APEX Science

Asteroid Prospection Explorer (APEX) is a 6U CubeSat developed for Hera mission being part of ESA-NASA AIDA

(Asteroid Impact & Deflection Assessment) project. APEX features a unique set of instruments designed to provide a global

characterization of the Didymos system – target of the joint ESA-NASA Asteroid Impact and Deflection Assessment

(AIDA) mission. The instrument set includes ASPECT (Asteroid Spectral Imager), ACA (Asteroid Composition Analyzer),

and MAG (Magnetometer).

ASTEROID PROSPECTION EXPLORER (APEX) CUBESAT FOR HERA MISSIONT. Kohout1,2, Jan-Erik Wahlund3 Tatsuo Shimizu4, Tomi Kärkkäinen4, Daniel Štefl5 and APEX team

1. Faculty of Science, University of Helsinki, Finland (tomas.kohout@helsinki.fi)

2. Institute of Geology, The Czech Academy of Sciences, Prague, Czech Republic

3. Swedish Institute of Space Physics (IRF), Upsalla, Sweden

4. Reaktor Space Lab, Espoo, Finland

5. Space Systems Czech, Prague, Czech Republic

Conclusions

APEX is a deep space CubeSat with a VIS-MIR hyperspectral imager, magnetometer, and secondary ion spectrometer.

Main science objectives are to characterize target surface, composition, and internal structure.

Acknowledgments

The project is done under ESA GSTP contract and is partly supported by Academy of Finland and ERC.

Scientific objectives

1. Map the global composition of the Didymos asteroids

→ Result: Mineral composition and homogeneity of the Didymos asteroid surface

→ Result: Elemental composition of the Didymos asteroid surface

→ Result: Constrain FeNi amount from induced component of the magnetic field

2. Determine the internal structure and evolution of the Didymos system

→ Result: Mineral and elemental composition differences between Didymos I and II

→ Result: Detection and origin of the magnetization of the Didymos asteroid material

→ Result: Size of building blocks of the Didymos asteroids inferred from their remanent

magnetic signature

3. Determine surface roughness or regolith grain size of the Didymos asteroids

→ Result: Surface particle size distribution and composition for Didymos I and II

4. Evaluate space weathering effects on Didymos II by comparing mature and freshly exposed

material

→ Result: Optical and possible elemental differences between mature and freshly exposed

material

5. Identify local shock effects on Didymos II caused by DART impact based on spectral

properties of crater interior

→ Result: Determine optical properties of the material within crater

→ Result: Determine elemental composition on surface, differences inside and outside the

crater

→ Result: Determine magnetic signature of the crater

6. Map global fallback ejecta on Didymos I and II

→ Result: Detailed global mapping of fallback ejecta on both Didymain and Didymoon

7. Characterize interaction of Didymos system with interplanetary environment

→ Result: Magnitude of interaction of the Didymos system with interplanetary magnetic fields,

detection of temporary megnetoshpere

→ Result: Determine the magnitude of solar wind ion disturbances/interaction with the binary

asteroid (Didymos system)

8. Determine mass of Didymos I and II from APEX orbit perturbations

→ Result: Mass of Didymos I and II

9. Determine strength of the near-surface material from APEX landing

→ Result: Surface material strength

AIDA target –binary asteroid Didymos

• Primary (Didymain) diameter 780 m, 2.1 g/cm3

• Secondary (Didymoon) diameter 160 m

• S-type composition

• Distance between centers 1.2 km

• Orbital period 12 h

• Apollo type NEA (Near-Earth Asteroid)

Radar shape, Benner and Naidu Shape model, Schwartz

• 6U configuration

• On-board data processing

• 15 kg, 15 W

APEX CubeSat

• New interplanetary AOCS

(Attitude and Orbit Control

System)

for semi-autonomous operations

and navigation includes:

→ 3-axis IMU (Inertial

Measurement Unit)

→ Propulsion

→ Reaction wheels

→ LIDAR

→ Navigation camera

AIDA scenario

The joint ESA-NASA AIDA project to binary asteroid Didymos

consists of Hera (ESA) and DART (Double Asteroid

Redirection Test, NASA). DART is targeted to impact Didymos

secondary component (Didymoon) and serve as a kinetic

impactor to demonstrate deflection of potentially hazardous

asteroids. Hera will serve as an observational spacecraft to

evaluate the effects of the impact and resulting changes in the

Didymos dynamic parameters.

The Hera mission will also carry APEX 6U CubeSat. This

arrangement opens up a possibility for secondary scientific

experiments. ASPECT aims to study the composition and

internal structure of the Didymos binary asteroid, effects of

space weathering, and DART impact crater and ejecta

distribution, in order to gain understanding of the formation and

evolution of the Solar System.

Didymos

Composition

ASPECT – mineralogy

ACA – chemistry

MAG - FeNi

Surface

ASPECT – roughness, space

weathering, ejecta

ACA – Solar wind interaction

Interior

MAG – internal structure

APEX

ESA - NASA -

A ID

A

• DLR, Bremen

• Space Systems Czech (SSC)

• The Czech Academyof Sciences

• Swedish Instituteof Space Physics (IRF)

• V-kvadrat AB

• Royal Instituteof Technology (KTH)

• OHB Sweden

• LC ISR, Ukraine

• Reaktor Space Lab (RSL)

• Aalto University

• VTT Research Centre of Finland Ltd

• University of Helsinki

APEX

AIDA scenario ASPECT

4 independent measurement channels:

VIS (500–900 nm, 1024 x 1024 px)

NIR1 (900–1600 nm, 640 x 512 px)

NIR2 (1600–2500 nm, 640 x 512 px)

Fabry-Perot Interferometer, 45 nm spectral resolution

1 m/px at 4 km, 3 cm/px at 200 m

MAG

Proximity measurements ( 100

FoV 40° full width cone

ASPECT VIS-NIR hyperspectral imager

ACA sputtered ion analyzer

MAG dual sensor magnetometer