TITLE: GCN CIRCULAR NUMBER: 29219 SUBJECT: Swift GRB210102.01: Global MASTER-Net observations report DATE: 21/01/02 00:24:22 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) 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 GRB210102.01 (trigger No 1015615,15h 38m 48.72s , -84d 11m 20.4s, R=0.05) errorbox 70 sec after trigger time at 2021-01-02 00:18:22 UT, with upper limit up to 13.5 mag. The observations began at zenith distance = 60 deg. The sun altitude is -30.5 deg. The galactic latitude b = -23 deg., longitude l = 307 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1517044 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 75 | MASTER-SAAO | P\ | 10 | 13.2 | 109 | MASTER-SAAO | P\ | 20 | 13.5 | 154 | MASTER-SAAO | P\ | 30 | 13.3 | 273 | MASTER-SAAO | P\ | 50 | 13.3 | The observation and reduction will continue. The message may be cited.