KLETSkous CubeSat Project     

SA AMSAT has embarked on the development and launching of two South African Amateur satellites. These satellites will be based on the CubeSat principle. The first, that is also the subject of this paper, will be a basic satellite with a short time to launch.

 Project Name
It is proposed that the development phase of the satellite been known as Project KLETSkous. This reflects nicely on the mission and functionality of the satellite: “Klets” is an Afrikaans work 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 it is recommended to run a competition to decide on an applicable name for the satellite as was the case for SumbandilaSat.

 Mission of KLETSkous
To give Radio Amateurs in Southern Africa easy access to a Low Earth Orbit (LEO) satellite on as many of the available passes as possible. 

Payload
While it is considered that a 2m uplink and 70 cm downlink is desirable from  an user perspective, the IARU advises that two metre uplinks are problematic as in many parts of the world there are too many non-amateur applications that may interfere. This means that a tone access system will be highly desirable.  

Given that most hand-hold transceivers sold today are both 70cm and 2 m capable, the problem of non availability of 70 cm transmitting equipment is fast diminishing  

A linear transponder with a bandwidth of 20 kHz which can be utilised for FM and SSB with an uplink on 70 cm, downlink on 2 m is proposed.  

However switchable tone access may be implemented. Over Southern Africa the tone access will be switched off to give Amateurs with modest equipment easy access to the satellite. For the rest of the world where the Amateur population is denser, tone access will be required to reduce unwanted interference even on 70 cm uplinks. 

For educational purposes a beacon and parrot functionality may be highly desirable. Proposals for additional payloads will be considered. It should however be remembered that the amount of available power is a limiting factor. 

Project to support SAiSAT 

A Light sensor for SAiSAT will be included to perform vital measurements required for the SAiSAT project.

 Design Philosophy 
The plan is to implement the above payload in 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 kg. This is indeed very compact. In order to achieve a realistic launch schedule many of the subsystems of the CubeSat will have to be bought from overseas suppliers. These will typically be the airframe, solar panels, batteries, the battery charger controller and the passive magnetic stabiliser system. Other subsystems will probably be added to the shopping list during the design phase of the SA AMSAT CubeSat. 

House Keeping
A Command Link will be required for housekeeping purpose 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. The Scheduler will also determine when the Access Tone will be required. It will be possible to set the onboard clock of the Controller to ensure that the Scheduler performs correctly. 

A Telemetry Downlink will be required. Some of the parameters that must be monitored on the ground including battery voltage and temperature. A “squelch counter” that counts the amounts of time that the transponder’s squelch was broken may give an indication of the activity through the satellite, especially if it is time stamped.

It is planned that the Command and Telemetry functions be based on those implemented on HABEX: (www.habex.za.net)

Power Budget

According to Johan, ZR1BMD who works at for ISIS in the Netherlands a typical 1U CubeSat will have 12 solar panels (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 3.6W "sunlit average" power available. After some time in space the efficiency will fall to about 21% and the available power budget will decrease to 2W and 2.7W respectively. The final values will be very dependant on the orbit selected

When the batteries eventually fail the satellite should be able to function when it is in sunlight.

With this amount of power available the maximum RF output of the satellite cannot exceed 0.5 W. There may be instances where the output power will have to be reduced to 200 mW or less.

Stabilisation

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 stable during a pass over Southern Africa. This is also the road followed by FunCube.

Preliminary Block Diagram

Johan, ZR1BMD drew a first order block diagram of the functionality that is going to be required to achieve the mission stated for the satellite.

JOIN THE TEAM

The project team held its first meeting. If you have an interest and would like to work on the project, send your details to saamsat@intekom.co.za