SOURCE

Stuttgart Operated University Research CubeSat for Evaluation and Education

SOURCE (Stuttgart Operated University Research CubeSat for Evaluation and Education) is a nanosatellite with dimensions of 10 x 10 x 36 cm that complies with the 3U+ CubeSat standard. It is being developed in a cooperation between KSat e.V. and the Institute of Space Systems (IRS) at the University of Stuttgart. As a student CubeSat, it is developed and operated exclusively by students under the supervision of the IRS. As part of the “CubeSat Technology Internship” module, many students have the opportunity to gain practical experience over the course of a semester and earn credit points for their work on the project. In addition to supervising the project, the IRS offers numerous opportunities to test and develop components. In addition, SOURCE is funded by ESA’s Fly Your Satellite! programme, which enables students to learn how to develop, test and document according to the standards of the European Cooperation for Space Standardization (ECSS).

SOURCE carries several scientific payloads, which are divided into two mission phases. Two cameras were integrated on SOURCE for the first phase. The MeSHCam (Meteor, Star and Horizon Tracking Camera) is used for meteor observation as well as star and horizon tracking for position determination. In addition, the smaller PRIma (PR imager) color camera is on board, which is used for PR images of the Earth. The second mission phase begins at 200km and examines the atmosphere during SOURCE’s re-entry. This includes FIPEX sensors on the front and rear sides, which measure the atomic oxygen concentration in orbit. In addition, heat flow, temperature and pressure sensors distributed around the satellite will collect data on the CubeSat’s environment.

Our Payloads

Mission Phase 1 - Orbit at 500km Altitude

Startracking

SOURCE’s star tracking system is an innovative method for determining the position of stars using an inexpensive, commercially available camera. First, the so-called Meteor, Star and Horizon Tracking Camera (MeSHCam) photographs the starry sky in space. The payload onboard computer then compares the images with known star patterns in order to precisely determine the orientation of SOURCE. This use of Commercial-Off-The-Shelf (COTS) components for star tracking is a pioneering technology demonstration as it shows that low-cost, off-the-shelf components can meet the stringent requirements of spaceflight without the need for specialized and more expensive equipment.

Meteor-Detection

The meteor detection payload on board SOURCE aims to observe meteors in the upper atmosphere. The data can expand our understanding of the origin of the solar system. The MeSHCam is capable of detecting even faint meteors, as the light from meteors in orbit is not absorbed by the atmosphere. The use of a commercial camera for these observations also demonstrates the potential for CubeSats to use low-cost optical systems for scientific studies in space. To distinguish between meteors and the background, the payload onboard computer runs the SpaceMEDAL detection algorithm, which is being developed by students at the University of Stuttgart.

PR Images

The PR Imager (PRIma) camera is also a low-cost, commercial camera without special qualifications for use in space. The camera is mounted at a slight angle on the front of the satellite. In contrast to the MeSHCam, the PRIma camera has a high-resolution color sensor. The small camera, measuring 3.5 cm x 2.5 cm, can therefore produce PR photos of the earth. One photo covers a ground area of approximately 450 km x 340 km, which corresponds to around 40% of the area of Germany.

Mission Phase 1 - External Payloads

IRAS – Multifunctional sandwich structure

SOURCE is the test platform for a 3D-printed, multifunctional sandwich structure (MSS) of the German Aerospace Center (DLR) Stuttgart and the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) as part of the Integrated Digital Reserach Platform for Affordable Satellites (IRAS) project. The IRAS MSS consists of a honeycomb structure made of carbon fibers. At certain points, the structure contains tungsten, which protects the electrical circuits from radiation. A small loudspeaker is also integrated, which can be used to confirm the integrity of the structure in space.

Thin-film solar cells

Almost every satellite mission requires solar cells to generate electricity. Reducing the weight of the cells would therefore offer major advantages for many missions. The DLR Institute of Space Systems is therefore investigating the performance of thin-film solar cells on SOURCE. In addition to saving mass, these also offer the advantage of being flexible: this means that more solar cells can be accommodated in a small space during the launch before they are deployed in space. On SOURCE, the thin-film solar cells are mounted on the top, right next to the satellite’s main solar cells.

