The authors report on the progress towards a chip scale rubidium (85Rb) oscillator for space applications. The clock integrates the Orolia’s mRO-50™ Electronics Package (EP) assembled with the patented micromachined Physics Package (PP) developed by the CSEM (Centre Suisse d’Électronique et Microtechnique SA). Unlike the others chip scale atomic clock based on Coherent Population Trapping (CPT) principle, the Double Resonance (DR) interrogation is used, simplifying the electronic design and allowing to achieve a relative frequency stability of 8E-11/√tau from 1 to 100s integration times and a power consumption of 160mW under vacuum at 25°C. To the knowledge of the authors, it is the best short term atomic frequency stability reported so far for the category of clocks based on MEMS atomic vapor cells. Three mRO-50™ made of Commercial Of The Shelf (COTS) components have been radiation tested up to 25 kRad with a dose rate of 928 Rad/day. One clock failed at 13 kRad and the root cause is reported. The two remaining clocks survived during the whole test and a frequency drift per Rad of -1.3E-14/Rad and -1.8E-14/Rad was measured.
