"You can't get to the station from a Hubble orbit. It is physically impossible. Commit to Hubble, you are going to Hubble. Or you are coming home. Without a safe haven how long can you stay airborne, while you are trying to fix whatever problem you have? If it's not fixable, obviously you want a rescue capability. How quickly can you get that there?"
The crew would depend on very basic repair methods if it found damage to the space shuttle while orbiting Earth.
Griffin, NASA's administrator, says his agency has learned much about inspecting for damage in the last three flights.
He is also confident NASA officials have solved the problem of foam shedding from the external tank.
A 1.67-pound piece of foam was determined to be the cause of the Columbia accident. The foam punctured a hole in Columbia's wing, allowing hot gases to penetrate the orbiter when it re-entered Earth's atmosphere, and triggering its destruction.
NASA has not been able to develop a repair method to fix a hole of that size on the orbiter should one be found on a future flight.
Milt Heflin was the lead flight director at the Johnson Space Center for the first Hubble servicing mission in December 1993. He says there is one picture from Hubble he cannot forget.
"It is the picture after the very first servicing mission. And it is the picture in the area of the Big Dipper -- that is the area where the handle and the Big Dipper comes together. It is an area if you stick your finger out, is the tip of your finger, is the size of the area Hubble is looking at where the handle and the Dipper comes together."
"What did Hubble see? Hubble saw hundreds, maybe even thousands of galaxies. Galaxies! We live in a galaxy. We are the star and the sun and planets around it. How arrogant of us to believe that we are it in this universe?"
Every day, the Hubble archives 3 gigabytes to 5 gigabytes of data and delivers between 10 gigabytes and 15 gigabytes to astronomers all over the world.
Hubble's gigabytes divulge precious information, and Hubble's images capture our imagination.