Reports from Pasadena

GETEMME (Gravity, Einstein’s Theory, and Exploration of the Martian Moons’ Environment), a mission which is being proposed in ESA’s Cosmic Vision program, shall be launched for Mars on a Soyuz Fregat in 2020. The spacecraft will initially rendezvous with Phobos and Deimos in order to carry out a comprehensive mapping and characterization of the two satellites and to deploy passive Laser retro-reflectors on their surfaces. In the second stage of the mission, the spacecraft will be transferred into a lower 1500-km Mars orbit, to carry out routine Laser range measurements to the reflectors on Phobos and Deimos. Also, asynchronous two-way Laser ranging measurements between the spacecraft and stations of the ILRS (International Laser Ranging Service) on Earth are foreseen. An onboard accelerometer will ensure a high accuracy for the spacecraft orbit determination. The inversion of all range and accelerometer data will allow us to determine or improve dramatically on a host of dynamic parameters of the Martian satellite system. From the complex motion and rotation of Phobos and Deimos we will obtain clues on internal structures and the origins of the satellites. Also, crucial data on the time-varying gravity field of Mars related to climate variation and internal structure will be obtained. Ranging measurements will also be essential to improve on several parameters in fundamental physics, such as the Post-Newtonian parameter β as well as time-rate changes of the gravitational constant and the Lense-Thirring effect. Measurements by GETEMME will firmly embed Mars and its satellites into the Solar System reference frame.

In Einstein's general relativity (GR), gravity is described by a massless spin‐2 metric field, and the extension of GR to include a mass term for the graviton has profound implication for gravitation and cosmology. Besides the gravity experiments carried out in the Solar System and those recently with gravitational waves (GWs), pulsar timing observations provide a complementary means to test the masslessness of graviton. In this contribution, I overview three methods in probing the mass of graviton from precision timing of binary pulsars via the modified gravitational radiation (hence, the observed damping rate of the orbital period), as well as from the pulsar‐timing‐array (PTA) experiments via the modified Hellings‐Downs angular‐correlation curve. These tests probe different aspects of gravitation in its kinematics and dynamics, complementing tests of other kinds and providing valuable information to the fundamental theory of gravity.

This thesis is dedicated to certain nonlocal aspects of conformal quantum field theories (CFTs). Two main directions are the study of CFTs on a particular globally-nontrivial spacetime corresponding to finite temperature, and the study of particular nonlocal CFT observables localized on light-rays. Specifically, we introduce bootstrap techniques for determining finite-temperature data of CFTs, and make novel predictions for the 2+1-dimensional Ising model. We propose the “stringy equivalence principle”, stating that coincident gravitational shocks commute, as a generalization of the strong equivalence principle of Einstein’s General Relativity that must hold in all consistent theories of gravity. We prove it in Anti-de Sitter (AdS) spacetimes by studying light-ray operators in the holographically dual CFT. We also derive an operator product expansion (OPE) for light-ray operators in CFT, by which two light-ray operators on the same light-sheet can be expanded as a sum of single light-ray operators. Light-ray operators model detectors — such as calorimeters. We use the light-ray OPE to compute energy event shape observables suitable for conformal collider physics. An additional part of this thesis determines the low-energy vacua of two-dimensional maximal super-Yang-Mills theory, which describes the dynamics of stacks of D-strings in Type IIB string theory. By computing an invariant of the renormalization group (RG) flow from high to low energy — a modified thermal partition function named the refined elliptic genus — we prove the existence of multiple vacua, and identify the superconformal field theories capturing their dynamics. The vacua correspond to bound states of (p,q)-strings in Type IIB string theory. Our computation serves as a check of the strong-weak S-duality of the Type IIB string.

