SAGE: A proposal for a space atomic gravity explorer Tino, Guglielmo M.; Bassi, Angelo; Bianco, Giuseppe ...
The European physical journal. D, Atomic, molecular, and optical physics,
11/2019, Letnik:
73, Številka:
11
Journal Article
Recenzirano
Odprti dostop
The proposed mission “Space Atomic Gravity Explorer” (SAGE) has the scientific objective to investigate gravitational waves, dark matter, and other fundamental aspects of gravity as well as the ...connection between gravitational physics and quantum physics using new quantum sensors, namely, optical atomic clocks and atom interferometers based on ultracold strontium atoms.
Graphical abstract
Global navigation satellite system (GNSS) satellites are equipped with very stable atomic clocks that can be used for assessing the models and strategies involved in the estimation processes, where ...the clock estimates should present high stability. For instance, GNSS products (including satellite and receiver clocks) are computed on daily basis, i.e., with the data of each day being processed independently from other days. This choice produces the well-known day-boundary discontinuities (DBDs) on clock estimates that stem from the estimation process, rather than to the nature of the atomic clock itself. The aim of the present contribution is to propose a strategy to estimate the satellite and receiver clock offsets that is capable to reduce the DBDs observed in the products of different analysis centers (ACs) within the International GNSS Service (IGS), ultimately improving the accuracy of clock estimates. Our approach relies on the use of unambiguous, undifferenced and uncombined carrier phase measurements collected by a network of permanent receivers on ground. The strategy considers the carrier phase hardware delays and assumes their possible variations along time. Our daily data processing aims to maintaining the natural continuity over days of the carrier phase measurements after integer ambiguity resolution (IAR), even if IAR is performed on daily batches. We compare our clock estimations with those computed by different IGS ACs, evaluating the linear behavior of the satellite atomic clocks on the day change. The results show the removal of DBD on clock estimates computed with the continuous and unambiguous carrier phase measurements. This DBD improvement may benefit the statistical characterization of long-term phenomena correlated with the on-board clocks.
Background: Military pilots show advanced visuospatial skills. Previous studies demonstrate that they are better at mentally rotating a target, taking different perspectives, estimating distances and ...planning travel and have a topographic memory. Here, we compared navigational cognitive styles between military pilots and people without flight experience. Pilots were expected to be more survey-style users than nonpilots, showing more advanced navigational strategies. Method: A total of 106 military jet pilots from the Italian Air Force and 92 nonpilots from the general population matched for education with the pilots were enrolled to investigate group differences in navigational styles. The participants were asked to perform a reduced version of the Spatial Cognitive Style Test (SCST), consisting of six tasks that allow us to distinguish individuals in terms of landmark (people orient themselves by using a figurative memory for environmental objects), route (people use an egocentric representation of the space) and survey (people have a map-like representation of the space) user styles. Results: In line with our hypothesis, military pilots mainly adopt the survey style, whereas nonpilots mainly adopt the route style. In addition, pilots outperformed nonpilots in both the 3D Rotation Task and Map Description Task. Conclusions: Military flight expertise influences some aspects of spatial ability, leading to enhanced human navigation. However, it must be considered that they are a population whose navigational skills were already high at the time of selection at the academy before formal training began.
In this article we give an overview of the applications of ultrastable clocks in space. We focus on the case of the ESA space mission ACES, which is scheduled for flight onboard the international ...space station in 2013. With a laser cooled cesium clock, PHARAO, a space hydrogen maser, SHM, and a precise time and frequency transfer system, MWL, several precision tests in fundamental physics can be performed such as a measurement of Einstein’s gravitational frequency shift with 2 ppm sensitivity and a search for time variations of the fundamental physical constants at 10
-17
/year. We present the advancement of the various mission instruments and present briefly applications in geodesy and Global Navigation Satellite Systems (GNSS).
The ACES/PHARAO space mission Laurent, Philippe; Massonnet, Didier; Cacciapuoti, Luigi ...
Comptes rendus. Physique,
06/2015, Letnik:
16, Številka:
5
Journal Article
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Proposed in 1997, the ACES/PHARAO experiment is a space mission in fundamental physics with two atomic clocks on the International Space Station, a network of ultra-stable clocks on the ground, and ...space-to-ground time transfer systems. The ACES flight instruments are near completion and launch in space is planned for the first half of 2017 for a mission duration of three years. A key element of the satellite payload is a cold-atom clock designed for microgravity environment, PHARAO, operating with laser-cooled cesium atoms. Here we first report on the design and tests of the PHARAO flight model, which is now completed and ready for launch. We then briefly present the status of development of the other instruments of the ACES payload, the Space Hydrogen Maser, the microwave time-transfer system (MWL), and the laser time transfer ELT.
