Whole-Disk Observations of Jupiter, Saturn, and Mars in Millimeter/Submillimeter Bands

New balloon-borne observations of whole-disk brightness ratios for Jupiter, Saturn, and Mars are reported in four millimeter/submillimeter bands of bandwidth Δν~1-2 cm^-1. Using the effective planetary radii of Hildebrand et al., we find that T_Mars/T_Jupiter=1.158+/-0.015, 1.189+/-0.015, 1.470+/-0.019, and 1.515+/-0.019 and T_Saturn/T_Jupiter=0.833+/-0.012, 0.758+/-0.010, 0.818+/-0.012, and 0.840+/-0.012, at ν=5.7, 9.5, 16.5, and 22.5 cm^-1, respectively. Using models for the brightness temperature of Mars, we also give the whole-disk brightness temperatures for Jupiter and Saturn for the four frequencies.