Geophysical Institute Research Articles

Structure of the Kathmandu basin inferred from microtremor measurements: a preliminary study

SUMMARY This research aims at characterizing the deep sedimentary basin of Kathmandu (Nepal) from microtremor measurements, by using two surveys carried out in November 2015 and November 2018. The data collected are sufficient for a qualitative investigation of the seismic response of such a complex basin. The measurements were undertaken in the framework of a collaboration between the NSET (National Society for Earthquake Technology, Nepal) and the OGS (National Institute of Oceanography and Applied Geophysics, Italy). During the two campaigns, a series of passive seismic surveys were made, taking into consideration both single broad-band sensors and arrays. The 2015 study initially focused on the Lalitpur area (southern part of Kathmandu) and was later extended to the northern and more urbanized area of the capital city of Nepal. The 2018 survey focused on estimating the S-wave velocity field of the entire stratigraphic sequence by array and a repetition of some Horizontal to Vertical Spectral Ratio (HVSR) measurements close to two boreholes with reliable stratigraphy. Two inversion methods, using the data from the seismic arrays, were useful to infer the S-wave velocity profiles of the shallower layers and to interpret some HVSRs. The outcome is a map of the periods of single station data representing the seismic response of the basin. Comparing these results with the strong motion data of the Gorkha 2015 main shock, we confirm that the longer periods are not only the effects of the earthquake source, but also of the local response of the basin itself.

A Multidisciplinary Approach to Evaluate the Environmental Impacts of Hydrocarbon Production in Khuzestan Province, Iran

From the late 1900s onward, hydrocarbon exploitation has led to severe environmental footprints in the Khuzestan province, Iran. However, no comprehensive study has been conducted to evaluate such issues. In this research, an inclusive analysis was performed to investigate these environmental impacts. To do this, first, two datasets related to a 15-year period (2006–2021) were collated: the satellite data from the Sentinel-1 mission and the seismic data recorded by the National Iranian Geophysics Institute as well as the catalog of the global Centroid Moment Tensor project (CMT). These datasets were processed using generic mapping tools (GMT), differential synthetic aperture radar (D-InSAR) techniques, and multiple processing algorithms using a specific toolbox for oil spill application in the sentinel application platform (SNAP) programming, respectively. The results revealed three critical footprints, including regional earthquakes, land subsidence, and oil spill issues in the area. The most frequent earthquakes originated from depths less than 15 km, indicating the disturbance of the crustal tectonics by the regional hydrocarbons. Furthermore, an annual rate of land subsidence equal to 10–15 cm was observed in the coastal areas of the Khuzestan province. Moreover, two regions located in the north and west of the Persian Gulf were detected as the permanently oil-spilled areas. The applied methodology and results are quite applicable to restrict the harmful consequences of hydrocarbon production in the study area. This research will benefit not only government officials and policymakers, but also those looking to understand the environmental challenges related to oil and gas production, especially in terms of sustainable goals for the management of natural resources.

