GCN Circular 3167

S. T.  Holland, M. Still (GSFC/USRA), W. Landsman (GSFC), Adam Morgan, S. 
Hunsberger (PSU), A. Breeveld (MSSL), P. Roming (PSU), K. Mason, P. Schady 
(MSSL), M.  Ivanushkina (PSU), T. Poole (MSSL), C. Gronwall (PSU),
A. Blustin (MSSL), P. Brown (PSU), S. Rosen, K. McGowan, M. De Pasquale (MSSL),
P.Boyd, S. T. Holland (GRFC/UMBC), H. Huckle (MSSL), P. Broos (PSU), T. 
Kennedy, P. Smith, B. Hancock (MSSL), H. Krimm (GSFC/USRA), S. Kock (PSU), 
M. Carter (MSSL), K. Gendreau (GSFC), M.Chester (PSU), D. Hinshaw 
(GSFC/SPSYS), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of the Swift 
UVOT team.

The Swift Ultra-Violet/Optical Telescope (UVOT) began observing the field 
of GRB 050402 at 06:12:01.6 UT, approximately 125 seconds after the BAT 
trigger.  The first image was sent down via the TDRSS link approximately 
300 seconds after the trigger.  This image was a 100 second exposure taken 
with the V filter.  It was centred on the BAT position, and had a size of 
5 x 5 arcminutes, which covered 88% of the BAT error circle. The image was 
binned 8 x 8 to reduce the bandwidth required for transmission.  A 
comparison against the DSS showed no new sources down to a 5-sigma 
limiting magnitude of approximately V = 18.84 +/- 0.09 , based on 
preliminary in-orbit zero points.