Satellite Tool Kit Research Articles

基于STKX的灵巧卫星成像仿真技术研究

基于STKX的仿真技术，既继承了STK (Satellite Tool Kit)的专业性与逼真性，又能够无缝集成于软件中，已成为航天领域内仿真研究的一项重点技术。本文以灵巧卫星对地观测成像为工程背景，阐述了STKX技术的基本原理，对场景仿真中卫星、相机和观测目标的创建等工程技术问题进行了细致地说明，并展示了灵巧卫星对地观测成像的仿真效果，旨在为STKX技术的工程应用提供参考与借鉴。 Simulation technology plays an essential role in aerospace engineering. STKX technology, which inherits the accuracy from STK (Satellite Tool Kit) and can be integrated in personal development software, has become a focus in current simulation technologies. This paper shows the principle of STKX technology based on the background of agile earth observing satellite; the technologies about creating the satellite object, sensor object and setting the satellite’s attitude are proposed in this paper. In addition, a simulation example is given for better understanding. These technologies are presented to offer references for simulation researches in aerospace engineering.

Implementing and Optimizing of Entire System Toolkit of VLIW DSP Processors for Embedded Sensor-Based Systems

VLIW DSPs can largely enhance the Instruction-Level Parallelism, providing the capacity to meet the performance and energy efficiency requirement of sensor-based systems. However, the exploiting of VLIW DSPs in sensor-based domain has imposed a heavy challenge on software toolkit design. In this paper, we present our methods and experiences to develop system toolkit flows for a VLIW DSP, which is designed dedicated to sensor-based systems. Our system toolkit includes compiler, assembler, linker, debugger, and simulator. We have presented our experimental results in the compiler framework by incorporating several state-of-the-art optimization techniques for this VLIW DSP. The results indicate that our framework can largely enhance the performance and energy consumption against the code generated without it.

Distributed Agile Development

Organizations have shown a significant interest in the adoption of emerging social technologies to support communication and collaboration needs of their Distributed Agile or Adaptive Development Environment (DADE). However, the challenge is how best to assess contemporary social technologies for supporting communication and collaboration in the DADE. Here, a communication technology assessment tool, called CTAT, is developed as a part of the Adaptive Enterprise Service System (AESS) toolkit by using the design research approach. This paper presents the evaluation of the CTAT construct through its use in the assessment of three social technologies within the context of a DADE. The results of this evaluation indicate that CTAT is shown to be useful, for example, when assessing a particular social technology for a specific DADE communication and collaboration context. The CTAT is intended to be used by senior developers for assessing social technologies for their DADE context.

Influence of earth's reflective radiation on space target for space based imaging

The space-based surveillance, which would mainly use the space-based visible, has great value for civil and military applications currently and for a fairly long future period. In space-based surveillance, the visible and near-infrared radiation characteristics of the space target are influenced by its attitude variation. This influence is especially prominent in space-based imaging. In some ways, solar radiation cannot arrive at the surface of the space target, or the arriving radiation is not uniformly distributed because of the space target's strong reflection at a particular position. In order to solve these problems, the visible and near-infrared illumination characteristics of the space target surface are analyzed. Moreover, a notion that earth's reflective radiation can be used as illumination for space target imaging is given, and an accurate modeling method is proposed. Firstly, based on diffuse reflectance model, a method of mathematically calculating the illumination at space target's position from earth's reflective radiation is established. And a formula for calculating illumination is derived. Secondly, the coordinates of sun and space target at any time can be obtained by the Satellite tool kit software, in which the complicated multiplying matrix and coordinate transformation algorithm introduced in some references are avoided. Thirdly, the method of estimating earth's reflective radiation region at arbitrary moment is introduced. The grid division method is generated and the uniform sampling is used in each small area. Fourthly, the position of a surface cell is transformed from the sphere reference frame into the J2000.0 inertial frame. The earth's reflective radiation can be calculated through numerical integration. Finally, the illumination from earth's reflective radiation to a sun synchronous orbit satellite in an imaging mission based on space is calculated by the given parameters. The results show that the earth's reflective radiation is luminous enough for space target imaging when the satellite passes through arctic. When the satellite moves on the orbit, we can obtain more detailed information about target satellites' bottom then the ground simulation imaging. The on-orbit imaging results demonstrate the validity of the modeling method, which could support the foundation of our space-based surveillance system theoretically and technically and could be used as a reference of space-based orbit measurement and determination in deep space exploration.