IRAS SmartHeater

In cooperation with Airbus Defense & Space through the IRAS project, a SmartHeater is integrated on SOURCE. This component automatically heats up to a fixed temperature when voltage is applied.This eliminates the need for temperature sensors or a control algorithm on the satellite.This makes the thermal system much more robust against software errors.In addition, unlike conventional heating elements, the SmartHeater contains a continuous matrix. Even punctual damage therefore does not hinder the operation of the SmartHeater.

Mission Phase 2 - Re-entry from 200km Altitude

Re-entry

SOURCE’s Re-Entry Measurement Payload is designed to investigate the conditions during the CubeSat’s re-entry into the Earth’s atmosphere. This includes pressure, temperature and heat flow measurements. The sensor data can be used to develop better material models for satellites, making it easier to predict re-entries. In addition, future satellites can be constructed according to the “design for demise” principle. This can prevent dangerous fragments from falling to earth instead of burning up completely in the atmosphere.

Atomic Oxygen

The sensors of the Flux Phi Probe Experiment (FIPEX) are another component of the re-entry sensor system. One sensor is attached to the front and one to the back of SOURCE. The sensors are heated to 800°C in order to determine the content of atomic oxygen in the environment. Atomic oxygen is very reactive and therefore leads to severe corrosion on all exposed surfaces. This affects solar cells in particular, causing the generated power to drop continuously over the duration of the mission. Therefore, accurate models for predicting the concentration in the orbit of a satellite are very important. SOURCE can complement these models well.

SOURCE Subsystems

Project Lead

The student project management team keeps track of everything. Whether it’s the schedule, team events, financing or public relations: this is where everything comes together. The project management is supported by staff from the Institute of Space Systems.

System Engineers

Mechanical, electrical and data interfaces between subsystems are coordinated by the system engineers. This also includes the management of mass and power budgets. The system engineers also plan all the necessary tests. In addition, all test documentation is compared with the internal test standard in order to promote high quality.

This subsystem develops and tests all in-house payloads. The team is divided into two groups: The first group deals with the camera system. This includes characterization of the cameras as well as software development for the payload onboard computer. The second group is developing the re-entry sensors. Although these are “Commercial-Off-The-Shelf” (COTS), they are controlled via circuit boards designed in-house. The core of these boards is a radiation-resistant Vorago microcontroller, which also collects data during re-entry. The payload subsystem also integrates the external payloads and the FIPEX payload.

The Attitude Control System is responsible for determining the position and attitude control of SOURCE. GPS, sun sensors, magnetometers and gyroscopes are integrated into the satellite to determine its position and orientation. After processing the data using a Kalman filter, the subsystem controls the orientation of SOURCE depending on the mission phase: after ejection from the rocket, SOURCE is stabilized and the solar panels are aligned with the sun. In nominal operation, the cameras can be rotated in their desired directions. During re-entry, the ACS subsystem will attempt to keep the satellite stable for as long as possible. To accomplish these tasks, 3 magnetorquers are used on SOURCE, which align themselves with the Earth’s magnetic field and thus rotate the satellite. These magnetorquers were developed and manufactured by students themselves.

The Onboard Data Handling and Onboard Software Subsystem is the central control system and monitors the status of the satellite, stores telemetry data and executes commands. It is based on an iOBC with a 400 MHz ARM9 processor and several memory modules and interfaces to ensure communication with other subsystems. The main tasks include data storage, transitions between operating modes, processing of control algorithms and error detection. The software uses the FreeRTOS real-time operating system and the Flight Software Framework (FSFW), which is being developed specifically for space applications by the Institute of Space Systems at the University of Stuttgart.

The Electrical Power System is responsible for generating, storing and distributing energy to other subsystems. It has a solar cell configuration developed in-house with 56 solar cells that generate up to 32W of power. This power is stored in an 86Wh lithium-ion battery from GomSpace. The in-house developed Power Conditioning and Distribution Unit (PCDU) then generates all the required voltage levels, which are then fed to other subsystems via 32 individually switchable outputs. This is controlled by a radiation-resistant Vorgao microcontroller. Maximum Power Point Tracking (MPPT) is performed onboard to maximize the performance of the solar panels. Redundant and failure-resistant components are installed for mission assurance.

