Southern Spectroscopic Observatory of the Valašské Meziříčí Observatory

The rapid development of recording technology over recent years, as well as increasingly higher demands for the accuracy of calculated multi-station meteor trajectories, led to the replacement of existing camera systems at individual stations of the CEMeNt network ( Central European Meteor Network ) with modern CMOS cameras with significantly higher sensitivity and higher (FullHD) resolution during July and August 2024. The expansion of the network to areas with very high quality observation conditions in the southern hemisphere was another step that will increase the quality of obtained data and also contribute to research of meteoric activity in the southern hemisphere, which until recently was practically neglected. The system concept was based on monitoring meteoric shower activity from two stations, where one is the controlling station equipped with spectrographs (La Silla Observatory) and the second serves as support for calculating multi-station trajectories (El Sauce Observatory). The Southern Spectroscopic Observatory of Valašské Meziříčí Observatory (SSOHVM) was created through collaboration between Valašské Meziříčí Observatory, the Astronomical Institute of the Czech Academy of Sciences (Exoplanet Research Group), and OBSTECH company (El Sauce Observatory).

Introduction

The pioneer in observing meteor showers in the southern hemisphere was the Australian DFN ( Desert Fireball Network ), whose operation began in test mode with three cameras in 2005. Isolated stations of the IMO VMN network ( International Meteor Organization Video Meteor Network ), mainly in Australia, have been active at southern hemisphere stations since 2011. CAMS network stations ( Cameras for All Sky Meteor Surveillance ) have been operating in New Zealand since 2014, with their full integration into the global CAMS network structure completed only in 2023. In 2013, the first stations of the Brazilian national network BRAMON ( Brazilian Meteor Observation Network ) were put into operation, which in 2015 consisted of 23 cameras. In 2016, automated cameras of the AMOS network ( All-sky Meteor Orbit System ) were installed in Chile, operated by the Faculty of Mathematics, Physics and Informatics of Comenius University in Bratislava, Slovakia. A change came with the development of the GMN network ( Global Meteor Network ), which was established in 2018. The first cameras of this network in the southern hemisphere were installed in 2022 in South Africa.

The installation of meteor cameras and spectrographs at high-altitude observatories (La Silla 2345 m above sea level, El Sauce 1603 m above sea level) in Chile brings numerous scientific and technical advantages that increase both the quality and quantity of obtained meteor data. High altitude means less atmosphere between the camera and meteor. This results in lower absorption and light scattering, especially in the near-UV region, where signal losses are otherwise considerable. This region is crucial for detecting spectral lines, such as Ca II emission lines (393.3 and 396.8 nm), which can reveal the chemical composition of the meteoroid and processes during its ablation. Dark, clear skies with minimal light pollution interference and minimal atmospheric scattering allow detection of meteors up to 1-2 magnitudes fainter than in lower-altitude locations. This means a contribution to studying smaller bodies in interplanetary space and obtaining larger data volumes for statistical analyses. La Silla and El Sauce are located in an area with very stable climate and minimal cloud cover. The number of clear nights is high (~320) and the observatories are usually above the inversion layer, which limits disturbing influences from the lower atmosphere. Cameras at higher altitudes can observe meteors to the horizon with less extinction. This extends the effective length of the observed trajectory and improves the accuracy of meteoroid trajectory calculations when using data from multiple stations. Meteor spectroscopy requires a high signal-to-noise ratio. Higher atmospheric transmission combined with lower background noise at high altitudes allows obtaining higher quality meteor spectra. It is thus possible to analyze weaker emission lines, track their temporal evolution, and determine the chemical composition of the meteoroid with greater accuracy. Meteors with high entry velocity (>50 km/s) begin ablating in very high atmospheric layers (~120 km and above). Observation from higher altitude increases the value of the initial height of the ablation trajectory and also the chance of obtaining time-resolved spectra from the beginning of ablation.

