Optimal planning of space surveillance network and automatic data processing

Nowadays, more than 17; 000 objects greater than 10 cm in diameter are tracked and available in public catalog. Just nearly a thousand and a half are active spacecraft. In low Earth orbit (LEO), the increasing of Cube-Sat missions launched in last years is contributing to the growth of the space object population. Furthermore, large constellations to LEO are under development. Such constellations will lead to an unprecedented, step increase in the number of satellites in LEO. Consequently, to prevent the generation of debris in the short-term and the growth of the debris population over the longer-term is mandatory to avoid Kessler syndrome. Therefore, due to the continuous growth of number of operative satellites and the consequent risk of impact among them, an improvement in the observation is constantly demanding. The presented solution to provide a reliable and timely response in case of contingencies is the development of a worldwide sky-coverage network. In the framework of the Italian Space Agency (ASI) – Sapienza University of Rome Agreement (N.2013-078-C.O) for scientific cooperation at the Broglio Space Center (BSC) in Malindi (Kenya), S5Lab research team is developing a network of optical observatories. The presented thesis deals with the development of the network composed by an Italian observatory named MITO (Mid-latitude Italian Observatory), located near Rome and an equatorial observatory called EQUO (Equatorial Italian Observatory). The combinatorial explosion in the number of intervals to be scheduled has been caused by the increasing number of space debris to be observed with optical ground station. Therefore, new scheduling approach are needed to provide a solution to the new requests. In the framework of the Agreement between Italian Space Agency (ASI) and National Institute of Astrophysics (INAF) Supporto alle attività IADC e validazione pre-operativa per SST (N.2015-028-R.0) a scheduler has been developed to manage the network. The presented thesis outlines the developed software called NICO (Networked Instrument Coordinator for space debris Observations) designed to allocate visibility windows to each optical sensor of the network by solving priority conflicts of the scheduling tasks. NICO goal is the harmonization of the different requests by taking care also of external limitations such as astronomical constraints and weather conditions. The development of a network of observatories and a scheduler to manage and organize the data acquisition routine has triggered the problem on how to manage the acquired data. Due to the increasing of the number of the observatory involved in data acquisition and the number of taken images per night, a new automated image processing tool for light-curves measurements was needed. This thesis presents the development and application of the automated software designed to process light curves acquisition. These are used to determine the dynamical state of the target in terms of attitude by processing the light reflected from the metallic surface of the object. Rapid changes in brightens of the response are investigated to reconstruct rapid changes in the attitude in the scale of a second or less. These data are extremely valuable to detect and investigate the attitude of an orbiting object and its evolution especially for future Active Debris Removal (ADR) missions

Comparisons of a Constrained Least Squares Model Versus Human-in-the-Loop for Spectral Unmixing to Determine Material Type of GEO Debris

Spectral reflectance data through the visible regime was collected at Las Campanas Observatory in Chile using an imaging spectrograph on one of the twin 6.5-m Magellan telescopes. The data were obtained on 1-2 May 2012 on the 'Landon Clay' telescope with the LDSS3 (Low Dispersion Survey Spectrograph 3). Five pieces of Geosynchronous Orbit (GEO) or near-GEO debris were identified and observed with an exposure time of 30 seconds on average. In addition, laboratory spectral reflectance data was collected using an Analytical Spectral Device (ASD) field spectrometer at California Polytechnic State University in San Luis Obispo on several typical common spacecraft materials including solar cells, circuit boards, various Kapton materials used for multi-layer insulation, and various paints. The remotely collected data and the laboratory-acquired data were then incorporated in a newly developed model that uses a constrained least squares method to unmix the spectrum in specific material components. The results of this model are compared to the previous method of a human-in-the-loop (considered here the traditional method) that identifies possible material components by varying the materials and percentages until a spectral match is obtained. The traditional model was found to match the remotely collected spectral data after it had been divided by the continuum to remove the space weathering effects, or a "reddening" of the materials. The constrained least-squares model also used the de-reddened spectra as inputs and the results were consistent with those obtained through the traditional method. For comparison, a first-order examination of including reddening effects into the constrained least-squares model will be explored and comparisons to the remotely collected data will be examined. The identification of each object's suspected material component will be discussed herein