According to general relativity, a spinning body of mass M and angular momentum S, like a star or a planet, generates a gravitomagnetic field which induces, among other phenomena, also the Lense-Thirring effect, i.e. secular precessions of the path of a test particle orbiting it.Direct and indisputable tests of such a relativistic prediction are still missing.We discuss some performed attempts to measure it in the gravitational fields of several bodies in the Solar System with natural and artificial objects.The focus is on the realistic evaluation of the impact of some competing classical forces regarded as sources of systematic uncertainties degrading the total accuracy obtainable.In the case of the test performed with the LAGEOS and LAGEOS II Earth's satellites * Speaker.

<p indent="0mm">Deep space exploration is one of the frontiers of scientific research and driven by human instincts to explore the unknown. Since the Moon Race in the 1960s and 1970s, deep-space probes have explored many celestial bodies in our solar system, including eight planets. These explorations have yielded tremendous scientific discoveries, but they also revealed many more unsolved mysteries. The 21st century has witnessed a remarkable increase in deep-space exploration activities, with several new agencies launching their spacecraft in the past few decades. As a result of technological advancement, exploration success rates have improved significantly. A systematic review of frontier scientific questions can provide invaluable references for mission planning strategies and boost scientific discoveries and breakthroughs in the future. In general, these questions are related to three primary scientific subjects: (1) One of the primary scientific objectives of deep-space exploration is to study the origin and evolution of the solar system. From the collapse of the solar nebula to the formation of the planetary system, the solar system has undergone a complex evolutionary process. The components of the current solar system, particularly the residual presolar material, can provide critical information for understanding the initial conditions and evolution of the solar system. The Moon, being the nearest celestial body to Earth, serves as an outpost for exploring other planetary bodies and is especially important for testing deep-space exploration equipment and studying solar system evolution. (2) Another objective of deep space exploration is to better understand the evolution of planetary habitability. The Sun is an important factor affecting habitability, and eruptions of solar activities can have a substantial impact on the space environment of the solar system. The environment of the Earth and other planets has changed dramatically over billions of years of evolution. Although life has only been confirmed on Earth, other celestial bodies might also have had habitable conditions along the evolutionary process. Decoding the evolution of the habitable environment of solar system planetary bodies is of great significance for understanding the formation and evolution of habitable Earth and the origin of life on Earth. (3) Extraterrestrial life detection is a critical scientific topic in deep space exploration, with far-reaching implications for understanding the origin, evolution, and distribution of life in solar and extrasolar systems. The current scientific challenges in the detection of extraterrestrial life primarily involve four aspects: the origin and evolution of life, extraterrestrial habitable environments, life signal identification, and analogy of terrestrial extreme environments. In endeavors to answer these scientific questions, more well-planned deep-space exploration missions are required to collect evidence. In order to outpace opponents in the continuing space exploration endeavor, the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), and other rising roles have made their ambitious roadmaps. NASA will encourage commercial companies to join future missions through the Artemis program, and has planned missions to explore Venus, asteroids, and icy bodies. The ESA proposed tens of missions in its white paper <italic>Voyage 2050</italic>. In the coming decades, China will lay the groundwork for the International Lunar Research Station through three Chang’e and four Russian Luna missions. Furthermore, Tianwen-2 and Tianwen-3 will return samples from asteroids and Mars, respectively; Tianwen-4 is intended to explore the Jupiter system. The success of these missions will yield unprecedented information for deciphering the mysteries of the solar system and life, as well as considerably expanding our knowledge of the universe we live in.

Four-dimensional Einstein's General Relativity is shown to arise from a gauge theory for the conformal group, SO(4,2). The theory is constructed from a topological dimensional reduction of the six-dimensional Euler density integrated over a manifold with a four-dimensional topological defect. The resulting action is a four-dimensional theory defined by a gauged Wess-Zumino-Witten term. An ansatz is found which reduces the full set of field equations to those of Einstein's General Relativity. When the same ansatz is replaced in the action, the gauged WZW term reduces to the Einstein-Hilbert action. Furthermore, the unique coupling constant in the action can be shown to take integer values if the fields are allowed to be analytically continued to complex values.

