Micro OXCO EWOS-0513: A 20 years space odyssey up to 67P/Churyumov-Gerasimenko

The story probably started somewhere on the planet Mars in the middle of the 90s' when the Sojourner rover demonstrated that it was possible to make great space missions with `low cost' systems. It was the beginning of the `Better / Faster / Cheaper' period. It led space agencies and space industry to develop space equipment using `professional' systems instead of full space qualified ones. In 1995, the CNES, the French Space Agency, decided to develop a family of `low cost' space miniaturized OCXOs. A so called EWOS-0500 micro OCXO, used up to then for distress beacons, was selected for this purpose. The EWOS-0500 was a very small size (DIL 14, 1.5 cm3) and low power (150 mW) OCXO with a short-term stability in the 10-11 range (A-Dev) and a frequency stability of 0.2 ppm in the temperature range [-30 °C; +60°C]. A specific qualification program was set up, to demonstrate the performances and the capability of this OCXO to fulfil space missions. The EWOS-0513 micro OCXO was born. The EWOS-513 was embarked on numerous space missions, mainly in low earth orbit. But some of them were also embarked on the Rosetta mission for a 10 years journey through the solar system up to the 67P/Churyumov-Gerasimenko comet. Once arrived, they contributed to the success of the mission, allowing telecommunication between the orbiter and the lander and being involved in the science program through the CONSERT instrument. This paper redraws the main steps and the main performances of this program that led an oscillator initially intended for distress beacons to contribute to the success of the Rosetta mission.