Aspera is an extreme ultraviolet (EUV) SmallSat mission designed to image and characterize the distribution of warm-hot phase gas emission from nearby galaxy halos for the first time. Aspera observes warm-hot phase gas via the O VI 1032 Å rest frame emission line using four parallel channels of Rowland-Circle-like configuration spectrographs. The design is based on the heritage of FUSE, and leverages recent technological improvements in UV coatings, gratings, and detectors. Here, we present the instrumentation of Aspera, its payload design, and projected performance. This faint and diffuse source optimized design enables line detection sensitivity down to 3.7E-19 erg/s/cm2/arcsec2/Å, more than three orders of magnitude fainter than HST-COS.