Prompt observation of Gamma Ray Bursts (GRBs) events are unanimously considered of paramount importance for GRB science and related cosmology. Such observations at NIR wavelengths are even more promising allowing one to monitor high-z Ly-alpha absorbed bursts as well as events occurring in dusty star-forming regions.

REM (Rapid Eye Mount) is a fully robotized alt-az 60-cm fast slewing telescope equipped with a high throughput NIR (four filters) camera dedicated to detecting the prompt IR afterglow of GRBs. REM can discover objects at extremely high redshift and trigger within minutes large telescopes to observe them. A dichroic placed at one of its Nasmith foci splits the beam in two. This way, REM can feed simultaneously ROSS (REM Optical Slitless Spectrograph).

ROSS monitors intensively the prompt optical continuum (450-900 nm) of GRB afterglows via a low dispersion GRISM. It will be also equipped with standard filters and (in the near future) a polarizer. REM is placed at ESO - La Silla (Chile) and it is now operational since 3 years. The first light is expected by the end of this year.

ROSS reforms, via a suitable fore-optics, a pupil where an AMICI prism is located. The spectra are then reformed on the focal plane via a magnification 1 camera. The CCD is a Marconi pre-mounted in a detector head cooled by a 3-stages peltier system made by Apogee (model AP47).

See also the REM Web page.