Control Systems

RX30 – ASTER (Attitude Stabilized Free Falling Experiment)

Luleå University of Technology, Sweden

Launch Date: 29 March 2023

Current attitude control systems are targeted at orbital flights and are therefore acting relatively slowly, with attitude control maneuvers measured in orbits rather than minutes or seconds. Furthermore, they are usually aimed at projects with extensive funding, making them excessively expensive for experiments operating under tight budgetary requirements. Sounding rocket experiments are generally lower budget missions and are heavily constrained by flight time, and as such they would benefit greatly from a low-cost, high-performance solution.

The project ASTER (Attitude STabilized free falling ExpeRiment) aims to develop a high-performance, low-cost and easy to integrate attitude control system for free falling experiments ejected from sounding rockets. The engineering solution utilises three electrically-powered reaction wheels to stabilise and orientate the free falling unit in three axes in a reduced gravity environment. The system shall be compact to ensure sufficient space to accommodate the payload of future missions. Additionally, it shall be able to achieve agile stabilization to increase the available time for experiments after successful stabilization. Furthermore, it should perform predefined slewing maneuvers to be adaptable to a wider range of applications.

RX28 – TUPEX-7 (TU Berlin Picosatellite Experiment 7)

Technische Universität Berlin, Germany

Launch Date: 07 November 2022

TUPEX-7 is a student mission to develop and demonstrate miniaturized space technologies for a 1U CubeSat bus through deployment of a Free-Falling Unit(FFU) in the milligravity environment. These technologies include Highly-Integrated Side Panels (HISPs) and a Software Defined Radio (SDR). The HISPs will incorporate several subsystems to minimize the overall space required. Principally, they will include pico Fluid Dynamic Actuators (pFDAs), an attitude actuation technology being developed at TU Berlin. The mission will demonstrate the volume efficiency of pFDAs and investigate their effectiveness in performing routine satellite maneuvers through attitude data collection and analysis.

The SDR, having frequency and modulation adjustable by software, allows for flexible communication between ground and satellite and will reduce the volume required for communication on varied channels. As a parachute is required for FFU recovery, a flexible monopole antenna will be developed and integrated with its cords to send and receive signals. The potential of the SDR system will be evaluated through its transmission and reception of data to and from ground.

The FFU will be launched on a REXUS launch vehicle and deployed in the milligravity environment, demonstrating the technologies’ potential for application in small satellites. The inclusion of a parachute, comprising a substantial volume of the FFU, will inherently demonstrate the expanded payload capacity. The high payload-to-volume ratio, successful communication by the SDR, and successful maneuvers performed by the HISPs and pFDAs would greatly contribute to new and expanded possibilities for small satellites.

RX26 – TUPEX-6 (TU Berlin Picosatellite Experiment 6)

Technische Universität Berlin, Germany

Launch Date: 19 March 2019

Modern day 1U CubeSats require precise attitude actuation typically provided by systems of three or four reaction w heels. How ever, due to their volume consumption, can render larger payloads difficult to integrate.

Pico satellite fluid dynamic actuators (pFDAs) are being researched at Technische Universitat Berlin as an alternative means of attitude control with improved volume utilisation. Previously, flat pFDAs have been developed to be 3D printed and integrated on printed circuit board based side panels of CubeSat, which requires six pFDAs for full redundency. The newly developed pFDA with

L-shape allow for redundant attitude control, using only four pFDAs.

TUPEX-6 is a student driven mission to demonstrate pFDA technology onboard a Free Falling Unit, roughly comparable to a CubeSat in a micro gravity environment. The primary purpose is to show redundant attitude control using four L-shaped pFDAs in a tetrahedral configuration.

REXUS w ill provide TUPEX-6 time in micro gravity for the pFDAs to perform attitude control maneuvers. Redundancy w ill be demonstrated by shutting down one of the pFDAs to simulate an in-flight failure. Attitude control and housekeeping data w ill be collected to verify the utility of pFDAs for 3-axis control of future CubeSat missions.

