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ESA’s Asteroid Impact Mission


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TRIPLE GOALS OF DOUBLE ASTEROID EXPLORATION

ESA’s Asteroid Impact Mission is a proposed venture to the Didymos double asteroid, which will come a comparatively close

16 million km to Earth in October 2022. The 800 m-diameter main body is orbited by a 170 m-diameter moon, informally called

Didymoon. This smaller body is AIM’s focus: the spacecraft will explore its properties, in particular probing its interior using radar.

It will also set down a microlander on Didymoon and deploy two CubeSats in the asteroid’s vicinity.

If the mission is approved, it would be launched in the window that opens in October 2020, with three main goals:

ASTEROID DEFLECTION

SCIENCE

TECHNOLOGY

AIM will thoroughly investigate Didymoon

and observe as a NASA probe collides with

it at high speed. The results will help to

build high-fidelity computer models

of impacts to help plan for deflecting

future approaching bodies.

AIM will be humanity’s first mission to

a double asteroid, which account for

around one in six of known asteroids.

Each close encounter has revolutionised

our understanding, and there is still

much more to know. Asteroid interiors

remain blank spots in our knowledge.

Are they loose rubble or large monoliths,

or are there gaping voids within them?

AIM will probe Didymoon’s deep

interior while investigating its

surface. How does asteroid material

behave in low gravity?

AIM will demonstrate new technologies

for future deep-space missions, including

high-bandwidth, long-distance

laser communications back to Earth,

flexible networking between CubeSats

and a lander, and close-proximity

operations in low gravity, including the

semi-autonomous deployment of

the microlander.

COLLISION COURSE

Four months after arriving at Didymos, AIM will be briefly joined

by a terrestrial companion: NASA’s Double Asteroid Redirection

Test (DART) probe will home in on Didymoon, crashing into it at

about 6 km/s in an attempt to divert its path. AIM will be on hand

to record the results of this historic first attempt to shift the orbit

of a Solar System body – a ground-breaking test of planetary

defence methods. These two missions are collectively known as

the Asteroid Impact and Deflection Assessment (AIDA) mission.

While built and run separately, the two spacecraft are being

planned in coordination to maximise their overall results. AIDA’s

main measurement will be the change in Didymoon’s orbit after

impact (the pair’s orbit around the Sun will remain unchanged).

The event will also be monitored by terrestrial telescopes and

radars thanks to the rare close approach to Earth.


MISSION PROFILE

After flying for about 18 months, AIM will reach Didymos in mid-2022 to begin the mission’s real work:

intensive study of its target by visual, thermal and radar instruments, delivery of its lander and CubeSats,

and laser-based communications back to Earth. Then comes DART’s collision with Didymoon, with AIM

providing a detailed before-and-after comparison of the asteroid and its changed orbit.

EARTH

1 EARLY CHARACTERISATION PHASE:

VISIBLE IMAGING

INFRARED IMAGING

HIGH-FREQUENCY RADAR

2

LASER COMMUNICATION WITH EARTH

THERMAL IMAGING

CUBESATS

MASCOT LANDER

3

CUBESAT DEPLOYMENT

DIDYMOON

4 DEPLOYMENT OF SMALL LANDER

5 DETAILED CHARACTERISATION PHASE:

LOW-FREQUENCY RADAR

HIGH-RESOLUTION IMAGING

INFRARED IMAGING

HIGH-FREQUENCY RADAR

7

POST-IMPACT CHARACTERISATION

6

IMPACT


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ANATOMY OF AIM

SPACECRAFT BODY

1.4 x 1.4 x 1.8 m (solar wings stowed); 1.4 x 1.4 x 7.7 m

(solar wings deployed). 12 bipropellant 1 N thrusters

for attitude control and close proximity operations;

four 22 N thrusters for orbit corrections.

MASCOT-2 ASTEROID MICROLANDER

AND CUBESATS

Deployed after arrival at Didymos.

OPTICAL COMMUNICATION SYSTEM

Laser communication system to test downlink capabilities

to ESA’s Optical Ground Station in Tenerife. Close to Earth,

it will be several times faster than the equivalent radio

system. As an altimeter, it will also help to navigate AIM

and to map the asteroid.

HIGH-GAIN ANTENNA

Fixed X-band antenna to receive telecommands from Earth.

CUBESAT COMPANIONS

ASTEROID TOUCHDOWN

All images: ESA/ScienceOffice.org

AIM will carry a pair of 3-unit CubeSats – nanosatellites based

on standardised 10 cm units, much cheaper and simpler to

build than standard satellites. Concepts being studied include

taking a close-up look at the composition of the asteroid surface,

measuring the gravity field, assessing the dust environment,

imaging the impact’s ejecta plume from close by, and landing

a CubeSat for seismic monitoring.

AIM will carry a 15 kg microlander for Didymoon, ESA’s first

touchdown on a small body since Rosetta’s Philae landed on a

comet in November 2014. Like Philae, Mobile Asteroid Surface

Scout-2 (Mascot-2) will be provided by the DLR German Aerospace

Center. Mascot-1 is already flying on Japan’s Hayabusa-2, launched

in December 2014 to land on an asteroid in 2018. Mascot-2 will

include low-frequency radar antennas to sound Didymoon’s

interior structure and a solar panel to let it survive for several

weeks on the surface. In addition it will carry a microcamera,

a radiometer and an accelerometer.

FACTS AND FIGURES

Spacecraft launch mass

Launch window

Duration

Mission

Target

740 kg (including 306 kg propellant)

October–November 2020 from Kourou, French Guiana on Soyuz rocket

1.5-year cruise and 6 months of operations at Didymos

Small mission of opportunity demonstrating asteroid deflection, investigating the properties of a binary asteroid

and demonstrating new technologies

AIM’s target binary asteroid, 65803 Didymos, was discovered in 1996. The smaller asteroid is in a 1.1 km-altitude,

11.9-hour orbit around the primary; both have been observed with radars from Earth

AIM would be a precursor for future small deep-space missions such as monitoring space weather and returning

samples from small Solar System bodies.

For more information: contactesa@esa.int www.esa.int

An ESA Communications Production Copyright © 2016 European Space Agency

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