  TUS (Tracking Ultraviolet Set-up), the first orbital telescope of ultra-high
energy cosmic rays (UHECRs), has demonstrated that instruments of this kind
have much broader capabilities and can also detect meteors, transient luminous
events, anthropogenic glow and other processes taking place in Earth atmosphere
in the UV frequency range. In this short letter, we address the question if an
orbital UHECR detector can also register gamma-ray bursts (GRBs) via the
fluorescent glow of irradiated nocturnal atmosphere. An analysis of the Fermi
GBM catalog of GRBs and properties of several active and perspective
instruments reveals that a detector with parameters of the optical system
similar to those of the KLYPVE-EUSO (K-EUSO) or POEMMA telescopes and an
appropriate \slow-mode" trigger will be able to observe only two GRBs in
average every year of operation. POEMMA will register up to 3-4 GRBs in a year
of operation in the stereo mode.
