Swift GRB 210318A: Global MASTER-Net observations report

MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 210318A ( E. Troja et al., GCN 29662) errorbox 50452 sec after notice time and 50501 sec after trigger time at 2021-03-18 17:56:12 UT, with upper limit up to 19.7 mag. Observations started at twilight. The observations began at zenith distance = 58 deg. The sun altitude is -14.2 deg. The galactic latitude b = -69 deg., longitude l = 248 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1570922 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 50591 | MASTER-SAAO | C | 180 | 19.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.