Earth conical shadow modeling for LEO satellite using reference frame transformation technique: A comparative study with existing earth conical shadow models

Abstract In this article, we propose an Earth conical shadow model predicting umbra and penumbra states for the low Earth orbiting satellite considering the spherical shape of the Earth. The model is described using the umbra and penumbra cone geometries of the Earth’s shadow and the geometrical equations of these conical shadow regions into a Sun centered frame. The proposed model is simulated for three polar Sun-synchronous Indian Remote Sensing satellites: Cartosat-2A, Resourcesat-2 and Oceansat-2. The proposed model compares well with the existing spherical Earth conical shadow models such as those given by Vallado (2013), Wertz (2002), Hubaux et al. (2012), and Srivastava et al. (2013, 2014). An assessment is carried out of the existing Earth conical shadow models with Systems Tool Kit (STK), a high fidelity commercial software package of Analytic Graphic Inc., and the real time telemetry data.

퍼지 로직 기반의 위성용 MPPT 개발 및 EBA를 통한 성능검증

The satellite should generate electric power efficiently to perform the mission successfully within limited power. For this reason, the electrical power system of LEO satellites usually regulates the power which is generated from the solar cells using MPPT (Maximum Power Point Tracking) method. This paper proposes advanced MPPT algorithm based on the fuzzy logic applied to small CubeSat satellite. The simulation has been performed to confirm the validity of the proposed method by interlocking between MATLAB/Simulink and STK (Systems Tool Kit). The EBA(Energy Balance Analysis) has also been performed at two different pointing modes of KAUSAT-5 for solar irradiation according to the satellite orbit and attitude, and load capacity varied with operation modes by Simulink and STK. The performance of fuzzy logic-based MPPT algorithm was verified through the EBA. The validity of the proposed MPPT algorithm based on the fuzzy logic was also confirmed by comparing with P&O (Perturbation & Observation) algorithm that is general in the MPPT.

Arabic Handwriting Text Offline Recognition Using the HMM Toolkit (HTK)

This Recognition of Arabic text handwritten awaits precise recognition solutions. There are a lot of difficulties facing a good handwritten Arabic recognition system such as unlimited variant in human handwriting, similarities of different character shapes, and their location in the word. This paper presents a handwriting Arabic text recognition system. It decomposes the text image into text line images and extracts a set of simple statistical features from a narrow window which is sliding a long that text line, then it injects the resulting feature vectors to the Hidden Markov Model Toolkit (HTK). HTK is a portable toolkit for speech recognition system. In recognized state, the concatenation of characters to form words is modelled by simple lexical models, each word is modelled by a stochastic finite-state automaton (SFSA), and the concatenation of words into sentences is modelled by an n-gram language model. The proposed system is applied to a data corpus constructed by Text lines examples from the “Arabic-Numbers”, which contains 1905 sentences and 47 words. This phrase is written by 5 different peoples.

Visual Modeling and Simulation Research of a Kind of On-Orbit Servicing Spacecraft

On-orbit servicing technology is a novel aerospace technology, which has important economic and military value. Reference to two on-orbit servicing programs named Orbital Express and Phoenix, the paper provides visual modeling and on-orbit module replacement simulation approach for a type of spacecraft based on satellite tool kit (STK). A kind of universal method for STK model building is presented, which includes multi-software model transformation and manual encoding. Some key problems about model integration and post processing, that helps complex STK model building, has also been summarized. An on-orbit replacement task simulation system based on co-simulation of MATLAB and STK can provide effective technical support for the aerospace program.

