NASA should move swiftly to build and launch a half-billion-dollar infrared space telescope optimized for spotting asteroids and comets if the U.S. space agency wants to come close to meeting a congressionally mandated 2020 deadline for detecting nearly all such near-Earth objects (NEOs) that could collide with Earth, the National Research Council said in a report released Jan. 22.

Congress in 2005 gave NASA 15 years to catalog 90 percent of NEOs with a diameter of 140 meters or larger. NASA spends $4 million annually on NEO surveys and well under $1 million studying ways to protect the Earth from potential collisions, according to the report, “Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies.” NASA’s current efforts, the report says, are inadequate to meet the goals Congress codified in the George E. Brown, Jr. Near-Earth Object Survey Act.

“If completion of the survey as close to the original 2020 deadline as possible is considered most important, a space mission conducted in concert with observation using a suitable ground-based telescope is the best approach,” the report says.

The National Research Council examined two existing mission concepts that could dramatically accelerate NASA’s NEO survey. Both involved half-meter infrared telescopes.

One is a Discovery-class mission proposal from NASA’s Jet Propulsion Laboratory in Pasadena. Calif., that entails positioning a roughly $500 million space telescope in orbit at the so-called Earth-Sun L1 Lagrange point. Such a spacecraft, drawing its heritage from the Spitzer Space Telescope and newly launched Wide-field Infrared Survey Explorer, or WISE, telescope, could discover 75 percent of all NEOs 140 meters across or larger within five years and 90 percent within 10 years, according to the report.

The other mission concept, proposed by Boulder, Colo.-based Ball Aerospace & Technologies Corp., calls for placing a $600 million space telescope in a Venus-trailing orbit, where it could detect 90 percent of the specified NEOs in slightly less than eight years. With help from a suitable ground-based telescope, the survey could be completed in fewer than five years, the report says.

If policymakers decide that containing costs is more important that meeting the 2020 deadline, a large ground-based telescope could be pressed into service to complete the survey by 2030, the report says.

The report includes other recommendations for improving NEO detection and collision-mitigation efforts, including immediate action to ensure continued operation of the Arecibo Observatory in Puerto Rico and the initiation of a targeted research program in the area of impact hazard and protection.