The first space-based, Nyquist-sampled cross-track microwave sounder, the Advanced Technology Microwave Sounder (ATMS), will provide atmospheric vertical profile information to improve numerical weather and climate modeling. Scheduled for launch in late 2011, ATMS will provide unprecedented global observations of precipitation and atmospheric dynamics. This presentation focuses on the ATMS spectrometer attributes, including spectral and spatial coverage, resolution, stability, and reliability. Comparisons with the heritage sensor, the Advanced Microwave Sounding Unit, highlight several improvements in spatial coverage and resolution. Illustrations of improved performance will be demonstrated using retrievals of precipitation and combined infrared/microwave retrievals of atmospheric vertical profiles. Finally, implications of sensor misalignment will analyzed using simulations based on high-resolution forecast models coupled with radiative transfer codes.