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MIO (Magnetosphere-Ionosphere Observatory) is designed to definitively fix a cause-and-effect problem: In the nightside magnetosphere-ionosphere system we don’t know what is connected to what. The MIO mission concept is to operate a powerful 1-MeV electron accelerator on a main spacecraft in the equatorial nightside magnetosphere: the electron beam is directed into the atmospheric loss cone to deposit ionizing electrons in the atmosphere sufficient to optically illuminate the magnetic footpoint of the spacecraft while 4 nearby daughter spacecraft make equatorial magnetospheric measurements. A network of ground-based optical imagers across Alaska and Canada will locate the optical beamspot thereby unambiguously establishing the magnetic connection between equatorial magnetospheric measurements and ionospheric phenomena. Critical gradient measurements will be made to discern magnetospheric field-aligned-current generator mechanisms. This enables the magnetospheric drivers of various aurora, ionospheric phenomena, and field-aligned currents to be determined. In support of the Solar and Space Physics (Heliophysics) 2022 Decadal Survey, an experienced team of engineers and scientists at The Johns Hopkins University Applied Physics Laboratory (APL) have developed a NASA HMCS (Heliospheric Mission Concept Study) mission concept that can achieve the science objectives. The mission concept presented here is the result of trade studies that optimized the mission with regard to factors such as science objectives, concept study requirements, space environment, engineering constraints, and risk. This Methods paper presents an overview of the MIO concept.

The major challenges of space research are monitoring and exploration of our planet, which are carried out through the use of remote sensing satellites (RSS) operating in near-Earth orbits. They provide invaluable information for assessing the environmental, epidemiological and other situations on our planet, including animal migration data. The ICARUS project (International Cooperation for Animal Research Using Space) implemented on the International Space Station (ISS) is an ideal laboratory for in-orbit testing of instrumentation and various space technologies aimed to refine methods for tracking movements of mammals and birds. The paper analyzes the experience in the operation of the animal migration monitoring system installed in the Russian segment (RS) of the ISS (ISS RS). The system has incorporated the latest accomplishments in space science, satellite navigation, control technology, and microelectronics. The scientific results on the study of animal and bird migrations obtained within the Russian research program are briefly discussed. [ABSTRACT FROM AUTHOR]

Onboard the International Space Station (ISS), as a part of the “Uragan” Earth exploration experiment, various observation devices are used, including photo and video spectral equipment, the orientation of which is carried out manually by the crew through the portholes. However, severe limitations are imposed on the planning of such experiments, primary related to the necessity taking into account the crew’s daily routine and the availability of time allocated for scientific experiments. The solution for expanding the ability to conduct experiments is the employing of automated orientation platforms (OP). One of these OPs is the video spectral equipment orientation system SOVA-1-426. A method for orientation angles forecasting of optical instruments for pointing at predefined objects on the Earth’s surface with SOVA-1-426 is presented. Moreover, in the described method, in addition to the coordinates of the center of mass, the current orientation of the ISS is taken into account, which makes it possible to perform the forecast with better precision. Taking into account the ISS orientation is carried out through the use of the ISS rotation quaternion to control the platform in automatic mode. The presented method for the orientation angles forecasting of high-resolution photo-camera aboard the ISS by employing SOVA-1-426 allows its automatic alignment on the Earth’s surface objects with accuracy up to seven kilometers. The described method is implemented in software and is currently used in the SOVA-1-426 OP aboard the ISS for the remote sensing of the Earth’s surface.