Nature of radioactivity of quarry drainage waters in the Novosibirsk region

This study is relevant for obtaining the first geochemical data (including information on radionuclides) on the drainage waters of developed and flooded quarries in the eastern areas of the Novosibirsk Region. The objective of the study was to identify the features of the chemical composition of drainage waters (a wide range of chemical elements from Li to U). The study was carried out by titrimetry, ion chromatography and mass spectrometry with inductively coupled plasma in a laboratory setting at the Hydrogeochemical Problem Research Laboratory (PNIL GGH) of the Engineering School of Natural Resources of Tomsk Polytechnic University (IShPR TPU). Measurements of 222Rn in waters were carried out at the Alfarad Plus facility of the Laboratory of Siberian Sedimentary Basins Hydrogeology of the A. A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences (INGG SB RAS). The data were divided into homogeneous geochemical populations using the coefficients Ca / Na, Ca/ Mg, Ca / Si, Mg/ Si, Na / Si. The chemical composition of the studied objects was found to be highly diverse. The dominant waters have the chemical formula SO4-HCO3 / Na-Mg-Ca with a TDS (total dissolved solids) of 400 to 700 mg/dm3. Three geochemical groups of waters were identified. The first is represented by drainage waters of the developed rubble stone quarries, the second includes facilities of the Gorlovka coal basin, and the third refers to abandoned flooded quarries. The first group is characterized by oxidizing conditions with Eh varying over a wide range from +84.6 to +261.0 mV, pH from 6.9 to 8.6, and O2dissoived from 3.43 to 14.39 mg/dm3. The radionuclide concentrations are (mg/dm3): 238U 9.30 • 10-3 - 1,40; 232Th 1,00 • 10-6 - 2,16 • 10-3; 222Rn activity varies from 1 to 572.5 Bq/dm3. The 232Th / 238U ratio ranges from 4.20 • 10-5 to 2.69 • 10-3 with an average of 8.40 • 10-4. The second group has a smaller Eh variation range of +133.2 to +199.6 mV, pH from 7.5 to 8.5, and O2dissolved from 6.81 to 10.43 mg/dm3. The radionuclide concentrations vary in the following ranges (mg/dm3): 238U 2.26 • 10-3 - 2.90 • 10-2; 232Th 7.5 • 10-6 - 5.57 • 10-4. The 232Th / 238U ratio ranges from 8.37 • 10-4 to 4.80 • 10-2 at an average of 9.54 • 10-3. The third group is also characterized by an oxidizingizing geochemical environment with Eh +131.3 - +250.0 mV, pH from 6.9 to 8.8 and O2dissolved from 4.00 to 16.59 mg/dm3. The radionuclide concentrations are (mg/dm3): 238U 3.00 • 10-4 - 2.74 • 10-2; 232Th 1.65 • 10-6 - 1.15 • 10-5; 222Rn activity varies from 2 to 31 Bq/dm3. The 232Th/ 238U ratio ranges from 2.36 • 10-4 to 1.02 • 10-3 at an average of 6.25 • 10-4. Overall, the 232Th / 238U ratio of the studied waters indicates their uranium nature of radioactivity. The data obtained indicate a slight impact of the drainage water discharge from the abandoned quarries on the environment.

Ask me anything: Nicholas Attree

Nicholas Attree is a postdoctoral researcher at the Institute for Geophysics and Extraterrestrial Physics at the Technical University of Braunschweig in Germany, studying comets through the European Space Agency’s Rosetta and Comet Interceptor missions.

Simulated Long‐Term Evolution of the Ionosphere During the Holocene

AbstractTo date, no natural media is available to derive the “ancient” ionosphere, so the current understanding of ionospheric long‐term trends mainly comes from analyzing ∼70 yr modern measurements supplemented by theoretical simulations. In this study, for the first time, we expanded the ionosphere simulation to the whole Holocene (9455 BCE to 2015 CE) using the Global Coupled Ionosphere‐Thermosphere‐Electrodynamics Model developed at the Institute of Geology and Geophysics, Chinese Academy of Sciences, driven by a realistic geomagnetic field, CO2 level, and solar activity, all of which are a combination of ancient media derivations and modern observations. Through a series of control runs, we found that the ionospheric oscillation of the global mean profile is characterized by a nonlinear variation versus geomagnetic field effect, a decrease (increase) above (below) ∼200 km due to CO2 increase, and violent oscillations in phase with changes in solar activity, with corresponding contributions of approximately 20%, 20%, and 60%, respectively. The CO2 effect became nonnegligible and even more significant after ∼1800 CE. The solar activity effect is marked by a frequently occurring grand solar minimum. The ionospheric characteristics show linear variations versus the dipole moment of the geomagnetic field, the CO2 level, and the F10.7 index, with the growth rate having significant local time and latitude variations. Our prediction shows that a 400 ppm CO2 increase will cause a global mean decrease of 1.2 MHz in foF2, 34 km in hmF2, and 4 tecu in TEC, which will directly influence radio wave communication.

