The highly-trained crew of the Space Shuttle Discovery worked as baggage handlers on Tuesday, as they unpacked supplies into the International Space Station.

The astronauts have until Thursday to transfer over 1,600 kilograms (3,600 pounds) of equipment from Discovery into the fledgling ISS.

Included in the supplies are tools, spare parts, computers, water, clothes and even exit signs ready to be fitted. The will make the ISS habitable for its first residents who arrive next March.

However, flight director Wayne Hale said: "It's not real easy. Every single bag, every single item has got an exact place it's supposed to go. It reminds me a lot of packing for going on a long camping trip."

Astronaut Tokarev mends Zarya's batteries

The astronauts form a line with Ellen Ochoa, the "loadmaster", at the start. She stays inside Discovery, handing the bulky, soft-sided suitcases to her crewmates, who do the carrying. At the other end Julie Payette checks off each bag as it arrives.

The astronauts went to bed on Tuesday with over half the material transferred and stowed.

Repair job

Monday's work had involved repairs and these have mostly gone well. A broken Earth-ISS communication system on the US-built Unity module was fixed by replacing two electronics boxes.

On the Russian-built Zarya module, 18 faulty meters were successfully replaced on six batteries which store solar power.

But the foam sound mufflers fitted over noisy fans and ducts inside Zarya had an unexpected effect - the relative humidity rose to 60%. This occurred because a kink in one of the mufflers hampered the air flow in one spot.

Astronaut Rominger attaches a noise muffler

The problem appears to have been solved after the kink was straightened out. Flight director Mark Ferring said the humidity always remained within acceptable limits.

The temperature in the space station was also up this morning, to a warm 25 Celsius (78 Fahrenheit). When the astronauts entered the ISS, the temperature was only 13 Celsius (55 F).

Home on Sunday

The hatches to the ISS will be sealed early on Thursday and Discovery will then pull away. The shuttle is due back on Earth on Sunday.

The $60bn ISS construction programme is the first truly international space mission. It brings the US, Russia, Japan, Canada and Brazil together with the 11 members of the European Space Agency.

The current mission, STS-96, is the first construction activity on the ISS since the first two pieces - Zarya and Unity - were launched late last year. It is due to be completed by 2005 after an estimated 158 more spacewalks.