Equipment and Data Processing

Survey Cameras

The designed system is fully unified, using identical system component compositions at both stations. A board camera with Sony Starvis IMX 327 LQR CMOS chip (Fig. 5) was chosen as the imaging element, controlled via OSD menu. The camera provides analog FHD signal with 1920 × 1080 px resolution (2.1 MPx), chip size is 1/2.8", quantum efficiency 85%, and for the needs of stations in Chile (as well as for the entire CEMeNt network) the variant with NTSC analog output signal with 30 fps frame rate was chosen. The used high-speed Starlight lens (f/0.95) with M16 aperture and fixed focal length (4 mm) is capable of covering chips up to 1/2.7" size and in this configuration provides a field of view of 89 (± 1) × 50°. The conversion of analog signal to digital is realized in two stages. The cable distribution implemented with coaxial cable with copper signal carrier (75 Ω) is connected via BNC connector to the AHD/HDMI converter. The second converter (HDMI/USB 3.2) converts the signal to USB (up to 3.2) interface of the station computer using the MS 2130 conversion chip and ensures sufficient capacity for FHD signal transmission at the required frame rate. All steps of recording and processing individual meteor records are realized using the UFO Tools software package, which includes UFO Capture HD program (for HD resolution and higher) for meteor recording, UFO Analyzer v4.32 for meteor astrometry and photometry, and UFO Orbit v3.05, which serves for calculating multi-station meteor trajectories.

GMN network camera systems were also installed, which use board cameras with Sony Starvis IMX 291 LQR CMOS chip in IP configuration as imaging elements. The camera provides digital FHD signal, which is usually reduced to HD with 1280 × 720 px resolution (0.9 MPx) within the GMN network, chip size is 1/2.8", quantum efficiency 80%, and for the needs of stations in Chile (as well as for the entire GMN network) the variant with output signal at 25 fps frame rate was chosen. The used high-speed Starlight lens (f/0.95) with M16 aperture and fixed focal length (6 mm) is capable of covering chips up to 1/2.7" size and in this configuration provides a field of view of 59 (± 1) × 33°. All steps of recording and processing individual meteor records are realized by open source RMS programs, with mini PC Raspberry Pi 4 and 5 (or Radxa Rock Pi 4 and 5) used for camera control and data recording. In the case of installation at La Silla and El Sauce stations, Raspberry Pi 5 mini PC was used and it was not necessary to reduce the output FHD signal to HD, so the cameras use FHD resolution of 1920 × 1080 px.

Spectrographs

For recording meteor spectra at La Silla Observatory, QHY5III 678M CMOS cameras (Fig. 6) with 3856 × 2180 px resolution (8.4 MPx) were chosen. Chip size is 1/1.8", quantum efficiency 83%, and frame rate is set to 10 fps at full resolution with 16-bit output. The used varifocal Tamron lens (f/1.5) with variable focal length (4-13 mm) has a field of view of 80 (± 1) × 45° in this configuration, using a diffraction grating with 1000 lines/mm density. The used CMOS camera has increased quantum efficiency in the NIR range (~20% for 900 nm) while maintaining relatively good quantum efficiency for the NUV region (~30% for 350 nm). Meteor spectra detection is performed using FireCapture program in 3-minute sequences. The resulting sequence is divided into individual frames, each frame is subsequently corrected for dark frame and flat field, in the case of dark frames using images preceding the spectrum recording. Spectrum calibration in the x-axis is performed using a 4th order polynomial using known emission lines that occur in meteor spectra and considering the specific properties of each recorded spectrum (e.g., intensity ratio of the spectrum track after meteor passage, meteor velocity, relative brightness, etc.). Spectrograph sensitivity calibration as a whole (y-axis) in the range of observed wavelengths is performed by combining line and continuous emission spectrum sources (e.g., Ne or Hg lamps). For test operation purposes, spectrograph housings were equipped with windows made of ordinary optical glass with reduced efficiency in the NUV region.

Results

Overall Summary (06/2025)

The station at La Silla Observatory (telescope E152) consists of five survey cameras total, with four using UFO software and one using RMS. Four installed spectrographs have the same field of view center as the above-mentioned survey cameras using UFO software. The station at El Sauce Observatory consists of four survey cameras total, with three using UFO software and one using RMS. The azimuths and elevations of individual cameras are set so that the fields of view partially overlap, which ideally ensures recording of at least part of meteors from more than two cameras (Fig. 8). Additionally, the azimuth ±30° from the southern direction at La Silla Observatory is affected by the dome of telescope E152, which would interfere with the cameras' field of view in these directions.