Microphysical measurements of hydrometeors using shadowgraph imaging technique

The size distributions of raindrops and precipitation particles were measured in a series of in situ experiments during various weather events in Warsaw, Poland. To perform the measurements, a shadowgraph instrument, “VisiSize D30”, was set up on the roof of the Institute of Geophysics, University of Warsaw, together with an “OTT Parsivel2” laser disdrometer. The VisiSize D30, recently introduced to atmospheric research, is capable of accurately determining a wide range of particle sizes, from micrometre-scale cloud droplets to millimetre-scale precipitation particles, while directly measuring droplets by capturing shadow images of them. A comparison of the data collected by the two instruments during simultaneous measurements shows that combining the shadowgraph technique with the optical disdrometer can prevent droplet size distribution truncation and provide more accurate results.

Auroral Drivers of Large dB∕dt During Geomagnetic Storms

AbstractForecasting geomagnetically induced currents (GICs) remains a difficult challenge, and open questions hindering our understanding include when and where GICs become large and what magnetospheric and ionospheric processes are responsible. This paper addresses these questions by determining the auroral drivers of large dB∕dt (>100 nT/min, a proxy for GICs) on the ground during geomagnetic storms. We study auroras because, although the current system driving dB∕dt is at times challenging to reconstruct, the accompanying auroras are routinely measured in high resolution. For various types of auroras, our community has already acquired a deep understanding of the driving mechanisms and spatiotemporal characteristics. Using coordinated observations from THEMIS and Geophysical Institute Magnetometer Array magnetometers and THEMIS all‐sky imagers, we statistically examine large dB∕dt intervals during storms from 2015 to 2016. A variety of auroral drivers have been identified, including poleward expanding auroral bulges, auroral streamers, poleward boundary intensifications, omega bands, pulsating auroras, etc. The onset, spatial variability, and duration of large dB/dt are well explained by those of the auroras. For example, poleward expanding auroral bulges drive large dB/dt that spread progressively poleward, and periodic injections of streamers drive large dB/dt that occur in periodic bursts. By referring to the magnetospheric source of the auroras, the magnetospheric source of large dB/dt can be inferred, whether it be dipolarization of the tail magnetic field, bursty bulk flows, instability, or wave‐particle interaction. Our results suggest that auroras can exert significant leverage on GIC research and forecast.

LZER0: A Cost-Effective Multi-Purpose GNSS Platform.

Recent advances in Global Navigation Satellite System (GNSS) technology have made low-cost sensors available to the mass market, opening up new opportunities for real-time ground deformation and structure monitoring. In this paper, we present a new product developed in this framework by the National Institute of Oceanography and Applied Geophysics-OGS in collaboration with a private company (SoluTOP SAS): a cost-effective, multi-purpose GNSS platform called LZER0, suitable not only for surveying measurements, but also for monitoring tasks. The LZER0 platform is a complete system that includes the GNSS equipment (M8T single-frequency model produced by u-blox) and the web portal where the results are displayed. The GNSS data are processed using the RTKLIB software package, and the processed results are made available to the end user. The relative positioning mode was adopted both with real-time and post-processing RTKLIB engines. We present three applications of LZER0-cadastral, monitoring, and automotive-which demonstrate that it is a flexible, multi-purpose platform that is easy to use in terms of both hardware and software, and can be easily deployed to perform various tasks in the research, educational, or professional sectors.

