# ESA Hera

**Type:** Planetary defense validation mission  
**Launch:** October 2024 (Falcon 9)  
**Target:** Didymos binary asteroid system  
**Arrival:** November 2026 (one month ahead of schedule)  
**Status:** En route after Mars swingby

## Mission Profile

Hera is ESA's follow-up mission to NASA's DART kinetic impactor test. After launching in October 2024, Hera performed a Mars swingby with Deimos flyby in March 2025. Second deep-space maneuver completed March 2026 (123 kg hydrazine, 367 m/s delta-v). Mission efficiency gains enabled one-month early arrival.

## Primary Objectives

1. **Crater characterization** — High-resolution survey of DART impact site on Dimorphos
2. **Mass determination** — Precise measurement enabling accurate β factor recalculation
3. **Internal structure** — Determine if Dimorphos is rubble pile throughout or has coherent core
4. **CubeSat deployment** — Milani (surface mineralogy) and Juventas (internal radar sounding)

## Planetary Defense Significance

Hera's characterization of Dimorphos internal structure will determine whether kinetic deflection is reliable for the full potentially hazardous asteroid population or limited to rubble-pile aggregates. DART's β=3.61 likely resulted from loose structure allowing free ejecta escape. More coherent asteroids would show β approaching 1 (no momentum amplification).

## Timeline

- **2024-10** — Launch on Falcon 9
- **2025-03** — Mars swingby with Deimos flyby
- **2026-03** — Second deep-space maneuver (123 kg hydrazine, 367 m/s)
- **2026-11** — Didymos arrival (one month ahead of baseline schedule)

## Related Programs

- NASA DART (kinetic impactor, September 2022)
- China kinetic impactor test (2026)

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*Mission validates planetary defense capability and determines generalizability of kinetic deflection technique across asteroid population.*