Sanjay Jayaram

A new fast converging Kalman filter for sensor fault detection and isolation

Purpose – The purpose of the paper is to present an approach to detect and isolate the sensor failures, using a bank of extended Kalman filters (EKF) using an innovative initialization of covariance matrix using system dynamics.Design/methodology/approach – The EKF is developed for nonlinear flight dynamic estimation of a spacecraft and the effects of the sensor failures using a bank of Kalman filters is investigated. The approach is to develop a fast convergence Kalman filter algorithm based on covariance matrix computation for rapid sensor fault detection. The proposed nonlinear filter has been tested and compared with the classical Kalman filter schemes via simulations performed on the model of a space vehicle; this simulation activity has shown the benefits of the novel approach.Findings – In the simulations, the rotational dynamics of a spacecraft dynamic model are considered, and the sensor failures are detected and isolated.Research limitations/implications – A novel fast convergence Kalman filter ...

Design and analysis of nano momentum wheel for picosatellite attitude control system

Purpose – Recent advances in nano and picosatellite missions and future such missions require faster and accurate pointing accuracies using reaction wheels for attitude control purposes. The ability to put one or three reaction wheels on the spacecraft in the 1‐20 kg range enables new classes of missions. The purpose of this paper is to present the detailed design, analysis, and construction of a miniature reaction wheel prototype. The designed pico‐reaction wheel promises to fulfill the need for low cost, low mass, low power, high reliability, and high‐accuracy attitude control systems for applications such as communications, remote sensing, and space science.Design/methodology/approach – Details about the design, analysis and development of pico‐reaction wheel are discussed. The development status of the system is outlined and the working prototype of the device is described and some preliminary test results are given. Requirements specifications, design and analysis and finite element analysis are cove...

Argus: A flight campaign for modeling the effects of space radiation on modern electronics

The effects of radiation on modern electronics are not well understood; devices with length scales below 60 nm are sensitive across a wider range of input energies and respond differently to different species than larger devices. This is not a trivial issue: existing predictive failure models are off by as much as three orders of magnitude. Complicating the problem is that modern devices have dozens of operating modes, requiring orders of magnitude more testing time. This increase in the required time (and cost) for ground testing, coupled with the greatly reduced cost (and development time) for space experimentation via CubeSats, has made spaceflight a sensible complement to ground testing. The Institute for Space and Defense Electronics (ISDE) at Vanderbilt University has partnered with the Space Systems Research Laboratory at Saint Louis University to develop Argus, a proposed flight campaign of perhaps a dozen CubeSat-class spacecraft spanning years. Argus will fly an array of radiation-effects modeling experiments; on-orbit event rates will be compared against ground predictions to help calibrate new predictive models developed at ISDE. Argus leverages COTS CubeSat systems and the extremely simple payload requirements to field a set of very low-cost, very automated passive platforms developed by students at both institutions. This paper will describe the challenges in modeling radiation effects on modern electronics as well as the new models developed at ISDE. The Argus campaign concept and drivers will be discussed, and the first two missions will be presented: COPPER, which flies in late 2012, and Argus-High, proposed for a 2013 launch.

The Argus mission: Detecting thruster plumes for Space Situational Awareness

The growing capability for proximity-operations missions requires a new capability in Space Situational Awareness (SSA): detecting the presence of other spacecraft operating within 2–5 km of a high-value asset. While significant effort is being devoted to visible-wavelength observation using ground-based systems, we believe that multi-spectral imaging (e.g., long-wavelength infrared, visible and ultraviolet) and particle impact detectors (e.g., mass spectrometers) could be used for in-situ detection of the thruster plumes of spacecraft entering an observational orbit around the high-value asset as well as maintaining it.12

Feasibility of a deployable boom aboard picosatellites for instrumentation and control purposes

Until the 1990s, satellites grew ever larger in both size and mass. NASA administrator, Daniel Goldin, urged for a “faster, better, cheaper” approach that created a wide variety of programs including microsatellite research. Picosatellites, weighing less than 1 kilogram, are one branch of these miniature spacecraft. Their reduced size allows them to be launched in mass quantities at low cost and provides many opportunities not always permitted by larger structures. Unfortunately, while small spacecraft technology has proved to reduce cost and development time, their small size limits the possibilities of certain design concepts. One way to widen the capabilities of these small satellite systems is by utilizing a deployable boom. The boom is stowed within a picosatellite prior to launch and extends into a deployed state once in low Earth orbit. Once in space, the boom serves a two-fold purpose. First, it can be used as a passive form of control to help stabilize and orient the satellite using a reliable gravity-gradient technique. Secondly, on-board instruments could be placed at the tip of the extended boom to minimize any magnetic and electronic interference with internal bus components. Extendable booms have proven space flight heritage on larger microsatellites like QuakeSat and PRISM. Initial research, however, suggests that this concept has not been adapted to the smaller class of picosatellites. This study takes a deeper look into the history of deployable structures on microsatellites in the hope of designing a boom capable of operating within a picosatellite. Various trade off studies are performed, placing heavy emphasis on choosing a suitable boom type and deployment technique while taking into consideration well defined mass, volume, and power constraints. After choosing an appropriate boom and deployment method, a computer-aided design (CAD) model will outline the final boom design both in its stored and deployed configurations. The structural integrity and physical limitations of the boom are demonstrated by performing a finite element dynamic analysis that simulates typical launch loads. Finally, a MATLAB code is utilized to simulate and verify the stability and effectiveness of the chosen gravity-gradient boom design. Introducing a deployable boom in a picosatellite allows for a reliable, inexpensive form of control while simultaneously allowing for more accurate instrumentation data by reducing system noise. By keeping cost and development time low, an extendable boom can expand the current capability of picosatellites to a wider aerospace population, including the university level.

