The space shuttle Discovery will have to wait at least another seven weeks before returning to duty, NASA decided last week. But preparations for an astronaut servicing mission to the Hubble Space Telescope will resume anyway — another sign that new NASA administrator Michael Griffin may reverse his predecessor's decision to abandon the telescope later in the decade.

NASA managers reluctantly revised Discovery's launch date from 22 May for several reasons, but primarily because of concerns about ice debris from the shuttle's giant fuel tank. The 2003 demise of Columbia, the last shuttle to fly, occurred after foam insulation falling from the tank shortly after launch gouged a hole in the shuttle's wing. NASA engineers consider foam the greatest danger, but a technical review last week concluded that falling ice still poses a small risk. So heaters will probably be installed to prevent ice forming on the tank — a time-consuming job.

The next available launch window for the shuttle — determined by factors ranging from the International Space Station's orbit to lighting conditions for cameras to inspect the vehicle as it leaves the launch pad — opens on 13 July and lasts until 31 July.

Meanwhile, engineers at the agency's Goddard Space Flight Center in Maryland will resume planning for the shuttle servicing mission to Hubble that was suspended by former administrator Sean O'Keefe.

Griffin won't decide whether to approve the mission until after the shuttle's return, but said last week that he wanted to keep the option open. Based on new estimates of when Hubble's batteries and gyroscopes will fail, project managers now think that the telescope can be serviced as late as 2010.

Griffin also said that, despite the delay in returning to flight, he considers the 2010 target for retiring the shuttle “very firm”, and that NASA is looking for ways to complete the space station using other launch vehicles. This could mean that the schedule for conducting research on the station will slip.

For now, though, the orbiting laboratory will get what it needs from elsewhere: a Russian Progress vehicle will deliver supplies next month that the shuttle would have carried. And although the station's international partners are disappointed by the delay, said programme manager Bill Gerstenmaier, “they understand the decision”.