Analysis of GPS-Based Relative Navigation Schemes for Earth Observation Missions Relying on Cooperating Satellites

In this paper performance of Carrier-phase Differential GPS (CDGPS) for relative navigation in applications where the inter-satellite distance highly varies along the orbit is investigated. Specifically, to satisfy high accuracy requirements, a hybrid filtering approach is proposed in which a dynamic filter is combined in cascade with a kinematic one. For the dynamic filter both an Extended Kalman Filter (EKF) and an Unscented Kalman Filter (UKF) are evaluated and compared to output high-accuracy estimates of the floating values of the carrier-phase integer ambiguities. These, once extracted with the LAMBDA method, are processed in the kinematic filer to come to highly precise relative position and velocity estimates

GPS- Relative Navigation in Earth Observation Missions Relying on Cooperative Satellites

This book was compiled from contributions given at the 7th IAA Symposium on Small Satellites for Earth Observation, May 4–8, 2009, Berlin (IAA – International Academy of Astronautics). From the 15 sessions for oral presentations and two poster sessions, 52 contributions were selected which are representative for the new developments and trends in the area of small satellites for Earth observation. They reflect the potentials of a diversity of missions and related technologies. This may be based on national projects or international co-operations, single satellites of constellations, pico-, nano-, micro- or mini-satellites, developed by companies, research institutions or agencies. The main focus is on new missions to monitor our Earth’s resources (Part I), and the environment in which our Earth is embedded (Part II). Part III deals with distributed space systems, a unique feature of small satellites and in most cases impractical to do with large satellites. Here we concentrate on constellations of satellites with focus on future missions relying on co-operating satellites. For all the new developments and projects we need well educated specialists coming from the universities. Many universities included already the development and implementation of small satellites in their curriculum. The university satellites chapter (Part IV) shows the high quality which is already reached by some of the universities worldwide. To achieve high performance Earth observation mission on the basis of small satellites, instruments and technologies are essential for both high performance and miniaturization. Part V gives insight into new developments on these sectors. The last two parts (Parts VI and VII) deal with subjects, necessary to make use of the data coming from the satellite systems: attitude and position. But high quality attitude control and navigation systems are essential not only for geocoding of high resolution spatial and spectral data. They are also of very high importance when performing formation flying missions as addressed in Part III

EFFECT OF COMPOSITION ON THE RELEASE FROM MELT EXTRUDED LAMINAR SYSTEMS BY APPLICATION OF MIXTURE EXPERIMENTAL DESIGN

EFFECT OF COMPOSITION ON THE RELEASE FROM MELT EXTRUDED LAMINAR SYSTEMS BY APPLICATION OF MIXTURE EXPERIMENTAL DESIG

A MICRO SUN SENSOR FOR EARTH-OBSERVATION NANOSATELLITES FLYING IN FORMATION

This paper deals with the validation of a micro sun sensor under development at the University of Naples. Sun line determination is performed by the centroiding of sun images on the focal plane obtained with a multiple-hole tiny mask. Sensor laboratory calibration is performed with neural-network-based techniques using a home-made test facility. Processing of 1-hole data demonstrates sensor precision better than 1-arcmin. Preliminary results with multiple-hole data show that sensor precision can be improved by averaging multiple sun-images

Mechanical and diffusive properties of homogeneous alginate gels in form of particles and cylinders

In this study, alginate polymers are used to get homogeneous cylindrical or spherical gels. MRI techniques are employed to study homogeneity of these gels. Four different alginates are used and, for each one, five different concentrations for mechanical tests and three different concentrations for release tests are studied. Mechanical tests are performed to get gels\u2019 linear viscoelasticity region and then to evaluate their crosslink density in relation to polymer concentration. Afterwards, three model molecules (theophylline, vitamin B12, and myoglobin) are loaded within gels to study the release kinetics in water from both cylindrical and spherical gels. Diffusion coefficients calculated from these experiments are then used to estimate the polymeric network mesh wideness. This work shows how crosslink density increases with polymer concentration regardless of the alginate type considered. In addition, while vitamin B12 diffusion coefficient is inversely proportional to crosslink density, myoglobin is too large to diffuse through the polymeric network, whatever the alginate type and polymer concentration. At the same time, theophylline is too small to be sensibly affected by increasing the polymeric network crosslink density. Finally, MRI analysis and vitamin B12 diffusion coefficient values prove that, structurally speaking, cylinders and spheres are similar and homogeneous. 2008 Wiley Periodicals, Inc. J Biomed Mater Res 87A: 808\u2013818, 200