The ability of the Hubble Space Telescope to be serviced by astronauts, using a space shuttle as a platform, is one of its design features. This proved its worth very early, with the first servicing mission installing COSTAR. The second such mission – a ten day effort with Discovery as the workhorse – took place in February 1997; two new instruments were installed (and two removed), the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Space Telescope Imaging Spectrograph (STIS), and many other, smaller, upgrades and repairs made.