The total number of recorded meteors during June 2025 from La Silla and El Sauce stations exceeded expectations. A total of 22,922 single-station meteors were recorded, from which 3,679 trajectories were calculated (Table 1; Figs. 11,12). Pairing efficiency is 39.13%, with cameras at La Silla station started on June 4, 2025, while cameras at El Sauce station were started on June 7, 2025. June is among the worst months of the year in this location in terms of clear nights, and additionally at La Silla station there was a higher number of favorable nights than at El Sauce station during June.

The station/trajectory ratio was 2.44, meaning that on average almost 2.5 meteor records from individual cameras correspond to one multi-station trajectory. When using qualitative reduction criteria applied within the EDMOND database ( European viDeo MeteOr Network Database ), the number of single-station meteors reached 18,948, the number of multi-station trajectories was 2,772, and the RAW/EDMOND trajectory ratio was 75.34%.

Meteor Shower Identification

In June, meteor shower activity on both hemispheres is low, with mainly meteor showers from the antihelion system with radiants in Ophiuchus, Sagittarius, and Scorpius being active. This corresponds to the overview of meteor showers with the highest number of recorded trajectories, with most trajectories corresponding to sporadic meteors (3,298), while independent clustering could not identify any unknown meteor shower with at least five trajectories. The highest number of recorded trajectories belonged to Southern mu Sagittariids (IAU MDC 0069 SSG; 65 trajectories), followed by Northern June Aquilids (0164 NZC; 44), delta Piscids (0410 DPI; 37), Southern June Aquilids (0165 SZC; 28), phi Piscids (0372 PPS; 19), Southern sigma Sagittariids (0168 SSS; 17), and Northern sigma Sagittariids (0167 NSS; 11). The modified trajectory similarity criterion D _N , defined by Valsecchi, was used as the basic tool for determining similarity between individual meteoroid trajectories. This criterion takes into account differences between orbital elements of the reference trajectory (e.g., catalog mean shower trajectory) and each meteor. For data processing and mean trajectory calculation of meteor showers from the trajectory set, a threshold value of criterion D _N < 0.1 was used. The DBSCAN algorithm ( Density-Based Spatial Clustering of Applications with Noise ) was applied to the input trajectory set from June 2025. This allows identification of areas of increased concentration without the need to predetermine the number of clusters. Key parameters were the maximum distance between two points in one cluster and the minimum number of points in a given area to be considered a cluster. The result is a statistically robust representation of the mean trajectory of individual substructures (clusters), these mean trajectories were compared with the existing list of meteor showers in the IAU MDC catalog ( International Astronomy Union Meteor Data Center ).

Southern mu Sagittariids (0069 SSG)

Southern mu Sagittariids are the southern branch of the mu Sagittariids complex, representing a relatively weak meteor shower. The meteor shower is active approximately between June 7 and July 6 with maximum around June 17 and corrected hourly rate lower than 3 meteors.

In June 2025, a total of 65 trajectories of Southern mu Sagittariids shower members were recorded, of which 56 were used for mean trajectory calculation using independent clustering and Valsecchi's trajectory similarity criterion with limitation D _N < 0.1 (Table 2, Fig. 13). Two meteor shower filaments were detected within independent clustering (SSG A and SSG B), and when increasing the trajectory similarity criterion limitation value, the two filaments did not merge, both filaments remained discretely separated. The average value of the similarity criterion of all SSG A filament members is D _N = 0.065±0.027, while for SSG B filament it is D _N = 0.036±0.016. The similarity criterion value between the mean trajectories of SSG A and SSG B filaments is D _N = 0.121, which shows the relationship between both filaments and we cannot speak of a different shower. The mean orbital trajectory of SSG A filament from data obtained at SSOVMO stations is consistent within standard deviation with the previously published mean orbital trajectory (Jenniskens, 2016), obtained from twice the number of meteors. When comparing both filaments, a difference in perihelion distance is evident as well as a shift in the mean radiant of SSG B filament in right ascension.

