Fast tracking mode predictive centroiding scheme

An autonomous star tracker (AST) is basically a `star field in, attitude out' device capable of determining its attitude without requiring any a priori attitude knowledge. In addition to this attitude acquisition capability, an AST can perform attitude updates autonomously and is able to provide its attitude `continuously' while tracking a star field. The Lockheed Palo Alto Research Laboratory is developing a reliable, low-cost, miniature AST that has a one arcsec overall accuracy, weighs less than 1.5 kg, consumes less than 7 watts of power, and is sufficiently sensitive to be used at all sky locations. The device performs attitude acquisition in a fraction of a second and outputs its attitude at a 10 Hz rate when operating in its tracking mode. Besides providing the functionality needed for future advanced attitude control and navigation systems, an AST also improves spacecraft reliability, mass, power, cost, and operating expenses. The AST comprises a-thermalized, refractive optics, a frame-transfer CCD with a sensitive area of 1024 by 1024 pixels, camera electronics implemented with application- specific integrated circuits, a compact single board computer with a radiation hard 32 bit RISC processor, and an all-sky guide star database. Star identification is performed by a memory- efficient and highly robust algorithm that finds the largest group of observed stars matching a group of guide stars. An important milestone has recently been achieved with the validation of the attitude acquisition capability through correct and rapid identification of all 704 true-sky star fields obtained at the Lick Observatory, using an uncalibrated prototype AST with a 512 by 1024 pixel frame-transfer CCD and a 50 mm f/1.2 lens that provided an effective 6.5 by 13.2 degree field of view. The overlapping fields cover 47% of the sky, including both rich and sparse areas. The paper contains a description of the AST, a summary of the functions enabled or improved by the device, an overview of the identification algorithm, results obtained with a realistic simulation program, a description of the true-sky star field identification method and a presentation of the results obtained. The AST tolerates the presence of bright objects as was demonstrated by a field that included Jupiter.

An autonomous star tracker is an avionics instrument used to provide the absolute 3-axis attitude of a spacecraft utilizing star observations. It consists of an electronic camera and associated processing electronics. The processor has the capability to perform star identification utilizing an internal star catalog stored in firmware and to calculate the attitude quaternion autonomously. Relevant parameters and characteristics of an autonomous star tracker are discussed in detail.

ABSTRACT: Autonomous star trackers are optical-electronic devices used for attitude determination of artificial satellites, having as a reference for this computation the positions of stars. There is one autonomous star tracker in development at the Aerospace Electronics Division of the Brazilian National Institute for Space Research. The autonomous star tracker imager is a complementary metal-oxide-semiconductor active pixel sensor, consisting of an integrated circuit with an array of them. Each pixel has a photodetector and an active amplifier. Since it has many amplifiers, the active pixel sensor has an additional fixed pattern noise, therefore its characterization is different from the traditional method used for the charge coupled devices. With this experiment, it was observed that the mean value per columns of fixed pattern noise is ~100% greater than the mean value of the pixel one. Taking into account this result, modeling the pixel fixed pattern noise will not be important to improve the autonomous star tracker sensibility. Furthermore, the random noise value was less than 1% of the fixed pattern noise range data, being possible to estimate it. In this work, we presented the fixed pattern noise new parametric model, which has a good agreement when compared with the experimental data. It was calculated Pearson’s product-moment correlation coefficient between the model and the observed data, in order to quantify the model accuracy and it was obtained 99% for flat field and 79% for dark current.

Compressive measurement and feature reconstruction method for autonomous star trackers

The traditional approach of a star tracker for reducing the dynamic error concentrates on a single frame of star images. Through correlating adjacent star images together with their angular relations sensed by a gyroscope unit (GU), the attitude-correlated frames (ACF) approach expands the view from one single frame to frame sequences. However, the star centroid is shifted from the star true position at the center time of the exposure period under complex dynamic conditions, which is called the complex motion induced error (CMIE) in this paper. The CMIE has a large effect on the performance of the ACF approach. This paper presents a method to compensate the CMIE through reconstructing the star trajectory with the angular velocity of the star tracker sensed by a GU, which achieves effective compensation of the CMIE crossing the boresight direction. Since the observation sensitivity to the CMIE along the boresight direction is low, the attitudes from two different fields of view (FOVs) are combined to improve its compensation accuracy. Then the ACF approach is applied to the obtained results where the CMIE has already been compensated completely. Simulations under shipboard dynamic conditions and experiments under oscillating conditions indicate that the proposed method is effective in improving the performance of the ACF approach and reducing the dynamic error of a star tracker under complex dynamic conditions.

