The U.S. Naval Observatory GRB team (F. J. Vrba, C. B. Luginbuhl,
A. A. Henden, S. E. Levine, J. Munn, B. Canzian, H. H. Guetter),
D. H. Hartmann (Clemson Univ.), and M. C. Jennings (IGPP, UCR visitor)
reports that it intends to observe the IPN/RXTE error box for GRB990506
reported in GCN 291 with the USNO 1.0-meter telescope in Rc-band,
beginning at about 0330 07May99 UT. Since we expect photometric
conditions for the night, we plan to produce a photometric calibration
sequence in B, V, Rc, and Ic bands for the field.