Initial Situation

As part of the IEEE MTT-Sat Challenge the University of Bremen SmallSatGroup investigates in this project an approach of a fully integrated telemetry and telecommand (TMTC) unit for spacecraft communication using a software-defined radio (SDR) architecture that is designed with modern system on chip (SoC) technology and state-of-the-art front-end devices. The desired approach allows an on-demand re-configuration of both, the data processing (e.g., selection of different modulation schemes or coding techniques) and RF specifications such as frequency band selections or sample rate adaption. These key technologies enable a highly integrated hardware architecture that is also suitable for small satellite missions, e.g., for low cost CubeSat projects. 

The University of Bremen SmallSatGroup is a group of students that are enrolled in the master programs “Space Sciences and Technologies”, “Space Engineering”, or “Electrical Engineering and Information Technology” and is guided by members of the Department of Communications Engineering and DLR-Institute of Space Systems. The goal of this group is to investigate techniques for future satellite communication on small satellites.

Problem Statement

Over the past decades, spacecraft communication has been conservative with the kind of employed architectures. The need for relying on well-established methodologies comes from the necessity of hardware reliability used in the harsh environments of space. This has held back the performance and efficiency levels that could potentially be attained. As an example for digital signal processing: using a system on chip (SoC) which comprises some FPGA fabric and high performance digital signal processor designs would allow higher levels of data processing integration into one device and could increase the performance and efficiency of such systems radically. The transfer of this SoC technology to space applications like the TMTC of spacecraft communication systems has been identified as a game changer and could bring huge benefits with respect to performance enhancement and also allow more flexibility, e.g. for in-orbit reconfiguration capabilities. The SoC hardware can be used to realize a variety of applications with the benefit of very flexible and cost efficient implementations.

Like most other aspects of a satellite, communication and data handling ought to be compliant with specific standards. The consultative committee for space data systems (CCSDS) is the institution to provide those standards, which ensure lower operating costs and risks while still supporting innovative capabilities. Hence, we will consider the communication related specifications of CCSDS for designing the links between ground and space. For a traditional communication subsystem on board a spacecraft, the requirement mainly lies in the aspect of signal processing in the physical layer of the open system interconnection (ISO/OSI) model. In particular, functions like analog-to-digital conversion, digital-to-analog conversion modulation/demodulation, radio frequency (RF) related processing (e.g., filtering, amplification, up-down conversion) are of importance. Other steps of the process are carried out on the onboard computer and data handling subsystem.

Objective and Contribution

The proposed TMTC application in combination with state of the art SoC technology and flexible front-end devices promises major benefits especially in the growing market of small satellites:

• The integrated design of such radio allows for integration in most small-satellite spacecrafts while adding the benefits of on-demand reconfiguration of the communication system. One can derive multiple use cases where this can be beneficial, e.g., multi-application satellites with more than one communication link or multiple radio-based experiments on one single spacecraft. In any case, the benefits lead to cost-reduction and reduced development-to-application times.
• With focus especially on the suggested TMTC application, the benefits will be flexible selection in a wide range of frequency bands, the adaption to new coding and modulation schemes. For instance, this could allow a fast adaptation to new communication standards or technologies, or communication with different ground stations or satellites, with quick re-configuration to their required communication schemes.
• The common reasons for relaunching of satellites mostly include fuel exhaustion, solar panel or hardware damage, aging, etc. This adds a lot to the space debris in terms of more defunct satellites. The need to mitigate effects of the space debris accumulated over the years makes us turn towards in-orbit repair, repurpose and recovery services which largely relies on configurability of subsystems. A reconfigurable platform like the integrated TMTC could help a servicing satellite to communicate with different types of existing satellites that need to be serviced.

Details