• The GAMMA-400 gamma-ray telescope performance for lateral aperture. • Detection of GRB from the lateral aperture in the energy range from ∼ 10 to ∼ 100 MeV. • The problem of connection between high- and low-energy gamma-ray emissions of GRBs. The currently developing space-based gamma-ray telescope GAMMA-400 will measure the gamma-ray and electron + positron fluxes using the main top-down aperture in the energy range from ∼ 20 MeV to several TeV in a highly elliptic orbit (without shading the telescope by the Earth and outside the radiation belts) continuously for a long time. The instrument will provide fundamentally new data on discrete gamma-ray sources, gamma-ray bursts (GRBs), sources and propagation of Galactic cosmic rays and signatures of dark matter due to its unique angular and energy resolutions in the wide energy range. The gamma-ray telescope consists of the anticoincidence system (AC), the converter-tracker (C), the time-of-flight system (S1 and S2), the position-sensitive and electromagnetic calorimeters (CC1 and CC2), scintillation detectors (S3 and S4) located above and behind the CC2 calorimeter and lateral detectors (LD) located around the CC2 calorimeter. In this paper, the capabilities of the GAMMA-400 gamma-ray telescope to measure fluxes of GRBs from lateral directions of CC2 are analyzed using Monte-Carlo simulations. The analysis is based on off-line second-level trigger construction using signals from S3, CC2, S4 and LD detectors. For checking the numerical algorithm the data from space-based GBM and LAT instruments of the Fermi experiment are used, namely, three long bursts: GRB 080916C, GRB 090902B, GRB 090926A and one short burst GRB 090510A. The obtained results allow us to conclude that from lateral directions the GAMMA-400 space-based gamma-ray telescope will reliably measure the spectra of bright GRBs in the energy range from ∼ 10 to ∼ 100 MeV with the on-axis effective area of about 0.13 m2 for each of the four sides of CC2 and total field of view of about 6 sr. [ABSTRACT FROM AUTHOR]

Insufficiently accurate magnetic-field-line mapping between the aurora and the equatorial magnetosphere prevents us from determining the cause of many types of aurora. An important example is the longstanding question of how the magnetosphere drives low-latitude (growth-phase) auroral arcs: a large number of diverse generator mechanisms have been hypothesized but equatorial magnetospheric measurements cannot be unambiguously connected to arcs in the ionosphere, preventing the community from identifying the correct generator mechanisms. Here a mission concept is described to solve the magnetic-connection problem. From an equatorial instrumented spacecraft, a powerful energetic-electron beam is fired into the atmospheric loss cone resulting in an optical beam spot in the upper atmosphere that can be optically imaged from the ground, putting the magnetic connection of the equatorial spacecraft’s measurements into the context of the aurora. Multiple technical challenges that must be overcome for this mission concept are discussed: these include spacecraft charging, beam dynamics, beam stability, detection of the beam spot in the presence of aurora, and the safety of nearby spacecraft.

The paper considers development of the Information Control System (ICS) of the Russian Segment of the International Space Station (ISS). The main ICS modules for carrying out scientific experiments comprise the Service Module, the Multipurpose Laboratory Module and the Science Power Module. At present specialists of Energia RSC are working to create high-tech conditions for scientific experiments on the new ISS modules, modernize the existing ones and combine them into a single onboard ISS information control complex. The information control system (ICS) is intended for automatic and manual control of space experiments. The effectiveness of modernization was confirmed by the results obtained during space experiments on the basis of the Information Control System. The ICS modernization started in 2012. At that time the ICS consisted of 4 onboard computers. The main task of ICS modernization was to introduce new computers and software-hardware systems. The software was supposed to have a flexible architecture and provide resources for all future onboard payloads. At the first stage one onboard computer was replaced. The main purpose of that stage was to test the new ISS hardware and software. The rest of the ICS computers will be replaced at the second stage, the Multipurpose Laboratory Module and the Science Power Module will also be equipped. The reliability of the system hardware is improved using functional backup. In 2014 2 cameras were installed on the ISS together with UrtheCast company (Canada).One of the cameras is a middle resolution camera; the other one is a high resolution camera. Today ground preparation of an experiment with Icarus scientific equipment is being carried out, jointly with the German Center of Aviation, DLR, and the SpaceTech company (Germany). The experience of the first stage of modernization suggests that the modernized ISS RS ICS will become an up-to-date system allowing the realization of most ambitious space experiments in automatic mode.

