Complementing future CMB ground-based data sets with balloon observations

Future CMB ground-based missions, like CMB-S4, have ambitious plans of constraining models of inflation by measuring the tensor-to-scalar ratio, r, with an uncertainty of 5×10^-4. A key challenge for measuring r is separating the CMB and Galactic foregrounds. Specifically, polarized dust emission is the major contaminant, and it is best characterized by observations at higher frequencies in the range of 300 to 3000 GHz. The CMB-S4 frequency bands extend up to 270 GHz. We explore the added value of complementary balloon observations at higher frequencies to assist with foreground cleaning for CMB-S4. We describe two possible instruments: an imager with frequency coverage from 150 to 360 GHz and a spectrometer with frequency coverage from 100 to 800 GHz. In both cases, we demonstrate the impact of these complementary balloon observations on the uncertainty and bias in the measurement of r when added to the CMB-S4 dataset.