Atmospheric Electric Propulsion Mission Performance Tool

The amount of available propellant limits low-Earth orbit satellite lifetime due to the necessity of drag makeup. An electric propulsion device that uses in situ ions as propellants is considered as an alternative method for satellite drag makeup. This work presents a tool that consists of a one-dimensional thruster mathematical model integrated with the NASA International Reference Ionosphere to provide ion and neutral species densities for an electrostatic electric propulsion approach. This mathematical model predicts thrust, drag, and thruster power. The thrust-to-drag ratio and thruster power are averaged over the entire mission duration of one year and compared with various circular orbits and satellite configurations: 300–1000 km orbit altitude, 0–60 deg orbit inclination, low to high solar activity, satellite frontal area, 1–10 kV acceleration voltage, and total grid area. The Satellite Tool Kit provides orbit propagation. An average thrust-to-drag ratio greater than one is achievable for many thruster and orbit configurations considered in this analysis, at power levels less than 90 W. Most satellite missions at altitudes of less than 400 km may fall into the region in which the thrust-to-drag ratio is less than one. Thrust-to-drag ratio values of less than one will still benefit satellites by extending mission lifetimes for months or years with average power requirements less than 100 W.

Spherical and oblate Earth conical shadow models for LEO satellites: Applications and comparisons with real time data and STK to IRS satellites

This article reports two conical shadow models: a spherical Earth conical shadow model (SECSM) and an oblate Earth conical shadow model (OECSM), and their comparative study to predict umbra and penumbra shadow regions for the low Earth orbiting (LEO) satellites. First model is described using a projection map technique considering the spherical shape of the Earth whereas the second model is illustrated using the line of intersection method for the oblate Earth. Both models have been implemented to four Indian Remote Sensing (IRS) satellites: Oceansat-2, Resourcesat-2, Cartosat-2A and Meghatropics-1. Computed results are compared well with the real time data and the commercial AGI package, Systems Tool Kit (STK).

基于光照条件的空间相机增益在轨自动调整

During the imaging process of space camera, small fixed gains are often used to avoid image saturation. As a result, obtained images have problems such as dark as a whole, short of digital number levels. An automatic on-orbit adjusting gains method of space camera based on lighting conditions is put forward. In this method sun zenith angle at substellar point is calculated in real time according to current position of spacecraft and time. Function relationship between sun zenith angle and radiance at entrance pupil of space camera corresponding to maximum reflection index of targets is established by non-linear curve fitting. In this way real-time calculation and adjustment of gains are realized. Results of contrastive experiment with results of simulation by satellite tool kit (STK) and computation by MODTRAN indicate that radiance fitting errors are no more than 0.3 W/(m2sr) as sun zenith angle belongs to [20, 70]. Relative errors are no more than 2.2%. Difference error between calculated sun zenith angles and those simulated is about 0.39(3). Results of on-orbit imaging experiments indicate that digital number levels are improved from 98 to 183 and entropies are improved about 19.2% after adjusting of gains as sun zenith angle is 62.5. Targets will be easier to be recognized as more digital number levels can be obtained.

Development of UNU-Casemix Grouper standard integration tool kit for hospital information system (HIS) in selected hospitals in Malaysia and Indonesia

Background UNU-Casemix Grouper is software used for grouping inpatient and outpatient cases into Case Base Group (CBG). UNU-Casemix can be used to enhance quality and efficiency of healthcare services. Hospital Information System (HIS) is used to collect all the patient-level data in a hospital that can be used to improve performance of a hospital. HIS also captures all of the patient’s demographic and clinical data required by the UNU-Casemix Grouper. Combining both systems in one platform can ensure that hospitals gain benefit from both systems. The main objective of the study was to develop a standard integration tool kit for UNU-Casemix Grouper for selected HIS hospitals in Malaysia and Indonesia.

An Open Framework for Dynamic Big-data-driven Application Systems (DBDDAS) Development

In this paper, we outline key features that dynamic data-driven application systems (DDDAS) have. A DDDAS is an application that has data assimilation that can change the models and/or scales of the computation and that the application controls the data collection based on the computational results. The term Big Data (BD) has come into being in recent years that is highly applicable to most DDDAS since most applications use networks of sensors that generate an overwhelming amount of data in the lifespan of the application runs. We describe what a dynamic big-data-driven application system (DBDDAS) toolkit must have in order to provide all of the essential building blocks that are necessary to easily create new DDDAS without re-inventing the building blocks.