Abstract The United Nations Office for Outer Space Affairs has developed a comprehensive set of capacity-building activities and associated partnerships providing access to experimental facilities on ground and to a wide range of Low Earth Orbit platforms. These opportunities are available to applicants from high-school to university level, as well as other research, governmental and inter-governmental institutions. This is a unique approach to space capacity-building, away from the traditional classroom or lecture methods, aimed at developing and emerging economies, as well as encouraging cooperation with agencies and institutions from developed nations. This paper summarizes the series of activities and related programmatic and roadmap of the Office. Highlights • The Office for Outer Space Affairs provides capacity-building in space technologies. • Experiment and payload opportunities with increasing complexity are available. • Opportunities include microgravity experiments on ground and in orbit. • Activities aim at facilitating access to space to developing and emerging countries. [ABSTRACT FROM AUTHOR]

The International Space Station (ISS) project involves Russian Progress transport cargo vehicles (TCV) which often retain residual resources of their basic systems after they have completed their main tasks in the ISS program. Utilization of these resources for research purposes during free flight of the TCV after undocking from the station increases the efficiency of both the TCV operation and the ISS research program as a whole. Transport cargo vehicles can be used for research in various fields: in-flight tests, trials, validation and certification of various equipment, materials, and systems to the benefit of other spacecraft programs; conducting experiments within the framework of the Earth study using additional equipment; microgravity experiments taking into account specific capabilities of TCV; launch of small satellites and explorers after TCV undocking from the station and settling into specified orbit, etc. To perform research using the Progress transport cargo vehicles, new efficient technologies are proposed. These technologies required some specific methods of control to be developed. This paper addresses these technologies, as well as some of the developed control methods. [ABSTRACT FROM AUTHOR]

The weak equivalence principle (WEP) is the cornerstone of general relativity (GR). Testing it is thus a natural way to confront GR to experiments, which has been pursued for four centuries with increasing precision. MICROSCOPE is a space mission designed to test the WEP with a precision of 1 in 10 15 parts, two orders of magnitude better than previous experimental constraints. After completing its two-year mission, from 2016 to 2018, MICROSCOPE delivered unprecedented precise constraintsη(Ti,Pt)=[-1.5±2.3 (stat)±1.5 (syst)]×10-15(at 1 σ in statistical errors) on the Eötvös parameter between one proof mass made of titanium and another made of platinum. This bound allowed for improved constraints on alternative theories of gravitation. This review discusses the science beyond MICROSCOPE-GR and its alternatives, with an emphasis on scalar-tensor theories-before presenting the experimental concept and apparatus. The mission's science returns are then discussed before future tests of the WEP are introduced., (© 2023 IOP Publishing Ltd.)

The GAMMA-400 telescope will measure the fluxes of gamma rays and cosmic-ray electrons and positrons in the energy range from 100 MeV to several TeV. These measurements will allow it to achieve the following scientific objectives: search for signatures of dark matter, investigation of gamma-ray point-like and extended sources, study of the energy spectrum of the Galactic and extragalactic diffuse emission, study of gamma-ray bursts and gamma-ray emission from the active Sun, together with high-precision measurements of the high-energy electrons and positrons spectra, protons and nuclei up to the knee. The bulk of cosmic rays are protons and helium nuclei, whereas the lepton component in the total flux is ∼10 −3 at high energy. In the present paper, the simulated capability of the GAMMA-400 telescope to distinguish electrons and positrons from protons in cosmic rays is addressed. The individual contribution to the proton rejection from each detector system of GAMMA-400 is studied separately. The use of the combined information from all detectors allows us to reach a proton rejection of the order of ∼4 × 10 5 for vertical incident particles and ∼3 × 10 5 for particles with initial inclination of 30° in the electron energy range from 50 GeV to 1 TeV. [ABSTRACT FROM AUTHOR]

