WASHINGTON — A private company made up of former NASA astronauts and US scientists said Thursday it is planning to build and launch its own space telescope to track dangerous asteroids and protect the Earth.

The project by the B612 Foundation aims to launch the "first privately funded deep space mission -- SENTINEL -- a space telescope to be placed in orbit around the sun."

The foundation is headed by Ed Lu, a former NASA astronaut who flew aboard the US space shuttle and Russia's Soyuz and worked at the International Space Station.

Lu said the project would expand on knowledge about asteroids -- NASA already tracks potentially dangerous near-Earth objects 24 hours a day -- and protect Earth's citizens.

"The orbits of the inner solar system where Earth lies are populated with a half million asteroids larger than the one that struck Tunguska (Russia, June 30, 1908)," Lu said in a statement.

"And yet we've identified and mapped only about one percent of these asteroids to date."

Sentinel expects to launch sometime around 2017 or 2018 on a five-year mission, possibly aboard a rocket owned by the US company SpaceX that recently sent its own cargo ship to the ISS and back.

During that time it would "discover and track half a million near Earth asteroids, creating a dynamic map that will provide the blueprint for future exploration of our solar system, while protecting the future of humanity on Earth," the foundation said in a statement.

The foundation is working with Colorado-based Ball Aerospace to design and build the space telescope, which will cost hundreds of millions of dollars.

Scanning the night sky every 26 days, it would send information back to NASA's Deep Space Network, the Laboratory for Space Physics, and research institutions and governments via NASA's Minor Planet Center.

NASA is already tracking asteroids and says it has found 9,064 near-Earth objects so far, about 847 of which are asteroids with a diameter of approximately one kilometer (0.6 miles) or larger.

Just over 1,300 have been classified as "Potentially Hazardous Asteroids" (PHAs).

"We believe our goal of opening up the solar system and protecting humanity is one that will resonate worldwide, said Lu.

"We've garnered the support and advice of a number of individuals experienced with successful philanthropic capital campaigns of similar size or larger, and will continue to build our network."