Star tracker is a high-precision attitude sensor that obtains carrier attitude information by processing star images, and star centroid extraction is an important step in the work of star tracker. This paper proposes a star centroid extraction algorithm based on Field Programmable Gate Array (FPGA), which consists of six parts: threshold segmentation, 3X3 matrix generation, pixel weight calculation, connected component labeling, star centroid weight summation, and divider IP core. In order to verify the accuracy of FPGA centroid extraction algorithm, three sets of experiments were conducted. Firstly, generate a noise-free simulated star image, and compare the extraction result which was done on the ModelSim platform with the setting real values to analyze the FPGA centroid extraction accuracy under ideal situation. Secondly, Gaussian noise was added to the simulated star image, and analyzed the FPGA extraction accuracy under noisy situation. Finally, a real star image is extracted on Matlab and ModelSim, respectively, and take the Matlab extraction result as a reference value to evaluate the FPGA extraction accuracy. Simulation and experimental results show that the proposed algorithm has high extraction accuracy ,which can meet the working requirements of star tracker.

Jena-Optronik GmbH (JOP) has a strong heritage in the development of cameras for numerous space-based applications. So far, our focus has been on cameras working in the visible & near-infrared range of the spectrum. The main application case for these cameras is the use as autonomous star trackers being part of a satellite’s Guidance, Navigation & Control System. JOP has been very successful with these cameras –for a long time and is the world market leader in providing such sensors to satellite prime manufactures. Investigating the possible applications of cameras in space, one realizes that thermal or long wave infrared (IR) cameras are necessary for specific applications. One major field for several of such applications is the field of Space Situational Awareness (SSA). SSA has been attracting more and more attention over the past years especially for space objects, natural debris as well as man-made threats & disturbances such as military conflicts. Two further application fields for IR cameras are formation flying and docking. The first rendezvous and docking with a non-cooperative satellite (Intelsat 901) in geostationary orbit by Northrop Grummans MEV-1 was a key milestone for docking capabilities. Additionally, the recent years have shown that a transition from few big and multi-purpose satellites towards small, medium or even large constellations consisting of numerous small satellites is taking place. Especially for constellations, a key aspect is formation flying which usually requires relative navigation. The relative angles between the satellites can be easily provided by IR cameras as they detect the satellites reliably and independently of local lighting conditions due to their elevated temperature against the cold space background. Based on the very successful ASTRO product range of space proven cameras, ASTROtir (tir = thermal infra-red) will extend JOPs product capabilities into the thermal / long wave infrared (LWIR) wavelength range to cover all of the applications cases listed above. Following a successful ESA co-funded first evaluation, the ASTROtir development project has been kicked-off in December 2022 in cooperation with ESA. Target of this project is to demonstrate TRL8 of ASTROtir. Future applications are formation flying (relative navigation), approach and docking with a non-cooperative space object as well as detailed image generation of near satellite objects. Currently, no European solution for an IR camera covering the application cases and mission scenarios is available as off-the-shelf product, which further increases ASTROtir’s already promising market potential. As the market demand, especially in the field of SSA, is rising further in the coming years, its development will be closely followed and its market entry is eagerly awaited. Jena-Optronik will present the preliminary design and development status of ASTROtir. As ASTROtir aims primarily at applications on small and medium satellites, its target mass budget of 300g is a driving requirement. Following our intermediate / preliminary design review scheduled for August 2023, Jena-Optronik aims at presenting first results from ASTROtir’s system analyses as well as the related plans for the EM and EQM campaigns.

