Electromagnetic compatibility (EMC) is an important requirement for spacecrafts due to the limitation of their volume and the possibilities of the layout of individual subsystems. Interference from satellite service systems are the main problem in conducting high-sensitivity measurements of magnetic fields when studying wave processes in plasma in the range of low frequencies. This is especially true for the becoming recently popular very small satellites - CubeSats (CS) with sensitive equipment for measuring electric and magnetic fields in the range from direct current to low frequencies. In order to minimize the mutual influence of the payload and service systems, it is necessary to determine the frequency and amplitude of the main spectral components of the emitted magnetic field of each satellite subsystem to reduce the level of the interference or, if not possible, to take into account when processing data. A special measuring system, created for registration and estimation of magnetic interference in the ULF range, is described in the article. This system consists of two identical three-component induction magnetometers, data acquisition unit, power supply unit, and control computer with a corresponding set of programs. With this system, the level of the AC magnetic field, generated by each of the subsystems of the CS, was measured and digital processing was performed. For the separation of the studied and background signals, data obtained from two identical three-component induction magnetometers of the system were used with the following solution of the inverse problem the determination of the parameters of the radiation source using the measured magnetic field generated by this source at two points. The results of the EMC tests for the CS developed under the SEAM project, the values and locations of the equivalent magnetic dipoles of the radiation of the separate subsystems, which are the sources of radiation in the CS, are given.

Abstract. The experiments on-board Vernov satellite were aimed on the study of high energy (relativistic and sub-relativistic) electron acceleration and losses in the trapped radiation areas as well as high altitude electric discharges in the upper Atmosphere. A separate task was study electromagnetic-wave phenomena in the near Earth space and the upper Atmosphere. During observations on 10 December 2014 interesting phenomena were discovered. They are connected to non-linear effects in wave activity of the type of two or three wave decays as well as splitting into two wave structures. Whistlers with specific unusual temporal structure of swallowtail type were observed on the spectral diagrams (sonograms), which were obtained for this time. It was shown that such signals can be caused by seismic activity. The signals of the type of whistler with long tail were also observed. Such signals were also detected by ground stations.

The "ClusterIon" is a fundamental scientific project devoted to the study of near-Earth space. The project is a response to the challenges posed by the modern development of knowledge about the Space Weather and the ionospheric responses to distributed over the globe natural and artificial sources of energy. Along with this, the project "ClusterIon" is a logical continuation of previous ionospheric missions realized throughout the space age, such as Dynamics Explorer 2 (1982-1984), Freja (1992-1993), DEMETER (2004-2010) as well as the upcoming" Ionosat-Micro" experiment onboard the "Microsat-M" satellite. The main innovation of the project is the launching into the ionosphere of a cluster of several (presumably 3) spacecraft equipped with identical sets of scientific instruments in order to provide simultaneous measurement of gas-plasma and electrodynamics parameters of the ionosphere. "ClusterIon" payload composition: Ion drift-meter ID, Electron temperature and concentration probe ETP; Magneto-Wave Complex MWC, including vector flux-gate magnetometer FGM, vector search-coil magnetometer IM and 2 electric potential probes EP.

Digital fluxgate magnetometers employ processing of the measured pickup signal to produce the value of the compensation current. Using pulse-width modulation with filtering for digital to analog conversion is a convenient approach, but it can introduce an intrinsic source of nonlinearity, which we discuss in this design note. A code shift of one least significant bit changes the second harmonic content of the pulse train, which feeds into the pick-up signal chain despite the heavy filtering. This effect produces a code-dependent nonlinearity. This nonlinearity can be overcome by the specific design of the timing of the pulse train signal. The second harmonic is suppressed if the first and third quarters of the excitation period pulse train are repeated in the second and fourth quarters. We demonstrate this principle on a digital magnetometer, achieving a magnetometer noise level corresponding to that of the sensor itself.

Small weight and dimensions of the micro- and nanosatellites constrain researchers to place electromagnetic sensors on short booms or on the satellite body. Therefore the electromagnetic cleanliness of such satellites becomes a central question. This paper describes the theoretical base and practical techniques for determining the parameters of DC and very low frequency magnetic interference sources. One of such sources is satellite magnetization, the reduction of which improves the accuracy and stability of the attitude control system. We present design solutions for magnetically clean spacecraft, testing equipment, and technology for magnetic moment measurements, which are more convenient, efficient, and accurate than the conventional ones.

The electromagnetic cleanliness becomes first priority problem for small satellites with very compact design, especially for CubeSats, what greatly impedes their application for scientific research, especially for electromagnetic ones. The analysis of electromagnetic interferences sources is given and the ways how to decrease their influence at satellite design are recommended. The instrument for electromagnetic cleanliness measurement and its operation algorithm are proposed.

