Project

Adelis SAMSON - Satellite Autonomous Mission for Swarming and Geolocating Nanosatellites

Goal: SAMSON will include autonomous 6U cubesats that will demonstrate long-term cluster flight and perform high-accuracy geolocation. Technion's Asher Space research Institute leads the project, with many collaborators from the industry and academia. The launch is planned in 2017. Most of the algorithms (cluster flight, differential drag, geolocation, attitude control) have been designed by Technion grad students.

Updates
0 new
9
Recommendations
0 new
21
Followers
0 new
62
Reads
3 new
1115

Project log

Pini Gurfil
added an update
Adelis-SAMSON will be launched on Saturday, March 20 at 6:07 UTC. A link to the live-stream of the launch can be found here:
A promo clip can be viewed here:
 
Pini Gurfil
added a research item
Space Autonomous Mission for Swarming and Geolocation with Nanosatellites (SAMSON) is a satellite mission led by the Distributed Space Systems Lab at the Technion-Israel Institute of Technology. SAMSON will include three 6U Cube-Sats. The mission is planned for one year, and has two main goals: (i) demonstrate long-term autonomous cluster flight of multiple satellites, and (ii) determine the position of a terrestrial emitter based on time difference of arrival (TDOA) and frequency difference of arrival (FDOA). In addition, SAMSON will perform three experiments: (i) continuous operation and thrust measurement of a micro pulsed plasma thruster; (ii) inter-satellite distance regulation using differential drag; and (iii) disaggregation of the command and on-board data handling based on the CubeSat Standard Protocol. In this paper, the development of flight algorithms for SAMSON and the implementation thereof are discussed. Since the SAMSON satellites are equipped with constant-magnitude warm-gas thrusters, the current work presents a cluster-keeping algorithm designed considering this technological constraint, and focuses on the performance evaluation of the control algorithm under thrust magnitude and direction dispersions.
Pini Gurfil
added an update
The Adelis-SAMSON satellites were sent today to Ben-Gurion Airport, en route to the Netherlands, where the company ISILaunch will integrate the satellites with the deployers. From the Netherlands, the satellites will be shipped to Baikonur, Kazakhstan, for launch.
Today marks the end of an era for ASRI. After 9 years of diligent work, the Adelis-SAMSON satellites -  the first Israeli formation flight mission - left ASRI. We are all very excited and hopeful that this groundbreaking project will have a successful launch.   
 
Pini Gurfil
added 9 research items
Calculating the projected cross-sectional area (PCSA) of a satellite along a given direction is essential for implementing attitude control modes such as Sun pointing or minimum-drag. The PCSA may also be required for estimating the forces and torques induced by atmospheric drag and solar radiation pressure. This paper develops a new analytical method for calculating the PCSA, the concomitant torques and the satellite exposed surface area, based on the theory of convex polygons. A scheme for approximating the outer surface of any satellite by polygons is developed. Then, a methodology for calculating the projections of the polygons along a given vector is employed. The methodology also accounts for overlaps among projections, and is capable of providing the true PCSA in a computationally-efficient manner. Using the Space Autonomous Mission for Swarming and Geo-locating Nanosatellites mechanical model, it is shown that the new analytical method yields accurate results, which are similar to results obtained from alternative numerical tools.
In disaggregated satellites, the functional capabilities of a single monolithic satellite are distributed among multiple free-flying, wirelessly communicating modules. One of the main challenges associated with disaggregated satellites is cluster flight, i.e., keeping the modules within a bounded distance, typically less than 100 km, for the entire mission lifetime. This paper presents a methodological development of cluster flight algorithms for disaggregated satellite systems in low Earth orbits. To obtain distance-bounded relative motion a new constraint on the initial conditions of the modules is developed. A concomitant analytical bound on the relative distance between the modules is proven based on a design model assuming time invariance of the environmental perturbations. It is then shown that if the actual astrodynamical model includes other possible time-varying effects, mild drifts between the modules are obtained. Furthermore, this paper presents a detailed impulsive cluster establishment and cluster-keeping algorithm for tracking a given nominal orbit, whose characteristics satisfy the previously developed no-drift constraint. This algorithm provides fuel balancing among the maneuvering modules, as well as the minimization of the total fuel consumption, while guaranteeing a collision-free operation. Numerical simulations using representative astrodynamical models are used to validate the analysis.
Calculating the projected cross-sectional area (PCSA) of a satellite along a given direction is essential for evaluating the forces and torques induced by atmospheric drag and solar radiation pressure. The PCSA is also required for implementing attitude control modes such as Sun pointing or minimum-drag. This paper develops a new analytical method for calculating the PCSAs, based on the theory of convex polygons. A scheme for approximating the outer surface of any satellite by polygons is developed. Then, a methodology for calculating the projections of the polygons along a given vector is employed. The methodology also accounts for overlaps among projections, and is capable of provid-ing the true PCSA in a computationally-efficient manner. Using the Space Autonomous Mission for Swarming and Geo-locating Nanosatellites mechanical model, it is shown that the new analytical method yields accurate results, which are similar to results obtained from alternative numerical tools. Copyright © (2015) by Technion Israel Institute of Technology. All rights reserved.
Pini Gurfil
added an update
Pini Gurfil
added an update
Getting ready for launch :-)
 
