The new-look vessel will take part in a three-month series of experiments, costing about pounds 1.5m, designed to learn more about the oceans and how they distribute heat and carbon dioxide around the planet - crucial elements in the complex equations of the greenhouse effect.
New laboratories and equipment on board will help scientists to understand how, for instance, deep underwater currents distribute huge quantities of heat from the tropical seas to the colder regions of the North and South Atlantic.
The Discovery will also take part in an international effort to study the large 'blooms' of phytoplankton - microscopic plants - that occur each spring as the winter ice recedes from the seas surrounding the North and South Poles. Researchers believe this plankton plays an important role in soaking up carbon dioxide from the atmosphere.
The Discovery has a distinguished pedigree. The original icebreaker, launched in 1901, took Scott and Shackleton in search of the South Pole. The present vessel was built in the early Sixties and was well beyond its expected 20-year lifespan when its operators, the Natural Environment Research Council, convinced the Government of the need for an pounds 11m refit, about half the price of a new ship.
Over a period of 30 months, Portuguese shipbuilders stripped the Discovery of its aluminium superstructure, leaving a rusty hulk which they cut in two during a hazardous three-day operation. Hydraulic machinery pulled the front and back ends of the hull apart on steel plates covered in grease. At one point the bow section slid dangerously out of line. Ship welders then fitted in a 12- metre wide section to increase the overall length to 90 metres. This made the new-look Discovery more stable in rough seas and provided extra space for the 28 scientists and their equipment.
The refit was completed with a wider aft section, housing heavy machinery for towing and pulling in equipment from the sea, and new engines and superstructure housing cabins and laboratories. The original propellor and shaft were left as they were.
A gravity meter in the centre of the vessel measures the smallest variations in Earth's gravitational field as the ship travels. Miles of cables are stored in the winch- room with pulleys able to lift 20- ton loads out of the sea.