In recent years the use of small multi mission satellites (SMMS) in Low Earth Orbit (LEO) for making voice, data and E-mail communications has been grown extensively. Low production cost, Low cost of lunching and low transmission power due to it’s low orbit of these satellites are some reasons for their vast usage. How over because of their low orbit they need to turn several times around the e...

Space is an unforgiving environment – one of harshest known to mankind. Yet, space is far less understood than other service environments in which DOD systems operate. It has been known to limit the useful life of satellites, with 20 to 25% of all mission failures being attributed to the effects of the space environment.[1] Since access to space is so costly, materials and components must funct...

Notwithstanding the limited commercial success of the first narrowband Low Earth Orbit (LEO) satellite systems, the interest of the scientific community in this type of systems has been revived on the basis of the current trend toward the migration to all IP-based services. LEO systems can play a pivotal role in providing services to areas where there is no substantial terrestrial infrastructur...

The precise orbit determination problem is to accurately determine the position and velocity vectors of an orbiting satellite. In this paper we review the general contents of the orbit determination process, with particular emphasis on Low Earth Orbit (LEO) satellites. The different orbit determination approaches and the different force models contained within are briefly discussed. The two mai...

This paper describes an architectural concept for a Small Lunar Exploration and Delivery System to operate as a platform for emplacing payloads into lunar orbit and onto the lunar surface, while providing mobility for surface exploration, science, and infrastructure. The concept leverages emerging services that are capable of delivering payloads to Low Earth Orbit (LEO), while utilizing new and...

A satellite, in its orbit, is affected by perturbing forces, such as atmospheric drag, solar radiation pressure, Earth oblateness, and gravity of the celestial masses (other than the Earth). In this paper, the effects of these forces on the trajectories of different types of LEO satellites and a sample satellite (Z-SAT) are discussed. A few analyses are done on these orbits and the relevant res...

In this paper, we discuss on two important issues through the realization of global personal communication networks with low earth orbital (LEO) satellites. The first issue is the selection of an effective multiple access scheme which can utilize the limited spectrum allocated to these systems. In this way, we focus on the schemes based on spread spectrum techniques and explain their unique cha...

This paper proposes a novel dynamic bandwidth assignment multiple access (DBAMA) protocol employing a dynamic packet reservation technique for direct user terminal access to a ATM-based low earth orbit (LEO) satellite communications system. Performance analyses by simulations are presented. Methods to efficiently integrate ATM-based BISDN traffic are considered.

In this chapter, we survey communication related issues arising in the context of Low Earth Orbit (LEO) satellite constellations. In particular, we study the impact of the predictable movement of the satellites on the techniques used in topological design, routing, and hand-over strategies.

In this paper, optimum trajectories in Earth Transfer Orbit (ETO) for a lunar transportation system are proposed. This paper aims at improving the payload ratio of the reusable orbital transfer vehicle (OTV), which transports the payload from Low Earth Orbit (LEO) to Lunar Low Orbit (LLO) and returns to LEO. In ETO, we discuss ballistic flight using chemical propulsion, multi-impulse flight usi...