TITLE: GCN GRB OBSERVATION REPORT NUMBER: 187 SUBJECT: GRB981220, sub-millimeter observations DATE: 99/01/02 22:20:45 GMT FROM: Ian Smith at Rice U I. A. Smith (Rice University), R. P. J. Tilanus and F. Baas (Joint Astronomy Centre) report on behalf of the James Clerk Maxwell Telescope (JCMT) GRB collaboration: We used the SCUBA sub-millimeter continuum bolometer array on the JCMT to observe the variable radio source J034228.94+170914.6 in the error box of GRB 981220 (Galama et al. GCN #168, Frail et al. GCN #170). The observation, performed in mediocre weather, started UT 1998 Dec 30.24 and lasted 3.8 hours. No source was detected at this location: the 850 micron flux density was 0.1 +/- 1.6 mJy. This report may be cited in publications.