"It is highly unlikely that the science life of Hubble would be extended with a robotic mission."

Beginning no later than 2008, we will send a series of robotic missions to the lunar surface to research and prepare for future human exploration.

"I would like to take the robotic mission off the plate," he said.

Without a human presence in space, support even for robotic missions is likely to dry up.

But if a robotic mission could not install the new instruments, which is the hardest task, "I would be disappointed," he said.

The first decade is planned to focus on robotic missions.

The science budget includes $75 million for planning a robotic mission to bring the Hubble telescope down safely at the end of its life.

These plans were later canceled, the robotic mission being described as "not feasible".

The exact shape of the 1994 robotic mission is still unknown, he said.

Find out if you've got the right stuff to plot the course for space shuttle and robotic missions.