Orbit Propagator and Geomagnetic Field Estimator for NanoSatellite: The ICUBE Mission

This research contribution is drafted to present the orbit design, orbit propagator and geomagnetic field estimator for the nanosatellites specifically for the upcoming CUBESAT, ICUBE the Institute of Space Technology (IST), Islamabad, Pakistan. The ICUBE mission is designed for the low earth orbit at the approximate height of 700KM. The presented research endeavor designs the Keplarian elements for ICUBE-1 orbit while incorporating the mission requirements and propagates the orbit using J2 perturbatio The attitude determination system of the ICUBE attitude determination sensors like magnetometer and sun sensor. The Geomagnetic field estimator is developed according to the model of International Geomagnetic Reference Field (IGRF) for co magnetic field measurements by the magnetometer for attitude determination. The output of the propagator namely the position and velocity vectors and the magnetic field vector compared and verified with the same scenario genera Satellite Tool Kit (STK). Keywords—CUBESAT, Geomagnetic Field, ICUBE Propagator, Satellite.

Simulations of Multiple Spacecraft Maneuvering with MATLAB/Simulink and Satellite Tool Kit

A software interface between the MATLAB/Simulink environment and the Satellite Tool Kit Environment is introduced. This research is based on the need for validating model performance and visualizing simultaneous multiple-spacecraft proximity maneuvers for emerging missions. It is common for spacecraft systems to be modeled with MATLAB and Simulink. Furthermore, the software package Satellite Tool Kit is often used for animating and evaluating spacecraft maneuvers. In this research, a MATLAB/Satellite Tool Kit interface was developed to propagate six-degree-of-freedom spacecraft models, compared against Satellite-Tool-Kit-generated ephemeris, and animated for analysis. MATLAB script with necessary formatting is used for Satellite Tool Kit initialization and animation. The MATLAB/Satellite Tool Kit simulation interface allows variations in number, shape, and dimensions of spacecraft. Additionally, numerous model and simulation parameters can be selected and synchronized between MATLAB and Satellite Tool Kit. Furthermore, either predetermined, or randomly distributed, initial spacecraft positions and orientations are permitted by the interface. The paper gives enough details to allow the interested readers to adapt to their needs and further develop the proposed software interface.

Geolocation Algorithm for Earth Observation Sensors Onboard the International Space Station

As a near orbit space platform, the International Space Station (ISS) has been increasingly used for Earth observing applications. This paper presents a quaternion-based forward geolocation algorithm for Earth observing sensors onboard the ISS. The input parameters include the orbital state and attitude information of the ISS and the look vector of the sensor. The proposed algorithm agrees with the commercial navigation product, Satellite Tool Kit®, within 0.5 m in ideal situations. The inherent uncertainties in ISS attitude and state determinations, and the International Space Station Agriculture Camera (ISSAC) tilting angle were estimated to introduce an error less than 800 m. However, the actual geolocation error evaluated using the images obtained by the ISSAC is roughly 4 km, much greater than the inherent uncertainty and mainly due to (a) delay caused by the Windows® operating system in acquiring images, and (b) the misalignment of the ISSAC sensor coordinate system with the ISS body-fixed coordinate system. A preliminary cal/val process using the Google Earth™ as reference was performed to quantify these two errors, the correction of which improved the geolocation accuracy to 500 m, well within the inherent uncertainty.

A NEW COURSE ON COMPUTING FOR SMALL SPACECRAFT ENGINEERING

The trend towards smaller and less expensive spacecraft continues. The University of Manitoba has participated in the design and implementation of a triple-pico-satellite (code TSat) since 2010, with over 100 undergraduate and graduate students from five faculties and 16 departments, as well as 50 advisors from academia, aerospace industries, business, military, and government. Such small satellites are used for atmospheric study and testing of new research concepts such as new forms of data communications, and constellations of space robots. A graduate course on small spacecraft engineering has recently been developed to address the needs of many students in this area. The course provides foundations for the design, implementation and testing of nano-, pico- and femto-satellites. The topics cover the anatomy of a small spacecraft, its design process with the specific design of its mission and payload, orbital mechanics, spacecraft subsystems, and mission operations handling. The specific subsystems include (i) attitude determination and control (ADC), (ii) telemetry, tracking, and command (TTC), (iii) command and data handling (CDH), (iii) power (PWR), (iv) thermal (TRM), (v) structures (STR), and (vi) guidance and navigation (GAV) [1-3]. Emphasis is given to the algorithms and computing tools for such small satellites. The basis for modeling and simulation is the Systems Tool Kit (STK) from Analytical Graphics Incorporated (AGI). The course is supported by our experience in developing the TSat1 nano-satellite. This paper describes the structure of the course, the methodology used, the set of topics covered, the set of course projects, and the lessons learned from the delivery of this unique course. Although the course is now intended for electrical and computer engineering students only, its scope will be expanded to accommodate mechanical and other engineering students.

