It is clear from the passage that the work of painting the steel structure of this telescope ----.

The Lovell Telescope is the world's oldest and most
sensitive radio telescope. It consists of a giant white
dish supported at a great height on a large and
complicated structure of steel. The telescope can
pick up signals in the universe that are 10 billion light
years away. And so it is truly extraordinary. The steel
structure that carries it, however, has the usual and
very ordinary disadvantage of being liable to rust.
This of course means that it has to be painted
regularly. Painting this, however, is not an ordinary or
a simple task. The men who do the painting are
given a special training which includes rescue work.
As they do the painting, the men work from ropes as
this is the method which has been found to be the
safest way of working at a height.