GCN Circular 11285
T. Sakamoto (UMBC/GSFC), D. Donato (UMCP/GSFC), N. Gehrels (GSFC), T. Okajima (JHU/GSFC), Y. Urata (NCU), C.A. Wallace (FGCU) We observed the field of GRB 100915A detected by Swift (trigger #434178; Littlejohns et al., GCN Circ. 11277) with the 14-inch Goddard Robotic Telescope (GRT) located at the Goddard Geophysical and Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/). A total 423 images of 5 sec (200 images), 30 sec (80 images), 60 sec (120 images) and 100 sec (23 images) exposures were taken in the R filter starting from September 15 01:33:32 (UT) about 146 seconds after the trigger (70 seconds after the BAT position notice) and stopped on September 15 05:49:30 (UT). We do not detect the optical afterglow both in the individual images and the stacked image, which only combined good quality 418 images, inside the XRT position (Osborne et al., GCN #11279). The estimated five sigma upper limit of the combined image (total exposure of 12500 sec) is ~19.8 mag using the USNO-B1 catalog.