Detection of radio interference in the UHF amateur radio band with the Serpens satellite

High packet losses when uplinking commands to small satellites have been reported in the UHF amateur band (430–440 MHz) since late 2013. Measurements of the uplink radio environment have shown high levels of in-band interference in previous works, but public measurement results are limited. Average interference levels are usually measured over some time to build heat maps. In this paper, the analysis is focused on sustained interference over a 24 ms time window using a maximum-minimum method. New heat maps and interference power distributions over Europe, Africa, the Middle East and the Americas were obtained using this method on measurements from the Serpens satellite. One of the missions of Serpens was to test an in orbit store-and-forward communication system to exchange short messages with ground sensors for disaster monitoring. The satellite operators had difficulties commanding the satellite due to interference, causing bit errors in uplink packets. Interference power of up to −70 dBm was detected during in-orbit measurements over Europe and North America, while expected received power from the ground stations was not more than −80 dBm. High power space-object tracking radars on the ground operating in the 420–450 MHz band could be the cause, but further measurements are required to verify this. Characterizing this interference can help develop mitigation techniques for future satellite communication systems

In-orbit Radio Measurements using Software-Defined Radios in Small Satellites

Environmental monitoring of the oceans and the Arctic is important to understand the impact of global warming and climate change. The use of different types of assets, such as satellites and autonomous agents, can contribute to this task at different spatio-temporal scales. However, the collection and distribution of scientiĄc data from sensors or robotic agents in these remote places are challenging due to limited infrastructure. Thus, a new communication system is needed to obtain faster and easier access to the data. To design a robust satellite communication system for energy-limited sensors, measurements of the communication channel and the interference environment are necessary. In addition to the mission design activities, the main contribution of this thesis is the analysis and characterisation of the in-orbit interference in two different relevant frequency bands in VHF and UHF for small satellite systems. The Ąrst band is the UHF amateur radio band (430Ű440 MHz), selected due to its common use for small satellite communication. This band was measured with payloads on board the Serpens and the LUME-1 satellites. Another contribution of this work is the design and development of an onboard measurement algorithm for small satellites with limited resources. We built a Software-DeĄned Radio (SDR) testbed similar to the actual satellite setup for testing before uploading the algorithm to LUME-1. In addition, we explored the uplink interference from more than 300 measurement locations all over the world. Band-limited pulsed interference was detected in areas where ground radars are located and wide-band pulsed interference was measured over central Europe. The other frequency band measured was the lower leg of the VHF Data Exchange (VDE)-SAT system (157 MHz band). This band was selected to explore the performance of a new communication system that is currently being demonstrated, the VDE-SAT, which will operate in the Arctic. We analysed the uplink interference environment of this system by analysing recordings from an SDR payload on board the NorSat-2 satellite over the Arctic. Pulsed interference of high power was also detected in this band. The pulse length and period were detected using a second algorithm developed in this thesis. The algorithms and software implemented in this thesis can be used in any frequency band to detect the frequency and time variability of different signals in any satellite with an SDR

A Satellite-USV System for Persistent Observation of Mesoscale Oceanographic Phenomena

Traditional tools and methodologies for mesoscale observation of oceanographic phenomena are limited by under-sampling and data latency. In this article we evaluate three different scenario variants of an architecture for how heterogeneous sensor nodes can be integrated with satellite remote sensing. Independent space and marine sensing platforms are interconnected either directly or by means of a ground-based mission control center responsible for data processing, relay, and coordination of the assets. A wave-propelled unmanned surface vehicle (USV) persistently collects in situ data of the targeted phenomenon. In two variants of the architecture, a dedicated small satellite acts as a sensor node, a data processing facility and a communication node. We have used a System-of-Systems (SoS) modeling approach coupled with operational simulations in different locations on Earth, in order to support the proposed methodology and investigate quantitatively the reduction the data latency to end-users. Through a combination of field experiments and simulations we estimate how the different scenarios perform with respect to providing remote sensing data that are used to create a measurement and navigation plan for the autonomous vessel