scholarly journals Improving the Measurement Quality of Small Satellite Star Trackers

2021 ◽  
Author(s):  
Tom Dzamba
Keyword(s):  
High Performance ◽  
Calibration Procedure ◽  
Detection Performance ◽  
Star Tracker ◽  
Small Satellite ◽  
Small Satellites ◽  
Commercial Off The Shelf ◽  
Detector Configurations ◽  
Validation Tests

Recent demand from the small satellite community has led to the development of a new series of star trackers that are specifically designed for small satellites. These units represent substantial improvements in mass, power consumption and cost over traditional star trackers, but suffer slightly in terms of accuracy and availability performance. The primary factors inhibiting their performance are the use of significantly smaller optics, and commercial off the shelf components (COTS). This thesis presents a series of strategies for improving the performance of small satellite star trackers (SSSTs). These goals are realized through the development of offline calibration procedures, flight software, validation tests, and optical trade studies to guide future development. This thesis begins with the development of a target-based focusing procedure that enables precision control over the focus of the sensor optics. This improves the detection performance for dim stars, and ultimately increases the availability of the attitude solution. Flight software is developed to compensate for the effects of electronic rolling shutters, which reside on most COTS image detectors. Combined with a developed camera calibration procedure, these tools reduce the uncertainty with which a star tracker can measure the direction vectors to stars in view, ultimately increasing sensor accuracy. Integrated tests are performed to validate detection performance in dynamic conditions. These tests specifically examine the effect of slew rate on star tracker detection, and availability performance. Lastly, this thesis presents a series of optical trades studies that seek to identify design requirements for high performance SSSTs. The trends in availability and accuracy performance are examined as a function of different lens/detector configurations as well dual/triple-head sensor configurations. Together, these strategies represent tools that aim to improve small satellite star tracker performance and guide future sensor development.

scholarly journals Improving the Measurement Quality of Small Satellite Star Trackers

2021 ◽  
Author(s):  
Tom Dzamba
Keyword(s):  
High Performance ◽  
Calibration Procedure ◽  
Detection Performance ◽  
Star Tracker ◽  
Small Satellite ◽  
Small Satellites ◽  
Commercial Off The Shelf ◽  
Detector Configurations ◽  
Validation Tests

Recent demand from the small satellite community has led to the development of a new series of star trackers that are specifically designed for small satellites. These units represent substantial improvements in mass, power consumption and cost over traditional star trackers, but suffer slightly in terms of accuracy and availability performance. The primary factors inhibiting their performance are the use of significantly smaller optics, and commercial off the shelf components (COTS). This thesis presents a series of strategies for improving the performance of small satellite star trackers (SSSTs). These goals are realized through the development of offline calibration procedures, flight software, validation tests, and optical trade studies to guide future development. This thesis begins with the development of a target-based focusing procedure that enables precision control over the focus of the sensor optics. This improves the detection performance for dim stars, and ultimately increases the availability of the attitude solution. Flight software is developed to compensate for the effects of electronic rolling shutters, which reside on most COTS image detectors. Combined with a developed camera calibration procedure, these tools reduce the uncertainty with which a star tracker can measure the direction vectors to stars in view, ultimately increasing sensor accuracy. Integrated tests are performed to validate detection performance in dynamic conditions. These tests specifically examine the effect of slew rate on star tracker detection, and availability performance. Lastly, this thesis presents a series of optical trades studies that seek to identify design requirements for high performance SSSTs. The trends in availability and accuracy performance are examined as a function of different lens/detector configurations as well dual/triple-head sensor configurations. Together, these strategies represent tools that aim to improve small satellite star tracker performance and guide future sensor development.

scholarly journals Modular Impulsive Green Monopropellant Propulsion System (MIMPS-G): For CubeSats in LEO and to the Moon

Aerospace ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 169
Author(s):  
Ahmed E. S. Nosseir ◽  
Angelo Cervone ◽  
Angelo Pasini
Keyword(s):  
High Performance ◽  
System Analysis ◽  
Propulsion System ◽  
Propulsion Systems ◽  
Small Satellites ◽  
Analysis And Design ◽  
Performance Space ◽  
Green Propellants ◽  
Commercial Off The Shelf ◽  
High Thrust

