HOUSTON - Astronauts are conserving power on the space shuttle Atlantis because bad weather in Florida may keep them in orbit longer than planned.

Storms could delay a scheduled Friday landing at Kennedy Space Center. NASA can try again in Florida on Saturday and if that doesn't work, they have several options for a Sunday landing.

Astronauts have the day off Wednesday. They told reporters during a news conference that they were looking forward to coming home after the 11-day mission.

They said their upgrades of the 19-year-old Hubble Space Telescope showed how important it is to have humans and machines work together in space.

Later Wednesday, President Barack Obama will make a private phone call to Atlantis.