The main technical and strategic aspects related to Space Surveillance and Tracking (SST) with optical sensors are set in context in this study to lead to an efficient inventory of the active satellites and un-cooperant space debris population at Low-Earth orbital regimes (LEO). In particular, special emphasis is devoted to the combined interplay between timing of observations, target illumination conditions, instrumental fine tuning and data acquisition mode (surveying vs. active tracking). At LEO altitudes, satellites are seen to cross the sky at very high angular velocity, in excess to 0.5-1.5 deg/sec, always making their positional measurements (and the inferred dynamical properties) a challenging task for ground telescopes. To this aim, objective criteria have to be identified for a best trade-off between instrument field of viev (FOV), CCD/CMOS platescale, telescope aperture and exposure time in order to maximize target(s) detection and reference grid of stars valuable for astrometry. Many counter-intuitive aspects are discussed in this regard, compared for instance with a more classical "astronomical" approach, delving in particular the widely recognized inherent link between time-tag accuracy and resolving power of optical imagery to track LEO objects. A number of tables and graphical plots are provided for practical use to the reader. (c) 2024 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Facing the increasing population of active and inactive objects along the different geocentric orbital regimes, the activities of Space Surveillance and Tracking (SST) are becoming more and more important for any efficient Space Traffic Management and Policy effort, in order to quantify and (when possible) mitigate the collision risk with/among any space junk. However, the astrometric observations of artificial satellites or space debris are not easy as for near-Earth asteroids: due to their high angular speed, to get a good orbit solution is necessary a temporal precision of the order of few milliseconds. In this work we illustrate our experience about astrometry of MEO/GEO satellites and space debris in the context of the European EU-SST cooperation with the ``G.D. Cassini'' telescope, a 1.52-m F/4.8 Ritchey-Chrétien managed by the Astrophysics and Space Science Observatory of Bologna (Italy). Under a Linux system we have developed the Bologna Astrometry Satellites Pipeline (BASP), with home-made Matlab and Python scripts. To achieve our goals we also incorporated into the Linux system freely available tools: Astrometry.net for plate solving, ASTRiDE for the recognition of satellite tracks and Find_Orb for geocentric orbits computation. These tools are called by Matlab scripts when needed. With BASP a good satellite astrometry is obtained in a short time, with average residues of the order of one arcsec. The software is freely available on GitHub, where anyone can download it and adapt as needed.

The ESA mission Comet Interceptor will target an Oort or interstellar comet during its first approach to the Sun. Meanwhile, the Vera Rubin LSST Survey will observe hundreds of active comets per month beyond 4 au from the Sun, where water vapour pressure is expected to be too low to eject dust. We discuss observations of dust tails at heliocentric distances larger than 4 au in order to retrieve the physical parameters driving cometary activity beyond Jupiter by means of a probabilistic tail model, which is consistent with the activity model defining the gas coma parameters due to the sublimation of carbon monoxide, molecular oxygen, methane, ethane, and carbon dioxide since the activity onset at 85 au from the Sun. We find that: (i) All the observed dust tails are consistent with the adopted activity model; (ii) The tail fits depend on three free parameters only, all correlated to the nucleus size; (iii) Tail fits are always improved by anisotropic dust ejection, suggesting activity of Oort nuclei dominated by seasons; (iv) Inbound seasons suggest cometary activity before the ejection of protocomets into the Oort cloud, as predicted by the activity model; (v) Oort nuclei larger than 1 km may be characterized by a fallout up to approximate to 100 m thick deposited during approximate to 60 yr inbound; (vi) On the other side, Oort nuclei smaller than 1 km may appear more pristine than Jupiter Family Comets when observed at 1 au from the Sun.

Within the framework of any Space Surveillance and Tracking activities, the capability of optical sensors to perform spectroscopic observations would add a unique value to acquiring supplementary information on any extemporary object crossing the telescope field of view. In addition to the astrometric information, probing the body's albedo via low-resolution spectroscopy would constrain the geometry and physical nature of the target and discriminate among spent rocket parts, coarse debris and intact spacecraft. The EU-SST project SuperFOSC, currently in progress at INAF-OAS, is a one square degree wide-field camera that will equip the "G.D. Cassini'" telescope, located close to Bologna (Italy). Besides the imaging capabilities, we also envisage an option to secure one-shot slit-less spectroscopy of all the (censed and uncensed) objects crossing the telescope field of view along with the observations of the bonafide planned targets. This will be done by placing a diffractive grism on a pupil image inside the camera. This paper investigates the system performance in terms of spectral resolution as a function of the intruding object(s) path for a grism with a fixed or variable position angle. In addition, as an innovative concept, we also discuss a three-faces grism (Trism) solution to catch any source three spectra at a time, each 120 deg apart in position angle on the sky, to maximise spectral resolution disregarding object trajectory. An added value of our Trism solution would be avoiding moving optical parts inside the instrument with a significantly improved image quality.

