ZS6BZP, B.Eng. Electronic (Pretoria), M.Sc. Space Physics (Rhodes)
AMSAT has decided to embark on the development and launching of a
South African Amateur satellite. The satellite will be based on the
CubeSat principle. The subject of this paper will be a basic
satellite with a short time to launch.
Mission (Purpose) of the CubeSat
While radio amateurs all over the world
raved about SumbandilaSat, local Hams missed out as the vast
majority of Southern African passes were used to download images,
the primary mission of SumbandilaSat. It can thus be argued that
SumbandilaSat did not fulfil its secondary mission of education and
creating an interest in science, technology, engineering,
mathematics and space in Southern Africa.
The mission of the new satellite is to
give radio amateurs (and educational institutions) in Southern
Africa easy access to a Low Earth Orbit (LEO) satellite on as many
of the available passes as possible and thus stimulate interest and
activity in space, satellites and amateur radio. A secondary mission
is to fly a scientific payload proposed and designed by an
educational institute in South Africa. This will further increase
the participation of the youth in the project, helping to create
interest in science and technology.
The development phase of the CubeSat is
currently known as (Project) KLETSKOUS. This reflects nicely on the
mission and functionality of the satellite: “Klets” is an Afrikaans
word for talking a lot. We want the Southern African radio amateurs
to talk and operate much more via satellite. “Kous” is the Afrikaans
word for a sock. The transponder that is planned for the satellite
can also be referred to as a “bent-pipe” transponder, aligning the
idea to the “sock”.
Once the satellite nears completion a
competition may be run to decide on an applicable name for the
satellite, as was the case for SumbandilaSat. On the other hand it
seems as if most people have grown fond of the project name and the
satellite may end up being referred to as KO xx, indicating
KLETSKOUS OSCAR xx.
While it is considered that a 2 m uplink
and 70 cm downlink is desirable from a user perspective, the
International Radio Union (IRU) advises that 2 metre uplinks are
problematic as in many parts of the world there are too many
illegal, non-amateur transmissions. The satellite may receive these
transmissions and make matters worse by re-broadcasting it on 70 cm.
Given that most hand-held transceivers
sold today are both 70 cm and 2 m capable, the problem of non
availability of 70 cm transmitting equipment will fall away and
KLETSKOUS should be as easy and convenient to work as what
For KLETSKOUS the uplink is on 70 cm,
and the downlink on 2 m. A linear transponder with a bandwidth of 20
kHz is utilised for both FM and SSB. A sub-carrier for a telemetry
downlink will be included. For command and control purposes a
separate 70 cm frequency will be used. Currently frequencies in the
435.100 to 435.140 MHz range are considered for the uplink and
145.860 to 145.980 MHz for the downlink. The above architecture will
ensure that the transponder is accessible for general use while the
satellite is being commanded and controlled by the ground station.
Maximum access by Southern African Hams to KLETSKOUS is thus
The development of the transponder has
progressed to the point where the second prototype is now ready for
on the air tests. The output power is at the required level (≥ 200
mWatt) and the gain of the RF path has also been increased to the
amount required. The transponder will be integrated with the On
Board Controller (OBC) after completion of the RF tests. The command
link and telemetry downlink will then also be addressed. Lessons
learned and updates that may be required will then be implemented on
a next prototype.
KLETSKOUS will also carry a scientific payload designed and
developed by an educational institute (school) and it will probably
be in the form of a magnetic sensor.
Worm holes are portals joining two
distant parts of space, a sort of shortcut through space and time.
However the question is are they real or just science fiction?
Theoretically worm holes are places
where the magnetic field of Earth connects to the magnetic field of
the Sun, creating an uninterrupted path leading from our own planet
to the sun's atmosphere 93 million miles away. Finding these
portals should be relatively easy; furthermore studying these
portals would provide us with much information on these cosmic
The aims and objectives of the Worm Hole
project are as follows:
Find portals between the sun and the
Earth’s magnetic fields by comparing predicted and measured
magnetic field strengths.
Send abnormal current and voltage
readings back to Earth for further analyses to try and prove the
existence of worm holes.
Implementing this project may be
challenging as KLETSKOUS is going to make use of passive magnetic
stabilization that may interfere with the scientific experiment.
The project was proposed by the Laudium
Secondary School Meet Trivedi.
KLETSKOUS will be a 1U CubeSat. The
dimensions are 10 cm x 10 cm x 10 cm. The total volume of the
satellite is 1 litre and the maximum weight 1.1 kg. This is indeed
very compact. In order to achieve a realistic launch schedule some
of the subsystems of the CubeSat will have to be bought from
Deon Coetzee is achieving the
unimaginable by crafting space frames in his home work shop. The
first two prototypes were very impressive. The University of
Stellenbosch has come on-board and the optimization of the space
frame is now a project addressed by a final year mechanical
engineering student, Francois Oberholzer.
Deon is also developing the mounting and
deployment mechanism for the antennas as well as investigating
multiple solar panels on KLETSKOUS.
A Command Link will be required for
housekeeping purposes and also maybe in-flight reprogramming of the
onboard controller, although this is risky business as the satellite
may be killed if the reprogramming is unsuccessful. The best option
would be to launch the satellite with flawless software already
loaded, if at all possible.
A Scheduler will switch the transponder
on and off at pre-determined times that will correlate to certain
areas being over flown by the satellite. It will be possible to set
the onboard clock of the Controller to ensure that the Scheduler
A Telemetry Downlink will be required.
Some of the parameters that must be monitored on the ground include
battery voltage and temperatures, orientation of the satellite via
the radiation sensors in the centres of the five solar panels and
the output voltages of the solar panels. It is planned that the
Command and Telemetry functions be based on those implemented on the
High Altitude Balloon Experiment, HABEX.
The first prototype On Board Controller
(OBC) has been completed and the house keeping software is currently
being developed and tested by Brian McKenzie.
Johan, ZR1BMD working for ISIS in the
Netherlands gave the following information: A Typical 1U CubeSat
will have 12 solar cells (2 each on the 6 facets of the cube). When
stabilised by a passive magnetic system the solar panels will have a
typical efficiency of about 28% at the start of their lives and for
a typical orbit will have 2.7 W "orbit average" and 3.6 W "sunlit
average" power available. After some time in space the efficiency
will fall to about 21% and the available power budget will decrease
to 2 W and 2.7 W respectively. (That is not much to play with!) The
final values will be very dependent on the orbit selected.
We are very fortunate that Denel
Dynamics have provided KLETSKOUS with three prototype solar panels
on a long term loan agreement. These solar panels have been
characterised and the data obtained is now being used by Fritz
Sutherland jnr. to develop the power supply for KLETSKOUS. The EPP
is an advanced design that ensures optimum utilization of the power
supplied by the solar panels. During flight all the electronics,
especially the Transponder must be powered with any surplus power
being used to charge the batteries. When the batteries
eventually fail the satellite should be able to function when it is
lit by sunlight.
With this amount of power available the
maximum RF output of the satellite cannot exceed 0.5 W. In general
the output power will have to be reduced to 200 mW or less.
Experience with other Low Earth Orbit (LEO) satellites; including
SumbandilaSat have indicated that successful communications with a
modest ground station is not a problem at this power level.
It will be difficult to implement
active stabilisation in a 1U package together with the transceivers
required for the main payload. A passive (magnetic) stabiliser
should keep the antennas adequately orientated during a pass over
Southern Africa. This is also the solution implemented on FunCube.