RX22 – RaCoS (Rate Control System)

University of Würzburg, Germany

Launch Date: 16 March 2017

The experiment shall reduce and control the angular rate of the REXUS sounding rocket in the roll axis by using a cold gas system. Therefore, a control algorithm shall use the measured angular rates to calculate opening times for valves regulating the gas jets.

Unlike existing systems, RaCoS shall be lightweight and inexpensive to build by using commercial off-the-shelf components. Moreover, RaCoS could help to improve the milli-gravity environment of the REXUS rocket.

The experience gained through this experiment could be useful for further university projects. For example, future cubesats of the University of Würzburg, like the ones that have already been successfully launched (UWE-1, UWE-2, UWE-3), could include a fully functional and affordable rate control system. In this case, the system would have to be miniaturized. In the future, the system could be easily extended to the other two axes for full attitude manoeuvrability.

RX20 – PATHOS (Position-vector Acquisitaion Through Horizon Observation)

Julius-Maximilians-Universität Würzburg, Germany

Launch Date: 15 March 2015

PATHOS is the acronym for Position-vector Acquisition Through Horizon Observation System. It’s a system which can determine the attitude of a spacecraft by using image data which are processed in an algorithm.

The practical utility of PATHOS is to extent satellites with another attitude determination system for emergency cases like uncontrolled spinning.

With the flight on the REXUS rocket the PATHOS-sensor will be tested for proper functioning. The rocket reaches a height were the curvature of the earth is visible, which is crucial for the horizon detection by the software. Due to the spinning and tumbling of the rocket, stress conditions can be simulated. The experiment shall prove that even those movements are no problem for the system.

The sensor takes images with usual cameras. Afterwards the algorithm recognizes the earth horizon and uses this line to calculate a vector towards the earth center.

Besides of the PATHOS sensor there has to be built infrastructure to command the experiment and to store and evaluate the scientific data.

BX18 – COUGAR (COntrol of Unmanned Ground vehicle from higher Altitude in near Real time)

University of Würzburg, Germany

Launch Date: 10 October 2014

The technical objective of the experiment is to control an unmanned ground vehicle from a ground station via a balloon. In our experiment we will demonstrate that such a command and control link can be achieved even if there is no direct line-of-sight between the ground station and the object to be controlled. The experiment will help in validating communication between multiple platforms on extra-terrestrial surfaces using moving intermediate relay stations (like balloons) where direct communication is not possible.

BX18 – POLARIS (POLymer-Actuated Radiator with Independent Surfaces)

University of Padova, Italy

Launch Date: 10 October 2014

The POLARIS experiment aims to study the performance of a new concept of heat radiator which can vary its configuration and equivalent thermal resistance, exploiting Dielectric Elastomer actuators, in variable environmental conditions.This should guarantee, through an active thermal control, the thermal steadiness of a dummy payload whose temperature have to remain within a given operational range. Moreover, the team wants to verify the correlation between the numerical model used to predict the thermal behaviour of the dummy payload and the measured data, in order to validate the theoretical model and understand the limitations of this radiator concept.

BX19 – GranaSAT (Attitude control for a microsatellite based in a Star Tracker, and Earth’s magnetic field measurements)

University of Granada, Spain

Launch Date: 8 October 2014

The aim of the experiment is to design an orientation control system based in a Star Tracker and magnetic sensors. Therefore, star images and magnetic field oscillation measurements are taken. For pointing antennas and sensors towards the Earth or other different astronomical objects, an accurate orientation control system with regard to a specific reference in satellites is needed. The precision required by these systems depends on each particular application, in broadcast systems it may be low, but for other scientific applications a higher accuracy is needed. Usually a satellite uses different sensors of orientation such as magnetic sensors, sun sensors, skyline sensors, etc. However, the Star Tracker is the most precise solution for a spacecraft, because it provides data with an accuracy of 20-90 arc seconds. As stars position remains relatively fixed in ECI the reference frame, the orientation of the satellite can be determined using different algorithms. This experiment is designed for being placed in a future university microsatellite, the GranaSAT.