Gravity resistance, mechanical resistance to the gravitational force, is a principal graviresponse in plants, comparable to gravitropism. The cell wall is responsible for the final step of gravity resistance. The gravity signal increases the rigidity of the cell wall via the accumulation of its constituents, polymerization of certain matrix polysaccharides due to the suppression of breakdown, stimulation of cross-link formation, and modifications to the wall environment, in a wide range of situations from microgravity in space to hypergravity. Plants thus develop a tough body to resist the gravitational force via an increase in cell wall rigidity and the modification of growth anisotropy. The development of gravity resistance mechanisms has played an important role in the acquisition of responses to various mechanical stresses and the evolution of land plants. [ABSTRACT FROM AUTHOR]

The Rosetta/Philae mission was launched in 2004 by the European Space Agency (ESA). It is scheduled to reach the comet 67P/Churyumov-Gerasimenko in November 2014 after traveling more than six billion kilometers. The Philae module will then be separated from the orbiter (Rosetta) to attempt the first ever landing on the surface of a comet. If it succeeds, it will engage a sequence of scientific exploratory experiments on the comet. In this paper, we describe a constraint programming model for scheduling the different experiments of the mission. A feasible plan must satisfy a number of constraints induced by energetic resources, precedence relations on tasks, and incompatibility between instruments. Moreover, a very important aspect is related to the transfer (to the orbiter then to the Earth) of all the data produced by the instruments. The capacity of inboard memories and the limitation of transfers within visibility windows between lander and orbiter, make the transfer policy implemented on the lander CPU prone to data loss. We introduce a global constraint to handle data transfers. The purpose of this constraint is to ensure that data-producing tasks are scheduled in such a way that no data is lost. Thanks to this constraint and to the filtering rules we propose, mission control is now able to compute feasible plans in a few seconds for scenarios where minutes were previously often required. Moreover, in many cases, data transfers are now much more accurately simulated, thus increasing the reliability of the plans. [ABSTRACT FROM AUTHOR]

Abstract: The study of cosmic and gamma-rays has a long history and was at the beginning of what we now call Particle Physics. During the last years a growing number of particle physicists is turning again to Cosmic rays bringing all the latest techniques developed at the big accelerator experiments and making CR physics again one of the most stimulating and active field in the study of fundamental physics as the presentations during this conference demonstrate. [Copyright &y& Elsevier]

Abstract: Russian Progress transport cargo vehicles have successfully been used in different space station programs since 1978. At present time, they play an important role in the International Space Station (ISS) project. Main tasks performed by the transport cargo vehicle (TCV) in the station program are the following: refueling of the station, delivery of consumables and equipment, waste removal, station attitude control and orbit correction maneuver execution. At the same time, the cargo vehicle basic systems still retain unused resources after the vehicle finishes its work with the station. It makes sense to use these resources to perform research in free flight of TCV after departure from the ISS when possible. The fields of research can be determined not only on the basis of the vehicle capabilities as a research platform but also taking into account needs of the research community. Possible fields could be the following: [–] In-flight tests, validation and certification of various equipment, materials, systems in the interests of other spacecraft, [–] Execution of experiments on the Earth or other objects remote sensing using additional equipment, [–] Microgravity research aboard TCV, [–] Launch of small satellites and probes after TCV undocking from the station and transfer to the specified orbit, etc. Solution of research tasks using the Progress TCV resources helps to increase efficiency of the ISS research program performance. The paper considers the TCV flight control features and the methods of the solution of the problems arising when various experiments are performed aboard the vehicle. [Copyright &y& Elsevier]

Abstract: Calorimetry plays an essential role in experiments observing high energy gamma and cosmic rays in space. The observational capabilities are mainly limited by the geometrical dimensions and the mass of the calorimeter. Since deployable mass depends on the design of the detector and the total mass of the payload, it is important to optimize the geometrical acceptance of the calorimeter for rare events, its granularity for particle identification, and its absorption depth for the measurement of the particle energy. A design of a calorimeter that could simultaneously optimize these characteristics assuming a mass limit of about 1.6t has been studied. As a result, a homogeneous calorimeter instrumented with cesium iodide (CsI) crystals was chosen as the best compromise given the total mass constraint. The most suitable geometry found is cubic and isotropic, so as to detect particles arriving from every direction in space, thus maximizing the acceptance; granularity is obtained by filling the cubic volume with small cubic CsI crystals. The total radiation length in any direction is very large, and allows for optimal electromagnetic particle identification and energy measurement, while the interaction length is at least sufficient to allow a precise reconstruction of hadronic showers. Optimal values for the size of the crystals and spacing among them have been studied. Two prototypes have been constructed and preliminary tests with high energy ion and muon beams are reported. [Copyright &y& Elsevier]