Three major predictions of Einstein's General Relativity — black holes, wormholes, and time machines — are reviewed for their development and current status.

SPACETIME STRUCTURE Einstein's general theory of relativity gives a mathematical description of space, time and gravitation which is extraordinarily concise, subtle and accurate. It has, however, the appearance of being concise only to those who are already familiar with the mathematical formalism of Riemannian geometry. To someone who is not familiar with that body of mathematical theory – a theory which, though remarkably elegant, is undoubtedly sophisticated, and usually becomes extremely complicated in detailed application – Einstein's General Relativity can seem inaccessible and bewildering in its elaborate structure. But the complication and sophistication lie only in the details of the formalism. Once that mathematics has been mastered, the precise formulation of Einstein's physical theory is, indeed, extremely compact and natural. Although a little of this formalism will be needed here, it will be given in a compact form only that should be reasonably accessible. The mathematical theory of Riemannian geometry applies to smooth spaces of any (positive whole) number N of dimensions. Such a space M is referred to as an N - manifold , and to be a Riemannian manifold it must be assigned a metric , frequently denoted by g , which assigns a notion of ‘length’ to any smooth curve in M connecting any two points a, b . (See Figure 3.1.) For a strictly Riemannian manifold, this length function is what is called positive definite which means that the length of any such curve is a positive number, except in the degenerate situation when a = b and the curve shrinks to a point, for which the length would be zero.

