The Fraunhofer EMI is developing he nanosatellite ERNST to demonstrate the potential of CubeSat-based small satellites for ambitious Earth observation tasks. Following the successful verification of the engineering qualification model, the critical design review marked the transition to the production and testing phase of the ERNST flight model, which is scheduled for launch in June 2022.
Innovations in the space sector are currently advanced by commercial suppliers. The most prominent company of this “New Space” industry is SpaceX. With the development of novel rocket launch systems and mega constellations of small satellites, SpaceX is emblematic for the core elements of New Space. Small satellites are not a new invention – however, they have, due to the development of high-performance systems, evolved from a niche product within the course of the last years. In the US, the hub of New Space, small satellites have moved into the focus of defense-related applications. For example, for space-based early warning systems for the detection of missiles, hundreds of small satellites that are connected via optical communication shall complement or even replace the classical, exclusive military satellites. The motivation lies in a fast response and high resilience through less expensive mass-produced small satellite constellations.
ERNST as demonstration mission for high performance CubeSat-based small satellites
ERNST is the first small satellite that supports military tasks in Germany. The goal of this mission is to demonstrate and to exploit the potential of this satellite class for the German Armed Forces (Bundeswehr). The main payload is an infrared camera for the detection of missile launches. In cooperation with the Fraunhofer IOSB, the unique data obtained by ERNST will be used to demonstrate an advanced detection concept and to verify corresponding numerical simulations. From a technical viewpoint, the integration of the infrared payload is particularly challenging. It includes a cryocooler that, due to its high demand of electrical energy and high emission of thermal energy as well as the excitation of vibrations, presents a major challenge to a satellite as small as 236 by 236 by 340 cubic millimeters. These dimensions correspond to 12U, i.e. a cuboid consisting of twelve combined ten centimeter cubes, the latter being the basic unit of so-called CubeSats. ERNST will be the first nanosatellite based on CubeSat technology that demonstrates a cryocooled payload in orbit.
In addition to the main payload, ERNST features a camera for Earth observation in the visible spectrum and a radiation detector developed by Fraunhofer INT. The latter, named FORS (Fraunhofer Onboard Radiation Sensor), measures high-energy protons and electrons and provides information on the influence of the radiation environment in orbit on the functionality of small satellites’ electronics.
12U satellite bus for the integration of various payloads for multi-sensor networks
The advantage of CubeSats is their standardization. High-performance CubeSat components are commercially available. For ERNST, we benefit from the high development level of these components and integrate commercial subsystems developed by diverse market leaders, including the onboard computer, power processing, X-band transmitter and the attitude control system, which has been demonstrated during NASA’s Insight Mars mission. These subsystems are complemented by in-house developments, for example the data processing unit and a de-orbit system. The latter deploys a drag sail with a size of 2.4 square meters that increases the atmospheric drag of the system after the end of a mission. Thus, it contributes to a sustainable use of orbit in terms of space debris prevention. The payloads are integrated on an additively manufactured optical bench. This method ensures a flexible integration of different payloads into the ERNST bus in the context of a responsive space using small satellites. The launch of ERNST in 2024 will be the first step to this for the German Ministry of Defence (BMVg).