Abstract: The search of dark matter signals in space has considerably progressed in the recent years by the PAMELA space mission and the long duration flight balloon-borne BESS Polar experiments. Interesting and intriguing results have been obtained by PAMELA in the positron to electron fraction, theoretically interpreted as contributions from dark matter annihilation or nearby pulsars. More standard explanations are not excluded. The results on the antiproton flux and the antiproton-to-proton ratio obtained by PAMELA and BESS are in agreement with secondary production mechanisms. AMS-02 operating outside the ISS since May 2011 should clarify the positron fraction puzzle and open new windows in the cosmic-rays study. [Copyright &y& Elsevier]

Abstract: Silicon Photomultipliers (SiPM) are considered very promising in many application where high timing performances, low cost, hardness to radiation damage and single photon counting are requested. Such applications go from astrophysics, high energy accelerator physics to medical physics. A group of SiPM from Hamamatsu has been tested with a low noise fast amplifier based on a hetero-junction FET, mounted on a proper front end board. A first telescope prototype has been used to test the electronics and results are shown. The SiPM time resolution has been measured to be σ∼30ps, in agreement with other studies reported in literature. The SiPM gain depends critically on temperature and a thermoelectric module to control the circuit was also studied in order to use the system for space detectors. [Copyright &y& Elsevier]

Abstract: The silicon photomultipliers (SiPM) are adopted in various physical applications, from medical physics to astrophysics, for their advantages in terms of cost and weight with respect to traditional photo detectors. Their low bias voltage supply (about 30V), hardiness and resistance to magnetic field are ideal characteristics for space application. In the frame of INFN-Irst collaboration, some of them have been developed and produced at FBK (Trento-Italy), and have been characterized in the INFN laboratories of Bologna (DaSiPM2 collaboration). The SiPM can be used in conjunction with fibres and counters in high energy physics experiments. To exploit the SiPM time resolution, a fast amplifier has been studied. The SiPM gain depends critically on temperature and a thermal stabilization is also necessary. The use of a thermoelectric cooler module based on a Peltier cell has been investigated, and the results are shown. [Copyright &y& Elsevier]

Abstract: In many physics experiments where calorimeters are employed, the requirement of an accurate energy measurement is accompanied by the requirement of very high hadron–electron discrimination power. Normally the latter requirement is achieved by designing a high-granularity detector with sufficient depth so that the showers can fully develop. This method has many drawbacks ranging from the high number of electronic channels to the high mass of the detector itself. Some of these drawbacks may in fact severely limit the deployment of such a detector in many experiments, most notably in space-based ones. Another method, proposed by our group and currently under investigation, relies on the use of scintillation detectors which are sensitive to the neutron component of the hadron showers. Here a review of the current status will be presented starting with the simulations performed both with GEANT4 and FLUKA. A small prototype detector has been built and has been tested in a high-energy pion/electron beam behind a “shallow” calorimeter. Results are encouraging and indicate that it is possible to enhance the discrimination power of an existing calorimeter by the addition of a small-mass neutron detector, thus paving the way for better performing astroparticle experiments. [ABSTRACT FROM AUTHOR]

Briefly overviewed is the state-of-art in investigation of SHS reactions in microgravity. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents the analysis of experimental data on electron fluxes with energies 10keV–10MeV. Data were obtained during 1978–2005 years in different space experiments (COSMOS-900, MIR Space Station, ACTIVE, SAMPEX, CORONAS-I, CORONAS-F, NOAA POES-17, TATYANA and others). Two areas of electron flux enhancements are studied in the paper: the near-equatorial (L <1.2) zone and the middle-latitude (1.2< L <1.9) zone. It is shown that electron flux enhancements are regularly registered at L <2 and the observed formations have some typical features. Electron peaks at L <1.2 appear sporadically while peaks at 1.2< L <1.9 are observed regularly. The approximations of spectra by several functions including kappa-function are presented. [Copyright &y& Elsevier]

