We interviewed Doreen Agaba, who is currently studying for her PhD in the Radar Remote Sensing Group at the University of Cape Town. She spoke about her research on “System Design for Detection, Tracking and Classification of Space Debris”.
I was born in Uganda in 1987. I obtained a BSc Physics/Maths, Physics major from Mbarara University of Science and Technology in Uganda (2006 to 2009).
In 2010, I moved from Uganda to South Africa, and completed my Honours in Astrophysics and Space Science in the National Astrophysics and Space Science Program (NASSP) at the University of Cape Town (UCT).
From 2011 to 2012, I studied for a Master of Philosophy in Electrical Engineering at UCT; my supervisors were Prof M.R. Inggs and Associate Prof P.J. Cilliers.
During this time, I was based at the South African National Space Agency (SANSA), Space Science Directorate, in Hermanus.
My professional objective is to perform research that is valuable to society with integrity and professionalism, under proper supervision, thereby empowering our African communities with skills and knowledge of science, teaching them how they can contribute to and gain from modern-day research.
The topic of my Master’s thesis was “Calibration of a SuperDARN Radar Antenna by means of a Satellite Beacon”.
This work was an essential tool during the construction and launching of the South African cubeSat (ZACUBE-1) and it has been summarized into a paper for publication. The results from this research have also been presented at international conferences, such as the International Geoscience and Remote Sensing Symposium (IGARSS), and have been acknowledged in a few papers. Four papers have been published, for which I am a co-author in relation to this work.
Tell us a bit more about SuperDARN?
SANSA’s new high frequency digital radar system is located at the South African Antarctic base, SANAE IV. The radar is part of an international network of 33 radars distributed over the northern and southern polar regions, called the Super Dual Auroral Radar Network (SuperDARN).
The new digital radar is going to replace the existing 17-year-old analogue radar, which was due to be decommissioned in 2012. The new radar will provide a more versatile, reliable and state-of-the-art research platform that will allow scientists to study the ionosphere and other space weather related phenomena.
Antarctica is the optimal place for space weather research instrumentation because the Earth’s magnetic field lines converge at the poles and act as a funnel for space plasma to travel into the Earth’s atmosphere. A single pair of radars in the network can measure the position and movement of ionospheric plasma in an area of approximately 4 million square km.
Image from: http://www.sansa.org.za/spacescience/resource-centre/news/529-understanding-space-plasma.
A cubeSat is a nano-satellite, usually with a volume of one litre and mass of about 1.3 kg (1 unit (U)). CubeSats are designed from off-the-shelf components, making them affordable. They also have a short life expectancy (up to 3 years), so they are required to have a de-orbiting mechanism. Because of their advantages over large satellites, cubeSats have become an increasing asset to space research.
First image captured by TshepisoSAT from space (Source: http://www.cput.ac.za/blogs/fsati/2013/12/15/first-image-captured-by-zacube-1-tshepisosat-from-space/)
ZACUBE-1 (also known as TshepisoSAT), the first nano-satellite to be constructed in South Africa, is a 1 U cubeSAT with dimensions of 10X10X10 cm (see also: Defenceweb article).
TshepisoSAT was built at the French South African Institute of Technology (FSATI), assisted by the University of Stellenbosch. FSATI is a specialised unit at the Bellville campus of the Cape Peninsula University of Technology (CPUT) Bellville, under Director Prof Robert van Zyl.
It consists of an on-board computer, a power system that consists of solar panels, a battery and a power controller to provide electrical energy to all the subsystems, a very high frequency (VHF) or ultra high frequency (UHF) radio receiver, and an Attitude Determination Control System (ADCS), which orients the satellite to point its communication antennas towards Earth.
The antenna on the cubeSat will transmit a simple radio signal that can be received by the Hermanus high frequency/direction finding (HF/DF) array and the SuperDARN radar in Antarctica, as well as the rest of the SuperDARN network.
In 2013, I started my PhD research on the topic “Radar System Design for Detection, Tracking and Classification of Space Debris”, as part of the Radar Remote Sensing Group at UCT. My supervisors are Prof M.R. Inggs and Dr A.K. Mishra.
Africa is increasingly becoming space “active”. It requires a large amount of work and funds to build and launch a satellite.
So, when these satellites are operational and providing data to perform necessary research such as in the field of space weather, it is very important to ensure their safety until they have served their purpose.
However, satellites have been sent into space since the late 1950’s, and in fact, most of them are still in space.
As a result, there is a growing number of objects (formed by explosions and collisions) that present a hazard to both manned and unmanned satellites and to humans on Earth.
This artificial space debris comes in various sizes (up to 10 cm in diameter) and tends to move at very high speeds (up to 28 km/hr).
There is evidence of satellite parts that have been damaged by these objects; an example of this can be seen in the picture above.
My research focuses on space debris in the Low Earth Orbit (LEO). The figure below shows the expected growth of these objects, as predicted by space debris models from NASA.
There is clearly a need to get a better understanding of these objects, in order to implement mitigation measures, such as their removal and collision avoidance. High resolution imaging, detection and monitoring of space debris can be done by use of available radio telescope receivers in a radar system.
Data obtained from the radar can be can be used to determine debris parameters, such as size, velocity and altitude, which are used to classify space debris. Some of the available radio telescopes are the KAT-7 radio telescope, MeerKAT (when completed), and the HF radar in Antarctica.
We wish Doreen much success with her PhD research.