The communication subsystem fulfills three main tasks: receiving control commands, sending status information and transmitting payload data. The control commands and status information are particularly critical, as incorrect commands can endanger the satellite. SOURCE communicates directly with the ground station during nominal operation in the S-band (2-2.4 GHz). Data is transmitted according to CCSDS standards with error-correcting algorithms. Since re-entry does not take place directly over a ground station, SOURCE can access the commercial Iridium satellite network via the L-band (1.6 GHz) to send data regardless of position. This system can also be used as a backup during the initial mission phase.

SOURCE’s Operations & Ground Subsystem is responsible for the planned control of the satellite and the construction of the ground infrastructure. This includes the IRS ground station, the mission control system and a mission planning tool including a flight dynamics tool. The existing ground station software must be adapted and automated for SOURCE in order to facilitate future satellite control. OPS&GND also creates the user manual, develops a satellite database for communication and is responsible for the creation and testing of operational procedures. In close cooperation with all other subsystems, the critical training for the launch and the early orbit phase is prepared and carried out.

In order to test the software of the onboard computer (OBC), the simulation and testbed subsystem is developing a simulator that can send artificial data to the OBC. This allows the reaction of the software to any scenario to be tested. This increases robustness and makes SOURCE safer in orbit. The subsystem also looks after the “FlatSat”: here, all of the satellite’s units are spread out on a table and then electrically connected. The exposure of all connections considerably simplifies troubleshooting.

We are looking for you!

Has SOURCE piqued your interest? We are always on the lookout for new members!

No matter whether you are just starting out in your first semester or are already a space expert and no matter what you are studying: we can find an exciting position for everyone in our team.
If you already know what you want to do, get in touch with us!

Participation in SOURCE is voluntary or possible as part of the subject-related SQ Praktikum CubeSat-Technik if you are studying at the University of Stuttgart. In addition, SQ participation is also possible as part of our SOURCE-2 and ATHENE projects. 3 ECTS will be credited for participation.

Write us!

Directly to the SQ!

Fly Your Satellite!

The ESA Fly Your Satellite! program is an educational offer from the European Space Agency (ESA) that enables universities and students to launch their self-developed CubeSats into space and gain practical space experience. Students gain valuable insights into the development, testing and operation of satellites and learn about the challenges of space travel.

The program offers selected teams comprehensive support, from planning and development to construction, testing, launch and mission execution. ESA provides mentors and access to specialized facilities to ensure that the CubeSats meet the high standards of the space industry and are optimally prepared for use in space.

To participate in the FlyYourSatellite program, interested teams must submit a project proposal describing technical concepts, mission objectives and benefits. ESA selects the best projects, which then go through several development phases. The program offers students a unique opportunity to gain hands-on experience and prepare for a career in the space industry.

Curious?

The Fly Your Satellite! program always offers the opportunity to support student teams in the development of their satellite.

It’s worth visiting the ESA website for the latest updates!

ESA Fly Your Satellite!

Timeline

2018

Start of the SOURCE project

Following the success of the Flying Laptop (FLP), the small satellite association KSat e.V. and the Institute of Space Systems IRS at the University of Stuttgart decide to build a CubeSat.

July 2018

PRR (Preliminary Requirement Review) and start of phase B

At the University of Stuttgart, the students of the SOURCE team present the exact boundary conditions of the mission. This concludes phase A, the mission analysis, and phase B, the definition phase, begins.

February 2019

PDR (Preliminary Design Review) and start of phase C

More than 70 reviewers, including members of Tesat-Spacecom, Thales Alenia Space, Airbus, DLR Bremen and friendly space groups, assessed the presented preliminary design of SOURCE. The reviewers agreed that SOURCE can proceed to Phase C, in which the final design is developed through iterative testing of units.

October 2019

Announcement Fly Your Satellite

The European Space Agency (ESA) is launching a call for proposals for the third round of the "Fly Your Satellite!" programme, which aims to support university students in the development and launch of CubeSats.

