In parallel with the Proba minisatellite missions, ESA is now also utilising much smaller ‘CubeSat’ nanosatellites. These are employed for the In-Orbit Demonstration (IOD) of miniaturised technologies and for small payload-driven missions.
What are CubeSats?
These nanosatellites typically weigh between 1 and 10 kilograms and follow the popular ‘CubeSat’ standard, which defines the outer dimensions of the satellite within multiple cubic units of 10x10x10 cm. For instance, a 3-unit CubeSat has dimensions of 10x10x30 cm and weighs about 3-4 kg. This is typically the minimum size which can accommodate small technology payloads.
Fixing the satellite body dimensions promotes a highly modular, highly integrated system where satellite subsystems are available as ’commercial off the shelf’ products from a number of different suppliers and can be stacked together according to the needs of the mission. Furthermore, the standard dimensions also allows CubeSats to hitch a ride to orbit within a container, which simplifies the accommodation on the launcher and minimises flight safety issues, increasing the number of launch opportunities as well as keeping the launch cost low.
Due to their high degree of modularity and extensive use of commercial off the shelf subsystems, CubeSat projects can be readied for flight on a much more rapid basis compared to traditional satellite schedules, typically within one to two years.
Why is ESA interested in CubeSats?
CubeSats have already proved their worth as educational tools. In addition, they have various promising applications in the ESA context:
- As a driver for drastic miniaturisation of systems, ‘systems-on-chips’, and totally new approach to packaging and integration, multi-functional structures, embedded propulsion
- As an affordable means of demonstrating such technologies, together with novel techniques such as formation flying, close inspection or rendezvous and docking
- As an opportunity to carry out distributed multiple in-situ measurements, such as obtaining simultaneous multi-point observations of the space environment (which might include the thermosphere, ionosphere, magnetosphere or charged particle flux)
- As a means of deploying small payloads – for instance, very compact radio receivers or optical cameras where the potential deficit in performance may be largely compensated by the multitude of satellites involved (e.g. in constellations or swarms)
- As a means of augmenting solar system exploration with – for instance, a stand-alone fleet capable of rendezvous with multiple targets (e.g. near-Earth objects) or a swarm carried by a larger spacecraft and deployed at the destination (e.g. Moon, asteroid/comet, Mars).
Technology in-orbit demonstration CubeSats
Since 2013, ESA has begun a number of CubeSat missions funded under the In-Orbit Demonstration part of the General Support Technology Programme (GSTP). The first IOD project was as follows:
- GOMX-3 (led by Gomspace, Denmark): a 3-unit CubeSat mission to demonstrate aircraft ADS-B signal reception and geostationary telecommunication satellite spot beam signal quality using an L-band reconfigurable software defined radio payload. A miniaturised high data rate X-band transmitter developed by Syrlinks and funded by the French space agency CNES was flown as a third party payload. The satellite was deployed from the International Space Station on 5 October 2015 and re-entered Earth’s atmosphere after 1 year of successful operations.
The following IOD missions are being readied for flight:
- GOMX-4B (led by Gomspace, Denmark): a 6-unit CubeSat mission to demonstrate Inter-Satellite Link and propulsion technologies when flying in tandem with the GOMX-4A (developed by Gomsapce for the Danish Ministry of Defence). The mission will also carrying additional technology payloads: the HyperScout compact hyperspectral imager (Cosine, The Netherlands), a new star tracker (Innovative Solutions in Space, The Netherlands), and the ESA CHIMERA experiment exposing new electronic components to space. The satellites are scheduled for launch in February 2018.
- QARMAN (led by the Von Karman Institute, Belgium): a 3-unit CubeSat mission to demonstrate re-entry technologies, particularly novel heatshield materials, a new passive aerodynamic drag stabilisation system, and the transmission of telemetry data during re-entry via data relay satellites in low-Earth orbit, due to be launched to/deployed from the International Space Station in 2018
- SIMBA (led by the Royal Meteorological Institute Belgium with KU Leuven): a 3-unit CubeSat mission to measure the Total Solar Irradiance and Earth Radiation Budget climate variables with a miniaturised radiometer instrument, due to be launched in 2019 on the Vega Small Satellite Mission Service (SSMS) Proof of Concept flight
- Picasso (led by Belgian Institute of Space Aeronomy with VTT Finland and Clyde Space, UK): a 3-unit CubeSat mission to measure Stratospheric Ozone distribution, Mesospheric Temperature profile and Electron density in the ionosphere using a miniaturised multi-spectral imager for limb sounding of solar disk, and a multi-Needle Langmuir Probe, due to be launched in 2019 on the Vega Small Satellite Mission Service (SSMS) Proof of Concept flight
- RadCube (led by C3S with MTA EK in Hungary, Imperial College London in UK, and Astronika in Poland): a 3-unit CubeSat mission to demonstrate miniaturised instrument technologies that measure in-situ the space radiation and magnetic field environment in Low Earth Orbit for space weather monitoring purposes. The platform developed by C3S will also be demonstrated in flight. The project is currently in the preliminary design phase and planned to be ready for flight in late 2019.
- PRETTY (led by RUAG Austria with TU Graz and Seibersdorf Laboratories): a 3-unit CubeSat mission to demonstrate the technique of GNSS Reflectometry at low grazing angles for altimetry (primarily for sea ice detection) using a new software-defined GNSS receiver. Additionally, a miniaturised radiation dosimeter will also be tested in flight. The project is currently in the preliminary design phase.
Mission application studies
In addition to the IOD missions, numerous studies focussed on the mission applications of nano-satellite systems and miniaturised payloads have been performed under funding of the ESA General Studies Programme (GSP), including:
- Remote Sensing with Cooperative Nano-satellites -four parallel ‘Sysnova’ studies
- Asteroid Impact Mission (AIM) Cubesat Opportunity Payloads with Intersatellite Networking Sensors (COPINS) –four parallel ‘Sysnova’ studies
- Lunar Cubesats for Exploration (LUCE) –four parallel ‘Sysnova’ studies
- SpectroCube mission: beyond LEO astrobiology/astrochemistry experiments –internal CDF study
- Miniaturised Asteroid Remote Geophysical Observer (MARGO) stand-alone deep space CubeSat –internal CDF study.