The semiconductor industry has enjoyed unprecedented growth over the last two decades fueled by the PC/internet era (2000s) and the Mobile/Social Media era (2010s). We are now entering the Artificial Intelligence/Big Data era which is predicted to push the industry towards $1T in revenue by the early 2030s1. AI applications require massive amounts of computational power and power consumption. To keep pace with expected computational demands and ensure that the industry does not put strain on the global power supply, device makers are looking at ways to increase compute while driving lower operational power consumption. The image below showcases TSMC’s device architecture roadmap on new transistor architectures and gives insight into a path on new integrated materials2. After gate-all-around nanosheets (entering trial production today), TSMC will enter the 3D regime with transistor stacking called CFETs (complementary field-effect transistors). 3D integration of devices is a common strategy across the industry from logic to memory to continue scaling trends. Stacking the devices is shown to increase performance, decrease area cost, and decrease power consumption. Realization of these complex architectures requires very stringent and rigorous fabrication steps with various patterning techniques and new processes. Selective deposition has been identified as one primary method to simplify integration schemes to lower complexity and cost. For example, selective deposition can mitigate issues encountered in fine pitch lithography such as edge placement error that can lead to reliability and performance issues like BEOL contact shorts. Applied Materials is the current leader in selective deposition processing, and we have fielded multiple products that are being used to fabricate cutting-edge devices at leading edge customers. This discussion will focus on the trials and tribulations of ASD, and how it is enabling our customers to reduce power consumption while increasing performance all at a lower area cost, which will be crucial to the future sustainability of this industry.1. https://www.semi.org/en/blogs/semi-news/global-semiconductor-industry-driving-%241-trillion-and-beyond-together2. TSMC 2023 North America Technology Symposium (April 26th, 2023) Figure 1

The drive for ultra efficient and low-cost portable devices continues to push the need for low power circuit designs. The increasing transistor density and complexity of IC designs aggravates the task of producing efficient low power and low cost design. The short time to market (TTM) also increases this burden on designers, as optimal designs have to be produced in an ever decreasing amount of time. This paper presents an optimization design flow methodology that optimizes the power (accounting leakage) consumption of integrated circuits (ICs). The design flow incorporates a stochastic gradient descent (SGD) based algorithm and is implemented using a 45 nm thermal sensor circuit as case study. Power-efficient high-sensitive thermal sensors are important to reduce the burden on the systems or circuits that they are implanted to sense. Experiments are performed to apply the proposed design flow methodology on the thermal sensor with the power consumption as the design objective while keeping the temperature resolution as a constraint. Experiments on full-blown (RCLK) netlist of sense amplifier show a reduction in power consumption by 38%.

Information systems are composed of various types of computers interconnected in networks. In addition, information systems are being shifted from the traditional client-server model to the peer-to-peer (P2P) model. The P2P systems are scalable and fully distributed without any centralized coordination. It is getting more significant to discuss how to reduce the total electric power consumption of computers in information systems in addition to developing distributed algorithms to minimize the computation time. In this paper, we do not discuss the micro level like the hardware specification of each computer. We discuss a model to show the relation of the computation and the total power consumption of multiple peer computers to perform Web types of processes at macro level. We also discuss algorithms for allocating a process to a computer so that the deadline constraint is satisfied and the total power consumption is reduced.

Current state-of-the-art commercial sensors and actuators do not meet many of NASA s next generation spacecraft and instrument needs. Nor do they satisfy the DoD needs for satellite missions, especially micro/nano satellite missions. In an effort to develop advanced optical devices and instruments that meet mission requirements, NASA Langley recently completed construction of a new cleanroom housing equipment capable of fabricating high performance active optic and adaptive optic technologies including deformable mirrors, reconfigurable lenses (both refractive and diffractive), spectrometers, spectro-polarimeters, tunable filters and many other active optic devices. In addition to performance, these advanced optic technologies offer advantages in speed, size, weight, power consumption, and radiation tolerance. The active optic devices described in this paper rely on birefringent liquid crystal materials to alter either the phase or the polarization of the incoming light. Design considerations and performance evaluation results for various NASA applications are presented. Applications presented will include large space telescopes, optical communications, spacecraft windows, coronagraphs, and star trackers. Keywords: Photonics, Adaptive Optics, Tunable Filters, MEMs., MOEMs, Coronagraph, Star Tracker

New developments in image sensors and optical materials have opened the door to dramatic mass and power reductions in celestial tracker design. The rapid development of active pixel sensors (APS) has provided a new detector choice offering high on-chip integration of support circuitry at reduced power consumption. Silicon-carbide optics are one of the new developments in low-mass optical components. We describe the celestial tracker needs of an Autonomous Feature and Star Tracking (AFAST) system designed for autonomous spacecraft control. Details of a low-mass celestial tracker based on a low-power APS array and optimized for an AFAST system are discussed.

