Research Topic: Mathematical optimization of space debris mitigation and Strategy analysis

Group:Dr. JK Wijeratne, Mr. C.R Rajapaksa.

Introduction:

Space activities conducted by humans on Earth orbit began with the first launch of the artificial satellite Sputnik1 in 1957.  Since then, orbital debris has increased with time and approximately 19,000 objects larger than 10cm and approximately 500,000 particles between 1 and 10 cm’s exist in space and probably tens of millions of particles smaller than 1cm roams in orbit today. U.S. Space Surveillance Network tracks larger orbital objects (> 10cm) and approximately 15,000 objects were in their catalogue as of 1st May 2010. Fifty percent of all orbital debris is vulnerable to collisions, which result in fragmentation of debris and that leads to a rise in the debris populations in the future even in the absence of future space launches.

    Mechanisms for Removing or reducing space debris

1)      Minimizing the break up potential during operational phases

2)      Limiting the accidental collision in orbit

3)      Avoiding intentional destructive and harmful operations (deliberate collisions) in orbit

4)      Limiting debris released during normal operations

5)      Limiting long-term presence of launch vehicle and the spacecraft in low earth orbit (LEO) region and geosynchronous (GEO) region after end of their missions

6)      Taking active measures to deorbit or move debris to alternative orbits

From the above mechanisms, the active measures to deorbit the debris object have been chosen for the suggesting study. The international space community has focused on debris mitigation measures that lasted a decade, and they have introduced policies and guidelines to address these issues.  In 2007, the United Nations adopted space debris mitigation guidelines. However, adopting these guidelines was not sufficient to stabilize the LEO debris environment, nevertheless active debris removal methods may help to control the situation. Moreover, active debris removal methods will enhance the reliability of future space systems. These methods need to address technological, financial and political constraints when being implemented. Furthermore, these systems should identify effective mitigation and removal strategies based on reliability, robust criteria and appropriate performance metrics. Previous studies used high-definition models of space debris environment to select these criteria and metrics on a relatively ad-hoc basis. Therefore, there is still a current requirement to identify a potentially optimal solution for space debris removal.

This field of research commenced more than twenty-five years ago and numerous methods were proposed to remove large debris.

Objectives of the research

It is suggested that when a single vehicle attempts to carry severaldeorbiting packages within different inclinations, even at same altitudes it requires a very high fuel mass and delta-v due to the plane changes that should be attended by the spacecraft. Equipped iron engines with satellites could also be used to direct debris back to the earth’s atmosphere. However, due to the high-energy requirements, this was also not worth being operational in the past. In addition, it requires a long-term power source and attitude control sub systems. This implies a practical approach to orbital debris removal process that needs to be developed more thoroughly to adopt a feasible system. This leads the main objective of the this research to find the best optimum solution to deorbit the debris to a position approximately below 100km of altitude to completely decay the debris object in the earth’s atmosphere. The optimum solution will be future analyzed to give out the best mission options in order to identify the most effective sequence of debris that needs to be de-orbited with priority. Technical communities have focused to obtain precise information about debris via the SGP4 model as it helps to predict these orbital debris objects more effectively. Consequently, the author of this study decides to use the SGP4(Simplified General Perturbation) model

Research Topic: Developing a mathematical model to study risk of Dengue transmission of Dengue.

Group: Dr. S.S.N. Perera,Dr.NC Ganegoda, Mrs. B.W.M.N.M De Silva

Introduction:

Dengue is one of the most prevalent viruses by mosquitoes where increasing incidence and severity claims severe social burden. This virus is common throughout the tropics and subtropics. Outbreaks have occurred in the US Virgin Islands, Cuba, Central America and many Asian and African countries. According to the World Health Organization, there are an estimated 50 million cases of dengue fever with 500,000 cases of dengue hemorrhagic fever requiring hospitalization each year. Nearly 40% of the world’s population lives in an area endemic with dengue.

Dengue fever is caused by family of viruses that are transmitted by Aedesmosquitoes. Though its claim classic form causes flu-like symptoms and is not life-threatening, more severe forms as dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) can be fatal, especially in children.

During the past few years, the characteristics of dengue in Sri Lanka appear to have changed. For instance, a decade ago, children were predominantly affected, but in recent years increasing numbers of adult dengue patients have been seen, with both significant morbidity and increasing number of adult deaths due to dengue. Therefore, it is very important to investigate, how this virus spreads while considering their age, gender and other demographic factors with the attitudes of the government and people.

There is no vaccination and standard treatment for dengue. Control the transmission of dengueis the only strategy to prevent the disease. Therefore, it is essential to know which factors to be controlled in what level and what strategies to be implemented.

Research Topic:Development of mathematical model for risk assessment of plant species during deliberate introductions to Sri Lanka

Group: Dr. S.S.N. Perera, Dr. S.M.W. Ranwala, Ms.H.O.W. Peiris

Introduction:

Invasiveness of a species is recognized as the ability of a species to spread, establish beyond it’s origin while harming the biodiversity of the new environment. Invasive alien plants are therefore considered as a serious threat to the existence of various ecosystems as they alter physical, chemical and biological components of the environment. Over the past few years there has been a growing interest to minimize these threats by introducing and implementing various management strategies at various levels. Common approaches for management of invasive alien species encompass prevention, early detection, eradication, control and containment.

It is well known that increased trade and tourism, human travel and migrations facilitated intentional and unintentional introductions of species all over the world.Many deliberate introductions have later caused worrying problems as they have not been subjected to any risk assessment during their introduction. However at present impacts of species introductions are being seriously considered in the international trade and environmental policy agendas through a variety of international agreements. Thus risk assessments (RA)have beenincorporated into quarantine legislation and procedures at national borders to regulate the entry of species into new environments. In Sri Lanka several government agencies such as National Plant Quarantine Services, Seeds Certificate Centre of the Department of Agriculture conduct qualitative investigations on likelihood of the entry, establishment and spread of aquatic or terrestrial invasive plants. At present, a specific risk assessment procedure to regulate introduction in invasive alien species (IAS) has been suggested by the Ministry of Environment.