The RADiation Impacts on Climate and Atmospheric Loss Satellite (RADICALS) is a low-Earth orbiting Canadian small satellite mission investigating the transport of space radiation into the atmosphere, and its impact on Earth’s climate. Scheduled for launch in late 2026, the mission will launch into a polar orbit with an integrated payload comprising two back-to-back look direction High Energy Particle (HEP) telescopes, an X-Ray Imager (XRI) to remote sense energetic particle precipitation using back-scattered Bremsstrahlung X-rays, and a boom mounted FluxGate Magnetometer (FGM) and Search Coil Magnetometer (SCM). Using an innovative Thomson spin-stabilized configuration, the satellite will sample the pitch angle distributions in the spin-plane twice per spin. The back-to-back HEP look directions allow for a contemporaneous view of the down-going and back-scattered up-going electrons, at the same time as XRI remote-senses the related Bremsstrahlung, and the magnetometers provide in-situ magnetic signatures of a range of plasma waves. The key measurement of the pitch angle resolved energetic electron precipitation (EEP) and related back-scatter, including a resolved loss cone, will allow a detailed assessment of the energetic particle energy input to the atmosphere. Measurements of EEP, in addition to measurements of solar energetic particle (SEP) precipitation, will represent a critical data set for assessing the role of space radiation in the climate system, for example through the catalytic destruction of ozone in the middle atmosphere by NOx and HOx. Accurately quantifying the impacts of this space radiation on climate requires accurate and loss cone-resolved characterization of the flux of these precipitating energetic particles for inclusion into whole atmosphere models. The RADICALS explorer will also enable research into potentially catastrophic space-weather radiation effects on satellite infrastructure, and assess impacts on space weather-related interruptions to high frequency radio communications including in relation to aircraft operations in polar regions. Additional cube- and micro-satellite missions, together with the RADICALS, could form a powerful mini--constellation exploring the space weather-climate system.

A signal-tracking Fabry-Perot interferometer (STFPI) has been successfully developed using a frequency-stabilized He-Ne laser as a pilot signal for real-time capturing of system parameters simultaneously during nightglow observations. Wind velocities were derived in laboratory experiments using a novel piloted deconvolution technique from non-contaminating interference fringes generated from the He-Ne laser and a Neon calibration lamp emission at 630.479 nm. The piloted measurement method substantially improves measurement accuracy and eliminates sensitivity to laser calibration interval time, maintaining a consistent system uncertainty of 1.07 m/s in wind measurements. It also effectively suppresses the influence of instrumental drift. Under high-precision thermal control of an etalon over a 24-hour experiment period, the conventional measurement has an instrumental drift in wind velocity of 61.09 m/s, whereas the piloted approach consistently corrects this drift to below 5.25 m/s. These results confirm the STFPI's capability to enhance the stability and reliability of wind measurements under variable thermal conditions, supporting its application in long-term optical observations of faint nightglow emissions.

A dual-wavelength spaceborne Martian polarized wind imaging Michelson interferometer based on liquid crystal tunable filters (LCTF-MPWIMI) has been proposed for the remote sensing detection of dynamic parameters such as wind speed and temperature in the middle and upper atmosphere of Mars. Using the detected Martian oxygen atom emission lines at 557.7 nm and 630.0 nm as observation spectral lines, this technology extends the detection altitude range for Martian atmospheric wind speed and temperature to 60–180 km. By leveraging the different spectral line visibility of the interferograms at the two wavelengths, a novel method for measuring Martian atmospheric temperature is proposed: the dual-wavelength spectral line visibility product method. This new approach reduces the uncertainty of temperature detection compared to traditional single spectral line visibility methods, while maintaining the precision of wind speed measurements. The feasibility of the LCTF-MPWIMI for measuring wind and temperature fields in the Martian middle and upper atmosphere has been validated through theoretical modeling and computer simulations. The interferometer, as a key component of the system, has been designed and analyzed. The proposed LCTF-MPWIMI instrument is free of mechanical moving parts, offering flexible wavelength selection and facilitating miniaturization. The dual-wavelength temperature measurement method introduced in this work provides superior temperature measurement precision compared to any single spectral line when the signal-to-noise ratio (SNR) of the interferograms is comparable. Moreover, this method does not impose specific requirements on the atomic state of the spectral lines, making it broadly applicable to similar interferometric wind measurement instruments. These innovations offer advanced tools and methodologies for measuring wind speeds and temperatures in the atmospheres of Mars and other planets.