Data acquired by spaceborne spectrometers operating in the visual (VIS) and near-infrared (NIR) spectral ranges, are commonly exploited to derive the microphysical properties of planetary atmospheric aerosols (e.g. Adriani et al., 2015; Sindoni et al., 2017; Fedorova et al., 2024; Oliva et al., 2016; Oliva et al., 2018; D’Aversa et al., 2022). The precision with which these properties can be constrained, depends on several parameters (e.g. optical constants, surface albedo spectrum, particles’ shape and size distribution, ecc.) and on the spectral information content in the data. VIS wavelengths alone (~ 0,4 – 0,7 μm) provide information on aerosols’ composition, particles’ density and sizes, allowing the estimation of the optical depth integrated along the line of sight (Oliva et al., 2016). However, in order to constrain these parameters with enhanced precision, the NIR range (~ 0,7 – 3,0 μm) is also required, since it allows to assess how the spectral shape bends towards longer wavelengths (Oliva et al., 2018).Our goal is to exploit the combined nadir datasets of the UVIS (0.2 – 0.65 µm) and LNO (2.2 – 3.8 µm) channels of the NOMAD spectrometer (Neefs et al., 2015) to contrain the microphysical properties of Martian dust (Oliva et al., 2025). The two spectral ranges present a large gap among each other, and this introduces biases in the retrieved parameters due to the unconstrained spectral information in the missing wavelengths. In order to benchmark these biases, we exploit MEx/OMEGA (Bibring et al., 2004) VNIR (0,35 – 1,05 µm) and SWIR-C (0.93 - 2.73 µm) channels’ data. Such an extended interval allows the retrieval of Martian dust clouds’ height and microphysical properties (e.g. Oliva et al., 2018; D’Aversa et al., 2022), that can be used as a proxy for the NOMAD retrievals. By studying dust’s densities and sizes 1) from the full OMEGA spectrum and 2) from the spectrum only covering UVIS and LNO wavelengths, we can derive the bias in the retrieved parameters. Moreover, this analysis allows to calibrate how many UVIS and LNO spectral points need to be considered in the retrieval, in order to balance the information content of the two channels.Preliminary results suggest that dust densities are systematically overestimated (as well as grains’ sizes to a lesser degree) if NIR wavelengths are completely neglected, while such a bias is reduced if LNO range is taken into account.ReferencesAdriani et al., 2015. Faint luminescent Ring over Saturn’s polar hexagon. Astrophys. J. Lett. 808 (1), 5. L16.Bibring et al., 2004. Omega: Observatoire pour La minéralogie, l’eau, Les Glaces Et l’activité. ESA SP-1240: Mars Express: The Scientific Payload. ESA Publications Division, Estec, Noordwijk, The Netherlands, pp. 37–49.D’Aversa et al., 2022. Vertical distribution of dust in the Martian atmosphere: OMEGA/Mex limb observations. Icarus 371, 114702.Fedorova et al., 2024. Distribution of atmospheric aerosols during the 2007 Mars dust storm (MY 28): Solar infrared occultation observations by SPICAM. Icarus 415, 116030Oliva et al., 2016. Clouds and hazes vertical structure of a Saturn’s giant vortex from Cassini/VIMS-V data analysis. Icarus 278, 215–237.Oliva et al., 2018. Properties of a Martian local dust storm in Atlantis Chaos from OMEGA/MEX data. Icarus.Oliva et al., 2025. Martian dust characterization: reanalysis of TGO/NOMAD UVIS and LNO channels’ nadir data. XX Congresso Nazionale di Scienze Planetarie, Pescara, 3-7 Febbraio 2025.Neefs et al, 2015. NOMAD spectrometer on the ExoMars trace gas orbiter mission: part 1—design, manufacturing and testing of the infrared channelsApplied Optics 54, 28, 8494-8520.Sindoni et al., 2017. Characterization of the white ovals on Jupiter’s southern hemisphere using the first data by the Juno/JIRAM instrument. Geophys. Res. Lett. https://doi.org/10.1002/2017gl072940.AcknowledgementsExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB- BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). This project acknowledges funding by the Belgian Science Policy Office (BELSPO), with the financial and contractual coordination by the ESA Prodex Office (PEA 4000103401, 4000121493), by the Spanish MICINN through its Plan Nacional and by European funds under grants PGC2018-101836-B-I00 and ESP2017-87143-R (MINECO/FEDER), as well as by UK Space Agency through grants ST/V002295/1, ST/V005332/1, ST/Y000234/1 and ST/X006549/1 and Italian Space Agency through grant 2018-2-HH.0. The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). This work was supported by the Belgian Fonds de la Recherche Scientifique – FNRS under grant numbers 30442502 (ET_HOME) and T.0171.16 (CRAMIC) and BELSPO BrainBe SCOOP Project. US investigators were supported by the National Aeronautics and Space Administration. Canadian investigators were supported by the Canada Space Agency.

This chapter describes the establishment process, purpose of establishment, mission, exploration plan, activities of the European Space Agency (ESA) and International Space Station (ISS), and an explanation of the contents of the treaty that is legal basis for its establishment. The European Space Agency (ESA) is an intergovernmental organization of 22 member states dedicated to the exploration of space. Established in 1975 and headquartered in Paris, France, ESA has a worldwide staff of about 2,200 in 2018 and an annual budget of about € 6.68 billion (US $ 7.43 billion) in 2020. ESA also works closely with space organizations outside Europe. ESA has missions planned for Jupiter (JUICE, 2022) and others that will seek dark matter (Euclid, 2020) and observe the energetic universe (Athena, 2028). The International Space Station (ISS) is a space station (habitable artificial satellite) in low Earth orbit. The ISS programme is a joint project between five participating space agencies: NASA (United States), Roscomos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada).

Scientists hope to learn what makes a ‘typical’ solar system using the European Space Agency’s €450-million ARIEL probe. Scientists hope to learn what makes a ‘typical’ solar system from the European Space Agency’s €450-million probe.

