The NRT project office have been busy working on preliminary designs covering all manner of aspects of the telescopes behaviour and performance. Key to this is the site and specifically the ground we are intending to build upon.
Telescopes require very accurate pointing and tracking of distant stars and therefore, very stable foundations. The telescope foundations are often isolated from the other building foundations by way of a reinforced concrete peer which is sunk deep into the ground. This peer has to provide a stable, position over the lifetime of the telescope so it is essential to know the underlying state of the ground. La Palma is a volcanic island and the geological makeup is more fragmented than many other mountain sites for telescopes, this could result in slippage of the structure over time.
The project office has recently commissioned geotechnical surveys to find out the exact composition and structure of the ground below our planned site on ORM, La Palma. Civil engineers need details about the ground layers in order to design stable foundations for the telescope and it’s protective enclosure. The geotechnical survey was carried out by a local company based on La Palma (ICINCO) who use a long drill to extract core samples down to depths of 18m! These cores can be analysed in a lab to find properties of the soil and rock at each depth. ICINCO also performed dynamic tests to measure the speed of waves underground between two holes which allows us to understand the structure of layers and density of the rock and earth.
All of this data will feed into our preliminary foundation design taking place later this year. This will inform the overall site layout, enclosure design and our telescope pointing and tracking performance models.