Spectroscopy and photometry of IGM's diffuse radiation (SPIDR): a NASA small explorer mission

The SPIDR mission is designed to test predictions of cosmological models of the structure of the universe. In addition, SPIDR will provide new information about hot gas in a variety of Galactic environments. These diagnostics will bo obtained through spectral imaging of selected astrophysical fields in the 100 - 160 nm band. In this paper we will provide an overview of the SPIDR mission and its observational approach.