Discover the cosmos! Each day a different image or photograph of
our fascinating universe is featured, along with a brief
explanation written by a professional astronomer. February 11,
1997 Explanation: Astronaut Carl Walz waves at his colleagues
from the aft end of the Space Shuttle Discovery's payload bay -
during a 1993 spacewalk to evaluate tools, tethers, and a foot
restraint slated for use in the first Hubble Space Telescope
servicing mission. Today's successful launch of Discovery begins
the second servicing mission to the Hubble. Discovery's crew
will rendezvous with the orbiting telescope and capture it with
the shuttle's manipulator arm. With Hubble in the payload bay
the crew will conduct spacewalks to replace two existing
instruments with new ones. To be installed are the Space
Telescope Imaging Spectrograph and the Near Infrared Camera and
Multi-Object Spectrometer. Other hardware will also be replaced
and upgraded including the telescope's Fine Guidance Sensor. The
improved instrumentation will