Green propellants are currently considered as enabling technology that is revolutionizing the development of high-performance space propulsion, especially for small-sized spacecraft. Modern space missions, either in LEO or interplanetary, require relatively high-thrust and impulsive capabilities to provide better control on the spacecraft, and to overcome the growing challenges, particularly related to overcrowded LEOs, and to modern space application orbital maneuver requirements. Green monopropellants are gaining momentum in the design and development of small and modular liquid propulsion systems, especially for CubeSats, due to their favorable thermophysical properties and relatively high performance when compared to gaseous propellants, and perhaps simpler management when compared to bipropellants. Accordingly, a novel high-thrust modular impulsive green monopropellant propulsion system with a micro electric pump feed cycle is proposed. MIMPS-G500mN is designed to be capable of delivering 0.5 N thrust and offers theoretical total impulse Itot from 850 to 1350 N s per 1U and >3000 N s per 2U depending on the burnt monopropellant, which makes it a candidate for various LEO satellites as well as future Moon missions. Green monopropellant ASCENT (formerly AF-M315E), as well as HAN and ADN-based alternatives (i.e., HNP225 and LMP-103S) were proposed in the preliminary design and system analysis. The article will present state-of-the-art green monopropellants in the (EIL) Energetic Ionic Liquid class and a trade-off study for proposed propellants. System analysis and design of MIMPS-G500mN will be discussed in detail, and the article will conclude with a market survey on small satellites green monopropellant propulsion systems and commercial off-the-shelf thrusters.

THE EFFECT OF PROCESSING METHODS ON THE NUTRITIONAL QUALITY OF AFRICAN BREADFRUITS (TRECULIA AFRICANA) SEEDS

2020 ◽  
Vol 16 (2) ◽  
pp. 60
Author(s):  
Nwozo Sarah Onyenibe ◽  
Julius Oluwaseun Oluwafunmilola ◽  
Stanley Udogadi Nwawuba
Keyword(s):  
Amino Acid ◽  
Amino Acid Composition ◽  
Acid Composition ◽  
Nutritional Quality ◽  
High Performance ◽  
Phytochemical Analysis ◽  
Mineral Contents ◽  
Processing Methods ◽  
African Breadfruit

The extracted seeds of African breadfruit are identified to be extremely healthy whenever it is correctly processed. Therefore, the aim of the present study was to evaluate the effects of processing methods on the nutritional quality of African breadfruit seed. A qualitative phytochemical analysis including: Alkaloid, Flavonoid, Saponin, Tannin, Anthraquinone, Terpenoids, Steroid, and Cardiac Glycosides for the different fraction of African breadfruit seed was performed using a standard method. The result revealed the presence and greater amount of phytochemical for the raw fraction; seven in eight, six in eight for steamed fraction, and four in eight for boiled and roasted respectively. Anti-nutrient, Proximate, and Mineral Content were also conducted using standard methods. The amino acid composition was determined using High-Performance Liquid Chromatography (HPLC). The results of the present study revealed that anti-nutrients including Phytate, Tannins, and Oxalate were significantly p<0.05 reduced in the boiled fraction 5.47±0.15, 3.42±0.02 and 6.89±0.05, and highest in the raw fraction 7.77±0.01, 5.09±0.03 and 9.34±0.14. The proximate composition including; percentage crude fat, Ash, Carbohydrate, Fatty acid, and Energy value were significantly lower p<0.05 in the boiled fraction relative to the other fractions. Mineral contents; calcium, magnesium, sodium, potassium, and phosphorus were also significantly p<0.05 elevated in the boiled fraction relative to the raw, steamed, and roasted fraction. The amino acid composition was highest in the roasted and boiled fraction 57.350 and 56.978, and lowest in the steamed and raw fraction 35.754 and 28.748 respectively. Therefore, boiling (cooking) is encouraged for the preparation of African breadfruit seed.

Simple Index to Assess the Calibration Quality of Safety Performance Functions Based on Multiple Goodness-of-Fit Metrics

2021 ◽  
pp. 036119812110088
Author(s):  
Raul E. Avelar ◽  
Karen Dixon ◽  
Boniphace Kutela ◽  
Sam Klump ◽  
Beth Wemple ◽  
...  
Keyword(s):  
Goodness Of Fit ◽  
Synthetic Data ◽  
Calibration Procedure ◽  
Safety Performance ◽  
Absolute Deviation ◽  
Data Set ◽  
Safety Database ◽  
Simple Index ◽  
Safety Performance Functions

The calibration of safety performance functions (SPFs) is a mechanism included in the Highway Safety Manual (HSM) to adjust SPFs in the HSM for use in intended jurisdictions. Critically, the quality of the calibration procedure must be assessed before using the calibrated SPFs. Multiple resources to aid practitioners in calibrating SPFs have been developed in the years following the publication of the HSM 1st edition. Similarly, the literature suggests multiple ways to assess the goodness-of-fit (GOF) of a calibrated SPF to a data set from a given jurisdiction. This paper uses the calibration results of multiple intersection SPFs to a large Mississippi safety database to examine the relations between multiple GOF metrics. The goal is to develop a sensible single index that leverages the joint information from multiple GOF metrics to assess overall quality of calibration. A factor analysis applied to the calibration results revealed three underlying factors explaining 76% of the variability in the data. From these results, the authors developed an index and performed a sensitivity analysis. The key metrics were found to be, in descending order: the deviation of the cumulative residual (CURE) plot from the 95% confidence area, the mean absolute deviation, the modified R-squared, and the value of the calibration factor. This paper also presents comparisons between the index and alternative scoring strategies, as well as an effort to verify the results using synthetic data. The developed index is recommended to comprehensively assess the quality of the calibrated intersection SPFs.