Power consumption is one of the leading producers of Greenhouse Gases and improving it will support Petroleum Development Oman (PDO) to meet its target of net-zero emissions. In 2020, PDO operations emitted tons of CO2 with the highest quantity coming from X field where High Voltage pumps, which consume about 15MW resulting in 75,000 tons of CO2 emissions per year, are used. This paper will discuss the approach used to investigate and solve the given problem. The six-Sigma methodology was used to investigate the high-power consumption in water injection and deep-water disposal processes. Pareto analysis, which was used to scope the project, showed that 35% of power consumption is related to High Voltage injection pumps. The historical data of the response (power consumption) and potential causes of the problem were gathered from the field database. Minitab, a statistical data analysis software, was used in this problem investigation in addition to other Six-Sigma methods including process capability, hypothesis testing, and control charts. Graphical and statistical tools were also used to examine the relationship between the response and variables. Process mapping identified 27 potential causes of higher power consumption in five High Voltage pumps. The historical data of the variables were statistically correlated to measure the strength of the relationship with the response. The analysis concluded that suction pressure for pumps 1510 and 1520 is the statistically significant cause of higher power consumption. The power consumption of these two pumps was directly linked to the suction pressure using the Pearson coefficient factor and p-value. The suction pressure was too low which caused the pumps to consume more energy to pressurize water. Hypothesis testing resulted in a p-value of 0.00, confirming a strong relationship between power consumption and suction pressure. Appropriate countermeasures were developed, and a new pump operation philosophy was implemented, whereby one pump is always kept on standby. This resulted in a 4MW reduction in power consumption and, ultimately, prevented the emission of 18,000 tons of CO2 annually. Other benefits to date include a saving of around $2.6 million per year, with the potential to save more through replication. Additional yet unquantified benefits include curbing the impacts of climate change on the environment. The Six Sigma statistical approach is used to understand the hidden causes of the increase in power consumption that result in higher CO2 emissions. The reduction of power consumption in PDO's X field has paved the way for 10 other projects in the Company to reduce their CO2 emissions. We can partner with other operators in the Sultanate of Oman to follow Petroleum Development Oman's example of using the Six Sigma approach in Energy Transition.

Objectives: Processors are computing elements of most of the embedded systems. As the technology is growing day by day, processors that are released in the market are mostly embedded processors. Processors are designed to perform concurrent operations and execution at a higher clock rate to meet the performance demands result in large heat dissipation and energy consumption. Thus there is an emphasis on power and energy consumption reduction in real time embedded processors. This work targets to reduce the processor power consumption without violating the real time constraints. Method: In this work, a dynamic power management technique named dynamic counters is employed in real-time system to minimize power consumption. The proposed method facilitates bounding of the events conservatively for effective bounding of future workload. It also employs scheduling ON and OFF time of the devices based on workload bounding at run-time. Simulation analysis is carried out to confirm the performance enhancement of the proposed method. Findings: Energy consumed by the processor increases with the number of event arrivals and switching of modes facilitates significant energy savings. Improvement: Run-time and memory overheads are overcome by dynamic counter technique. Effective bounding of future workload enhances computational efficiency.

Small satellites are now capable of performing missions that require accurate attitude determination and control. However, low weight, size, power, and cost requirements limit the types of attitude sensors that can be used on a small craft, making attitude estimation difficult. In particular, star trackers -- often the attitude sensors of choice for spacecraft, ballistic missile etc., are not practical for small satellites, and CMOS APS is a good substitute for attitude sensors. Some of the technical advantages of CMOS APS are no blooming, low power consumption, direct digital output, small size and little support circuitry, simple to design, etc. This paper discusses the application probability of CMOS APS technology in star tracker for use in small satellites. A ground-based prototype vision system based on CMOS APS has been built to demonstrate the advantages of using CMOS APS in star tracker. Resolving capability, noise, radiation hardening and some other characteristics are discussed in detail. CMOS image sensor is sure to be a potential replacement of CCD in the field of attitude sensors.