Complex sentence: A Spacelab component was used on 25 shuttle flights, but the components were decommissioned in 1998--science work was supposed to be moved to the International Space Station and Spacehab module, a pressurized carrier similar to the Spacelab Module.
Split into simpler sentences: A Spacelab component was used on 25 shuttle flights, but the components were decommissioned in 1998. Science work was to be moved to the International Space Station and Spacehab module, a pressurized carrier similar to the Spacelab Module.