Changes in near-surface permafrost temperature and active layer thickness in Northeast China in 1961–2020 based on GIPL model

Characteristics of active layer processes depend on the conditions of the ground surface, coupled water-heat balance, soil hydrology, and soil properties under frozen and thawed states at shallow depths. Mean annual temperature at the bottom of the active layer (MATBAL) and active layer thickness (ALT) are important metrics in studying the features of active layer processes and the thermal stability of permafrost. Affected by the changing climate, permafrost regions in Northeast China have undergone remarkable changes in the past 30 years, many of which are still ongoing. In Northeast China, however, model studies on examining hydrothermal dynamics and on changes in frozen ground have faced serious challenges, including a complex ecological environment and rugged terrains. In this study, the Geophysical Institute Permafrost Lab (GIPL) model was used to map temporal and spatial variations in MATBAL and ALT in Northeast China, where discontinuous, island, and sporadic permafrost coexists with seasonal frost. Using the parameters of ground surface temperature (GST) and soil properties as input, we applied the GIPL model to analyze the distributive characteristics of near-surface permafrost in Northeast China. The results indicate a sharply shrinking permafrost area from 5.49 × 105 to 2.29 × 105 km2 but rapidly rising rates of 0.17–0.83 °C/decade in MATBAL in Northeast China during the period from 1961 to 2020. Under a persistently warming climate, accelerating permafrost degradation will inevitably affect the hydrological environment, boreal ecosystem, soil biology, and engineering infrastructure. This work fills a gap in the distribution of MATBAL and ALT in Northeast China.

A Robust Algorithm for Multi-GNSS Precise Positioning and Performance Analysis in Urban Environments

In this paper, we propose a partial ambiguity method of global navigation satellite system (GNSS) reliable positioning based on a robust estimation model to address the problems of the low reliability and availability of GNSS positioning in urban complex environments. First, the high-precision observations selected on the basis of the signal-to-noise ratio (SNR) were used to solve ambiguities. Then, the fixed ambiguities were used as constraints to solve the ambiguities of low-quality observations. The robust estimation method was used to reduce the impact of outliers for the ambiguity solutions. The robust estimation was also used to solve the position parameters to reduce the influence of the residual errors and uncorrected ambiguities for GNSS high-accuracy positioning. Static and dynamic data were used to evaluate the proposed algorithm. These experiments show that the proposed algorithm with the robust estimation can reduce the fixed time of ambiguity initialization, compared with the conventional algorithm without the robust estimation. The positioning accuracy and solution rate are similar regardless of whether the robust estimation is used in the GNSS unblocked environment. In blocked environments, the solution rate improves to more than 99%, and the three-dimensional (3D) position accuracy improves by more than 70% when the robust estimation is used. When the observation number of simulated small gross error accounts for 40.91% of total observations, the centimeter-level positioning accuracy can still be obtained via several robust estimation models. In the urban blocked environment, the IGG (Institute of Geodesy and Geophysics) III scheme has a better performance than other robust schemes discussed in this paper with regard to the positioning performance and computational efficiency.

Сейсмический датчик для систем мониторинга. Разработка и результаты

The short-period seismic sensor IGES-006 developed at the NAS RA Institute of Geophysics and Engineering Seismology after A. Nazarov is presented. The IGES-006 sensor can be used both as part of various seismic monitoring systems and for solving special engineering problems. The sensor prototype has successfully passed laboratory and field tests, including the seismic monitoring mode. A comparative analysis of seismic signals recorded using IGES-006 and sensors in the time and frequency domains have been carried out.

System of Imaging Photometers for Upper Atmospheric Phenomena Study in the Arctic Region

A Pulsating Aurora Imaging Photometers Stereoscopic System (PAIPS) is suggested and described in the paper. The system is based on two lens telescopes with a matrix of multianode photomultiplier tubes as photodetectors placed in two high latitude observatories of the Polar Geophysical Institute. Telescopes provide simultaneous observations of a large volume of the atmosphere at altitudes in the range 50–100 km with high temporal resolution (up to 2.5 μs) and a spatial resolution of about 2 km. This is a novel system for pulsating aurora study aimed to determine the energies of precipitating electrons responsible for the pulsating aurora occurrence. The system can be used for other atmospheric phenomena studies: meteors, transient luminous events, etc. One telescope has been operating since September 2021 and has measured a variety of optical phenomena.

