TITLE: GCN CIRCULAR NUMBER: 31358 SUBJECT: GRB 220101A: CAHA 2.2m/CAFOS detection DATE: 22/01/01 22:29:15 GMT FROM: Alexander Kann at IAA-CSIC A. de Ugarte Postigo (Obs. Cote d'Azur), D A. Kann (HETH/IAA-CSIC), C. C. Thoene, M. Blazek (both HETH), J. F. Agui Fernandez (HETH/IAA-CSIC), P. Martin, and I. Hermelo (both CAHA) report: We observed the afterglow of GRB 220101A (Swift detection: Tohuvavohu et al., GCN #31347; Fermi/LAT Detection: Arimoto et al., GCN #31350; AGILE detection: Ursi et al., GCN #31354; afterglow detections: Kuin & Tohuvavohu, GCN #31351; Fu et al., GCN #31353; Hentunen et al., GCN #31356; Perley, GCN #31357; redshift z = 4.61: Fu et al., GCN #31353) with CAFOS, mounted on the 2.2 m telescope, at the Calar Alto Observatory (Almeria, Spain). The observation started at 19:35:31 UT on 01 January 2022 (13.47 hr after the GRB) and consisted of 6 x 90 s integrations in the i' band. The afterglow is well-detected in the individual images. Against comparison stars from SDSS, we measure i' = 18.45 +/- 0.03 mag (AB) in the stacked image at mid-time 0.60177 d after the trigger. We note this is a very bright GRB and afterglow, further follow-up is encouraged.