GRB 210802A: MITSuME Okayama optical upper limits

We observed the field of GRB 210802A (V. Lipunov et al. GCN Circular #30586, P. A. Evans et al. GCN Circular #30587, F. Longo et al. GCN Circular #30589, O.J. Roberts et al. GCN Circular #30590, B. Sbarufatti et al. GCN Circular #30591, Y.-D. Hu et al. GCN Circular #30592, Alan M. Watson et al. GCN Circular #30593) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope Okayama. The observation with a series of 60 sec exposures started at 2021-08-03 10:34:24 UT (14.4 hours after Fermi trigger). We stacked the images with good conditions. We did not detect any uncatalogued sources within the XRT error region (B. Sbarufatti et al. GCN Circular #30591). We obtained the 5-sigma limits of the stacked images as follows. T0+[hour] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ 15.8 2021-08-03 11:54:24 1080 Rc>17.2, Ic>16.9 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used PS1 catalog for flux calibration. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).