... The program was integrated with the above algorithms and the OREKIT library [Maisonobe, 2010] was used for the time and frame handlings. Furthermore, the results are compared with the metadata of the provided image. ...
The aim of this study is to calculate the geolocation of an image acquired from an electro-optic earth observation satellite using the satellite external and internal orientation parameters. The main purpose of this study is to determine the intersecting coordinates of an ellipsoid model defined according to WGS84 and a looking vector. In the first phase, these calculations will be conducted without any Digital Terrain Model (DTM). In order to compare the results, in a second phase, the same calculations will be conducted with DTM. For demonstration purposes, a geolocation software will be developed using open-source libraries. This software will be tested with sample data from the SPOT-5 satellite. There are several plug-ins for certain open source and commercial Geographical Information Systems (GIS) software. One of the objectives of this study is to later develop an independent program which will be used to assist in the development of a satellite and a ground station image processing unit. This program is also intended to be used in the training of individuals with various areas of expertise.
... Bu çalışmada güneş senkronize ve yer izi tekrarlı dairesel donuk yörünge tasarım algoritması icra edilmiş ve kullanıcı ara yüzü ile birleştirilerek bir tasarım aracı haline getirilmiştir. Temel olarak OREKIT 10.0 Uçuş Dinamikleri kütüphanesinden yararlanılmıştır [Maisonobe, 2010]. Bu bölümde tasarım aracı içerisindeki algoritma üzerinde durulacak ve tasarımın matematiği aktarılacaktır. ...
Bu çalışmada güneş senkronize ve tekrarlı yer izine sahip donuk dairesel yörüngeleri tasarlayabilen bir yazılım geliştirilmiş, matematiksel temelleri açıklanmış ve kullanıcılar için bir arayüz oluşturulmuştur. Bu bağlamda oluşturulan yazılım Java tabanlı olup OREKIT 10.0 kütüphanesi kullanılarak yazılmıştır. Çalışmanın temel hedefi, “FreeFlyer Demo V7.5” programı içerisinde bulunan “Güneş Senkronize Tekrarlı Yer İzi Yörünge Tasarım Sihirbazının” hesapladığı yörünge verisini açık kaynak kodlu kütüphaneler ve literatürde sıklıkla kullanılan hesaplamalar ile üretmek, bu sayede ticari yazılım bağımlılığını ortadan kaldırmaktır. Yazılım içindeki algoritma, OREKIT 10.0 kütüphanesinde bulunan örnekler yardımıyla “FreeFlyer” algoritmasına yakınsanmıştır. Yazılım çıktıları olan “Ekvatoral Geçiş Noktaları” ve “Gök günlüğü”, “FreeFlyer” çıktıları ile karşılaştırılmış, hata analizi yapılarak sonuçların tutarlılığı gösterilmiştir.
... Orekit has been selected in early 2011 by CNES to be the basis of its next generation space flight dynamics systems, including operational systems, study systems and mission analysis systems. 12 Tide modelling is a recent Orekit feature, released in December 2013. It is based on the IERS conventions models. ...
Open source software tools have been gaining acceptance in the astrodynamics community for some applications, though heritage tools still dominate precision orbit determination and propagation. This paper examines recent tide modeling improvements in the open source Orbit Extrapolation Toolkit (Orekit) and compares it with the US Naval Research Laboratory's (NRL) heritage Orbit Covariance Estimation And ANalysis (OCEAN) system. First, the two tools are compared directly against each other by propagating a given state vector for Stella, a geodetic satellite sensitive to tidal variations in the geopotential. Second, orbits were fit to International Laser Ranging Service (ILRS) laser ranging data using OCEAN and orbit determination software built around Orekit so that a more useful comparison could be made. Five days of data were used to solve for orbital parameters using OCEAN and Orekit. This solution orbit is then propagated forward 25 days and compared to subsequent five day orbit solutions. This comparison between predicted and fitted orbit solutions is used as a metric to compare the quality of each piece of software's dynamic modeling capability. Results from the direct orbit propagation comparison indicate the RSS of postion difference between the OCEAN and Orekit propagated orbit grow to only 7 meters over 25 days. It is also seen that the difference between OCEAN's and Orekit's implementation of Earth tides are less than 3% of the total tidal effect. The results of the orbit determination analysis show that the Orekit orbit solution comparison is at worst on the same order of magnitude in accuracy as the OCEAN orbit solution comparison, and at best more accuate than the OCEAN orbit solution comparison. While OCEAN produces a more accurate orbit prediction than Orekit in the majority of the cases studied, more testing is need to understand the origin of the difference.
In this study, a computer software so called "ColAvo" is introduced along with the developed algorithms. The "ColAvo" can parse the Conjunction Data Messages, illustrates the possible conjunction between two earth orbiting objects and computes the collision avoidance maneuver. The main objective of this study is to help the satellite operators to reduce the decision time of the collision avoidance maneuver, since the conjunction assessment operations require quick actions. The software initially let the user to understand the possible collision by visualizing the provided Conjunction Data Message via Visualization Tool For Space. Afterwards, the developed targeting algorithm is used to calculate the collision avoidance maneuver according to the user inputs. The software development is done by using OREKIT 10.0 library in JAVA. Furthermore, the algorithm tests are done with the GMAT and the FreeFlyer software.
Japanese Title: 多重ディスパッチとメタプログラミングに着目した構成可能なアストロダイナミクスソフトウェアの構築 Abstract: Modern planetary exploration missions increasingly operate in ever more complex dynamical environments, and require designs for lower cost, higher efficiency, and more ambitious trajectories. Current computational astrodynamics practice utilises techniques from simulation and analysis of dynamical systems to better understand and exploit the chaotic dynamics of the solar system. In this thesis, new computational astrodynamics tools are developed to leverage Julia, a modern, high-performance numerical programming language that combines high-level abstraction with the computational efficiency of dynamic compilation. Julia enables the development of highly composable and extensible programs, with state-of-the-art performance and applications across many scientific fields. Its unique combination of language features, most notably of multiple dispatch and meta-programming, provide opportunities to develop software that exploits performant automatic differentiation and automated composition to enable more composable, accurate, and higher performance software designs. These modern numerical programming language features are applied in OrbitalTrajectories.jl, a proof-of-concept trajectory design toolkit developed as part of this thesis to demonstrate the consequences of such features towards applications in astrodynamics. The toolkit’s composability, extensibility, and performance are briefly compared to JAXA’s in-house jTOP trajectory propagation and optimisation tool, outperforming it by up to an order of magnitude in orbital propagation. Advanced capabilities are also demonstrated, including composition of dynamical models, generic N-order State Transition Tensors (STTs) with support for Automatic Differentiation (AD) and symbolic Variational Equations (VE), dynamic retrieval of ephemeris kernels, and more. In addition, simple motivating proof-of-concepts are provided for generating quasi-periodic orbit families via a generic single-shooting correction scheme, as well as for computing expectations under orbital uncertainty. Through these demonstrations, the motivation, implementation, and application of the developed toolkit serve to motivate the use of modern numerical language features towards more efficient development of next-generation astrodynamics software. Ancillary material is available online: https://github.com/dpad/OrbitalTrajectories.jl