scholarly journals Design of a high-stability heterogeneous clock system for small satellites in LEO

GPS Solutions ◽  
2021 ◽  
Vol 25 (3) ◽  
Author(s):  
Damon Van Buren ◽  
Penina Axelrad ◽  
Scott Palo
Keyword(s):  
Low Power ◽  
High Stability ◽  
Time Frame ◽  
System Stability ◽  
Small Satellite ◽  
Crystal Oscillator ◽  
Small Satellites ◽  
Clock System ◽  
Wide Range

AbstractWe describe our investigation into the performance of low-power heterogeneous timing systems for small satellites, using real GPS observables from the GRACE Follow-On mission. Small satellites have become capable platforms for a wide range of commercial, scientific and defense missions, but they are still unable to meet the needs of missions that require precise timing, on the order of a few nanoseconds. Improved low-power onboard clocks would make small satellites a viable option for even more missions, enabling radio aperture interferometry, improved radio occultation measurements, high altitude GPS navigation, and GPS augmentation missions, among others. One approach for providing improved small satellite timekeeping is to combine a heterogeneous group of oscillators, each of which provides the best stability over a different time frame. A hardware architecture that uses a single-crystal oscillator, one or more Chip Scale Atomic Clocks (CSACs) and the reference time from a GPS receiver is presented. The clocks each contribute stability over a subset of timeframes, resulting in excellent overall system stability for timeframes ranging from less than a second to several days. A Kalman filter is used to estimate the long-term errors of the CSACs based on the CSAC-GPS time difference, and the improved CSAC time is used to discipline the crystal oscillator, which provides the high-stability reference clock for the small satellite. Simulations using GRACE-FO observations show time error standard deviations for the system range from 2.3 ns down to 1.3 ns for the clock system, depending on how many CSACs are used. The results provide insight into the timing performance which could be achieved on small LEO spacecraft by a low power timing system.

scholarly journals Development and application of a spectrophotometric method in quality evaluation of benzimidazole anthelminthics in Nairobi city county

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Johnson K. Murage ◽  
Beatrice K. Amugune ◽  
Peter Njogu ◽  
Stanley Ndwigah
Keyword(s):  
Spectrophotometric Method ◽  
High Performance ◽  
Neglected Tropical Diseases ◽  
Developing Economies ◽  
Raw Materials ◽  
Poor Quality ◽  
Prolonged Treatment ◽  
Good Precision ◽  
Market Surveillance

Abstract Background Neglected tropical diseases (NTDs) are a group of communicable diseases which are prevalent in the tropics affecting more than one billion people. Treatment and prevention of these infections is very costly to developing economies. Helminthiases are classified among NTDs. The communities afflicted are poor and have limited access to essential resources for their livelihood. Poor-quality drugs for NTDs may lead to death or prolonged treatment without achieving the desired results. The limited resources used in purchasing poor-quality drugs will therefore be wasted instead of being put to good use. Most of the methods available for the analysis of benzimidazole anthelminthics utilize high-performance liquid chromatography. They are therefore time consuming, require sophisticated and expensive equipment, utilize rare and expensive reagents and solvents, and call for skilled personnel. A simple, rapid, and inexpensive ultraviolet spectrophotometric method of analysis would therefore come in handy especially in the analysis of many samples as occurs during post-authorization market surveillance for quality. Results The suitable solvent for the spectroscopic analysis was established as 0.1 M methanolic HCl. The wavelength of analysis was set at 294 nm. Upon validation, the method was found to have good linearity. The range over which linearity was established was way beyond the 80 to 120% of the working concentration specified by the ICH. The method exhibited good precision. Out of 32 commercial samples analyzed, five (15.6%) did not comply with compendial specifications. Intra-brand batch variation was also observed. Out of three batches of product A002T analyzed, one did not comply with compendial specifications. Conclusion A major limitation in the analysis of benzimidazole anthelminthics is the lack of reliable, simple, rapid, and low-cost methods of analysis with high throughput. The developed method serves to fill this gap. It can be used in the analysis of raw materials and finished products. It can also be used in the establishment of the quality of products prior to registration. The method will prove very useful in post-market surveillance of quality of benzimidazole anthelminthics.