Abstract: A sample of Silicon Photomultipliers was tested because they looked promising for future space missions: low consumption, low weight, resistance to radiation damage and insensitivity to magnetic fields. They have been studied in laboratory by means of the same characterization methods adopted to calibrate the fine mesh photomultipliers used by the Time Of Flight of the AMS-02 experiment. A detailed simulation was made to reproduce the SiPM response to the various experimental conditions. A possible counter design has been studied with front end electronics card equipped with SiPMs and Peltier cell for thermoregulation. A proper simulation based on COMSOL Multiphysics package reproduces quite well the Peltier cell nominal cooling capability. [Copyright &y& Elsevier]

Optical frequency standards and femtosecond comb measurement capabilities now rival and in some cases exceed those of microwave devices, with further improvements anticipated. Opportunities are emerging for the application of highly stable and accurate optical frequency devices to fundamental physics space science activities, and the European Space Agency (ESA) has recently commissioned studies on different aspects of optical clocks in space. This paper highlights some examples, including the difficulty of comparing very accurate terrestrial clocks at different locations due to fluctuations of the geoid; by locating a primary frequency standard in space, one could avoid geoid-related gravitational redshifts. [ABSTRACT FROM AUTHOR]

The constant of gravitation, G, is the least well-known of the physical constants. A new, independent method of measurement, estimated as having a potential uncertainty at least as small as that achieved by existing methods, would be useful for an improvement in G determination. This experiment is based on the measurement of the relative motion of two freely falling test bodies (discs), caused by their gravitational attraction. The uncertainties are analyzed for two parallel tungsten discs with masses of about 30 kg. The use of test bodies with an incorporated optical system of multipass two-beam interferometers, as well as of multibeam interferometers, is proposed to measure their relative displacement. The estimations were made for laboratory experiment with free fall duration of 0.714 s. In this case, the relative displacement to be measured is about 0.1 μm. These estimates show that relative uncertainties lower than 5 × 10-5 can be obtained in G measurement in a single drop of the test bodies. The proposed experiment can be made in outer space. In space a lower uncertainty can be achieved because the time interval of the measurement of relative motion of the test bodies can be increased. [ABSTRACT FROM AUTHOR]

Abstract: We have studied the ability of microorganisms to cope with the complex interplay of the parameters of space in experiments in low Earth orbit and using space simulation facilities on ground. Emphasis was laid on space parameters other than cosmic rays. The studies are directed towards understanding prebiotic chemical evolution and biological evolution processes, and interplanetary transfer of life. Effects of space vacuum: Space experiments have shown that up to 70% of bacterial and fungal spores survived short-term exposure to space vacuum. The chances of survival in space were increased when spores were embedded in chemical protectants such as sugars, or salt crystals, or when they were exposed in multilayer. During the six years lasting LDEF mission up to 80% of bacterial spores survived exposure to space vacuum. A 10-fold increased mutation rate over the spontaneous rate has been observed in spores of Bacillus subtilis after exposure to space vacuum, which is probably based on a unique molecular signature of tandem-double base change at restricted sites in the DNA. In addition, DNA strand breaks have been observed to be induced by vacuum treatment. Effects of extraterrestrial solar UV radiation: Solar UV radiation has been found to be the most deleterious factor of space. The reason for this is the highly energetic UV-C and vacuum UV radiation that is directly absorbed by the DNA and which induces specific photoproducts in the DNA that are highly mutagenic and lethal. The damaging effect of extraterrestrial solar UV radiation was even aggravated, when the spores were simultaneously exposed to both, solar UV radiation and space vacuum. In order to investigate the mutagenic potential of solar UV radiation, DNA of the Escherichia coli plasmid pUC19 was exposed to selected wavebands of UV radiation (from vacuum UV to UV-A) by use of a solar simulator and space simulation facilities. Action spectra revealed that for vacuum UV different kinds of photochemical damage contribute to inactivation and mutation induction. Sequencing of the UV-induced lacZ′ mutants provided mutation spectra and mutational hot spots for the various UV regions. In all UV regions, the predominant base substitution was the G:C to A:T transition. A:T to T:A transversions were increasingly produced by short-waveband UV, whereas G:C to C:G transversions predominated after exposure to UV-A. Deletions of more than one base pair were only detected after exposure to vacuum UV radiation. [Copyright &y& Elsevier]

