# DART Mission

**Type:** NASA planetary defense demonstration mission  
**Status:** Mission complete (impact September 2022), analysis ongoing  
**Primary Goal:** Validate kinetic impact as asteroid deflection technique  
**Target:** Dimorphos, moon of asteroid Didymos  

## Overview

The Double Asteroid Redirection Test (DART) was NASA's first planetary defense technology demonstration. The spacecraft deliberately impacted the asteroid moon Dimorphos on September 22, 2022, to test whether a kinetic impact could measurably change an asteroid's orbit.

## Key Results

**Binary Orbit Change:** DART changed Dimorphos's orbital period around Didymos by 33 minutes, far exceeding the minimum success criterion of 73 seconds.

**Heliocentric Orbit Change:** March 2026 analysis published in Science Advances revealed that DART changed the Didymos/Dimorphos binary system's solar orbital period (770 days) by less than one second, with orbital velocity change of ~11.7 microns/second. This is the first confirmed human-caused alteration of a celestial body's path around the Sun.

**Beta Factor:** β = 3.61 (+0.19/-0.25, 1σ), meaning ejecta amplification transferred ~3.6x more momentum than the spacecraft impact alone. The range β=2.2-4.9 across likely density estimates confirms that ejecta recoil dominates momentum transfer on rubble-pile asteroids.

## Follow-up Mission

ESA's Hera mission is en route to Didymos, arriving November 2026. Hera will refine the beta factor measurement, characterize the DART crater, and determine Dimorphos's internal structure to assess whether kinetic deflection is as effective on denser, more monolithic asteroids.

## Timeline

- **September 22, 2022** — DART spacecraft impacts Dimorphos, changing binary orbital period by 33 minutes
- **March 2026** — Science Advances publishes analysis showing DART changed the binary system's heliocentric orbit, first human-caused alteration of a celestial body's solar path
- **November 2026** — ESA Hera mission scheduled to arrive at Didymos for detailed post-impact analysis