Design and construction of a low‐cost economical thermal vacuum chamber for spacecraft environmental testing

Purpose – The purpose of this paper is to describe the design and construction of a custom‐built low‐cost thermal vacuum chamber (TVC) for spacecraft environmental testing and verification. The paper provides detailed analysis and an insight into the design and development of the chamber. The chamber was specifically constructed for carrying out the thermal and vacuum environmental tests in a 16″ dia × 16″ long horizontal thermal vacuum chamber. The chamber is constructed using a combination of mechanical (roughing) pump and turbo‐molecular pump, used to pump the chamber down to 10−5 Torr and a combination of radiation heaters and nitrogen gas is used to vary the temperature within the chamber from +80 to −50°C.Design/methodology/approach – The TVC equipment is built as part of the picosatellite and nanosatellite program at Space Systems Research Laboratory of Saint Louis University. The equipment is built at a low cost and is suited for testing an entire picosatellite and several components and subsystem...

Design of template to fabricate magnetic torquer coils for nano and picosatellite missions

Purpose – Recent advances in nano and picosatellite missions and future such missions require three axis attitude control system hardware for attitude control purposes. A simple, cost effective, yet an efficient devise that is used for active attitude control is magnetic torquer coil. The purpose of this paper is to describe the design and fabrication of a template to manufacture magnetic torquer coils of varying sizes and shapes.Design/methodology/approach – Details about the development of the template design, analysis, and fabrication are discussed. The development status of the system is outlined and the working prototype of the device is described and some preliminary test results are given.Findings – A fully functional prototype of the template has been developed and testing has been conducted that demonstrated the effectiveness of the device. Magnetic torquer coils of varying sizes were fabricated and tested. A finite element analysis was performed by modeling the characteristics of the fabricated ...

Development of payload housing for temperature and pressure control of bio fuel cells for space applications

Purpose – Alternative energy sources and power generation techniques for long‐term space missions are gaining importance in recent years for future bases and colonies on the Moon or Mars. Current technologies used for manned or unmanned missions to the Moon or Mars use either solar panels (bulky, expensive/kilogram to space, and inefficient) or nuclear energy (extremely dangerous and unpopular). Enzyme based bio fuel cells can be used as alternative energy sources, but its survival depends on maintaining appropriate temperature and pressure in space. The purpose of this paper is to detail the concept design and development of a payload tank to house bio fuel cells for operations in space environment.Design/methodology/approach – Details about the development of the design methodology for such housing are discussed. A full‐scale payload tank is designed to house a small biological fuel cell using space grade materials. Requirements analysis, design, validation, and manufacturing process are covered.Finding...

Fault tolerant autonomous rendezvous and docking architecture for spacecraft in presence of control actuator failures

Purpose – The purpose of this paper is to present novel robust fault tolerant control design architecture to detect and isolate spacecraft attitude control actuators and reconfigure to redundant backups to improve the practicality of actuator fault detection.Design/methodology/approach – The Robust Fault Tolerant Control is designed for spacecraft Autonomous Rendezvous and Docking (AR&D) using Lyapunov direct approach applied to non‐linear model. An extended Kalman observer is used to accurately estimate the state of the attitude control actuators. Actuators on all three axes (roll/pitch/yaw) sequentially fail one after another and the robust fault tolerant controller acts to reconfigure to redundant backups to stabilize the spacecrafts and complete the required maneuver.Findings – In the simulations, the roll, pitch and yaw dynamics of the spacecraft are considered and the attitude control actuators failures are detected and isolated. Furthermore, by switching to redundant backups, the guarantee of overa...

PRO/MECHANICA-based structural and random vibration analysis of picosatellite structure

This paper focuses on the structural and vibration analysis of a low-cost picosatellite structure to the launch load environment. This picosatellite complies with the CubeSat program design specifications, where the satellite is less than one kilogram in mass with a dimension of 10 cm3. The satellite structure is treated as a combination of beams and thin plate elements. A detailed finite element model is developed to observe its responses to the quasi-static accelerations induced by the launch vehicle. The natural frequencies of the prototype were computed numerically through finite element based methods and compared with the natural frequencies induced by the launch vehicle. It was also found that the maximum stress experienced by the structure during launch was well within the stress limits of the material.