How Nasa can detect near-Earth objects that pose hazard to our planet

A new report from the National Research Council in the US has laid out options Nasa could follow to detect more near-Earth objects (NEOs) - asteroids and comets that could pose a hazard if they cross Earth's orbit.According to the report, the $4 million the US spends annually to search for NEOs is insufficient to meet a congressionally mandated requirement to detect NEOs that could threaten Earth.Congress mandated in 2005 that NASA discover 90% of NEOs whose diameter is 140 metres or greater by 2020, and asked the National Research Council in 2008 to form a committee to determine the optimum approach to doing so. In an interim report released last year, the committee concluded that it was impossible for Nasa to meet that goal, since Congress has not appropriated new funds for the survey nor has the administration asked for them. In its final report, the committee lays out two approaches that would allow Nasa to complete its goal soon after the 2020 deadline. The approach chosen would depend on the priority policymakers attach to spotting NEOs. If finishing Nasa's survey as close as possible to the original 2020 deadline is considered most important, a mission using a space-based telescope conducted in concert with observations from a suitable ground-based telescope is the best approach, according to the report. If conserving costs is deemed most important, the use of a ground-based telescope only is preferable. The report also recommends that Nasa monitor for smaller objects — those down to 30 to 50 metres in diameter - which recent research suggests can be highly destructive. However, the report stresses that searching for smaller objects should not interfere with first fulfilling the mandate from Congress. Beyond completion of that mandate, the report notes the need for constant vigilance in monitoring the skies, so as to detect all dangerous NEOs. In addition, the report says that the US should undertake a peer-reviewed research program to better investigate the many unknown aspects connected with detecting NEOs and countering those that could be a threat.