Recognising the threat of near-Earth objects (NEOs), many ground-based surveys have been deployed worldwide. However, ~20% of these potential impactors are estimated to be approaching us from the day-side, and are thus very difficult to detect using ground surveys. Over the last decade, several space-based capabilities have emerged in an effort to discover and catalogue NEOs, yet little research has gone into dealing with imminent-impacting NEOs. The aim of this thesis is to perform a mission analysis of a space-based telescope that provides warning for Earth-impacting NEOs down to 20 m in size, by determining the performance of both a visible and an infrared (IR) space-based telescope used in two different mission candidates. The best space-based NEO survey system is concluded to be an IR telescope placed at the Sun-Earth solar-sail displaced L1 point due to the long warning times obtained and the beneficial contribution to existing ground-based surveys.