Experimental Reflection Evaluation for Attitude Monitoring of Space Orbiting Systems with NRL Arch Method

The increasing number of satellites orbiting around Earth has led to an uncontrolled increase in objects within the orbital environment. Since the beginning of the space age on 4 October 1957 (launch of Sputnik I), there have been more than 4900 space launches, leading to over 18,000 satellites and ground-trackable objects currently orbiting the Earth. For each satellite launched, several other objects are also sent into orbit, including rocket upper stages, instrument covers, and so on. Having a reliable system for tracking objects and satellites and monitoring their attitude is at present a mandatory challenge in order to prevent dangerous collisions and an increase in space debris. In this paper, the evaluation of the reflection coefficient of different shaped objects has been carried out by means of the bi-static reflection method, also known as NRL arch measurement, in order to evaluate their visibility and attitude in a wide range of frequencies (12–18 GHz). The test campaign aims to correlate the experimental measures with the hypothetical reflection properties of orbiting systems.

A Research Study on Protocol Stack of Space-Based Optical Backbone Network

Facing the growing high data rate and large communication capacity demands, optical communications are widely recognized to be used to implement satellite communications. For a space-based optical backbone network, an appropriately designed protocol stack is important. In this paper, we proposed a protocol stack that is suitable for a space-based optical backbone network. Following this, we then used software to simulate this stack, built a hardware platform to test it, and finally, analyzed the results. The results showed that the proposed protocol stack was well designed to provide efficient control and management of the space-based optical backbone network. It could improve management efficiency by collecting resources and automatically calculating and building route paths. It could also facilitate data forwarding in intermediate satellite nodes with limited source and power, by using an advanced orbiting systems (AOS) frame switching scheme to avoid unnecessary processes, such as unpacking, upper-layer processing and repacking for passing services. The protocol stack could also support the use of unidirectional links to improve the link resource utilization. Finally, it could also provide transparent transmission for different kinds of services.

Conceptual Prototypes of Composite Structures for Aerospace

Shape memory composites (SMCs) are very interesting for self-deployable structures in aerospace applications. SMCs have been widely developed but not yet fully applied to space. In this study a lab-scale production of SMC prototypes for aerospace is described. Conceptual design of small-scale structures were prototyped with the aim to define several configurations which are able to self-deploy. SMC prototypes were manufactured by using two layers of carbon/epoxy prepreg with a shape memory epoxy resin interlayer. Two different configurations were produced to prototype complex shape for multiple folding and 3D deployments of de-orbiting structures. In particular, the first prototype tests a de-orbiting system without the sail to study the complex folding and de-folding mechanisms. The second configuration evaluates a de-orbiting dual-sail for satellite applications. The SMC structures were produced in the opened shape and subsequently memorized in the closed configuration. The initial deployed configuration is recovered by heating the prototype. The closed configuration increases the packing efficiency of large structures for space orbiting systems. The shape memory properties were provided only to folding zones. Memory-recovery-cycles have been performed to test SMC performances. As a result, the two configurations can successfully self-deploy following the desired design constraints and recovering the original flatness without noticeable defects.

A Comparative Study of Satellite Orbits as Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO)

It is known facts that satellites are used to receive the signal at geostationary orbit by remaining stationary above a particular point on the Earth. The orbit that is chosen for a satellite depends upon its application. Those used for direct broadcast television use geostationary orbit. Many communication satellites similarly use geostationary orbit. Other satellite systems used for satellite phones use Low Earth orbiting systems. Similarly, satellite systems used for navigation like Nav-star or Global Positioning (GPS) system occupy a relatively Low Earth Orbit. There are also many other types of satellites : Weather satellites Research satellites and many others. Each will have its own type of orbit depending upon its application. The actual satellite orbit that is chosen will depend on factors including its function, and the area of serving. At some instances, the satellite orbit may be as low as 100 miles (160 km) for a Low Earth Orbit (LEO), whereas others may be over 22 000 miles (36000 km) high as in the case of a Geostationary Orbit (GEO). The satellite may even has an elliptical rather than a circular orbit.