Fluidization and Transport of Vibrated Granular Matter:A Review of Landmark and Recent Contributions

We present a short retrospective review of the existing literature about the dynamics of(dry)granular matter under the effect of vibrations.The main objective is the development of an integrated resource where vital information about past findings and recent discoveries is provided in a single treatment.Special attention is paid to those works where successful synthetic routes to as-yet unknown phenomena were identified.Such landmark results are analyzed,while smoothly blending them with a history of the field and introducing possible categorizations of the prevalent dynamics.Although no classification is perfect,and it is hard to distillate general properties out of specific observations or realizations,two possible ways to interpret the existing results are defined according to the type of forcing or the emerging(ensuing)regime of motion.In particular,first results concerning the case where vibrations and gravity are concurrent(vertical shaking)are examined,then the companion situation with vibrations perpendicular to gravity(horizontal shaking)is described.Universality classes are introduced as follows:(1)Regimes where sand self-organizes leading to highly regular geometrical“pulsating”patterns(thin layer case);(2)Regimes where the material undergoes“fluidization”and develops an internal multicellular convective state(tick layers case);(3)Regimes where the free interface separating the sand from the overlying gas changes inclination or develops a kind a patterned configuration consisting of stable valleys and mountains or travelling waves;(4)Regimes where segregation is produced,i.e.,particles of a given size tend to be separated from the other grains(deep containers).Where possible,an analogy or parallelism is drawn with respect to the companion field of fluid-dynamics for which the assumption of“continuum”can be applied.

Recent Progress of the Solar Wind Magnetosphere Ionosphere Link Explorer (SMILE) Mission

The SMILE(Solar wind Magnetosphere Ionosphere Link Explorer)mission is a joint space science mission between the Chinese Academy of Sciences(CAS)and the European Space Agency(ESA),aiming to understand the interaction of the solar wind with the Earth’s magnetosphere in a global manner.As of May 2024,the SMILE mission is in phase-D with an expected launch date of September 2025.This report summarizes developments in the mission during the past two years.

Space-to-space Radio Interferometry System from Medium Earth Orbits

This paper presents a new concept to perform space-to-space Very Long Baseline Interferometry which enables the imaging of cosmic sources at high-resolution and high-sensitivity with small antennas.Several individual apertures are embarked on separate identical satellites staggered in height into Polar or Equatorial Circular Medium Earth Orbits(PECMEO orbits).These orbits are stable and allow GNSS-based on-the-fly centimeter-level relative positioning.Coherent operation is possible by exchanging local oscillator components and measured signals through Inter-Satellite Links(ISL).On-board cross correlation is performed at each satellite over a delay window compatible with the accuracy of the on-the-fly relative positioning and the result sent to the ground.Image reconstruction is completed on the ground thanks to sub-millimeter baseline retrieval from accurate GNSS orbits,ISL ranging and spacecraft attitude information.The application of this concept to image the Super Massive Black Hole Sgr A*is hinted.

Remote sensing and its applications using GNSS reflected signals:advances and prospects

The Global Navigation Satellite Systems(GNSS),including the US’s GPS,China’s BDS,the European Union’s Galileo,and Russia’s GLONASS,offer real-time,all-weather,any-time,anywhere and high precision observations by transmitting L band signals continuously,which have been widely used for positioning,navigation and timing.With the development of GNSS technology,it has been found that GNSS-reflected signals can be used to detect Earth’s surface characteristics together with other signals of opportunity.In this paper,the current status and latest advances are presented on Global Navigation Satellite System-Reflectometry(GNSS-R)in theory,methods,techniques and observations.New developments and progresses in GNSS-R instruments,theoretical modeling,and signal processing,ground and space-/air-borne experiments,parameters retrieval(e.g.wind speed,sea surface height,soil moisture,ice thickness),sea surface altimetry and applications in the atmosphere,oceans,land,vegetation,and cryosphere are given and reviewed in details.Meanwhile,the challenges in the GNSS-R development of each field are also given.Finally,the future applications and prospects of GNSS-R are discussed,including multi-GNSS reflectometry,new GNSS-R receivers,GNSS-R missions,and emerging applications,such as mesoscale ocean eddies,ocean phytoplankton blooms,microplastics detection,target recognition,river flow,desert studies,natural hazards and landslides monitoring.