Meteor Spectra

The main goal of meteor spectroscopy is to better understand the physical and chemical properties of meteoroids through simultaneous video and spectral observations of meteors compared with laboratory spectra of meteoritic material. In June 2025, a total of 10 spectra from 8 individual bolides were recorded at La Silla station. Due to the nature of weather in the location during the mentioned period, most spectra are affected by high cloud cover.

For calculating the atmospheric trajectory of bolide 20250609_095442 SPO and the meteoroid trajectory in the Solar System, recordings from La Silla SW (Fig. 17), NW and El Sauce W and N stations were used. The bolide traveled an ablation trajectory of 59.2±0.1 km length in 1.07±0.01 s. Initial height was 125.5±0.1 km, final height 75.5±0.1 km, and the bolide reached maximum absolute magnitude -5.6±0.5 ^m . The body entered Earth's atmosphere at a relatively high angle of 57.60±0.04°, velocity before atmospheric entry was 56.73±0.16 km/s. This was therefore a fast bolide, geocentric velocity of the meteoroid was 55.46±0.16 km/s, the body belonged among sporadic meteors. Before atmospheric entry, the body moved in an elongated retrograde orbit (Fig. 16) with high eccentricity e= 0.924±0.013, high inclination to the ecliptic plane i= 102.83±0.12°, and perihelion q= 1.0112±0.0002 AU. The body was of cometary origin with unknown parent body, belonging to long-period comets of the 1P/Halley group.

For estimating the initial mass of the body and its other physical properties in the case of bolide 20250609_095442, we can proceed from heliocentric orbital elements, atmospheric trajectory, and also chemical properties obtained from analysis of the bolide spectrum from LS SPNW spectrograph (Fig. 17). For initial determination of meteoroid heliocentric trajectory parameters, the Tisserand parameter of the trajectory relative to Jupiter was calculated. Depending on the Tisserand parameter value, orbital inclination, and aphelion distance, bodies can be divided into 4 groups. Bolide 20240602_204346 has Tisserand parameter value TP _J = 0.119±0.058, according to this classification the bolide belongs to the HT group, i.e., to the group of meteoroids of cometary origin with long-period parent body (1P/Halley comet group). According to parameter K _B (5.930±0.006), which is a function of material properties and surface temperature, it belongs to group D (fragile cometary bodies). According to parameter P _E (-4.922±0.053), the bolide belongs to group II (carbonaceous chondrites). Using parameters that characterize the shape, velocity, and other properties of the body, it was possible to calculate the initial mass of the body. Parallel to calculating the dynamic entry mass m _d , a calculation of photometric entry mass m _f was performed. The initial dynamic mass of the meteoroid before entering Earth's atmosphere was 10.4±2.6 g. The calculation of meteoroid fragmentation strength proceeds from the equality of dynamic pressure and body strength as a whole at the moment of meteoroid breakup. Atmospheric model parameters at the given breakup height are calculated according to the NRLMSISE-00 model (2002). The moment of body breakup (fragmentation) was determined from the course of absolute brightness values of the bolide from La Silla NW station. The fragmentation strength of the main part of the body was 0.022±0.002 MPa, which places the body in the group of common cometary bodies. The determined mineralogical density of the body (0.58±0.04 g/cm ³ ) indicates it was a fragile body.

The spectrum of bolide 20250609_095442 was recorded by LS SPNW spectrograph (Fig. 17), unfortunately the recording is affected by high cloud cover. In some aspects, this is a typical spectrum of a cometary body with high entry velocity, the intensity of atmospheric component emission lines in the NIR part of the spectrum is dominant, especially in the case of OI-1 triplet. Common emission lines of ionized magnesium and silicon multiplets are also present (MgII-4 triplet, SiII-2 doublet), hydrogen Balmer series emission line HI-1 (Hα), and also many emission lines of ionized iron multiplets FeII. However, atypical for these bodies is the low representation of calcium, both CaI-2 multiplet and ionized calcium doublet CaII-1. The intensity of ionized calcium triplet emission lines in the NIR region (CaII-2) is also very low. In the case of high-velocity cometary bodies, the CaII-1 doublet (and often also CaII-2 triplet) is usually dominant in the spectrum and often reaches higher intensities than atmospheric component multiplets in the NIR region of the spectrum.