December 2019

Selection of SOURCE for Fly Your Satellite

The SOURCE team participates in the selection workshop at the ESTEC research center in the Netherlands and is selected as one of four projects to participate in the "Fly Your Satellite! 3" program.

July 2021

Completion of the CDR (Critical Design Review)

The review board of the "Fly Your Satellite!" program confirms the quality and completeness of the SOURCE design, enabling the transition to the integration phase.

August 2021

Start of Phase D – Integration and Testing Phase

SOURCE is entering Phase D, where the satellite hardware is built, tested and assembled into a complete system.

January to August 2023

Construction of the structural model and system-wide shaker tests

From January to March, SOURCE will be fully integrated for the first time. The goal is to qualify all units in a shaker test of the entire system. After the test campaign, SOURCE will be fully qualified to withstand the stresses of launch in a rocket.

November 2024

Carrying out the MRR (Manufacturing Readiness Review)

The "Fly Your Satellite!" program team checks the qualification of all components very carefully. After the review, it is clear: The SOURCE team can start producing the flight hardware.

Beginning of 2026

Planned launch of the SOURCE satellite

The SOURCE satellite is scheduled to launch in early 2026, although the exact date will depend on launch vehicle availability and other factors.

CubeSats

CubeSats are small, standardized satellites originally developed for educational purposes and space research. They usually consist of modular cubes measuring 10 x 10 x 10 cm (a so-called “unit” or 1U) that can be combined to form larger CubeSats. CubeSats are relatively cheap to build and launch, which makes them interesting for universities and research institutes.

An important advantage of CubeSats is their flexibility and versatility. They are often used for scientific measurements, communications tasks or earth observation. CubeSats can also be launched into space by commercial launch providers together with other payloads (so-called “rideshare” launches), which further reduces costs compared to larger satellites. Their compact size and modular design make them suitable for specialized, short-term missions.

Shakertests

When launched in a rocket, satellites are violently shaken by the rocket’s vibrations. A shaker test confirms that the satellite arrives in orbit fully functional even after these stresses.

The test is divided into several sections: First, a resonance search is carried out. The satellite is slightly excited at different frequencies and the resulting acceleration is measured, which allows the resonance frequencies of the hardware to be determined. Then a quasi-static test is carried out, in which the satellite is excited at a constant frequency with high acceleration. Next comes the excitation with random frequencies in a certain range with changing acceleration. Finally, the resonance search is carried out again.

A shaker test is only fully passed after the functionality of the entire system has been subsequently tested and confirmed.

Thermal Vacuum Tests

After a satellite is released from the launch vehicle, it experiences the environmental conditions of space: vacuum and large temperature fluctuations caused by the alternation of sunlight and darkness in orbit.

Despite these conditions, the satellite must be able to operate nominally. To confirm that all components are ready for use, thermal vacuum tests are carried out. A large part of the atmosphere is pumped out of a pressure chamber. The components are mounted on a heating and cooling plate. Then temperature cycles are run to simulate orbits. After several days in the chamber, a functional test confirms that all components have passed the test.

FlatSat

Depending on the internal configuration, all interfaces of the units of a satellite are often difficult to reach when fully integrated. To simplify software development and cross-subsystem testing, a FlatSat can be used.

All units are spread out on a table and connected with additional cables. This enables many electrical connections to be read and makes identifying and correcting errors much easier. For example, an oscilloscope can be used to check the signal quality on a bus system.

The FlatSat also enables improved integration of a simulator to test various components in different mission scenarios. The FlatSat thus significantly increases the robustness of the system.

Plasma Wind Channel Tests

These tests are rather unusual and not part of every satellite’s test campaign. However, the University of Stuttgart is investigating the behavior of materials and components during re-entry. For this, tests in comparable environments are essential.

A plasma wind tunnel generates similar values for the specific enthalpy and total pressure as those that occur during re-entry. Several test campaigns were carried out for SOURCE: First, individual components such as a camera, battery or circuit board were burned in the channel. Data was collected using a pyrometer, an infrared camera, spectroscopy and other instruments.

An overall model was then positioned near the plasma jet. This confirmed the suitability of SOURCE’s re-entry sensors.