REM is triggered by a signal from a high-energy satellite such as Swift and rapidly points to the detected location in the sky.

The two cameras can observe simultaneously thanks to a dichroic placed before telescope focus the same field of view of 10×10 arc minutes.

The instrument was optimized for photometry of fast transients with a best time resolution of about 0.1 s. The observatory is operated for the Instituto Nazionale di Astrofisica by the REM Team.

[3] Since its installation and commissioning at ESO, REM rapid and multi-band observations allowed to contribute to several important discoveries in some cases widely reported by ESO press releases; for instance, the observations a few seconds after its discovery of GRB060418, GRB06067A and GRB080319B.

In addition, a larger set of observations of targets different from GRBs has been performed, securing long time series of data for variable stars, AGNs, etc.