Eviatar Edlerman
added a research item
Adelis-SAMSON is a nano-satellite mission aimed at performing geo-location of target signals on Earth using a tight three-satellite formation in space. To maintain formation, each nano-satellite is equipped with a cold gas propulsion system. The design, qualification, and integration of the Adelis-SAMSON nano-satellite propulsion system is presented in this paper. The cold gas propulsion system mass is approximately 2 kg, takes a volume of 2U, and generates a thrust of 80 mN from four thrusters using krypton as a propellant. We first present the propulsion system requirements and corresponding system configuration conceived to meet the mission requirements. Subsequently, we present the system architecture while listing all the components. We overview the particular role and qualification process of four of the propulsion system’s components: the propellant tank, thruster assembly, pressure regulators, and fill and vent valve. We detail the tests performed on each component, such as proof pressure tests, vibration tests, and external leak tests. Finally, we present the propulsion system level tests before delivery for satellite integration and discuss the propulsion system’s concept of operations.
Pini Gurfil
added an update
Pini Gurfil
added an update
Hao Zhang
added a research item
The concept of flying multiple satellites in formation has evolved to encompass challenging concepts such as disaggregated space architectures and in-orbit assembly, which include very large numbers of modules flying autonomously in a cluster. Whereas control laws for satellite formations are abundant, guidance and control algorithms for operating large numbers of satellites in close proximity are ongoing research. One approach is to use artificial-potential-based guidance and control laws. This technique uses the definition of several behavior functions like Gather, Avoid and Dock, which form a virtual potential from which desired velocities are computed. A controller is used to achieve these velocities by commanding the on-board thrusters. In a joint research project between the Distributed Space Systems Lab at the Technion and DLR’s Institute of Space Systems this approach has been implemented in two different test facilities. Experiments performed in simulation and on the testbeds include formation acquisition and reconfiguration as well as collision avoidance. This paper will present the algorithms as well as the experimental results. They will show the performance and the robustness of the implemented guidance algorithm, as well as the adaptability of the method to different test setups.
Eviatar Edlerman
added a research item
Space Autonomous Mission for Swarming and Geo-locating Nanosatellites (SAMSON) is a satellite mission led by the Asher Space Research Institute (ASRI) at the Technion and supported by the Adelis Foundation. SAMSON includes three nano-satellites, designed by ASRI, that fit into a 6U CubeSat structure and weighs about 8kg. The three satellites will be launched together to form a cluster with relative distances ranging from 1km up to 250 km and perform autonomous relative orbital element corrections to satisfy the relative distance constraints. The mission is planned for at least one year, and has two main goals: (1) Demonstrate long-term autonomous cluster flight of multiple satellites, and (2) determine the position of a cooperative terrestrial emitter based on time difference of arrival (TDOA) and frequency difference of arrival (FDOA). The time-synchronized sensors in each member of the cluster measure independently the emitter's received signal, and record the respective TDOA and FDOA, resulting in a combined estimation of the position of the detected transmitter. In this paper, we outline the design of the GPS-Disciplined Oscillators used for generating precise time synchronization among the satellite clusters, enabling the geolocation processing. Each satellite carries a GPS receiver that calculates its own position and generates a highly accurate 1PPS signal, which is used as a major synchronization trigger between the satellites. An ultra-high stability OCXO serves as an added input for enhanced synchronized timing between the satellites, aiming at higher geolocation accuracy. The combination of an OCXO whose output is controlled to agree with signals broadcasted by GPS and/or GNSS satellites is referred to as a GPS Disciplined Oscillator (GPSDO). The synchronization requirements of SAMSON's geolocation mission call for accurately measuring the received TDOA and FDOA of the emitter signal at each of the three nano-satellites of the cluster. All GPSDO parts: AD9548 synchronization circuitry, NovAtel, OEM615 compact GPS receiver and the ultra-high stability OCXO, fit into a single 1U size PCB. The GPSDO was tested for initial performance evaluation and flight model boards are in production and will follow intensive performance evaluation.