System Design for the Event Horizon Imaging Experiment Using the PECMEO Concept

The concept for space interferometry from Polar or Equatorial Circular Medium Earth Orbits(the PECMEO concept) is a promising way to acquire the image of the"shadow"of the event horizon of Sagittarius A*with an angular resolution of circa 5 microarcseconds. The concept is intended to decrease the size of the main reflector of the instrument to about 3 m using a precise orbit reconstruction based on Global Navigation Satellite System (GNSS) navigation, inter-satellite range and range-rate measurements, and data from the Attitude and Orbit Determination System (AODS). The paper provides the current progress on the definition of the subsystems required for the concept on the basis of simulations, radio regulations, and available technology. The paper proposes the requirement for the localization of the phase centre of the main reflector. The paper provides information about the visibility of GNSS satellites and the needed accuracies of the AODS. The paper proposes the frequency plan for the instrument and its Inter-Satellite Links (ISLs).The concepts for measurement of range and range-rate using ISLs (as well as for the data exchange at these ISLs) are presented. The block diagram of the interferometer is described and its sensitivity is estimated. The link budget for both ISLs is given as well as their critical components. The calculated measurement quality factors are given. The paper shows the expected performance of the sub-systems of the interferometer. The requirements for the localization of the main reflectors and the information about the availability of the GNSS satellites are based on the simulations results. The frequency plan is obtained according to the PECMEO concept and taking into account the radio regulations. The existing technology defines the accuracies of the AODS, both the link budgets and the fundamental measurement accuracies for ISLs, and the sensitivity of the instrument. The paper provides input information for the development of the orbit reconstruction filter and the whole PECMEO system.

Recent Advance in the Solar Wind Magnetosphere Ionosphere Link Explorer(SMILE)Mission

The SMILE(Solar wind Magnetosphere Ionosphere Link Explorer)mission is a joint space science mission between the European Space Agency(ESA)and the Chinese Academy of Sciences(CAS),aiming to understand the interaction of the solar wind with the Earth’s magnetosphere in a global manner.The mission was adopted by CAS in November 2016 and by ESA in March 2019 with a target launch date in the year 2024-2025.We report the recent progress of SMILE mission by May,2022.

When It Strikes,Are We Ready?Lessons Identified at the 7th Planetary Defense Conference in Preparing for a Near-Earth Object Impact Scenario

Near-Earth object(NEO)impact is one of the examples of high impact and low probability(HILP)event,same as the Covid-19 pandemic the world faces since the beginning of 2020.The 7 th Planetary Defense Conference held by the International Academy of Astronautics(IAA)in April 2021 included an exercise on a hypothetical NEO impact event,allowing the planetary defense community to discuss potential responses.Over the span of the 4-day conference this exercise connected disaster response and management professionals to participate in a series of panels,providing feedback and perspective on the unfolding crisis scenario.The hypothetical but realistic asteroid threat scenario illustrated how such a short-warning threat might evolve.The scenario utilized during the conference indicates a need to prepare now for what might come in the future,because even with advance notice,preparation time might be minimal.This scenario chose Europe for the impact,which may likely cope with such a disaster,through the Union Civil Protection Mechanism(UCPM)and other solidarity and support mechanisms within the European Union(EU),as well as with potential support from international partners.This short article raises concern about other areas in the world on how they may access NEO impact information and cope with such disasters.It also provides an idea on vast scale of such disaster vis-a-vis the current capacity of response systems to cope with a larger event in Europe or elsewhere.This scenario showed that planetary defense is a global endeavor.Constant engagement of the planetary defense and disaster response communities is essential in order to keep the world safe from potential disasters caused by NEO impacts.

Accretion in strong field gravity with eXTP

In this paper we describe the potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies related to accretion flows in the strong field gravity regime around both stellar-mass and supermassive black-holes. eXTP has the unique capability of using advanced "spectral-timing-polarimetry" techniques to analyze the rapid variations with three orthogonal diagnostics of the flow and its geometry, yielding unprecedented insight into the inner accreting regions, the effects of strong field gravity on the material within them and the powerful outflows which are driven by the accretion process.