The vision behind the PHASER project is to provide the European Space Industry with a new Analog to Digital conversion system that allows the direct digitalization of typical RF signals from K up to Ka band. PHASER will develop a space-grade, high speed digitizer capable of direct RF-sampling up to Ka band signals, exhibiting an improvement of more than two order of magnitude in the digitizer frequency response respect to the SoA, which enables a dramatic hardware complexity reduction for the next generation satellite payloads, as preliminary assessed in an ESA research program where the fundamental concept was already demonstrated by the consortium. The High speed, high frequency Electro-Photonic ADC system capable of down-converting and digitalize a high frequency band pass signal will be composed by a high speed optical sub-sampling architecture as a key element, capable of working in a very wide range of frequencies (from few kHz up to tens of GHz) and down-converting high bandwidth signals without electronic mixing hardware or intermediate frequency stages. After this signal down-conversion, the system will use a suitable electrical ADC to digitalize the signal.PHASER system will be able to be integrated in any medium or large satellite platform in order to provide the different system designers with one of the key elements necessary to arrive to the so called “Digital Defined Satellite”. Having a Digital Defined Satellite means that all the possible evolutions in customers’ needs can be covered by the suitable reprogramming of the on board signal processing elements, thus extending the useful satellite lifetime over 25 years increasing in a proportional way the satellite profitability.