Hao Zhang
added 3 research items
Satellite cluster flight is an enabling technology for disaggregated space architecture. A nonlinear distributed control law is developed considering fixed-magnitude thrust, in order to establish satellite cluster flight under perturbations. Mean orbital elements are used as feedback. Notation of partial stability is adopted to describe the stability. Uniform stability and asymptotic stability are proven for the relative motion control. State selection for establishing a low Earth orbit cluster is also discussed. Several numerical studies are performed to assess the performance of the control law. Comparisons are provided to show the fuel-balancing merits of the current control law. The effects of drag on the long-term performance are also investigated. The current control law is shown to be feasible and effective for satellite cluster flight.
One of the emerging topics in the realm of distributed space systems is cluster flight of nanosatellites. As opposed to formation flight, cluster flight does not dictate strict limits on the geometry of the cluster, and is hence more suitable for implementation in nanosatellites, which usually do not carry highly accurate sensors and actuators. The actuators are usually simple fixed-magnitude thrusters, which are prone to many sources of errors, such as attitude determination and control errors. In this context, the purpose of this paper is to develop a cluster-keeping control law that is capable of long-term operation under thrust uncertainties, assuming fixed-magnitude thrust provided by a simple cold-gas thruster. To that end, mean orbital elements are used for designing an inverse-dynamics controller. It is shown that, in the differential mean elements space, this controller is time-optimal. An adaptive enhancement is developed to mitigate the thrust pointing errors and restore the original optimal performance, thus saving much fuel. Several simulations and comparative studies are performed to validate the analytical results.
In space systems consisting of a large number of satellites, coordinating orbits among satellites is necessary throughout the entire mission lifetime. Although previous works mainly focused on the boundedness of relative motion between satellites in the group, in this work, an extra degree of freedom is also addressed in order to manipulate an arbitrary number of orbital elements, which is represented as coordinating a general orbital transfer and an in-space assembly. The underlying concept is using consensus theory to characterize the properties of the control objective as in a multi-agent system. To that end, this paper assumes that the communication in the networked satellite system is represented as an undirected graph, and then implements the governing system dynamics in a control-affine form as described by the Gauss's variational equations. For the general orbital transfer problem, an edge-error-based controller is developed and proven asymptotically stable. Definitions of error functions are also investigated to understand the behavior of developed controllers. Several strategies for assembly control are discussed, namely, via changing of variables or in a two-phase control process based on the dynamical structure. Numerical simulations are performed to validate the analysis and demonstrate the results. IEEE
Hao Zhang
added 2 research items
Nano-satellite clusters and disaggregated satellites are new concepts in the realm of distributed satellite systems, which require complex cluster management mainly regulating the maximal and minimal inter-satellite distances on time scales of years while utilizing simple on-off propulsion systems. The simple actuators and long time scales require judicious astrodynamical modeling coupled with specialized orbit control. This paper offers a satellite cluster orbit control law which works for long time scales in a perturbed environment while utilizing fixed-magnitude thrusters. The main idea is to design a distributed controller which balances the fuel consumption among the satellites, thus mitigating the effect of differential drag perturbations. The underlying methodology utilizes a cyclic control algorithm based on a mean orbital elements feedback. Stability properties of the closed-loop cyclic control system do not adhere to the classical Lyapunov stability theory, so an effort is made to define and implement a suitable stability theory of noncompact equilibria sets. A state selection scheme is proposed for efficiently establishing a low Earth orbit cluster. Several simulations, including a real mission study, and several comparative investigations, are performed to show the strengths of the proposed control law.
Pini Gurfil
added a research item