Robust Environmental Sensing Using UAVs

2021 ◽  
Vol 2 (4) ◽  
pp. 1-20
Author(s):  
Ahmed Boubrima ◽  
Edward W. Knightly
Keyword(s):  
Air Pollution ◽  
Gas Sensors ◽  
High Performance ◽  
Weather Conditions ◽  
Ambient Air ◽  
Mission Planning ◽  
Pollution Monitoring ◽  
Compound Pollution ◽  
Planning Algorithm

In this article, we first investigate the quality of aerial air pollution measurements and characterize the main error sources of drone-mounted gas sensors. To that end, we build ASTRO+, an aerial-ground pollution monitoring platform, and use it to collect a comprehensive dataset of both aerial and reference air pollution measurements. We show that the dynamic airflow caused by drones affects temperature and humidity levels of the ambient air, which then affect the measurement quality of gas sensors. Then, in the second part of this article, we leverage the effects of weather conditions on pollution measurements’ quality in order to design an unmanned aerial vehicle mission planning algorithm that adapts the trajectory of the drones while taking into account the quality of aerial measurements. We evaluate our mission planning approach based on a Volatile Organic Compound pollution dataset and show a high-performance improvement that is maintained even when pollution dynamics are high.

scholarly journals Optimisation of Shrinkage and Strength on Thick Plate Part Using Recycled LDPE Materials

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1795
Author(s):  
Norshahira Roslan ◽  
Shayfull Zamree Abd Rahim ◽  
Abdellah El-hadj Abdellah ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Katarzyna Błoch ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Thick Plate ◽  
Processing Parameters ◽  
Processing Parameter ◽  
Plastic Injection Moulding ◽  
Optimal Setting ◽  
Quality Of Products ◽  
Validation Tests ◽  
Plastic Injection

Achieving good quality of products from plastic injection moulding processes is very challenging, since the process comprises many affecting parameters. Common defects such as warpage are hard to avoid, and the defective parts will eventually go to waste, leading to unnecessary costs to the manufacturer. The use of recycled material from postindustrial waste has been studied by a few researchers. However, the application of an optimisation method by which to optimise processing parameters to mould parts using recycled materials remains lacking. In this study, Response Surface Methodology (RSM) and Particle Swarm Optimisation (PSO) methods were conducted on thick plate parts moulded using virgin and recycled low-density polyethylene (LDPE) materials (100:0, 70:30, 60:40 and 50:50; virgin to recycle material ratios) to find the optimal input parameters for each of the material ratios. Shrinkage in the x and y directions increased in correlation with the recycled ratio, compared to virgin material. Meanwhile, the tensile strength of the thick plate part continued to decrease when the recycled ratio increased. R30 (70:30) had the optimum shrinkage in the x direction with respect to R0 (100:0) material where the shrinkage increased by 24.49% (RSM) and 33.20% (PSO). On the other hand, the shrinkage in the y direction for R30 material increased by 4.48% (RSM) and decreased by 2.67% (PSO), while the tensile strength of R30 (70:30) material decreased by 0.51% (RSM) and 2.68% (PSO) as compared to R0 (100:0) material. Validation tests indicated that the optimal setting of processing parameter suggested by PSO and RSM for R0 (100:0), R30 (70:30), R40 (60:40) and R50 (50:50) was less than 10%.

Pursuit of Operational Excellence

2016 ◽  
Vol 3 (2) ◽  
pp. 21-34
Author(s):  
Christine Welch ◽  
Tammi Sinha ◽  
Nigel Ward
Keyword(s):  
Change Management ◽  
Continuous Improvement ◽  
High Performance ◽  
Effective Leadership ◽  
Value Systems ◽  
Goods And Services ◽  
Team Working ◽  
Performance Teams ◽  
Operational Excellence

Operational Excellence (OE) is achieved when high performance teams are seeking for continuous improvement in well-designed processes, using appropriate tools and technologies. Excellence is underpinned by a philosophy in which problem-solving, team-working and effective leadership combine to focus upon customer needs, and all employees are empowered to act to maintain optimal flows of value. OE is clearly a desirable quality of organizations seeking both effectiveness and efficiency in their production of goods and services for customers. OE is underpinned by concepts such as team-working, effective leadership and change management, and depends upon effective flows of value. Systems Thinking (ST) is consequently at the heart of genuine excellence. This paper was conceived in the context of a Community of Practice of business improvement professionals, who took Operational Excellence as their agenda for inquiry during sessions in 2015. Reflection upon practice discussed at these meetings, together with the literature of change management and continuous improvement, have led to development of a systemic ‘landscape' model for pursuit of Operational Excellence. The elements of this model are set out, showing how they can contribute to OE.

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