We describe the phase space structures related to the semi-major axis of Molniya-like satellites subject to tesseral and lunisolar resonances. In particular, the questions answered in this contribution are: (1) we study the indirect interplay of the critical inclination resonance on the semi-geosynchronous resonance using a hierarchy of more realistic dynamical systems, thus discussing the dynamics beyond the integrable approximation. By introducing ad hoc tractable models averaged over fast angles, (2) we numerically demarcate the hyperbolic structures organising the long-term dynamics via fast Lyapunov indicators cartography. Based on the publicly available two-line elements space orbital data, (3) we identify two satellites, namely Molniya 1-69 and Molniya 1-87, displaying fingerprints consistent with the dynamics associated to the hyperbolic set. Finally, (4) the computations of their associated dynamical maps highlight that the spacecraft are trapped within the hyperbolic tangle. This research therefore reports evidence of actual artificial satellites in the near-Earth environment whose dynamics are ruled by hyperbolic manifolds and resonant mechanisms. The tools, formalism and methodologies we present are exportable to other region of space subject to similar commensurabilities as the geosynchronous region.

The aim of this work is to analyze the orbital evolution of the mean eccentricity given by the Two-Line Elements (TLE) set of the Molniya satellites constellation. The approach is bottom-up, aiming at a synergy between the observed dynamics and the mathematical modeling. Being the focus the long-term evolution of the eccentricity, the dynamical model adopted is a doubly-averaged formulation of the third-body perturbation due to Sun and Moon, coupled with the oblateness effect on the orientation of the satellite. The numerical evolution of the eccentricity, obtained by a two-degree-of-freedom time dependent model assuming different orders in the series expansion of the third-body effect, is compared against the mean evolution given by the TLE. The results show that, despite being highly elliptical orbits, the second order expansion catches extremely well the behavior. Also, the lunisolar effect turns out to be non-negligible for the behavior of the longitude of the ascending node and the argument of pericenter. Finally, a frequency series analysis is proposed to show the main contributions that can be detected from the observational data.

We report dense light-curve photometry, BVRc colours and phase-mag curve of (6478) Gault, an active asteroid with sporadic comet-like ejection of dust. We collected optical observations along the 2020 July-November months during which the asteroid appear always star-like, without any form of perceptible activity. We found complex light curves, with low amplitude around opposition and a bit higher amplitude far opposition, with a mean best rotation period of 2.46(+/- 0.02) h. Shape changes were observed in the phased light curves after opposition, a probable indication of concavities and surface irregularities. We suspect the existence of an Amplitude-Phase Relationship in C band. The mean colours are B - V = +0.84(+/- 0.04), V - R-c = +0.43(+/- 0.03), and B - R-c = +1.27(+/- 0.02), compatible with an S-type asteroid, but variables with the rotational phase index of a non-homogeneous surface composition. From our phase-mag curve and Shevchenko's empirical photometric system, the geometric albedo result p(V) = 0.13(+/- 0.04), lower than the average value of the S-class. We estimate an absolute mag in V band of about + 14.9 and this, together with the albedo value, allows us to estimate a diameter of about 3-4 km, so Gault may be smaller than previously thought.

The uncontrolled re-entry of spacecraft and upper stages is quite common, occurring nearly every week. Among them, intact objects having a mass greater than five metric tons re-enter, on average, 1–2 times per year. Therefore, the re-entry of the first Chinese Space Station, Tiangong-1, was far from unusual, but attracted anyway a great worldwide attention and some concerns. For these reasons, the Italian component of the European SST (Space Surveillance and Tracking) consortium took this opportunity for carrying out a national exercise. According to Chinese official sources, the ground control of Tiangong-1 was lost in March 2016, precluding the planned de-orbiting in the South Pacific Ocean Unpopulated Area (SPOUA). Tiangong-1 consisted of a cylindrical section, 10:5 m in length and 3:4 m in (maximum) diameter, with two rectangular solar panels of 3 m  ×  7 m. The mass was estimated to be around 7500 kg.

