The Dutch Rubin Enhanced Atmospheric Monitor – DREAM – brings high-resolution, real-time information on all-sky transparency and cloud coverage to the Vera C. Rubin Observatory. Leveraging the MASCARA legacy, DREAM employs five wide-field cameras, pointing upward and in the four cardinal directions. It precisely measures the brightness of all bright stars (V < 8.4) with a cadence of 6.4 seconds. To disentangle instrumental and stellar brightness variations from transmission fluctuations, a comprehensive spatial-temporal calibration is applied. The resulting transmission variations are calibrated and processed to generate an all-sky image of transparency, providing the actual cloud cover at an approximate cadence of 30 seconds. DREAM also produces calibrated light curves for stars brighter than magnitude 8.4, extending the temporal coverage of the MASCARA southern hemisphere survey. Integrated and tested at Leiden Observatory in 2023, DREAM was shipped in November of the same year and installed in close proximity to the Vera C. Rubin Observatory. In its initial phase, DREAM supplies cloud coverage and transparency data to the Auxiliary Telescope. Once the LSST Camera of the Vera C. Rubin Observatory becomes operational, DREAM will play a crucial role in optimizing the survey strategy by providing input to the scheduler, particularly in non-photometric conditions.
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