In typical Intelligence Surveillance and Reconnaissance (ISR) missions, persistent surveillance is commonly defined as the exercise of automatic intelligence discovery by monitoring a wide area coverage at a high altitude leveraging an aerial platform (manned or unmanned). It can be large enough to carry a matrix of high resolution cameras and a rack of high performance computing images processing and exploitation units (PEU). The majority of the small unmanned aerial vehicles (sUAV) are able to carry optics payloads, allowing them to take aerial images from strategic viewpoints. This capability constitutes a key enabler for an immense number of applications, such as crowd monitoring, search and rescue, surveillance scenario, industrial inspection and so on. The constrained onboard processing power in addition to the strict limit in the flying time of sUAV are amongst the serious challenges that have to be overcome to enable a cost effective persistent surveillance based on sUAV platforms. In this paper, we conduct a feasibility study for developing a potential sUAV based persistent surveillance system with tethered power supply.