GCN Circular 11193
W. Landsman (GSFC/Adnet) and T. Sakamoto (NASA/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 100902A 326 s after the BAT trigger (Sakamoto et al., GCN Circ. 11181). No optical afterglow consistent with the XRT position (Beardmore et al., GCN Circ. 11188) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 326 475 147>20.4 white 326 1008 295>20.8 w1 532 18249 823>20.7 m2 1063 14541 1136>20.8 w2 632 12947 1528>21.2 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.31 in the direction of the burst (Schlegel et al. 1998).