Nanosat fleet proposed for voyage to 300 asteroids
September 19, 2017

European Planetary Science Congress 2017 Press Notice
Tuesday, 19th September

Nanosat fleet proposed for voyage to 300 asteroids

A fleet of tiny spacecraft could visit over 300 asteroids in just over three years, according to a mission study led by the Finnish Meteorological Institute. The Asteroid Touring Nanosat Fleet concept comprises 50 spacecraft propelled by innovative electric solar wind sails (E-sails) and equipped with instruments to take images and collect spectroscopic data on the composition of the asteroids. Each nanosat would visit six or seven asteroids before returning to Earth to deliver the data. The concept will be presented by Dr Pekka Janhunen at the European Planetary Science Congress (EPSC) 2017 in Riga on Tuesday 19th September.

“Asteroids are very diverse and, to date, we’ve only seen a small number at close range. To understand them better, we need to study a large number in situ. The only way to do this affordably is by using small spacecraft,” says Janhunen.

In the mission scenario, the nanosats flyby their target asteroids at a range of around 1000 kilometres. Each nanosat carries a 4-centimetre telescope capable of imaging the surface of asteroids with a resolution of 100 metres or better. An infrared spectrometer analyses spectral signatures in light reflected or emitted by the asteroid to determine its mineralogy. The instruments can be pointed at the target using two internal reaction wheels inside the nanosats.

“The nanosats could gather a great deal of information about the asteroids they encounter during their tour, including the overall size and shape, whether there are craters on the surface or dust, whether there are any moons, and whether the asteroids are primitive bodies or a rubble pile. They would also gather data on the chemical composition of surface features, such as whether the spectral signature of water is present,” says Janhunen.

E-sails make use of the solar wind – a stream of electrically charged particles emitted from the Sun – to generate efficient propulsion without need for propellant. Thrust is generated by the slow rotation of a tether, attached at one end to a main spacecraft carrying an electron emitter and a high-voltage source and at the other to a small remote unit. The spinning tether completes a rotation in about 50 minutes, tracing out a broad, shallow cone around a centre of mass close to the main spacecraft. By altering its orientation in relation to the solar wind, the nanosat can change thrust and direction.

The thrust generated by E-sails is small; a 5 kilogramme spacecraft with a 20-kilometre tether would give an acceleration of 1 millimetre per second at the distance of the Earth from the Sun. However, calculations show that, on top of the initial boost from launch, this is enough for the spacecraft to complete a tour through the asteroid belt and back to Earth in 3.2 years. Nanosatellites do not have the capacity for a large antenna, so the concept includes a final flyby of Earth to download the data. The overall mission would cost around 60 million Euros, including launch, giving a cost of about 200,000 Euros for each asteroid visited.

“The cost of a conventional, state-of-the-art mission to visit this number of asteroids could run into billions. This mission architecture, using a fleet of nanosats and innovative propulsion, would reduce the cost to just a few hundred thousand Euros per asteroid. Yet the value of the science gathered would be immense,” says Janhunen.

EPSC 2017 abstract:


Artist’s concept of the spacecraft. Credit: FMI

The single-tether E-sail spacecraft. Credit: Janhunen et al

The orbital trajectory of the 3.2 year mission tour. Credit Janhunen et al

Science Contact
Pekka Janhunen
Finnish Meteorological Institute

Media Contacts
Anita Heward
EPSC 2017 Press Officer
+44 07756 034243

Livia Giacomini
EPSC 2017 Press Officer

Notes for Editors
EPSC 2017
The European Planetary Science Congress (EPSC) 2017 ( is taking place at the Radisson Blu Latvija in Riga, from Sunday 17 to Friday 22 September 2017. EPSC is the major European annual meeting on planetary science and in 2017 is hosted for the first time in the Baltic States. Around 800 scientists from Europe and around the world will attend the meeting and will give around 1,000 oral and poster presentations about the latest results on our own Solar System and planets orbiting other stars.
EPSC 2017 is organised by Europlanet and Copernicus Meetings. The Local Organising Committee is led by Baltics in Space, a not-for-profit organisation that is supporting 25 members centred around nine Baltic space facilities for the conference. The meeting is sponsored by Investment and Development Agency of Latvia, the Latvian Ministry of Education and Science, Latvijas Mobilais Telefons, Finnish Meteorological Institute, The Estonia-Latvia programme, The Representation of the European Commission in Latvia, the Planetary Science Institute, Latvijas Universitate and The Division for Planetary Sciences of the AAS.
Details of the Congress and a full schedule of EPSC 2017 scientific sessions and events can be found at the official website:

Since 2005, the Europlanet project has provided European’s planetary science community with a platform to exchange ideas and personnel, share research tools, data and facilities, define key science goals for the future and engage stakeholders, policy makers and European Citizens with planetary science. Europlanet is the parent organisation of the European Planetary Science Congress (EPSC), and the EPSC Executive Committee is drawn from its membership.

The Europlanet 2020 Research Infrastructure (RI) is a €9.95 million project to address key scientific and technological challenges facing modern planetary science by providing open access to state-of-the-art data, models and facilities across the European Research Area. The project was launched on 1st September 2015 and has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 654208. Europlanet 2020 RI is led by the Open University, UK, and has 33 beneficiary institutions from 19 European countries.
Project website:
Outreach website:
Follow @europlanetmedia

Baltics in Space
The philosophy of the nonprofit organization, Baltics in Space, is to “Inventory, Identify, and Integrate” with a sprinkling of Inspiration to build a space product greater than the sum of its parts. The best resource in the space business is people. With an eye to strengthening the triple helix links (Industry, Education, Research), its planned outcomes are integrating Baltic-wide space events, compiling catalogs of skill-sets for prospective users and Baltic space project development with distributed teams and Baltic space education.