The Infrared Space Observatory (ISO) was a successor to the Infrared Astronomical Satellite (IRAS). ISO was launched in November 1995, and was activated on November 28, 1995. It was about the same size as IRAS, and was constructed in about the same way. It had much more sensitive infrared instruments, however, including two infrared spectrographs. Unlike IRAS, which surveyed as much of the sky as it could, ISO was targeted at specific astronomical objects and regions for detailed studies. It helped pave the way for the current-generation infrared space telescope, the Spitzer.