Submillimeter Wave Astronomy Satellite observations of extended water emission in Orion

We have used the Submillimeter Wave Astronomy Satellite to map the ground-state 1(10)-->1(01) transition of ortho-H2O at 557 GHz in the Orion molecular cloud. H2O emission was detected in Orion over an angular extent of about 20', or nearly 3 pc. The water emission is relatively weak, with line widths (3-6 km s(-1)) and V-LSR velocities (9-11 km s(-1)) consistent with an origin in the cold gas of the molecular ridge. We find that the ortho-H2O abundance relative to H-2 in the extended gas in Orion varies between 1 and 8 x 10(-8), with an average of 3 x 10(-8). The absence of detectable narrow-line ortho-(H2O)-O-18 emission is used to set a 3 sigma upper limit on the relative ortho-H2O abundance of 7 x 10(-8).