Limiting factors for the precise orbit determination POD of low-earth orbit LEO satellite using dual-frequency GPS are nowadays mainly encountered with the in-flight phase error modeling. The phase error is modeled as a systematic and a random component each depending on the direction of GPS signal reception. The systematic part and standard deviation of random part in phase error model are, re...

The purpose of this rersearch is to analyze the effective application of particular earth orbits in dynamical modeling of relative motion problem between two spacecraft. One challenge in implementing these motions is maintaining the relations as it experiences orbital perturbations (zonal harmonics J2 and J3), most notably due to the Earth’s oblateness. Certain aspects of the orbital geometry c...

As a preparation for future possible orbit determination of GNSS satellites by VLBI observations an initial three-station experiment was planned and performed in January 2009. The goal was to get first experience and to verify the feasibility of using the method for accurate satellite tracking. GNSS orbits related to a satellite constellation can be expressed in the Terrestrial Reference Frame....

An innovative orbit determination method which makes use of gravity gradients for Low-Earth-Orbiting satellites is proposed. The measurement principle of gravity gradiometry is briefly reviewed and the sources of measurement error are analyzed. An adaptive hybrid least squares batch filter based on linearization of the orbital equation and unscented transformation of the measurement equation is...

In-orbit relative navigation between a networked swarm of centimeter-scale femto-spacecraft would add considerable value to range space mission concepts and applications, such as for multipoint sensing distributed sparse aperture interferometry. For femto-spacecraft, position determination be possible by inferring coarse estimates from the received signal strength indication associated with com...

intraocular metastatic tumors have been increasingly reported in the recent past. unlike choroidal metastasis, metastasis to retina is very rare and so far has been reported in very few case reports only. case presentation : a 56 year-old male who presented with a history of adenocarcinoma of the cecum and underwent lap colectomy for the primary cecal tumor, received adjuvant chemotherapy for a...

Final coalgebras capture system behaviours such as streams, infinite trees and processes. Algebraic operations on elements of a final coalgebra can be defined by distributive laws (of a syntax Σ functor over a behaviour functor F ). Such distributive laws correspond to abstract specification formats. One such format is a generalization of the GSOS rules known from structural operational semanti...

We present a novel identification framework that enables the use of first-order methods when estimating model parameters near a periodic orbit of a hybrid dynamical system. The proposed method reduces the space of initial conditions to a smooth manifold that contains the hybrid dynamics near the periodic orbit while maintaining the parametric dependence of the original hybrid model. First-order...

A topological existence proof is presented for certain symmetrical periodic orbits of the collinear three-body problem with two equal masses, called Schubart orbits. The proof is based on the construction of a Wazewski setW in the phase space. The periodic orbits are found by a shooting argument in which symmetrical initial conditions enteringW are followed under the flow until they exit W. Top...