We presented an approach to understanding the performance of a fully digital fluxgate magnetometer. All elements of the design are important for the performance of the instrument, and the presence of the digital feed-back loop introduces certain peculiarities affecting the noise and dynamic performance of the instrument. Ultimately, the quantisation noise of the digital to analogue converter is found to dominate the noise of the current design, although noise shaping alleviates its effect to some extent. An example of magnetometer measurements on board a sounding rocket is presented, and ways to further improve the performance of the instrument are discussed.

The reduction of financial support of space scientific research forces the scientists to develop new small spacecrafts for the experiments realization. The most popular recently are cubesats which are available as commercial construction kit with the size 10×10×10 cm, by this several cubes (nU) may be connected together. But with such kits mostly technological and demonstration experiments may be realized. To create scientific grade structure able to provide high resolution measurements within so small volume it is necessary to solve several important problems, between which the most complicated one is providing electromagnetic compatibility of all units composing the nU cubesat and electromagnetic cleanliness (EMC) of all structure. The goal of this report is to outline the problems connected with the EMC procurement within so small and densely packed volume. Also a dedicated system development which will be able to determine the electromagnetic interference sources location and their radiated power is described. The results of experimental works realized with such a system during the development of 3U cubesat for electromagnetic study in space plasma are discussed.

The main goals of the Chibis-M mission are the testing of a new micro-satellite technology, the study of new physical processes related to lightning activity and the verification of possible monitoring techniques of Space Weather phenomena. In frames of the Chibis-M mission an electromagnetic wave complex MWC is installed on board of the satellite composed of electromagnetic sensors and SAS3 measuring unit. The obtained data show that the scientific instrumentation operates properly and produces interesting information. Here we present the first results of the first year of operation of the MWC in the ELF–VLF bands in different operation modes. An important conclusion is that basing on the experience of the first year it is possible to realize an effective and reliable Space Weather monitoring system using micro-satellites and simultaneously operating ground support equipments.

The objective of the SQUID project is to develop and in flight verify a miniature version of a wire boom deployment mechanism to be used for electric field measurements in the ionosphere. In February 2011 a small ejectable payload, built by a team of students from The Royal Institute of Technology (KTH), was launched from Esrange on-board the REXUS-10 sounding rocket. The payload separated from the rocket, deployed and retracted the wire booms, landed with a parachute and was subsequently recovered. Here the design of the experiment and post fight analysis are presented.

Valery Korepanov, vakor@isr.lviv.ua Lviv Centre of Institute of Space Research NAS-NSA of Ukraine, Lviv, Ukraine Igor Rokityansky, rokityansky@gmail.com Ukraine Fedir Dudkin, fd@isr.lviv.ua Lviv Centre of Institute of Space Research NAS-NSA of Ukraine, Ukraine Serhiy Belyayev, belyayev@isr.lviv.ua Lviv Centre of Institute of Space Research NAS-NSA of Ukraine, Lviv, Ukraine Artem Tereshin, rokityansky@yahoo.com Ukraine

The fluxgate magnetometers (FGM) are probably the most widespread instruments used onboard spacecrafts for both scientific and service purposes. The recent trend to decrease the weight and size of the spacecrafts requires creating as small as possible but enough sensitive FGM. A joint Swedish-Ukrainian team made the development of such a magnetometer and as the result the Small Magnetometer In Low mass Experiment (SMILE) a digital fluxgate microsatellite magnetometer – was created [1]. Majority of electronic units of this FGM were combined in a digital integrated circuit a Field Programmable Gate Array (FPGA). The FPGA provides full processing (determined by a digital correlation algorithm) of amplified and digitized fluxgate sensor output signals and provides both FGM output data and feedback signals. Such digital design makes the instrument very flexible, reduces power consumption and opens possibilities for customization of the operation modes. It allows miniaturizing the electronic unit and, together with the smallest in the world low noise three-component fluxgate sensor with the side dimension of 20 mm and weight about 20 grams only, the small but enough sensitive space qualified FGM is created. SMILE magnetometer was successfully flown onboard the NASA Cascades-2 sounding rocket, and is to fly in the LAPLander package onboard the ESA REXUS-8 student sounding rocket [2]. Unfortunately, such a design of electronic circuit does not allow us to realize all possibilities of the miniature sensor. The separate tests of the sensor with highest-class analog electronics showed that its noise level may be reduced to as low value as 10. . . 15 picoTesla at 1 Hz. Also the use of volume compensation in the sensor provides high geometrical stability of the axes and improved performance compared to component compensated sensors. The measured parameters appear to be comparable or even better than these of best stationary FGM and, if realized in small enough volume and weight, such a sensitive but small FGM could be a good candidate for planned Lunar missions where the weight is the major restriction factor. This stimulated further research in the direction of the analysis and elimination of noise sources of digital design, as well as of the optimization of FGM electronic circuit structure. The description of the obtained results of the electronic unit upgrade and recent FGM model tests are given and future improvement directions are discussed. These works are partially supported by NSAU contract No. 1499.

