Current International Space Station residents Leroy Chiao and Salizhan Sharipov should soon be receiving some welcome supplies if the launch of an unmanned Soyuz resupply mission goes ahead as planned this evening.

Lift-off is scheduled for 1909 GMT from the Baikonur Cosmodrome. The payload includes "160 days' worth of food, 494 kilograms of water, and 175 kg of fuel for the station's Russian thrusters" as well as "109 kg of air and oxygen, equipment for the primary oxygen-generating and carbon dioxide-removal systems, and 32 oxygen-generating canisters" the New Scientist reports.

Also aboard are are a replacement temperature-controlling heat exchanger for the airlock and new valves, filters and fungicide for the ISS's currently non-functioning toilet.

The mission will also pre-supply the ISS as part of a shuttle emergency contingency plan. Shuttle Discovery is due to launch on 15 May. In the event of any incident similar to that which resulted in the destruction of Columbia (in that case a hole in the wing), the shuttle crew will take refuge in the ISS and await a rescue mission.

However, even with the latest delivery, the ISS could not sustain an extra seven people for a month, so Discovery will itself carry further emergency supplies - just in case.

In Florida, meanwhile, NASA will today attach Discovery's main fuel tank to the two solid rocket boosters in preparation for a 60-hour "final long simulation" on Wednesday. ®

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