Deflecting an asteroid headed for Earth

How ready are we to find and deflect a dangerous asteroid in time?

A kinetic impactor has been tested once on a real asteroid. NASA's DART spacecraft hit Dimorphos, the moonlet of the Didymos binary, in September 2022, and changed the time Dimorphos takes to orbit Didymos by 33 minutes, plus or minus one minute. Finding the asteroids that matter is less far along. By 2021 about a third of the estimated 25,000 near-Earth objects of 140 metres or larger had been found, and the congressional goal of finding 90% by 2020 was missed. Survey telescopes are only now starting: Rubin Observatory has begun its ten-year survey, and NASA's NEO Surveyor is not due to launch before September 2027. ESA's Hera is due at the DART target in November 2026 to study the aftermath of the impact.

AI illustration · Illustrative scene, not a photograph of the specific device or experiment.
WHERE WE AREEngineering prototypes

Getting closer. Prototypes exist, but not in real-world use.

A kinetic impactor has been flown against a real asteroid and produced a measured orbit change, so the method has been tested in flight. That test was on one small binary moonlet, and the size of the effect depends on a mass that is still uncertain. No operational system exists that can find a threatening object and send a deflection mission in time. The stage is therefore engineering prototype: a working deflection test has been carried out, but no detect-and-deflect system is ready for a real threat.

The tech tree

Everything recorded on Vrulum that this future needs, oldest foundations at the top and the goal at the bottom. Lines show what each step requires.

What it takes: Deflecting an asteroid headed for Earth Unlocked Being researched Locked
  1. 2022Planetary defenceResearch and prototypes Being researched.
  1. 2021Near-Earth objects of 140 m or larger found by surveyIn progress Being researched.
  2. 2022Spacecraft hits a small asteroid on purposeDone Unlocked.
  3. 2023Orbit change measured after the impactDone Unlocked.
  4. 2026ESA's Ramses mission to asteroid ApophisIn progress Being researched.
  5. 2026Follow-up of a newly found object of about 60 mDone Unlocked.
  6. 2026Rubin Observatory ten-year survey startedDone Unlocked.
  7. Date not recordedNEO Surveyor infrared space telescopeNot started Locked.
  8. Date not recordedESA's Hera reaches the DART targetIn progress Being researched.
  9. Date not recordedDeflection mission ready for a real threatNot started Locked.
  1. GoalDeflecting an asteroid headed for EarthGoalRequires: Planetary defence, Near-Earth objects of 140 m or larger found by survey, Rubin Observatory ten-year survey started, NEO Surveyor infrared space telescope, Spacecraft hits a small asteroid on purpose, Orbit change measured after the impact, ESA's Hera reaches the DART target, ESA's Ramses mission to asteroid Apophis, Follow-up of a newly found object of about 60 m, Deflection mission ready for a real threat. Locked.

The road so far

4 of 9 steps done, 3 in progress.

  1. In progress · 2021Near-Earth objects of 140 m or larger found by survey

    The National Academies' 2023 decadal strategy estimates close to 25,000 near-Earth objects larger than 140 m. It says that by 2021 only about one-third had been discovered. The report notes that the survey completion deadline set by Congress was not met, and describes completion in under ten years as a reasonable timetable. [1]

  2. Done · Jun 2026Rubin Observatory ten-year survey started

    Rubin Observatory has begun its ten-year Legacy Survey of Space and Time after a period of system optimisation. In the optimisation phase it found more than 11,000 previously unknown asteroids, including 33 near-Earth objects. The sources reviewed give no completeness figure for 140 m objects from the full survey. [2]

  3. Not startedNEO Surveyor infrared space telescope

    NASA's NEO Surveyor is a space telescope with infrared detectors, built to find potentially hazardous asteroids and comets. Its detectors can pick up dark objects, and it can find asteroids approaching from the Sun's direction. NASA's mission page lists launch as no earlier than September 2027. NASA's 2021 announcement had said the goal was to find 90% of asteroids 140 m and larger within a decade of launch. [3][4]

  4. Done · 26 Sept 2022Spacecraft hits a small asteroid on purpose

    NASA's DART spacecraft impacted Dimorphos, the moonlet of the Didymos binary, on 26 September 2022. NASA describes DART as the first mission dedicated to demonstrating one method of asteroid deflection, a kinetic impactor. [5]

  5. Done · 1 Mar 2023Orbit change measured after the impact

    NASA reports that the orbit period of Dimorphos around Didymos changed by 33 minutes, plus or minus one minute. Ejected material added to the push. The momentum enhancement factor ranges from 2.2 to 4.9, depending on Dimorphos's mass, which is still uncertain. NASA says a deflection needs several years of warning at a minimum, but preferably decades. [6]

  6. In progressESA's Hera reaches the DART target

    ESA's Hera launched on 7 October 2024. On 7 October 2026 it first saw the Didymos system from about 236,500 km, as a single point of light. ESA's October 2025 announcement said arrival is on track for November 2026, a month earlier than planned. At Didymos, Hera will study the aftermath of the DART mission and help people learn to alter an asteroid's path. [7][8]

