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Introduction and rationale
The numbers and figures in this document relates to numbers in other design documents and are summed up in HSI for CubeSat.
In order to save time, which is likely the most valuable resource for this project, it is advised that the payload downlink (and other communication systems) will be bought together with the satellite bus. The requirements will be presented to suppliers in form of a tender in Q4 '17 or Q1 '18. From this, it is expected that bidding suppliers will suggest hardware and systems that will meet our requirements. Various I’m not too concerned about the lack of set facts at the moment, for several reasons: Before we have the tender in place (where our requirements will be) and until we get the offers from suppliers we don’t really know what we will be playing with. Since we are doing things as quick as possible, we cannot build the comm system for the SC ourselves. So basically, we have to know what options we have to derive final details. The various suppliers will have different equipment and possibly also different requirements/options/offerings for GSs. This goes both for the comm systems (TM/TC, payload downlink, ground stations) as well as software for operation. I will expect that the suppliers are able to deliver needed software to operate their satellites. Then we will have to see if that cuts it for us or if/how much we will have to implement our own.
Satellite hardware
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Satellite hardware
At the time of writing, a payload S-band downlink capable of 1-4 Mbps seems reasonable, as it is a product available for CubeSats. These systems will also have an output power that can be supported by the CubeSat. In practice, this output power will be quite low (typical 1-10 W). In order to close the link budget, such systems will require an antenna dish of some size (TBC), perhaps with a diameter of 3 to 4 meters on a steerable mast. This must be verified with a link budget calculation when the space segment sub-system is known.
Suppliers such as GOMSpace, ISIS, ClydeSpace and UTIAS SFL all have S-band radios available. If higher datarates are needed, X-band can be an option, but availability of such systems will be more limited. sss
Ground stations
As Tor Arne says, we have several options for operational ground stations, including KSAT Svalbard (and other locations) as well as perhaps Kystverkets station in Vardø. I believe it would be vise to have access to an operational service to rely on, in addition to:
• Our own ground station. Currently not near meeting our requirements wrt. S-band. However, getting funding for a heavy upgrade looks very promising. We should know this month, I think. Again, depending on cost/schedule/options we then could buy some GS hardware/software from the satellite supplier or set up our own general equipment (or both).
• Partners: Porto, Vigo and also other universities can be potential supporter and help with data acquisition. However, cost and time to build ground stations must be considered (that is why I think we should approach professional operators to have at least a fall-back). We should be able to supply a hardware design for a versatile ground station (one version of it is currently being set up at the local radio club ARK) as well as our own; but the partners must endure the time and cost to implement it.
• Access to NASAs huge antennas could be very interesting, especially if things does not work out as it should, and also if we are able to set up more advanced experiments based on the SDR-payload in next steps.
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