Study of the B−→Λc+Λˉc−K−B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} decay

The decay $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV using data corresponding to an integrated luminosity of 5 $\mathrm{fb}^{-1}$ collected by the LHCb experiment. In the $\Lambda_{c}^+ K^{-}$ system, the $\Xi_{c}(2930)^{0}$ state observed at the BaBar and Belle experiments is resolved into two narrower states, $\Xi_{c}(2923)^{0}$ and $\Xi_{c}(2939)^{0}$, whose masses and widths are measured to be $$m(\Xi_{c}(2923)^{0}) = 2924.5 \pm 0.4 \pm 1.1 \,\mathrm{MeV}, \\ m(\Xi_{c}(2939)^{0}) = 2938.5 \pm 0.9 \pm 2.3 \,\mathrm{MeV}, \\ \Gamma(\Xi_{c}(2923)^{0}) = \phantom{000}4.8 \pm 0.9 \pm 1.5 \,\mathrm{MeV},\\ \Gamma(\Xi_{c}(2939)^{0}) = \phantom{00}11.0 \pm 1.9 \pm 7.5 \,\mathrm{MeV},$$ where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt $\Lambda_{c}^{+} K^{-}$ sample. Evidence of a new $\Xi_{c}(2880)^{0}$ state is found with a local significance of $3.8\,\sigma$, whose mass and width are measured to be $2881.8 \pm 3.1 \pm 8.5\,\mathrm{MeV}$ and $12.4 \pm 5.3 \pm 5.8 \,\mathrm{MeV}$, respectively. In addition, evidence of a new decay mode $\Xi_{c}(2790)^{0} \to \Lambda_{c}^{+} K^{-}$ is found with a significance of $3.7\,\sigma$. The relative branching fraction of $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ with respect to the $B^{-} \to D^{+} D^{-} K^{-}$ decay is measured to be $2.36 \pm 0.11 \pm 0.22 \pm 0.25$, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb public pages

Measurement of the ratios of branching fractions R(D∗)\mathcal{R}(D^{*}) and R(D0)\mathcal{R}(D^{0})

The ratios of branching fractions $\mathcal{R}(D^{*})\equiv\mathcal{B}(\bar{B}\to D^{*}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}\to D^{*}\mu^{-}\bar{\nu}_{\mu})$ and $\mathcal{R}(D^{0})\equiv\mathcal{B}(B^{-}\to D^{0}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(B^{-}\to D^{0}\mu^{-}\bar{\nu}_{\mu})$ are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb${ }^{-1}$ of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode $\tau^{-}\to\mu^{-}\nu_{\tau}\bar{\nu}_{\mu}$. The measured values are $\mathcal{R}(D^{*})=0.281\pm0.018\pm0.024$ and $\mathcal{R}(D^{0})=0.441\pm0.060\pm0.066$, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is $\rho=-0.43$. Results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb public pages

Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a $Z$ boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 $< p_{\textrm{T}} < 100$ GeV and in the pseudorapidity range $2.5 < \eta < 4$. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb$^{-1}$. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages

Averting biodiversity collapse in tropical forest protected areas

The rapid disruption of tropical forests probably imperils global biodiversity more than any other contemporary phenomenon¹⁻³. With deforestation advancing quickly, protected areas are increasingly becoming final refuges for threatened species and natural ecosystem processes. However, many protected areas in the tropics are themselves vulnerable to human encroachment and other environmental stresses⁴⁻⁹. As pressures mount, it is vital to know whether existing reserves can sustain their biodiversity. A critical constraint in addressing this question has been that data describing a broad array of biodiversity groups have been unavailable for a sufficiently large and representative sample of reserves. Here we present a uniquely comprehensive data set on changes over the past 20 to 30 years in 31 functional groups of species and 21 potential drivers of environmental change, for 60 protected areas stratified across the world’s major tropical regions. Our analysis reveals great variation in reserve ‘health’: about half of all reserves have been effective or performed passably, but the rest are experiencing an erosion of biodiversity that is often alarmingly widespread taxonomically and functionally. Habitat disruption, hunting and forest-product exploitation were the strongest predictors of declining reserve health. Crucially, environmental changes immediately outside reserves seemed nearly as important as those inside in determining their ecological fate, with changes inside reserves strongly mirroring those occurring around them. These findings suggest that tropical protected areas are often intimately linked ecologically to their surrounding habitats, and that a failure to stem broad-scale loss and degradation of such habitats could sharply increase the likelihood of serious biodiversity declines.Keywords: Ecology, Environmental scienc