Proposée en 1997, l'expérience ACES/Pharao est une mission spatiale en physique fondamentale avec deux horloges atomiques sur la Station spatiale internationale, un réseau d'horloges ultra-stables à terre et de systèmes de transfert de temps de l'espace jusqu'au sol. Les instruments de vol ACES sont proches de l'aboutissement et leur lancement dans l'espace est planifié pour la première moitié de 2017 pour une durée de mission de trois ans. Un élément-clé de la charge utile du satellite est une horloge atomique à atomes froids conçue pour la microgravité, Pharao, qui fonctionne avec des atomes de césium refroidis par laser. Nous commençons par décrire la conception et les essais du modèle de vol Pharao, qui est maintenant opérationnel et prêt pour le lancement. Nous présentons ensuite brièvement l'état de développement des autres instruments de la plateforme ACES, le maser passif à hydrogène, le système de transfert de temps par liaisons micro-ondes (MWL) et le transfert de temps par lien laser (ELT).
The crucial issue of supervising and managing electrical energy in the context of aircraft electrification, known as More-Electric Aircraft (MEA), is addressed in this paper. In the pursuit of ...developing energy-efficient solutions with reduced environmental impact, this research contributes valuable insights into innovative control strategies crucial for advancing aircraft electrification technologies. Through optimization techniques, the management of energy aims to maximize the proposed objectives. With a focus on controlling battery power for charging, discharging, and load shedding, this study employs Model Predictive Control (MPC) alongside an optimizer solving a mixed-integer linear programming (MILP) problem. Constraints encompass various aspects, including battery charging, maximum generator power, battery absorption, discharge limits, and converter power limitations. Theoretical results and detailed simulations demonstrate the effectiveness of the proposed approach in finding a good compromise among the objectives subjected to the system constraints. Practical validation of the proposed approach is conducted through the European project ORCHESTRA, utilizing comprehensive system simulations in Matlab/Simulink (2022b).
We present in detail the scientific objectives in fundamental physics of the Space–Time Explorer and QUantum Equivalence Space Test (STE–QUEST) space mission. STE–QUEST was pre-selected by the ...European Space Agency together with four other missions for the cosmic vision M3 launch opportunity planned around 2024. It carries out tests of different aspects of the Einstein Equivalence Principle using atomic clocks, matter wave interferometry and long distance time/frequency links, providing fascinating science at the interface between quantum mechanics and gravitation that cannot be achieved, at that level of precision, in ground experiments. We especially emphasize the specific strong interest of performing Equivalence Principle tests in the quantum regime, i.e. using quantum atomic wave interferometry. Although STE–QUEST was finally not selected in early 2014 because of budgetary and technological reasons, its science case was very highly rated. Our aim is to expose that science to a large audience in order to allow future projects and proposals to take advantage of the STE–QUEST experience.
Atomic clock ensemble in space Cacciapuoti, L; Salomon, C
Journal of physics. Conference series,
01/2011, Letnik:
327, Številka:
1
Journal Article
Recenzirano
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Atomic Clock Ensemble in Space (ACES) is a mission using high-performance clocks and links to test fundamental laws of physics in space. Operated in the microgravity environment of the International ...Space Station, the ACES clocks, PHARAO and SHM, will generate a frequency reference reaching instability and inaccuracy at the 1 · 10−16 level. A link in the microwave domain (MWL) and an optical link (ELT) will make the ACES clock signal available to ground laboratories equipped with atomic clocks. Space-to-ground and ground-to-ground comparisons of atomic frequency standards will be used to test Einstein's theory of general relativity including a precision measurement of the gravitational red-shift, a search for time variations of fundamental constants, and Lorentz Invariance tests. Applications in geodesy, optical time transfer, and ranging will also be supported. ACES has now reached an advanced technology maturity, with engineering models completed and successfully tested and flight hardware under development. This paper presents the ACES mission concept and the status of its main instruments.
One of the major limitations of atomic gravimeters is represented by the vibration noise of the measurement platform, which cannot be distinguished from the relevant acceleration signal. In this ...paper we perform atom interferometry measurements of the gravitational acceleration with high resolution without any need for a vibration isolation system or post-corrections based on seismometer data monitoring the residual accelerations at the sensor head. Using two different schemes, a Ramsey and a Ramsey–Bordé interferometer, we measure the velocity variation of freely falling cold atom samples, thus determining the gravitational acceleration experienced by them. Our instrument has a fractional stability of 2.7 × 10
−6
at 1 s of integration time, more than one order of magnitude better than a standard Mach–Zehnder interferometer when operated without any vibration isolation or applied post-correction.
Graphical abstract
Cold Atom Clocks in Microgravity: The ACES Mission CACCIAPUOTI, Luigi; SALOMON, Christophe
Journal of The Japan Society of Microgravity Application,
2008/07/31, Letnik:
25, Številka:
3
Journal Article
Odprti dostop
Atomic Clock Ensemble in Space (ACES) is a mission in fundamental physics which will operate a new generation of atomic clocks in the microgravity environment of the International Space Station. ...Designed to be installed at the external payload facility of the Columbus module, ACES will accommodate the cold-atom clock PHARAO and the active hydrogen maser SHM. The on-board time scale will reach fractional frequency instability and inaccuracy of few parts in 1016. The ACES clock signal will be distributed on Earth by a link in the microwave domain and used for the comparison of atomic frequency standards, both space-to-ground and ground-to-ground. Based on these comparisons, ACES will perform accurate tests of Einstein's theory of general relativity and develop applications in time and frequency metrology, global positioning and navigation, geodesy, and gravimetry. After a general overview of the mission concept and its scientific objectives, the present status of the ACES mission is discussed.
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