Spacecraft formation flying and satellite cluster flight have seen growing interest in the last decade. However, the problem of finding the optimal debris collision avoidance maneuver for a satellite in a cluster has received little attention. This paper develops a method for choosing the timing for conducting minimum-fuel avoidance maneuvers without violating the cluster inter-satellite maximal distance limits. The mean semimajor axis difference between the maneuvering satellite and the other satellites is monitored for the assessment of a maneuver possibility. In addition, three techniques for finding optimal maneuvers under the constraints of cluster--keeping are developed. The first is an execution of an additional cluster--keeping maneuver at the debris time of closest approach, the second is a global all-cluster maneuver, and the third is a fuel-optimal maneuver, which incorporates the cluster--keeping constraints into the calculation of the evasive maneuver. The methods are demonstrated and compared. The first methodology proves to be the most fuel efficient. The global maneuver guarantees boundedness of the inter-satellite distances, as well as fuel and mass balance. However, it is rather fuel-expensive. The last method proves to be useful at certain timings, and is a compromise between fuel consumption, and the number of maneuvers.
Pini Gurfil
added 2 research items
Satellite Mission for Swarming and Geolocation (SAMSON) is a new satellite mission initiated and led by the Technion – Israel Institute of Technology and supported by Israeli space industries and other partners. SAMSON shall include three inter-communicating nano-satellites, based on the Cubesat standard. The mission is planned for at least one year, and has two goals: (1) demonstrate long-term autonomous cluster flight of multiple satellites and (2) geolocate a cooperative radiating electromagnetic source on Earth. Additional payloads may include a micro Pulsed Plasma Thruster and a new space processor. The configuration of each satellite is a 6U Cubesat, comprising of an electric power system with deployable solar panels, communication system, on-board data handling system, attitude control system and a cold-gas propulsion system for orbit and cluster-keeping. The SAMSON mission commenced in early 2012 and is planned to be launched in 2015. All three satellites shall be launched with the same inclination and semi-major axis into a near-circular orbit. In orbit, they shall separate to form a cluster with inter-satellite relative distances ranging from 100 m to 250 km. One satellite shall be designated as "leader", and the rest would serve as "followers". The leader shall station-keep to control the nominal mean orbital elements, while the followers shall only perform relative orbital element corrections to satisfy the relative distance constraints. During the course of the mission, the cluster shall also perform geolocation experiments, using signals received from known locations on Earth. SAMSON will serve as a platform for academic research and hands-on engineering education. It will also contribute to the advancement of Search and Rescue mission technologies.
Generally, any initially-close satellites—chief and deputy—moving on orbits with slightly different orbital elements, will depart each other on locally unbounded relative trajectories. Thus, constraints on the initial conditions must be imposed to mitigate the chief-deputy mutual departure. In this paper, it is analytically proven that choosing the chief’s orbit to be a frozen orbit can mitigate the natural relative drift of the satellites. Using mean orbital element variations, it is proven that if the chief’s orbit is frozen, then the mean differential eccentricity is periodic, leading to a periodic variation of the differential mean argument of latitude. On the other hand, if the chief’s orbit is non-frozen, a secular growth in the differential mean argument of latitude leads to a concomitant along-track separation of the deputy from the chief, thereby considerably increasing the relative distance evolution over time. Long-term orbital simulation results indicate that the effect of choosing a frozen orbit vis-à-vis a non-frozen orbit can reduce the relative distance drift by hundreds of meters per day.
Pini Gurfil
added an update
Mechanical design of the SAMSON Cubsat is almost done...See the complete process here
 
Pini Gurfil
added an update
Gas tanks for the propulsion system are ready!
 
Pini Gurfil
added a project goal
SAMSON will include autonomous 6U cubesats that will demonstrate long-term cluster flight and perform high-accuracy geolocation. Technion's Asher Space research Institute leads the project, with many collaborators from the industry and academia. The launch is planned in 2017. Most of the algorithms (cluster flight, differential drag, geolocation, attitude control) have been designed by Technion grad students.