A Temporary Broadband Seismic Array in the Largest Desert of China: TASTE

Abstract In early Permian, a mantle plume heated up the Tarim block and formed the Tarim large igneous province. It is an interesting phenomenon to explore the interaction between mantle plume and a thick continent lithosphere, because mantle plume has been proposed to be an important route of material and energy transportation in the earth. Currently, the Tarim block is surrounded by Tibetan plateau to its south edge and Tian Shan orogeny to its north edge. The combined effects of both mantle plume activity and plate tectonics should have significantly changed the structure and composition of the Tarim block because of its amalgamations in Neoproterozoic. Seismic imaging plays a key role on revealing the deep structure of the Earth, which could help unravel the questions mentioned before. However, the harsh natural environment in the central part of the Tarim basin, the Taklimakan desert—the largest desert in China—has seriously hampered the broadband seismological observation. From July 2017 to November 2019, the Institute of Geology and Geophysics, Chinese Academy of Sciences deployed a 2D broadband seismic array named the Tarim seismic Array for lithoSpheric signaTure of mantle plumE (TASTE) over the inner part of the Tarim basin with an averaged spacing of 60–70 km. The primary target of this project is to obtain a detailed lithospheric structure to resolve the possible lithospheric signatures of Permian mantle plume activity. Here we introduce the basic information of the TASTE network and the performance of these instruments by analyzing the background noise level. Preliminary results of receiver function and ambient noise analyses are also shown, which may suggest a thick sedimentary layer, as well as complicated crust and lithospheric feature.

Orbit Predictions for Space Object Tracked by Ground-Based Optical and SLR Stations

In many cases, we have few optical observations over a short time span, and most of the information generated is too limited to compute a full orbit according to the angles-only method. This study aims to develop a mathematical model to determine the precise orbit from the optical observation data by the least squares method. We have used a set of the Global Navigational Satellite Systems, which are tracked by the Optical Satellite Tracking Station (OSTS) at the National Research Institute of Astronomy and Geophysics (NRIAG), Egypt, to access high-quality predictions for the orbits. We analyzed the orbit predictions from the observations of these satellites that are tracked from seven world stations using the laser ranging method, and the obtained results are compared with orbital elements produced using the Two-Line Element (TLE). The results showed that the orbital prediction accuracy differs for optical observations from laser observations because of the inaccuracy of the NORAD catalog information used; this is due to the difference between the time of observation and the epoch time of TLE.

Dependence of the Index of Biologically Active Ultraviolet Radiation on the Season and Time of Day

In the present work, the data from the monitoring of the biologically active ultraviolet (UV) radiation of the Sun at the National Institute of Geophysics, Geodesy and Geography, Bulgarian Academy of Sciences for the period 2007–2021 were used. Based on the data analysis, a statistical method is proposed for determining the UV radiation index values in clear weather. As a result, estimated values of the UV-Index for each day of the year and for each hour are obtained, which can be used for predicting when reporting the cloud forecast. In the present paper, the applicability of the theoretical dependence of the UV-Index on the square of the cosine of the zenith angle of the Sun is investigated. The seasonal dependence of UV-Index values at fixed zenith angles of the Sun is discussed. Through regression analysis, the influence of the Total Ozone Column (TOC) and the concentration of particulate matter with d < 10 μm (PM10) on the UV-Index in the conditions of the city of Sofia was investigated. Explanations of the obtained results are offered.

