NASA’s New NEO Mission Will Substantially Reduce Time to Find Hazardous Asteroids

NASA’s New NEO Mission Will Substantially Reduce Time to Find Hazardous Asteroids

With its first tranche of funding for NASA’s new mission to search for Near Earth Objects (NEOs), Congress is underscoring its interest in protecting Earth from these Potentially Hazardous Objects.  After directing NASA in 2005 to find 90 percent of NEOs greater than 140 meters in diameter within 15 years, it is now funding a dedicated space telescope to make that a reality.  The original deadline cannot be met, but the new mission will reduce from 30 to 10 the number of years still needed to achieve the goal.

NEOs are asteroids and comets that come close to Earth and pose the risk of collision with literally Earth-shattering consequences.  The extinction of the dinosaurs has been traced to such a collision 65 million years ago, and the 1908 Tunguska event in Russia is another sobering example from history though no one is thought to have been harmed that time. But the 2013 explosion of a meteor over Chelyabinsk, Russia captured on countless dashcam cameras and shared around the world reminded everyone of the threat.  Over 1,000 people were injured by flying glass from windows broken by the accompanying sonic boom, but fortunately the damage was limited.

Congressional concern about the threat dates back two decades.  In 1998, Congress directed NASA to find and catalog 90 percent of NEOs 1 kilometer or more in diameter within 10 years.  A NEO in that class is thought to be responsible for the extinction of the dinosaurs as debris billowed up high in the atmosphere, blocking sunlight and altering the climate.

NASA accomplished that objective and then took on a new mandate set by the George E. Brown Jr. Near-Earth Object Survey Act, part of the 2005 NASA Authorization Act:  find 90 percent of  NEOs 140 meters or more in diameter within 15 years.  That size NEO might not wipe out entire species, but would have significant regional effects.  (For comparison, the Chelyabinsk meteor was about 20 meters wide.)

That set 2020 as the deadline.  NASA has been working on it, but is not close to finding the majority of them.  NEOs are classified as “small bodies” in the solar system and at a meeting of NASA’s Small Bodies Assessment Group (SBAG) last Tuesday, Kelly Fast showed how far they have come, and how far they still have to go. She said it would take 30 years or more to find 90 percent of NEOs 140-meters or more in diameter at the current rate of discovery.  Fast manages the NEO Observation program at NASA headquarters.

Graphic from Kelly Fast’s presentation to NASA’s Small Bodies Assessment Group, January 14, 2020. Screengrab.

Finding these smaller NEOs is much more difficult.  The best way is by detecting their infrared (IR) signatures rather than looking with optical or radio telescopes.  A space-based IR telescope would speed up the discovery rate because it could see the entire sky.

Amy Mainzer proposed such a mission, NEOCam, for many years while she worked at the Jet Propulsion Laboratory (JPL), but it could not compete against science missions in NASA’s Discovery series and never made it past the “Phase A” concept stage.  Some scientists do not consider searching for asteroids to be “science,” but “planetary defense.” Hence it historically has not been included in the Decadal Surveys conducted by the National Academies of Sciences, Engineering, and Medicine every 10 years that set NASA’s science priorities.

Mainzer left JPL to join the University of Arizona’s Lunar and Planetary Laboratory last fall.  About that time, the National Academies published a separate report endorsing a space-based IR telescope specifically to locate NEOs in order to meet the congressional mandate.  The report agreed that it is planetary defense, not science, but argued that the solution is to create a planetary defense category apart from NASA’s science projects.

By then, NASA Administrator Jim Bridenstine had already come out publicly in support of such a mission noting that he gets asked about it at congressional hearings.  Soon thereafter, Thomas Zurbuchen, the head of NASA’s Science Mission Directorate, announced that NASA would proceed with a “Near Earth Object Surveillance Mission” (NEOSM) if Congress funded it.  He conceded that he was one of those who did not support the mission because it is not science, but had come to understand that there is more than science involved and many voices must be heard and consensus reached.

He estimated the cost at $500-600 million with launch no earlier than FY2025.

Congress came through with the first tranche of funding, $35.6 million, in the FY2020 appropriations bill.

At the SBAG meeting, Lindley Johnson cautioned there is “some work to do” in getting the rest of the money for future years.  He heads NASA’s Planetary Defense Coordination Office (PDCO) that has an annual budget of about $150 million and is already paying to develop the Double Asteroid Redirection Test (DART) to test a method to deflect incoming asteroids.  Congress did not increase the total PDCO budget to compensate for the money allocated to NEOSM, but “did make a pretty strong statement that they want NASA to pursue this capability,” Johnson pointed out.

The NEOSM spacecraft will be called NEO Surveyor.  JPL has been assigned to develop it.  Mainzer reiterated that it is the same spacecraft as NEOCam.  She was the Principal Investigator (PI) for NEOCam when she was at JPL.  Now she is “Survey Director” for NEOSM.

Johnson explained to that NEOSM is part of an international system of systems to identify and track NEOs.  Mainzer is responsible for the entire NEOSM project, which involves not only building and operating NEO Surveyor, but an investigation team based at the University of Arizona to process and analyze the data.  It will be added to data collected separately by ground-based telescopes, all of which is input to the catalog of NEOs maintained by the Minor Planet Center at the Harvard-Smithsonian Astrophysical Observatory.

Illustration of NEO Surveyor. Credit: University of Arizona.

NEO Surveyor will be placed at the Sun-Earth L1 Lagrange point 1.5 million kilometers from Earth towards the Sun.  As NEOCam, it passed a Systems Requirement Review/Mission Definition Review in February 2018 and its IR telescope instrument passed another milestone review in November 2018.  Johnson said NEO Surveyor is therefore ready for Phase B, preliminary design and technology development.

Mainzer said once it is working, it will take 5 years to cross the two-thirds mark in meeting the congressional mandate and 10 years to reach the final goal of 90 percent.

If NEO Surveyor launches in 2025, that would achieve Congress’s goal around 2035, long past the original deadline, but much sooner than without it.

This article has been updated.

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