We report on the extended observing campaign of the surviving Soviet/Russian spacecraft Molniya, carried out in the years 2014–17 at Mexican and Italian telescopes. Spectrophotometry and astrodynamical analysis have been carried out for all the 43 demised payloads still in uncontrolled HEO orbit at late 2017, in order to assess dynamical and reflectance properties of such a wide family of virtually identical orbiting objects, as well as their long-term orbit evolution, according to full historic Two-Line Elements (TLE) datasets in synergy with mathematical modeling to properly size up the prevailing effect of lunisolar perturbation and atmospheric drag.

Two meteorite pieces have been recovered in Italy, near the town of Cavezzo (Modena), on 4 January 2020. The associated fireball was observed on the evening of New Year’s Day 2020 by eight all-sky cameras of the PRISMA fireball network, a partner of FRIPON. The computed trajectory had an inclination angle of approximately 68 and a velocity at infinity of 12.8 km s. Together with the relatively low terminal height, estimated as 21.5 km, those values were indicating the significant possibility of a meteorite dropping event, as additionally confirmed by the non zero residual total mass. The strewn-field was computed taking into account the presence of two bright light flashes, revealing that the meteoroid had been very likely subject to fragmentation. Three days after the event, two samples, weighing 3.1 g and 52.2 g, were collected as a result of a dedicated field search and thanks to the involvement of the local people. The two pieces were immediately recognised as freshly fallen fragments of meteorite. The computed orbital elements, compared with the ones of known Near-Earth Asteroids from the NEODyS database, are compatible with one asteroid only; 2013 VC10. The estimated original mass of the meteoroid, 3.5 kg, and size, approximately 13 cm, is so far the smallest among the current 35 cases in which meteorites were recovered from precise strewn-field computation thanks to observational data. This result demonstrates the effectiveness of accurate processing of fireball network data even on challenging events generated by small size meteoroids.

Context: Until recently, camera networks designed for monitoring fireballs worldwide were not fully automated, implying that in case of a meteorite fall, the recovery campaign was rarely immediate. This was an important limiting factor as the most fragile - hence precious - meteorites must be recovered rapidly to avoid their alteration. Aims: The Fireball Recovery and InterPlanetary Observation Network (FRIPON) scientific project was designed to overcome this limitation. This network comprises a fully automated camera and radio network deployed over a significant fraction of western Europe and a small fraction of Canada. As of today, it consists of 150 cameras and 25 European radio receivers and covers an area of about 1.5 million square kilometers.

ABSTRACT We report on accurate BVRc observations of (6478) Gault, a 5–6 km diameter inner main-belt asteroid in the Phocaea family, notable for its sporadic, comet-like ejection of dust. This curious behaviour has been mainly interpreted as reconfigurations after YORP spin-up, although merging of a contact binary system cannot be fully excluded. We collected optical observations along the 2019 March–April period, at orbital phase angles between 12° and 21°, to search for direct evidence of asteroid quick spinning rotation. A prevailing period value of 3.34 ± 0.02 h is supported by our and other photometric observations. In the YORP spin-up hypothesis, this period points to a bulk density ρ ≈ 1 $\textrm{g}\, \textrm{cm}^{-3}$. The mean colours are B − V = +0.82±0.3, V − Rc = +0.28±0.06, and B − Rc = +1.11±0.4, but we have observed a trend towards bluer colour during the April session, with about Δ(B − V) ∼ 0.35 ± 0.09 mag. This colour change can be due to asteroid rotation and support the hypothesis that there is a bluer surface under the Gault’s dust.

On May 30, 2017, at about 21 h 09 min 17 s UTC a green bright fireball crossed the sky of northeastern Italy. The fireball path was observed from some all-sky cameras starting from a mean altitude of $$81.1 \pm 0.2$$ km (Lat. $$44.369^{\circ } \pm 0.002^{\circ }$$ N; Long. $$11.859^{\circ } \pm 0.002^{\circ }$$ E) and extinct at $$23.3 \pm 0.2$$  km (Lat. $$45.246^{\circ } \pm 0.002^{\circ }$$ N; Long. $$12.046^{\circ } \pm 0.002^{\circ }$$ E), between the Italian cities of Venice and Padua. In this paper, on the basis of simple physical models, we will compute the atmospheric trajectory, analyze the meteoroid atmospheric dynamics, the dark flight phase (with the strewn field) and compute the best heliocentric orbit of the progenitor body. Search for meteorites on the ground has not produced any results so far.