Evaluation of indoor/outdoor urban air pollution by magnetic parameters; preliminary study

The paper presents a comparison of outdoor and indoor air pollution by means of magnetic properties of dust gathered outdoors and indoors on air filters. Outdoor dust (particulate matter smaller than 10 μm, PM10) was collected by means of a PM sampler that was placed in the yard of the building of the Institute of Geophysics, Polish Academy of Sciences (IG PAS), in Warsaw, Poland. Indoor dust samples were collected with the same type of PM sampler, placed inside this building. The magnetic methods were applied for the estimation of concentration and magnetic mineralogy of the magnetic particles present in PM. Magnetic measurements, such as low and high-temperature dependence of volume magnetic susceptibility κ(T), hysteresis parameters, and frequency dependence of mass magnetic susceptibility χfd show that outdoor and indoor PM contain ultra-fine-grained magnetite-like minerals, particularly in a size range < 30 nm. This pointed to the common outdoor sources of pollution intruding inside the building through windows, ventilation systems, and partly carried on dresses by people. The mass of PM10 collected outdoors is of the same range as the mass of PM10 from inside the building. The mass susceptibility of indoor filters, however, is about 1/3 of the mass susceptibility of outdoor filters. The relationship between volume susceptibility and mass indicates a relatively homogenous composition of indoor dust but a varying composition of outdoor dust, with a variable influx of nonmagnetic exogenous particles.

History of Kakioka Magnetic Observatory

Abstract. Kakioka Magnetic Observatory (KMO) was founded in 1913 by the Central Meteorological Observatory (CMO, later the Japan Meteorological Agency) as a successor to Tokyo Magnetic Observatory. Kakioka was a village 70 km north of Tokyo and was selected to escape from tram noise in Tokyo. At first, it was an unstaffed observatory only for geomagnetic field observation. Then, the Great Kanto Earthquake in 1923 changed the fate of KMO because the earthquake severely damaged the CMO in Tokyo, and recording papers of KMO were lost. KMO was staffed in 1924 and was redesigned as an institute for geophysics rather than geomagnetism. KMO operated a variety of observations, such as the atmospheric electric field, the geoelectric field, the seismicity, the air temperature, the wind velocity, the sunspot and solar prominence as well as the geomagnetic field, by the 1940s. In addition, research activity flourished with the leadership of the first director, Shuichi Imamichi. After World War II was over in 1945, KMO formed a network of observatories in Japan by founding several branch observatories originally for geoelectric field observation. Two branch observatories at Memambetsu and Kanoya survived, with geomagnetic field observation added in the International Geophysical Year project (1957–1958). Efforts in development of instruments for geomagnetic absolute measurement and systems of high-sampling recordings in the 1950s to 1970s resulted in the development of the Kakioka Automatic Standard Magnetometer (KASMMER) system in 1972. KASMMER measured the geomagnetic field every 3 s at the highest standard in the world in digital form, giving 1 min digital values of the geomagnetic field available. This system has been updated, and the high-sampling technology was applied to geoelectric field observation and atmospheric electric field observation. Later, adding geomagnetic field observation at Chichijima in 1971, KMO established a unique electric and magnetic observation network at Kakioka, Memambetsu, Kanoya and Chichijima and provided precise and high-speed sampling data (1 min, 1 and 0.1 s values) by 2001. On the other hand, KMO gradually terminated or automated their observations and reduced their staff in the last several decades following the government's reform policy. The two branch observatories at Memambetsu and Kanoya were unstaffed in 2011, and the atmospheric electric field at Memambetsu was terminated at that time. The geoelectric field observations at Kakioka, Memambetsu and Kanoya were terminated in 2021 as well as the atmospheric electric field at Kakioka. KMO focuses on geomagnetic observation for now and puts efforts into total force observation at volcanoes and the digitization of historic analog data.

