# DART (astro-ph)
###### tags: `Astronomy` `Talk`

## Intro: Planetary Defense
### Basic strategy
1. Finding asteroids
2. Calculate their orbit
3. Find dangerous asteroids
4. Somehow deal with it

### Find, track and predict
For the first 3 steps, we have significant progress in the last 30 years.

Those that are close to Earth are called Near Earth object (NEO) / Near Earth asteroid (NEA). Those that are dangerous are called Potentially hazardous object (PHO) / Potentially hazardous asteroid (PHA).

Credit: Panstarrs

Number of NEA discovered each year. Credit: [Alan B. Chamberlin](https://en.wikipedia.org/wiki/File:Neo-chart.png)
Number of NEA with $R>1~km$ discovered each year.
Showing this population is almost complete.
Credit: [Alan B. Chamberlin](https://en.wikipedia.org/wiki/File:NEA_1_km_or_more.png)

Rubin / LSST under construction, it will help a lot in the future.
Credit: Rubin Obs/NSF/AURA

### What's next?
Many methods have been proposed. Non of them are tested.
The composition and structure of asteriods remains a great uncertainty.

No method has been tested. Credit: [Scientific American](https://www.scientificamerican.com/article/are-we-doing-enough-to-protect-earth-from-asteroids/)

### Goal of DART
Test the simpliest method: Direct impact.

## DART concept
Try hitting one, see what happen.
Low-cost tech. demo. mission. (\$324.5 million, 0.003 JWST)

### Name
DART = Double Asteroid Redirection Test

### Target
Double Asteroid system **Didymos** and **Dimorphos**.
NEA but not really dangerous.
Close to Earth, orbital plane aligned with Earth $\Rightarrow$ good transit observation.


## DART design
### DRACO
Camera similar to that used on New Horizon


### NEXT-C
State-of-the-art ion thruster.


### ROSA
Rolled out solar array.


### Impact
Date: October 2022
Velocity: 6.6 km/s.
Expected result: 73 s decrease of orbital period.
Effects on the orbit of the asteroids will be precisely measure by radars.

## Follow up mission: HERA
More advenced orbiter that will investigate the system in more details.
Equiped with Lidar, IR camera, etc.

Credit: ESA - ScienceOffice