An ablation system for ablating tissue in need for treatment, comprising: an ablation catheter having at least one electrode, a power source coupled to said at least one electrode, said power source being programmable to deliver at least one programmable level of power; a voltage measurement device for measuring a voltage signal being delivered to the tissue; a current measurement device for measuring a current signal being delivered to the tissue; a phase measurement device to determine an amount of phase change between the measured voltage signal and the measured current signal; a clock to measure a time period during which ablative power is delivered by the power source; a lesion analysis processor for estimating lesion formation as a function of at least: the measured phase change between the voltage signal and the current signal; information indicating the programmable power level at which the power source delivers ablative power to tissue in need of treatment; and the measured time period for which ablative power is delivered by the ablation catheter to tissue in need of treatment; and a controller coupled to the power source and the lesion analysis processor for controlling the power source based on information provided by the lesion analysis processor, wherein the power source is coupled to a first electrode and is used to deliver ablation energy to the tissue in need of ablation, said system further comprising: a second power source coupled to a second electrode on the catheter, said second power source being configured to deliver assessment power for measurements by the voltage measurement device and the current measurement device to assess the degree of contact between the second electrode and the tissue in need of treatment. an ablation catheter having at least one electrode, a power source coupled to said at least one electrode, said power source being programmable to deliver at least one programmable level of power; a voltage measurement device for measuring a voltage signal being delivered to the tissue; a current measurement device for measuring a current signal being delivered to the tissue; a phase measurement device to determine an amount of phase change between the measured voltage signal and the measured current signal; a clock to measure a time period during which ablative power is delivered by the power source; a lesion analysis processor for estimating lesion formation as a function of at least: the measured phase change between the voltage signal and the current signal; information indicating the programmable power level at which the power source delivers ablative power to tissue in need of treatment; and the measured time period for which ablative power is delivered by the ablation catheter to tissue in need of treatment; and a controller coupled to the power source and the lesion analysis processor for controlling the power source based on information provided by the lesion analysis processor, wherein the power source is coupled to a first electrode and is used to deliver ablation energy to the tissue in need of ablation, said system further comprising: a second power source coupled to a second electrode on the catheter, said second power source being configured to deliver assessment power for measurements by the voltage measurement device and the current measurement device to assess the degree of contact between the second electrode and the tissue in need of treatment. a second power source coupled to a second electrode on the catheter, said second power source being configured to deliver assessment power for measurements by the voltage measurement device and the current measurement device to assess the degree of contact between the second electrode and the tissue in need of treatment.