<p>WASHINGTON – NASA may be aiming for the moon and even Mars, but it has not yet laid the groundwork for modernizing the aging space- shuttle fleet, a government report said Friday.</p>
<p>A year after the shuttle Columbia disintegrated over Texas, killing all seven astronauts aboard, NASA has not figured out how to upgrade the three remaining shuttles to make them safe and usable for at least the next 15 years, the General Accounting Office said.</p>