GranaSAT Final SED


BX17 – ARCADE R-2 (Autonomous Rendezvous Control And Docking Experiment Reflight 2)

University of Padova, Italy

Launch Date: 10 October 2013

ARCADE-R2 is a technology demonstrator, whose aim is to prove the feasibility of a small scale docking system, including automatic attitude determination and control capabilities. The experiment main objectives are to test three custom subsystems able to perform relative proximity navigation, relative attitude control and docking between a small aerial vehicle and its target on the gondola and to determine the correlation between each subsystem performance and the disturbances due to the external environment. The idea is to execute several navigation control-docking sequences at different altitudes and to collect data on the external pressure, temperature, wind speed and direction, in order to fully characterize the external environment and thus the atmospheric loads applied on the vehicle. The experiment setup is composed by a gondola-mounted target vehicle and a small external chaser vehicle, mounted on a rigid support structure that provides a secure connection with the gondola. The small vehicle is provided with two degrees of freedom, one translational perpendicular to the gondola and one rotational around its yaw axis and the two units feature relative navigation sensors, attitude control actuators and a docking mechanism interface, along with temperature sensors, pressure sensors and probes to monitor the direction of the wind. The development of such technologies is fundamental to build, in the near future applications, fleets of cooperative, automatic aerial unmanned vehicles, which will be possibly exploited over the next decades in various scenarios, including mapping, surveillance, inspection and remote observation of hazardous environments that are inaccessible to ground vehicles.



BX13 – ARCADE (Autonomous Rendezvous Control And Docking Experiment)

University of Padova, Italy

Launch Date: 26 September 2011

The primary goal of the ARCADE experiment is to perform an automatic rendezvous between a SMAll Vehicle (SMAV) and a docking interface mounted on the BEXUS gondola, thereby evaluating the performances of a docking mechanism plus a navigation and attitude control system. Data will also be collected to characterise the external environment in terms of temperature, pressure and wind velocity, which determines the disturbances induced on the SMAV. The inspiration for this project comes from the growing interest regarding in-flight inspection, refurbishment and refuelling of both air and spacecraft. These activities are expected to be performed by small vehicles such as MAVs or nano-satellites in the near future. Considering the above scenario, the ARCADE system will consist of three main elements: A four DOF small vehicle suspended outside the gondola – which will carry the free-flyer portion of the docking mechanism – as well as navigation sensors and a reaction wheel for yaw-axis control; a structure which supports the SMAV outside the gondola, providing the control for pitch, roll and translation towards the gondola; and a proximity box mounted on the gondola, which provides the docking interface and houses all electronics as well as the beacons for the navigation sensors. The experiment will consist of several docking-release sequences, involving the navigation, attitude control and docking subsystems, and continuous environmental data collection.


BX11 – SCOPE 2.0 (Stabilised Camera Observation Platform Experiment 2.0)

Warsaw University of Technology, Poland

Launch Date: 23 November 2010

The objective of the SCOPE 2.0 experiment was to develop and test a two-and-a-half degree of freedom video camera stabilisation and control mechanism, which was designed to compensate for any movements that occur in balloon-borne experiment platforms. Video recordings from stratospheric balloons are often of a very low quality due to the uncontrolled oscillatory and rotational motion experienced during flight. SCOPE 2.0 aimed to combat this effect by using real time data obtained from an Inertial Measurement Unit (IMU) and GPS receiver to determine the attitude of the camera with relation to its target, and to compensate for any unwanted motion using stepper motor actuators. The IMU measured the cameras angular velocity, whilst the GPS calculated the direction of the cameras point of focus, and the correctional data was then processed and transferred to the stabilisation system. During the flight, video footage was transferred to a ground station, and the motion of the SCOPE 2.0 system was registered and compared against theoretical predictions post-flight.

SCOPE 2.0 Conference Paper