Abstract: DC electric fields can combine with test mass charging and thermal dielectric voltage noise to create significant force noise acting on the drag-free test masses in the Laser Interferometer Space Antenna (LISA) gravitational wave mission. This paper proposes a simple technique to measure and compensate average stray DC potentials at the mV level, yielding substantial reduction in this source of force noise. We discuss the attainable resolution for both flight and ground based experiments. [Copyright &y& Elsevier]

Abstract: Since their discovery, almost one century ago, cosmic rays provide a powerful tool to investigate phenomena covering both astrophysical and fundamental physics issues. The detection of cosmic rays from low to extreme energies is potentially linked to some of the most intriguing and still unsolved questions of physics and cosmology. Among them, are the nature of the dark matter, the apparent disappearance of the antimatter, the existence of a new exotic form of matter, e.g., strangelets. At the highest energies, the sources and the mechanisms by which cosmic rays are generated and/or accelerated are still a puzzling issue for today’s astrophysicists. In order to answer these questions several experiments are planned during the next decade, from space, stratosphere or ground, to perform a multifrequency exploration of the cosmic ray spectrum. [Copyright &y& Elsevier]

Abstract: The OPTIS satellite mission is an international collaboration initiated by three German University institutes aiming at improving tests regarding the foundations of Special and General Relativity. The mission idea – which has already passed the state of the initial feasibility study – is to contribute to the most challenging project of physics in this century – the search for a Theory of Quantum Gravity. This theory should resolve the incompatibilities between the quantum theory and Einstein''s General Relativity. All approaches for a Quantum Gravity Theory predict small deviations from Special and General Relativity. If such deviations could be found (e.g. an anisotropy of the speed of light, violations of the universality of gravitational red shift or of the universality of free fall) the way to a new understanding of the time and space structure of the universe would be open. Therefore the goal of the OPTIS satellite mission is an accuracy improvement of tests regarding the foundations of Special and General Relativity by up to three orders of magnitude. For that purpose several experiments will be carried out on board the OPTIS satellite testing (i) the isotropy of the speed of light, (ii) the independence of the speed of light from the velocity of the laboratory system, (iii) the universality of the gravitational redshift, (iv) the absolute gravitational redshift and (v) the special relativistic time-dilation. Furthermore, orbit analyses will be done in order to measure (vi) the Lense–Thirring effect and (vii) perigee advance as well as to test (viii) the Newtonian gravitational potential. The benefit from bringing these experiments into space is the nearly disturbance free environment allowing precise measurements and large measurement times. The OPTIS mission will use already available key technologies like optical cavities, highly stabilised lasers, atomic clocks, frequency combs, capacitive gravitational reference sensors, drag-free control, laser tracking and laser linking systems. For most of the proposed tests the measurements are done by comparing the rates of different clocks. For the test of the isotropy of the velocity of light (Michelson–Morley experiment) the frequencies of resonators (‘light clocks’) pointing in different directions are compared. Concerning the constancy of the speed of light (Kennedy–Thorndike experiment) a resonator and atomic clocks under varying velocities are compared. For tests of the time dilation the rates of clocks in different states of motion and for testing the universality of the gravitational redshift clocks at different positions in the gravitational field are compared. This paper will give an overview about the OPTIS satellite mission, including the science goals, science requirements, key technologies, measurement principles and devices. [Copyright &y& Elsevier]