The J_K = 1_0 → 0_0 transition of ammonia at 572.5 GHz has been detected in OMC-1 from NASA's Kuiper Airborne Observatory. The central velocity of the line (V_(LSR)≈ 9 km s^(-1)) indicates that it originates in the molecular cloud material, not in the hot core. The derived filling factor of ≳ 0.09 in a 2' beam implies a source diameter of ≳ 35" if it is a single clump. This clump area is much larger than that derived from observations of the 1_1 inversion transition. The larger optical depth in the
1_0 → 0_0 transition (75-350) can account for the increased source area and line width as compared
with those seen in the 1_1 inversion transition
