## 2 LUME-1 Satellite  
LUME-1 was launched on 27 December 2018 from Vostochny in Russia into a 510 km Sun-synchronous orbit. This 2U Cubesat was part of the European project Fire RS, where the University of Porto (Portugal), The Laboratory for Analysis and Architecture of Systems (France), the University of Vigo (Spain), and Alen Space (Spain) collaborated together [23]. The mission ended in June 2019, but the satellite is still operational and available for other research. LUME-1 has a TOTEM SDR on-board [23], allowing the upload of new software with new functionality.  
The Norwegian University of Science and Technology (NTNU) collaborates with the University of Vigo and Alen Space to develop and perform new communication experiments with the satellite. The objective is to estimate the in-band radio interference environment in the UHF radio amateur band (430-440 MHz). New software to estimate the time-frequency characteristics of this radio interference was developed at NTNU during 2020. This software was designed considering the constraints of the LUME-1 satellite. The main limitation is the data throughput and communication window. The default gross data rate configuration is 4.8 kbps, extendable to 9.6 kbps, over the UHF amateur radio band at 437.060 MHz, but the obtained net data rate is significantly lower. When using the 4.8 kbps configuration, given the few daily passes over the Vigo ground station due to latitude (42\({}^{\circ}\)) and the high level of interference experienced in the uplink, a continuous 1 kbps downlink rate for 5 min per day is a realistic estimate. For the uplink, the communication is degraded, and the estimated actual data throughput is 200 bps for 5 min per day.  
In addition, the satellite is tumbling (at approximately 1 rpm), since the Attitude Control and Determination System (ACDS) is planned to be activated at a later stage. The UHF antenna used is the ANT430 antenna from GomSpace, whose antenna pattern is not completely omnidirectional. According to the total gain measured on the GOMX-1 satellite [24] (a 2U CubeSat), the gain can vary between \(-1.5\) to 1.6 dBi, depending on the pointing. The antenna is circularly polarised only when seen from the top (left-hand) and bottom (right-hand). Additional losses can be experienced when pointing differently.  
The measurements were planned so that operations were as simple as possible. The TOTEM SDR on-board can have a maximum duty cycle of 50% due to power budget limitations. The RF front-end can be tuned within the 435-438 MHz band, and the dynamic range is approximately 66 dB. The RF bandwidth can be adjusted between 200-56,000 kHz [25], and the ideal sample frequency can be configured within 521-56,000 kSps. In order to use sample frequencies higher than 2 MSps, some digital signal processing must be ported to the Field-Programmable Gate Array (FPGA), requiring extra development. The interference measurement software was developed using GNURadio libraries in C++ and shell scripting.  
If the Automatic Gain Control (AGC) was activated, the gain of the Analogue to Digital Converter (ADC) would adapt to the dynamic range of the signal. As the gain cannot be read in real-time, the AGC was deactivated, resulting in a fixed gain for the measurements in this article. Thus, strong signals may saturate the ADC, and weak signals may be below the resolution threshold.