EPICS device support module as ATCA system manager for the ITER fast plant system controller

This paper presents an Enhanced Physics and Industrial Control System (EPICS) device support module for the International Thermonuclear Experimental Reactor (ITER) Fast Plant System Controller (FPSC) project based in Advanced Telecommunications Computing Architecture (ATCA) specification. The developed EPICS device support module provides an External System Manager (ESM) solution for monitoring and control the ITER FPSC ATCA shelf system and data acquisition boards in order to take proper action and report problems to a control room operator or high level management unit in case of any system failure occurrence. EPICS device support module acts as a Channel Access (CA) server to report problems and publish ATCA system data information to the control room operator, high level management unit or other CA network clients such as Control System Studio Operator Interfaces (CSS OPIs), Best Ever Alarm System Toolkit (BEAST), Best Ever Archive Utility (BEAUTY) or other CA client applications. EPICS device support module communicates with the ATCA Shelf manager (ShM) using HTTP protocol to send and receive commands through POST method in order to get and set system and shelf components properties such as fan speeds measurements, temperatures readings, module status and ATCA boards acquisition and configuration parameters. All system properties, states, commands and parameters are available through the EPICS device support module CA server in EPICS Process Variables (PV) and signals format. ATCA ShM receives the HTTP protocol messages from the EPICS device support module, validates and takes proper action in order to execute and acknowledge the required command operation and respond with an operation success or error return code. Each ATCA board contains inventory data that can be retrieved by the ShM controller to determine if there is enough power available for the payload process, provide manufacturer data information, retrieve board model and serial numbers and check number of available board sensors their types and fields. The ShM can provide this inventory data information to the EPICS device support module if is required. ShM module communicates with the ATCA boards through the Intelligent Platform Management Interface (IPMI) controller via IPMI communication protocol on redundant IPMI bus. This communication protocol is managed by the embedded Intelligent Management Platform Controller (IPMC) in the ATCA board side and by the embedded Shelf Management Controller (ShMC) in the ShM side. Queried inventory data information becomes available in the EPICS device support module upon ShM command response. EPICS device support module can be a valuable and good approach for ATCA ESM aiming the integration in the ITER Control and Data Acquisition (CODAC) core system according the ITER specification.

Open source Ch Control System Toolkit and web‐based control system design for teaching automatic control of linear time‐invariant systems

AbstractThe Ch Control System Toolkit (CCST) is a software package for the design and analysis of control systems. It is a C/C++ class with member functions for solving control problems in a user‐friendly C/C++ interpreter, Ch. Based on the CCST, a Web‐based Control System Design and Analysis System (WCSDAS), and a Web‐based Controller/Compensator Design Module (WCCDM), have been developed. In this article, using the CCST, WCSDAS, and WCCDM for teaching automatic control of linear time‐invariant systems is presented. With the CCST, students are able to solve control problems with only a few lines of C/C++ code. The CCST can also be used to develop various interactive utility programs that will assist students in learning control systems without any programming requirements. With the Web‐based WCSDAS and WCCDM tools, students can interactively design and analyze control systems via a Web browser. The CCST, WCSDAS, and WCCDM are open source software packages. These software tools have been used for teaching undergraduate control courses at the University of California, Davis and Michigan Technological University. © 2010 Wiley Periodicals, Inc. Comput Appl Eng Educ 21: 95–112, 2013

Research and Realization of Highly Accurate Data Generation Based on Channel Simulator

With high accuracy, the channel simulator plays an important role in the docking experiment between the ground and the responder beacon. To begin with, this paper introduces the data generation algorithm including the data generation based on simulation technology, the principle of the linear least squares algorithm and then proposes the least squares quadratic spline method to generate highly accurate data in this channel simulator. Secondly, this paper introduces the system design to realize the data generation. Finally, a case which studies the approximation and an error analysis of the data generation algorithm is realized. The algorithm is considered to be accurate and easy to get the source data. The core of the algorithm is using data from Satellite Tool Kit to generate distance and speed sequence, and using the least squares to approximate real data and quadratic spline to fit for obtaining highly accurate data.