  7. In progress · 10 Feb 2026ESA's Ramses mission to asteroid Apophis

    ESA signed the main spacecraft contract for Ramses on 10 February 2026, with OHB Italia. The mission is a joint effort with JAXA. ESA plans a launch in spring 2028 and a rendezvous with Apophis ahead of its close flyby of Earth on 13 April 2029. Ramses is not yet flown. [9]

  8. Done · May 2026Follow-up of a newly found object of about 60 m

    ESA reports that asteroid 2024 YR4 was discovered on 27 December 2024 by the ATLAS telescope. ESA's January 2025 estimate gave a 1.2% chance of Earth impact on 22 December 2032. NASA now says it poses no significant impact risk to Earth in 2032 or beyond. A 2026 JWST study ruled out a lunar impact in 2032, which shows the value of space-based follow-up for objects that ground telescopes can no longer track. [10][11][12]

  9. Not startedDeflection mission ready for a real threat

    The sources reviewed show no deflection mission built and held ready for a real threat. NASA's 2018 national plan named developing deflection and disruption technologies as one of five goals, and the 2023 national strategy keeps that goal. [13][14]

Why it matters

An asteroid large enough to cause regional damage could be found with little warning. Whether people can respond depends on finding it early enough, knowing its path well enough, and having a way to change that path in time. Each step shown so far, from survey to impact test to follow-up, narrows the gap. The gaps that remain are finding small objects early and having a deflection mission ready to fly.

What stands in the way

  • By 2021 only about one-third of the estimated 25,000 near-Earth objects of 140 m or larger had been found, and the 2020 congressional goal of 90% was missed.
  • Survey telescopes are only now coming online. Rubin's ten-year survey has begun, and NEO Surveyor is not due to launch before September 2027.
  • Decametre-scale objects are hard to see and to track. The 2026 JWST study of 2024 YR4, about 60 m across, says such objects rapidly fade below detection limits after discovery, so hazard assessment can depend on targeted space-based observations.
  • Deflection has been measured once, on one small binary moonlet. The size of the momentum boost depends on Dimorphos's mass, which the published range leaves uncertain.
  • Warning time is the main constraint. NASA says a deflection needs several years of warning at a minimum, but preferably decades.
  • No deflection mission is ready to fly against a real threat, and the sources reviewed give no date for one.

Published forecasts

What others have predicted. These are their estimates, not ours.

WhoForecastTimeframeMade
European Space Agency (Hera mission)Hera is on track to arrive at Didymos in November 2026, a month earlier than the original plan. [7]20267 Oct 2025
NASA (NEO Surveyor, 2021 announcement)NEO Surveyor's launch was then scheduled for the first half of 2026. [4]202611 Jun 2021
NASA (NEO Surveyor mission page)NEO Surveyor launch no earlier than September 2027. [3]20276 May 2026

Signals to watch

  • Hera arriving at Didymos in November 2026 and reporting the DART crater and Dimorphos's response.
  • Rubin's full-survey near-Earth object counts, with a completeness figure for objects of 140 m or larger.
  • NEO Surveyor passing launch readiness and launching no earlier than September 2027.
  • Ramses launching in spring 2028 and reaching Apophis before its 13 April 2029 flyby of Earth.
  • A dated official target for a deflection mission that is built and ready, rather than a test.

Sources

  1. review article
    Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032 (Chapter 18: Planetary Defense: Defending Earth Through Applied Planetary Science)
    National Academies of Sciences, Engineering, and Medicine (National Academies Press), 2023.
  2. other
    Action! NSF-DOE Vera C. Rubin Observatory Begins Capturing the Greatest Cosmic Movie Ever Made
    Vera C. Rubin Observatory (NSF and DOE), 30 Jun 2026.
  3. government report
    NEO Surveyor
    NASA Science, 6 May 2026.
  4. government report
    NASA Approves Asteroid Hunting Space Telescope to Continue Development
    NASA, 11 Jun 2021.
  5. government report
    Double Asteroid Redirection Test (DART)
    NASA Science, 26 Sept 2022.
  6. government report
    NASA's DART Data Validates Kinetic Impact as Planetary Defense Method
    NASA, 1 Mar 2023.
  7. government report
    ESA's Hera targets early arrival at Didymos asteroids
    European Space Agency, 7 Oct 2025.
  8. government report
    Destination sighted: Hera's first glimpse of Didymos
    European Space Agency, 7 Oct 2026.
  9. government report
    ESA awards contracts for Ramses mission to Apophis
    European Space Agency, 10 Feb 2026.
  10. government report
    ESA actively monitoring near-Earth asteroid 2024 YR4
    European Space Agency, 29 Jan 2025.
  11. government report
    2024 YR4 Facts
    NASA Science, 19 Oct 2026.
  12. peer reviewed paper
    JWST Observations of Asteroid 2024 YR4 Rule Out a 2032 Lunar Impact and Demonstrate a New Regime for Planetary Defense Follow-up
    Julien de Wit et al.. The Astrophysical Journal Letters (IOP Publishing), 19 May 2026.
  13. government report
    Federal Government Releases National Near-Earth Object Preparedness Plan
    NASA, 20 Jun 2018.
  14. government report
    National preparedness strategy & action plan for potentially hazardous near-Earth objects and planetary defense
    White House Office of Science and Technology Policy (USGS record), 2023.

Last reviewed 22 Oct 2026.