The Small Magnetometer in Low-Mass Experiment (SMILE) is a miniaturized triaxial fluxgate magnetometer with volume compensation incorporating efficient signal processing algorithms within a field programmable gate array (FPGA). SMILE was designed in collaboration between the Lviv Centre of Institute for Space Research (LC ISR) in Ukraine where the sensor was developed and the Royal Institute of Technology (KTH) in Stockholm, Sweden where the electronics used to operate the instrument were designed and programmed. The SMILE magnetometer compares well with modern digital FGMs in resolution (20 bit, corresponding to 0.1 nT per bit ) and sample rate (up to 250 sample per second), but has significantly lower consumption (about 260 mW), smaller size (the sensor 20x20x20 cubic millimeters, the first prototype of the electronic board – 120x80 square millimeters) and lower weight (the sensor 21 g and the board 80 g). Using the cubic coils for volume compensation, optimizing the sensor design and using Macor for main sensor parts resulted in achieving uniquely stable geometric parameters for such a small sensor. A calibration of the SMILE instrument was carried out at the Nurmijarvi Geophysical Observatory, showing high linearity (deviation no more than 6 nT along total ±50 μT scale) and low orthogonality error (<22 arcmin). The temperature coefficients of the scale factors were below 11 ppm/C and the deviation of the magnetic axes was about 3 arcsec per C in the range of −30 to +45 centidegrees. The bar-core fluxgate sensors are based on the two strips of amorphous Co–Fe–Si–B alloy of the dimensions 16x1x0.02 cubic millimeters. The sensors noise level is less than 30 pT/sqrt(Hz)at 1 Hz that it is rather good for such modest magnetic core volume. In the recent publications [1-3] the peculiarities of the electronic unit design, the signal detection algorithm and the results of the numerical simulation of the sensor magnetic core behavior during its excitation were described. In this report the possibilities to reduce total power consumption and noise level of the SMILE instrument will be considered. First of all we will present a new approach to the synthesis of the compensation coil system that allows considerably enlarge the sensor length relatively to the coil system dimensions simultaneously keeping the errors caused by compensation field non-uniformity as small as possible. The novel approach is based on the fitting of the spatial distribution of the compensation field to the sensor core dimensions. Another advantage of the proposed technique is rather simple construction of coil windings. The experimental test bench and the results, which prove the effectiveness of the proposed solution, will be described too. Secondly, the analysis of the consumed power of the magnetometer components will be made. Basing on the improved design of the super low power analogue magnetometer LEMI-031 recently developed in LC ISR, the applicability of the novel engineering solutions for decreasing power consumption of both the sensor and some electronic blocks of the SMILE instrument will be considered. And finally the possibilities of the noise level decreasing of the sensor will be studied. The last issue is very important for successful using of the modified version of the SMILE instrument in the Global Electromagnetic Moon Surveyor (GEMS) payload for the Indian spacecraft Chandrayaan-II.

A novel design of an Earth field digital fluxgate magnetometer is presented, the small magnetometer in low-mass experiment (SMILE). The combination of a number of new techniques results in significant miniaturization of both sensor and electronics. The design uses a sensor with volume compensation, combining three dual rod cores in a Macor (R) cube with the side dimension of 20 mm. Use of volume compensation provides high geometrical stability of the axes and improved performance compared to component compensated sensors. The sensor is operated at an excitation frequency of 8 kHz. Most of the instrument functionality is combined in a digital signal processing core, implemented in a field programmable gate array (FPGA). The pick-up signal is digitized after amplification and filtering, and values of compensation currents for each of the axes are determined by a digital correlation algorithm, equivalent to a matched filter, and are fed to a hybrid pulse-width modulation/delta-sigma digital-to-analogue converter driving the currents through the compensation coils. Using digital design makes the instrument very flexible, reduces power consumption and opens possibilities for the customization of the operation modes. The current implementation of the design is based on commercial off-the-shelf components. A calibration of the SMILE instrument was carried out at the Nurmijarvi Geophysical Observatory, showing high linearity (within 6 nT on the whole +/- 50 mu T scale), good orthogonality (22 arcmin) and very good temperature stability of the axes.