

Space observation radar TIRA

A new cover for the space observation radar TIRA#

Almost 50 years after it was constructed, the space observation radar TIRA now has a new cover. The so-called radome protects the highly sensitive radar system from wind and weather. To ensure that the radar would not be exposed to the elements for several months, the new radome was first constructed from the inside before the old radome was removed. The new radome with a diameter of 47.5 m is a little bit smaller than its predecessor. The overall size, however, is still a world record.

Sun, rain and wind had left their mark on the cover over the last five decades. The time had now come to replace the entire radome after almost 50 years in an exposed location in Wachtberg.

After years of planning and preparing for the replacement of the world's largest radome, i.e. the cover of the space observation radar TIRA Wachtberg, work finally commenced in January 2014 with the construction of the scaffolding inside the cover. The aim was to gradually raise the scaffolding to just below the parabolic reflector, i.e. to a height of approximately 44 meters. The maximum height was reached early in the summer after constructing 780 tons of scaffolding.

1,800 boreholes to mount the support ring

A new support surface first had to be created to facilitate the construction of the new cover inside the old radome. To this end, a new support ring made of reinforced concrete was fixed to the upper edge of the concrete building. To make sure it was really secure, steel rods were inserted into 1,800 boreholes – with a diameter of 20 mm and a depth of up to 120 cm – in the existing building and a one-meter-wide support ring was created with concrete formworks.

Parallel to this, the new triangles made of aluminum struts and the membrane – which is permeable

for electromagnetic waves – were manufactured in the factory of the specialized company in Ireland. In April, dozens of trucks delivered the 1,330 panels right next to the "ball". Soon afterwards, the fitters from Ireland and the USA commenced with the installation of the first triangles. Four large elevators were integrated in the scaffolding to transport the triangles to the upper levels. The scaffolding was raised in line with construction progress.

In August, the cover was completed to such an extent that it already protruded above the edge of the parabolic reflector. At this stage, three-quarters of the new radome had now been completed. In the meantime, the cap for the new radome was assembled next to the »ball«. Everything had now been prepared for the »cap swap«.

Completion of the new radome with the »cap swap«

After weeks of waiting and studying the weather forecasts, four days of dry and windless weather were finally forecast for the beginning of September. On 1st September, a crane exceeding 91 meters in height was erected to remove the old cap, which weighed a number of tons, and position the new cap. At sunrise on 2nd September, the workers started connecting the ropes of the crane to the old cap so that it could be separated from the rest. At approx. 2 p.m., the upper section of the cover was separated and raised. Just 15 minutes later, it was on the ground and the »ball« looked like a decapitated egg. For the first time in nearly 50 years, the 34-meter parabolic reflector was once again visible from the air – even through the night until the next morning.

In the morning of 3rd September, the workers transferred the ropes from the old cap to the new one. The safety ropes were then removed and the cap was raised into the correct position. The crane slowly moved the cap over the "ball" and then lowered it correctly into place. The radome was sealed by noon. When the cap was tightly secured to the cover, the workers started to dismantle the old cover. All of the old triangular membranes were cut out leaving just a metal skeleton to ensure that the old cover could not damage the new cover in windy conditions.

The old frame was gradually removed over the next couple of weeks with three truck cranes. Hundreds of struts had to be separated, in some cases individually, and lowered to the ground. Parallel to this, the radome was sealed against water and the scaffolding inside the radome was dismantled. All of the scaffolding was removed by November and TIRA could recommence normal operation.

Due to the oncoming winter, the remainder of the work was put off until the spring of 2015. The project is scheduled to be completed by the end of May 2015. FHR project manager Jürgen Marnitz: "After years of planning, I am delighted and relieved that most of the work could be completed successfully. And I am convinced that the new radome will protect the valuable radar system for many years to come once it has been fully completed.