Tracking, photometry and spectroscopy of space debris: the Malindi, Loiano, Las Campanas and Cerro Tololo observation campaign results

The main purpose of my thesis has been the analysis of the space debris environment and their characterization through optical measurements. In particular I had the opportunity to contribute to the Italian Space Agency activities in space debris optical observation campaign and I cooperated directly with NASA Orbital Debris Program Office by working at the Astronomy Department of the University of Michigan for six months

Lessons learned in automatic operation of observatories for space debris observation

In the last years, the growing number of operative Italian’s satellites has triggered the necessity of a space debris observation facility. The first Italian’s observatory totally dedicated to space debris was the Spade observatory, developed at University of Rome La Sapienza and now located in Matera. To understand in depth the space debris environment it was needed to install another observatory for increasing the surveying capability, the EQUO observatory. The EQUO observatory, which is part of the ASI-Sapienza Agreement for the Broglio Space Center (BSC) in Malindi, Kenya, is an Equatorial Observatory, located at the BSC developed by Sapienza Space Systems and Space Surveillance Laboratory (S5Lab) research group. The project’s target is twofold. The primary goal is to detect and characterize space debris using optical methods. For a precise characterization of the space debris it is needed to calculate their position from raw optical images. Data are the input for the orbit determination phase that allow to calculate more accurate conjunction warnings due to realistic covariance and probability of collisions. The possibility of observe the same object from two different locations, one at mid latitudes and one at the Equator, increases the position determination accuracy. The secondary goal is the training of the Sapienza’s students, gaining experience in observatory automation procedures. The main efforts are in the selection of the best patterns and practices for fault tolerant systems to improve the system availability, that were used in designing the software for the EQUO project. The observatory is equipped with a 200 mm diameter f/4 optical tube in Newtonian configuration mounted on a motorized altazimuth mount. It uses a CCD sensor with a wide Field of View (FOV) of about 9 degrees squared. Everything is housed in a robotized dome and it is commanded by a rugged PC, selected to improve the overall system reliability in the equatorial humidity and relatively hot operation conditions. The final result is the realization of an automatic observatory able to remotely acquire space debris images from Italy. In this paper we discuss the design requirements of such a robotic observatory aimed to operate automatically, mainly focused on efficiency and robustness, and the lessons learnt during all the project phases from design to normal operation

Analysis of the brightness variability of GEO objects

In order to study the short-term brightness variability of uncontrolled objects at geosynchronous Earth orbit (GEO), observations are obtained while the telescope is tracking at the sidereal rate, and the GEO object is trailed across the field of view (FOV). Analysis of intensity changes along the trail reveals the primary frequencies of the object’s brightness variations on time scales of a second or less. These observations were performed using two telescopes: • The University of Michigan’s 0.6m Curtis-Schmidt telescope located at the Cerro Tololo InterAmerican Observatory (Chile) equipped with a thinned, backside illuminated CCD with 1.45 arcseconds/pixel and a FOV of 1.6x1.6 deg. • The 1.5m Cassini telescope in Loiano (Italy), operated by the INAF (National Institute for Astrophysics) Astronomical Observatory of Bologna, equipped with BFOSC (Bologna Faint Object Spectrograph and Camera), a multipurpose instrument for imaging and spectroscopy, with 0.58 arc-seconds/pixel and a FOV of 13x 12.6 arc-min. Exposures of the same star field both before and after the GEO object crosses the FOV have been acquired to remove contamination by stars of the GEO trails. Photometric standard star fields were observed for absolute calibration purposes. This paper describes the results of the detection of primary frequencies of brightness changes of a sample of uncontrolled GEO objects