Upper-atmosphere winds from a meteor radar and a field-widened Michelson interferometer, co-located at the Polar Environment Atmospheric Research Laboratory in Eureka, Nunavut, Canada (80° N, 86° W) are compared. The two instruments implement different wind-measuring techniques at similar heights and have very different temporal and spatial observational footprints. The meteor radar provides winds averaged over a ∼ 300 km horizontal area in 3 km vertical bins between 82 and 97 km on a 1 h cadence. The E-Region Wind Interferometer II (ERWIN) provides airglow-weighted winds (averaged over volumes of ∼ 8 km in height by ∼ 5 km radius) from three nightglow emissions (O(1S), oxygen green line, 557.7 nm, 97 km; an O2 line, 866 nm, 94 km; and an OH line, 843 nm, 87 km) on a ∼ 5 min cadence. ERWIN's higher precision (1–2 m s−1 for the O(1S) and OH emissions and ∼ 4 m s−1 for the O2 emissions) and higher cadence allows more substantive comparisons between winds measured by meteor radar and Doppler shifts in airglow emissions than previously possible for similar meteor radar/airglow Doppler shift comparisons using Fabry–Perot interferometers. The best correlation is achieved using Gaussian weighting of meteor radar winds with peak height and vertical width being optimally determined. Peak heights agree well with co-located SABER airglow observations. Offsets between the two instruments are ∼ 1–2 m s−1 for the O2 and O(1S) emissions and less than 0.3 m s−1 for the OH emission. Wind directions are highly correlated with a ∼ 1:1 correspondence. On average, meteor radar wind magnitudes are ∼ 40 % larger than those from ERWIN. Gravity wave airglow brightness weighting of observations is discussed. Non-quadrature phase offsets between the airglow weighting and gravity wave associated wind and temperature perturbations will result in enhanced or reduced layer-weighted wind amplitudes.

A four-quadrant wind imaging interferometer is a new generation of wind imaging interferometer with the valuable features of being monolithic, compact, light, and insensitive to temporal variations in the source. Its applications include remote sensing of the wind field of the upper atmosphere and observing important dynamical processes in the mesosphere and lower thermosphere. In this paper, we describe a new phase step determination approach based on the Lissajous figure, which provides an efficient, accurate, and visual method for the characterization and calibration of this type of instrument. Using the data from wavelength or thermal fringe scanning, the phase steps, relative intensities, and instrument visibilities of four quadrants can be retrieved simultaneously. A general model for the four-quadrant wind imaging interferometer is described and the noise sensitivity of this method is analyzed. This approach was successfully implemented with four-quadrant wind imaging interferometer prototypes, and its feasibility was experimentally verified.

The stratospheric wind field provides significant information on the dynamics, constituent, and energy transport in the Earth's atmosphere. The measurement of the atmospheric wind field on a global basis at these heights is still lacking because few wind imaging interferometers have been developed that can measure wind in this region. In this paper, we describe an advanced compact static wind imaging Michelson interferometer (SWIMI) developed to measure the stratospheric wind field using near-infrared airglow emissions. The instrument contains a field widened and thermal compensated interferometer with a segmented reflective mirror in one arm, which replace the moving mirror in a conventional Michelson interferometer, to provide interference phase steps. The field widened, achromatic, temperature compensated scheme has been designed and manufactured. The characterization, calibration, inversion software, and test of the instrument have been completed. The capacity of two-dimensional wind, temperature, and ozone measurement of the instrument has been verified in the lab experiment and model simulation. What we believe to be the novel principle, modeling, design, and experiment demonstrated in this paper will offer a significant reference to the static, simultaneous and real-time detection and inversion of the global wind field, temperature, and ozone.

