NASA is studying the placement of an instrument on a commercial or U.S. government communications satellite to detect and track asteroids near Earth for potential human visits.

An image from the WISE spacecraft looking for Earth-Trojan asteroids. Credit: NASA

The space agency has released a request for information seeking ideas for a sensor to discover a hypothesized set of asteroids very near Earth, opening the possibility for exploration by future astronaut crews.

Instead of funding a dedicated spacecraft to survey asteroid populations, NASA is considering a piggyback instrument on a satellite in geosynchronous orbit, a perch more than 22,000 miles above the equator tailored for communications missions.

The request for information will supply NASA officials with information on what options exist to obtain data on asteroids near Earth, objects which would be easiest to reach on a human expedition.

NASA is planning a crewed mission to an asteroid in the 2020s, but officials have not selected a destination yet for the first voyage. Spacecraft bound for asteroids near Earth would require less fuel to complete their missions.

Scientists are also looking for Earth-Trojan asteroids, which share Earth's orbit and circle the sun either behind or ahead of the planet. NASA's WISE infrared space telescope discovered the first Earth-Trojan asteroid in 2010.

Earth-Trojan asteroids are difficult to find because they appear close to the sun and are often only visible in daylight.

The Itokawa asteroid was visited by the Hayabusa spacecraft. Credit: JAXA

Respondents should offer instrument solutions ready for launch as soon as 2016, costing less than $50 million, and capable of operating for at least five years, according to the RFI.

NASA is asking for instrument concepts which could find asteroids as small as 30 meters, or about 100 feet, across.

A dedicated spacecraft for near-Earth asteroid detection would cost much more than a hosted instrument on a communications satellite, according to scientists. Another, more costly way to detect near-Earth asteroids would be to dispatch a telescope to be stationed near the orbit of Venus looking back toward Earth, and away from the sun.

"The instrument would point outward from Earth and must be capable of detecting near-Earth asteroids in very Earth-like orbits, and capable of detecting asteroids of as little as 30 meters in diameter," officials wrote in the RFI. "Additional factors of interest include the ability to quantify spin rate and calculate the size and shape of detected asteroids."

Scientists must respond to the RFI by Sept. 17.