TITLE: GCN CIRCULAR NUMBER: 8778 SUBJECT: GRB 090102: GRT Optical Observation DATE: 09/01/04 17:13:41 GMT FROM: Takanori Sakamoto at NASA/GSFC T. Sakamoto (UMBC/GSFC), D. Donato (ORAU/GSFC), N. Gehrels (GSFC), T. Okajima (JHU/GSFC), T. N. Ukwatta (GWU/GSFC), Y. Urata (Saitama U), C. Wallace (FGCU) We observed the field of GRB 090102 detected by Swift (trigger #338895; Mangano et al., GCN #8762) with the 14-inch Goddard Robotic Telescope (GRT) located at the Goddard Geophysical and Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/). Ten set of 5 sec and five set of 10 sec and 30 sec exposures were taken in the R filter starting from Jan. 2 03:11:58 (UT) about 16.2 min after the trigger. We do not detect the optical afterglow (Klotz et al., GCN #8761, Mangano et al., GCN #8762) both in the individual images and the combined image. The estimated three sigma upper limit of the combined image (total exposure of 250 sec) is ~17.9 mag using the USNO-B1 catalog.