Building a Distributed Satellite Ground Station Network - A Call To Arms

This is a project closely related to the academic femto-satellite movement, ham radio, Constellation@Home.

The area of small satellites (femto-satellite <0.1 kg up to mini-satellite 100-500 kg) is currently pressed forward by Universities and enables scientific research at a small budget. Gathered data, both scientific and operational, requires communication between satellites and ground stations as well as to the final recipients of the data. One either has to establish own transmission stations or rent already existing stations. The project “distributed ground station” is an extension to the project which will offer, at its final expansion state, the ability to receive data from satellites and relay them to the final recepients. It is therefore proposed that a world-wide distributed network of antennas is to be set up which will be connected via the internet allowing the forwarding of received signals to a central server which will in turn forward signals to further recepients. Individual antennas will be set up by volunteers (Citizen Scientists) and partner institutions (Universities, institutes, companies). The core objective of the project is to develop an affordable hardware platform (antenna and receiver) to be connected to home computers as well as the required software. This platform should enable everyone to receive signals from femto-satellites at a budget and in doing so, eradicating black patches where there is currently no ground station to receive signals of satellites passing over-head. Emphasise is put on contributions by volunteers and ham radio operators who can contribute both passively by setting up a receiver station or actively by shaping the project making it a community driven effort powered by open-source hardware and applications.

Purposes The distributed ground stations will enable many different uses. Using distributed ground stations one could receive beacon signals of satellites and triangulate their position and trajectory. It would therefore be possible to determine the kepler elements right after launching of a new satellite without having to rely on official reports made at low frequency. Beacon tracking is also not limited to just satellites but can be used to track other objects like weather balloons and areal drones and record their flight paths. Additionally, beacon signals (sender ID, time, transmission power) could be augmented with house-keeping data to allow troubleshooting in cases where a main data feed is interrupted. Details regarding the protocol and maximum data packet length are to be defined during the feasibility study phase. Furthermore, distributed ground stations can be used as "data dumping" receivers. This can be used to reduce load on the main ground station as well as to more quickly distribute data to final recipients. The FunCube project, an out-reach project to schools, is already using a similar approach. Another expansion stage would be increasing the bandwidth of the individual receivers. As a side-effect, distributed ground station could also be used to analyse meteorite scattering and study effects in the ionosphere by having a ground-based sender with a known beacon signal to be reflected off meteorites and/or the iononosphere and in turn received by the distributed ground stations. Depending on the frequency used further applications in the field of atmospheric research, eg. local and regional properties of the air and storm clouds, can be imagined. Depending on local laws and guidelines, antennas could also be used to transmit signals. The concept suggests the following expansion stages:

1. Feasibility study for the individual expansion stages
2. Beacon-Tracking and sender triangulation
3. Low-bandwidth satellite-data receiver (up to 10 Kbit/s)
4. High-bandwidth satellite-data receiver (up to 10 Mbit/s)
5. Support for data transmission Each stage is again split up into sub-projects to deal with hardware and software design and develoment, prototyping, testing and batch/mass production, Network The networking concept demands that all distributed ground stations are to be connected via the internet. This can be achieved using the Constellation platform. Constellation is a distributed computing project used already for various simulations related to aerospace applications. The system is based on computation power donated by volunteers which is combined to effectively build a world-wide distributed super-computer. The software used to do this is BOINC (Berkeley Open Infrastructure for Network Computing) which also offers support for additional hardware to eg. establish a sensor network. Another BOINC-project is the Quake Quatcher Network which is using accelleration sensors built into laptops or custom USB-dongles to detected earthquakes. Constellation could be enhanced to allow use of the distributed ground station hardware. Constellation is an academic student group of the DGLR (german aerospace society) at Stuttgart University and is supported by Rechenkraft.net e.V and Selfnet e.V.. Ham radio and volunteers Special consideration is given to the ham radio community. Femto-satellites make use of the ham radio bands in the UHF, VHF, and S-Band range. As a part of the ham radio community ham radio operators should be treated as part of the network. Ham radio operators hold all required knowledge about the technology required to operate radio equipment and are also well distributed world-wide. To also make the system attractive to volunteers, hardware should be designed in a way that allows manufacturing and distribution on a budget. All designs should also be made public to allow own and improved builds of the system by the community. The hardware should be designed to be simple to use correctly and hard to be used wrong. Supporters
   [1] Constellation Plattform, aerospaceresearch.net/constellation [2] shackspace Stuttgart, www.shackspace.de References [1] IRS Kleinsatelliten, Universität Stuttgart, kleinsatelliten.de [2] Constellation Plattform, aerospaceresearch.net/constellation [3] BOINC, Berkely University, boinc.edu [4] Quake Catcher Network, qcn.stanford.eu [5] DGLR Bezirksgruppe Stuttgart, stuttgart.dglr.de [6] Rechenkraft.net e.V., rechenkraft.net [7] Selfnet e.V., selfnet.de