Italian Spring Accelerometer (ISA) is a scientific payload of the European Space Agency&amp;#8217;s BepiColombo mission to Mercury. It aims to measure the Non Gravitational Perturbations acting on the MPO (Mercury Planetary Orbiter) spacecraft, allowing to consider it as a test-mass free falling in the planetary gravity field and hence disclosing the possibility to study the &amp;#160;Mercury's interior, surface, and environment, as well as to preform tests of Einstein's General Relativity theory.ISA sensitivity to thermoelastic deformations of the spacecraft panel on which it is mounted on, is one of the limiting factors of the achievable acceleration measurements accuracy, whose target value is 10-8&amp;#160;m/s2 .To address this challenge, a data analysis and reduction procedure is being developed; it is based on machine learning techniques and allows to compute an acceleration measurements correction signal, starting from the data provided by multiple supplementary sensors. Specifically, we employed the temperatures recorded by several thermometers and the information about power dissipated across the MPO in order to compute the correction signal to be applied to the ISA output. Indeed, these temperatures and dissipated power variations are responsible for the thermoelastic deformations of the mounting plate housing ISA.The technique is being developed during the mission's cruise towards Mercury, exploiting also the outcomes of the GAIN &amp;#8220;Gravimetro Aereo INtelligente&amp;#8221; project, which developed a similar methodology for airborne gravimetry.The preliminary results related to measurement sessions during the cruise phase will be presented, and considerations on the implementation of such techniques for future space missions will be provided.Indeed, despite ISA was not specifically designed for the use of the "GAIN method&amp;#8221;, the preliminary results are promising, underscoring its potential and allowing to envisage that future space missions could benefit of a full implementation of such a method that should go through the development of purpose built and trained multi-sensor systems.

The Moon has long been a part of our consciousness. Although 30 years have passed since our first human journey, we have returned only through the use of observation satellites. Spurred, in part, by the prospect of at least 3 billion metric tonnes of water ice at each pole of the Moon as indicated by both Clementine and Lunar Prospector, a renewed interest in utilizing the resources and venue of the Moon as an aid to human exploration and development of space has once again encouraged long-time advocates of lunar utilization. International organizations, such as the International Academy of Astronautics (IAA), have continuously championed the return of humans to the Moon. Meetings such as the Commercial Lunar Base Symposium in July 1999 and International Astronautical Federation (IAF)/IAA-sponsored International Astronautical Congress in Amsterdam, the Netherlands in October 1999 have generated a new impetus. Briefings at these meetings by industrial companies, the European Space Agency (ESA), NASA, and the National Space Agency of Japan (NASD A) plus private individuals and representatives of several universities have all indicated a renewed interest in future lunar use. Many prospective approaches were taken to the technical, political, legal, andpotential commercial development of the Moon. Work reported included Lunar Prospector results; the use of propellant mined and manufactured on the Moon; legal aspects; new enabling technologies; long-range, lunar-base architecture; logistics; and the role of lunar materials in base construction and solar power systems. Several papers dealt with various aspects of commercialization, and plans for lunar programs by NASDA, the Institute of Space and Astronautical Science (ISAS) and ESA were promulgated. Teams are forming to begin the first steps toward humankind's return to our Moon as a site to develop, as a testbed and resource supply source for future exploration system development, and eventually as a factory for products needed on the Moon, in space, and on Earth.

Lovelock theory is a natural extension of the Einstein theory of general relativity to higher dimensions in which the first and second orders correspond, respectively, to general relativity and Einstein-Gauss-Bonnet gravity. We present exact black hole solutions of $D\geq 4$-dimensional spacetime for first-, second-, and third-order Lovelock gravities in a string cloud background. Further, we compute the mass, temperature, and entropy of black hole solutions for the higher-dimensional general relativity and Einstein-Gauss-Bonnet theories and also perform thermodynamic stability of black holes. It turns out that the presence of the Gauss-Bonnet term and/or background string cloud completely changes the black hole thermodynamics. Interestingly, the entropy of a black hole is unaffected due to a background string cloud. We rediscover several known spherically symmetric black hole solutions in the appropriate limits.

Speleology as an analogue to space exploration: The ESA CAVES training programme