Juda Kreisler (1904–1940s?): A Bio-Bibliographical Sketch of a Lviv Physicist and a Popularizer of Science

We present a detailed biographical account and analysis of works of Juda Kreisler (1904–1940s?), a theoretical physicist from Lviv. He was born in Tlumach (Ukrainian: Тлумач, Polish: Tłumacz, Yiddish: טאלמיטש ), nowadays a town in Ivano-Frankivsk oblast in the western part of Ukraine. In 1923, Juda Kreisler finished a gymnasium in Stanislaviv and entered the Philosophical Faculty of the University of Lviv (Wydział Filozoficzny Uniwersytetu Jana Kazimierza [UJK] we Lwowie) in order to study physics. In 1932, he was promoted to the doctoral degree in physics under the supervision of Professor Stanisław Loria. For a short period in the 1930s, Juda Kreisler worked at the Department for Theoretical Physics of the University of Lviv, and returned to the University in 1940, after the Soviets had reorganized it upon taking over Lviv in September 1939. His fate remains unknown: he is listed among murdered by Nazis Jewish employees of the University of Lviv in 1941–43. Dr. Kreisler authored four scientific papers and four abstracts of conference presentations delivered at the Congresses of Polish Physicists in 1932–36. There is, however, another field, where he was extremely prolific in the late 1930s. We have discovered 122 of his popular articles in “Chwila” (English: “Moment”), a local daily newspaper published by the Jewish community in Lviv during 1919–39. These articles covered various subjects, that can be tentatively divided into the following major topics: chronicles and personalia; history of science; discoveries, new studies and inventions; the applied value of science (for medicine and economy in particular); interconnection between science and war; organization of scientific life; Hitler’s Germany and the problem of so-called ‘Aryan science’. While various branches of physics formed the largest part within disciplines reflected in Juda Kreisler’s articles, he also discussed biology, chemistry, meteorology, and geology. The latter field is closely related to his professional career at Lviv’s Geophysical Institute of “Pionier”, a joint-stock company for the exploration and exploitation of bituminous materials, where he spent nine months in 1936.

Development of the Sanya Incoherent Scatter Radar and Preliminary Results

AbstractLed by the Institute of Geology and Geophysics, Chinese Academy of Sciences, we have built a brand‐new modular active digital phased array, with all solid‐state transmission and digital receiving incoherent scatter radar (ISR) in Sanya (18.3°N, 109.6°E), a station in low latitude China called Sanya ISR (SYISR) since 2015. The development of SYISR involved the indoor design and development of key components, an outdoor prototype test, and the production and debugging of the entire array. The unique features of SYISR include a single‐channel directly connected T/R unit and antenna, a radar array monitoring and calibration network, environmental adaptability design and open architecture. The entire radar has 4,096 channels and 5,930 modules in total. All the technical indices, mainly including a &gt;2 MW peak power, a 43 dBi antenna gain and a &lt;120 K noise temperature, either meet or are superior to the designed value through an independent evaluation. Waveforms of single pulse, linear frequency modulation, Barker code, long pulse and alternating code have been implemented to meet multiple purposes. Four observational modes for ionospheric experiments, including zenith stare, perpendicular to geomagnetic field, meridian scan, and all sky scan, have been developed. We have implemented time domain decoding, frequency domain decoding, and statistical inversion methods in calculating the autocorrelation function and power spectra in signal processing. The preliminary experimental results on ionospheric parameters, plasma lines, irregularities and hard targets are reasonable and encouraging, which greatly enhances our confidence in achieving our scientific goals in the future.

The Test Flight of iFTEM-I Fixed-Wing Airborne Time-Domain Electromagnetic System in Binxian, Heilongjiang Province, China

The fixed-wing time-domain airborne electromagnetic method (FTEM) has been widely used in metal mining exploration, groundwater mapping and other fields worldwide, and in recent decades, its use has gradually also become more prevalent in China. The first generation of the fixed-wing time-domain airborne electromagnetic system (iFTEM-I), researched and developed by the Institute of Geophysical and Geochemical Exploration (IGGE), has been demonstrated in recent years. In this article, we introduce the brief working principle and system parameters of iFTEM-I, and we show that the effective prospecting depth of iFTEM-I is up to 350 m, which is indicated by a comparison of the results between iFTEM-I and a ground TEM system (TEM-30B) carried out in Binxian.