Christopher Lowe
Mac Robertson Scholarship – Post visit report
My name is Christopher Lowe, I am 30 years old, British
and a final year PhD student in the Advanced Space
Concepts Laboratory in the University of Strathclyde’s
Department of Mechanical and Aerospace Engineering.
My research is in the field of inter-networking for
resource limited satellite constellations and I received a
total of £3950 in 2014 from the Mac Robertson
Scholarship in support of my visit to the Technische
Universität München (TUM), in Germany. For the final
four months of 2014 I was kindly welcomed into the
Lehrstuhl für Raumfahrttechnik (LRT) (Institute of
Astronautics), under the guidance and supervision of
Professor Ulrich Walter, and joined the team as a full time
researcher at the institute.
10 February 2016
At the top of the Untersberg, near Salzburg
The objectives of my visit were threefold; firstly, to develop my work on efficient design of small satellite
constellations through collaboration with a new consort of intelligent thinkers; secondly, to build
contacts in mainland Europe, in particular Germany, which is a global hub of activity in the Space industry
and; thirdly, to experience life in a new city, experience a new culture and improve my language skills.
Each of these objectives contributes to the overarching goal of improving future prospects for
collaboration between the UK and other nations in Europe. From the point of view of my research, the
LRT employs some of the leading researchers in the field of Astronautics, which were able to provide
valuable advice and assistance. Weekly research meetings with the group offered a great opportunity to
obtain feedback on developments made and allowed me to participate in the wide range of topics being
investigated there. Spending a significant amount of time in one of Europe’s leading technical Universities
has certainly helped me focus on this goal and it would not have been possible without financial
assistance from the Universities of Strathclyde and Glasgow.
My research is focussed on a particular design aspect
of Earth orbiting, intermittently connected, small
satellite constellations, which already offer the global
population products from weather data, to worldwide
sat-phone services, to ship identification for antipiracy operations. In general, a satellite mission can be
described as a process of data transfer, where
information is collected from targets and delivered to
a customer or user. Within this definition, data could
be for example an image, a text message or an
environmental sensor measurement, with the target
being a location on the ground, a ship crossing the
Atlantic or point in the upper atmosphere. The
customer is more often than not the satellite operator,
who may then distribute the received data to other
Example satellite constellation
downstream users throughout the world by some
other means (i.e. the internet). To design a mission effectively, we wish to maximise the performance,
typically viewed as a combination of the volume of data delivered, average source-to-destination delay
and the regularity with which we collect data. In addition, we always aim to minimise cost, producing the
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Christopher Lowe
Mac Robertson Scholarship – Post visit report
10 February 2016
characteristic cost vs. performance trade-off. A high performance can be achieved through intelligent
placement of satellites into specific orbits, selection of suitable ground stations (with which the satellites
communicate) and careful routing of data through the network. It is this final metric which is the focus of
my work and I aim to develop novel routing algorithms specific to the performance of intermittently
connected satellite networks. During my time in Germany, I developed software models to simulate
satellite networks, which captured the respective flow of data from the source to destination,
incorporating routing schemes based on graph-theoretical methods such as a modified Dijkstra’s shortest
path algorithm. This approach can be applied to find the fastest journey, when moving between
neighbouring satellites, in order to reach the destination as quickly as possible. Important to consider
however, is that since the networks being considered here are generally not fully connected, routing
methods for internet-type systems will not work. Instead, a store-carry-forward approach must be taken,
which has received significantly less attention as an area of research. Furthermore, satellite networks are
special in that their motion is highly deterministic, meaning certain methods that do not work for such
things as human-social networks, can be applied successfully. The models I developed have since been
applied to aid in the design of a medium-sized (20-30) satellite constellation to provide micro-wave
measurements required for severe weather forecasting. This system would offer better global revisit
times with shorter delay, than currently possible, which would support the capable network of satellites
already in orbit. Work is still on-going to develop these models further, incorporating resource
limitations, such as memory storage and energy, into the routing decision-making process. These
limitations are a real problem for all satellites, but especially so on small- and nano-satellites, upon which
our models are based.
In addition to my own research, I
became an active member of the
student group, Wissenschaftliche
Arbeitsgemeinschaft
für
Raketentechnik
und
Raumfahrt
(WARR), and took part in the
development
of
their
2nd
Nanosatellite, the Munich Orbital
Verification Experiment 2 (MOVE-2). I
was also able to participate in a visit
to Stuttgart University to meet with
MOVE-2 team at Stuttgart University with The Flying Laptop satellite
the team building the Flying Laptop
satellite (image). I hope this
experience, and the contacts made within the MOVE team, will offer a fantastic group of contacts for the
future. The Scottish CubeSat industry is expanding rapidly, so having potential collaborators with a
significant amount of experience in the field can only be positive. A bi-weekly journal club offered the
chance for the whole group to discuss different elements of a recently published journal paper, with the
aim of improving our academic writing skills as well as becoming effective reviewers.
During my time at the University I enjoyed a very interactive office space with two other PhD researchers,
who offered endless advice on German grammar and general life in Munich. With a door looking out onto
the kitchen, which accommodated the four (yes, four) different coffee machines, our office maintained
its reputation as a social hub allowing me to get to know most of the researchers well. Regarding coffee,
it was clear from an early stage that this would become a significant feature of my stay and it soon
became clear why Munich is often referred to as Italy’s most northerly city. Lunch was the other main
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Christopher Lowe
Mac Robertson Scholarship – Post visit report
10 February 2016
event each day, for which a number of the laboratory members and I typically took the short journey
over to a nearby canteen at the Max Plank Institute for Plasma Physics.
Outside of the work place, I made many new friends in and
around Munich, who introduced me to the city and joined me
in creating numerous unforgettable experiences, such as
Oktoberfest, a day at Munich Zoo and trips to the Alps. I did my
fair share of sightseeing in and around Munich, which is a
stunning city with beautiful architecture and a rich history. The
old town hall (Altes Rathaus) and four main “gates” into the city
centre were a particular highlight, which date back to the
Middle-ages, and really express the grandeur of that time. Near
to Munich, hidden in the Alps, is one of the most famous
landmarks of Bavaria, King Ludwig’s Schloss Neuschwanstein,
on which Walt Disney based the design of Sleeping Beauty’s
Castle.
Making new friends at the Oktoberfest
The Mac Robertson scholarship has
allowed me to conduct a research
placement that has helped consolidate
research that has been on going in
Glasgow for many years and enabled me
to obtain fresh ideas from external
researchers in similar fields. This type of
collaboration is worth an enormous
amount and I consider my experience at
TUM one of the most beneficial I have had
The view of Schloss Neuschwanstein
in my career so far, from both a research
and industrial point of view. Furthermore, having some time in a new environment provides a good
opportunity to think with a clear head and I am confident this has helped me move forward with
elements of my research which were perhaps stagnating. I will look back on my visit to Munich with fond
memories and it is certainly a highlight of my post-graduate experience. I would urge anyone to take on
the challenge of studying abroad, and am very thankful of the assistance provided through the Mac
Robertson scholarship scheme.
View of the Alps from the Klettersteig Höhenweg, near Munich
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