Submillimeter Wave Astronomy Satellite observations of Jupiter and Saturn:Detection of 557 GHz water emission from the upper atmosphere

We have used the Submillimeter Wave Astronomy Satellite to carry out observ ations on Jupiter and Saturn in two bands centered at 489 and 553 GHz. We d etect spectrally resolved 557 GHz H2O emission on both planets, constrainin g for the first time the residence levels of external water vapor in Jupite r's and Saturn's stratosphere. For both planets, the line appears to be for med at maximum pressures of about 5 mbar. For Jupiter, the data further sho w that water is not uniformly mixed but increases with altitude above the c ondensation level. In each planet, the amount of water implied by the data is 1.5-2.5 times larger than inferred from Infrared Space Observatory data. In addition, our observations provide new whole-disk brightness measuremen ts of Jupiter and Saturn near 489 and 553 GHz.