<p>In this talk we report about the recent finding of two meteorite samples in Italy, near Cavezzo (Modena). The meteorite-dropping fireball was observed on the evening of New Year's Day 2020 by eight all-sky cameras of the PRISMA network, partner of FRIPON. The two fragments, weighing 4 g and 52 g respectively, were collected as a result of a dedicated field search and thanks to the involvement of the local population. </p>

We report on the extended 2014–17 observing campaign of the 43 surviving Soviet/Russian spacecraft Molniya, carried out at Mexican and Italian telescopes. Spectrophotometry and astrodynamical analysis have been carried out for all the dead payloads now in uncontrolled HEO orbit, in order to assess the possible differential age effect on the dynamical and reflectance properties of such a wide family of virtually identical orbiting objects, under the influence of Sun’s radiation and gravitational and geomagnetic perturbation.

We report on extensive BVRcIc photometry and low-resolution (lambda/Delta lambda similar to 250) spectroscopy of the deep-space debris WT1190E, which impacted Earth offshore from Sri Lanka, on 2015 November 13. In spite of its likely artificial origin (as a relic of some past lunar mission), the case offered important points of discussion for its suggestive connection with the envisaged scenario for a (potentially far more dangerous) natural impactor, like an asteroid or a comet. Our observations indicate for WT1190F an absolute magnitude R-c = 32.45(+/- 0.31), with a flat dependence of reflectance on the phase angle, such as dR(c)/d phi similar to 0.007(+/- 2) mag deg(-1). The detected short-timescale variability suggests that the body was likely spinning with a period twice the nominal figure of P-flath = 4547(+/- 0.0005) s, as from the observed lightcurve. In the BVRcIc color domain, WTI 190F closely resembled the Planck deep -space probe. This match, together with a depressed reflectance around 4000 and 8500 angstrom may be suggestive of a "grey" (aluminized) surface texture. The spinning pattern remained in place also along the object fiery entry in the atmosphere, a feature that may have partly shielded the body along its fireball phase perhaps leading a large fraction of its mass to survive intact, now lying underwater along a tight (similar to 1 x 80 km) strip of sea, at a depth of 1500 m or less. Under the assumption of Lambertian scatter, an inferred size of 216(+/- 30)/root alpha/0.1 cm is obtained for WT1190F. By accounting for non gravitational dynamical perturbations, the Area -to -Mass ratio of the body was in the range (0.006 <= AMR <= 0.011) m(2) kg(-1). Both these figures resulted compatible with the two prevailing candidates to WT1190E's identity, namely the Athena II Trans -Lunar Injection Stage of the Lunar Prospector mission, and the ascent stage of the Apollo 10 lunar module, callsign "Snoopy". Both candidates have been analyzed in some detail here through accurate 3D CAD design mockup modelling and BRDF reflectance rendering to derive the inherent photometric properties to be compared with the observations. (C) 2018 COSPAR. Published by Elsevier Ltd. All rights reserved.

We present intermediate-resolution (R$\sim$1000) spectra in the $\sim$3500-10,000 A range of 14 globular clusters in the magellanic irregular galaxy NGC 4449 acquired with the Multi Object Double Spectrograph on the Large Binocular Telescope. We derived Lick indices in the optical and the CaII-triplet index in the near-infrared in order to infer the clusters' stellar population properties. The inferred cluster ages are typically older than $\sim$9 Gyr, although ages are derived with large uncertainties. The clusters exhibit intermediate metallicities, in the range $-1.2\lesssim$[Fe/H]$\lesssim-0.7$, and typically sub-solar [$\alpha/Fe$] ratios, with a peak at $\sim-0.4$. These properties suggest that i) during the first few Gyrs NGC 4449 formed stars slowly and inefficiently, with galactic winds having possibly contributed to the expulsion of the $\alpha$-elements, and ii) globular clusters in NGC 4449 formed relatively "late", from a medium already enriched in the products of type Ia supernovae. The majority of clusters appear also under-abundant in CN compared to Milky Way halo globular clusters, perhaps because of the lack of a conspicuous N-enriched, second-generation of stars like that observed in Galactic globular clusters. Using the cluster velocities, we infer the dynamical mass of NGC 4449 inside 2.88 kpc to be M($<$2.88 kpc)=$3.15^{+3.16}_{-0.75} \times 10^9~M_\odot$. We also report the serendipitous discovery of a planetary nebula within one of the targeted clusters, a rather rare event.

On 2015 November 13, the small artificial object designated WT1190F entered the Earth atmosphere above the Indian Ocean offshore Sri Lanka after being discovered as a possible new asteroid only a few weeks earlier. At ESA's SSA-NEO Coordination Centre we took advantage of this opportunity to organize a ground-based observational campaign, using WT1190F as a test case for a possible similar future event involving a natural asteroidal body.