An international joint research project, entitled Interhemispheric Coupling Study by Observations and Modelling (ICSOM), is ongoing. In the late 2000s, an interesting form of interhemispheric coupling (IHC) was discovered: when warming occurs in the winter polar stratosphere, the upper mesosphere in the summer hemisphere also becomes warmer with a time lag of days. This IHC phenomenon is considered to be a coupling through processes in the middle atmosphere (i.e., stratosphere, mesosphere, and lower thermosphere). Several plausible mechanisms have been proposed so far, but they are still controversial. This is mainly because of the difficulty in observing and simulating gravity waves (GWs) at small scales, despite the important role they are known to play in middle atmosphere dynamics. In this project, by networking sparsely but globally distributed radars, mesospheric GWs have been simultaneously observed in seven boreal winters since 2015/16. We have succeeded in capturing five stratospheric sudden warming events and two polar vortex intensification events. This project also includes the development of a new data assimilation system to generate long-term reanalysis data for the whole middle atmosphere, and simulations by a state-of-the-art GW-permitting general circulation model using the reanalysis data as initial values. By analyzing data from these observations, data assimilation, and model simulation, comprehensive studies to investigate the mechanism of IHC are planned. This paper provides an overview of ICSOM, but even initial results suggest that not only GWs but also large-scale waves are important for the mechanism of the IHC.

The first, to our knowledge, successful laboratory implementation of an approach to image winds using simultaneous (as opposed to sequential) fringe imaging of suitable isolated spectral emission lines is described. Achieving this in practice has been a long-standing goal for wind imaging using airglow. It avoids the aliasing effects of source irradiance variations that are possible with sequential fringe sampling techniques. Simultaneous fringe imaging is accomplished using a field-widened Michelson interferometer by depositing phase steps on four quadrants of one of the mirrors and designing an optical system so that four images of the scene of interest, each at a different phase, are simultaneously produced. In this paper, the instrument characteristics, its characterization, and the analysis algorithms necessary for use of the technique for this type of interferometer are described for the first time, to the best of our knowledge. The large throughput associated with field-widened Michelson interferometers is sufficient for the spatial resolutions and temporal cadences necessary for ground based imaging of gravity waves in wind and irradiance to be achieved. The practical demonstration of this technique also validates its use for proposed monolithic satellite instruments for wind measurements using airglow on the Earth and Mars.

Thermospheric wind observations from high to mid latitudes are compared with the newly developed Multiscale Atmosphere Geospace Environment (MAGE) model for the Nov 3–4 geomagnetic storm. The observation and simulation comparison shows a very good agreement and is better at high latitudes in general. We were able to identify a thermospheric poleward wind reduction possibly linked to a northward turning of the Interplanetary Magnetic Field (IMF) at ~22 UT on Nov 3 and an enhancement of the poleward wind to a southward turning near 10 UT on Nov 4 at high latitudes. An IMF southward turning may have led to an enhancement of equatorward winds at Boulder, Colorado near midnight. Simultaneous occurrence of aurora may be associated with an IMF By turning negative. The MAGE model wind simulations are consistent with observations in these cases. The results show the model can be a very useful tool to further study the magnetosphere and ionosphere coupling on short time scales.

EDITORIAL article Front. Astron. Space Sci., 23 February 2022 | https://doi.org/10.3389/fspas.2022.857766

近年来,中国的火星探测任务引起了人们对行星科学探索的极大兴趣.文章提出一种利用多普勒迈克尔逊干涉测量技术测量火星大气风场的概念模拟.基于火星大气动力学观测项目（DYNAMO）设计的卫星仪器,利用迈克尔逊方程构建了由轨道子模型、大气背景场子模型和仪器子模型组成的DYNAMO测量的正演模型,模拟了仪器测量火星大气中1.27μm气辉光谱来观测火星大气风场.研究发现,正演模型计算的视场上的干涉图信号与滤波器的透过率函数、气辉的体发射率、风速、温度和迈克尔逊相位有关.利用简单的反演算法从模拟的干涉图信号推导了大气信号,推导的大气参数与正演模型的输入参数一致,验证了所建的正演模型的有效性.

While knowledge of the energy inputs from the Sun (as it is the primary energy source) is important for understanding the solar-terrestrial system, of equal importance is the manner in which the terrestrial part of the system organizes itself in a quasi-equilibrium state to accommodate and re-emit this energy. The ROSMIC project (2014–2018 inclusive) was the component of SCOSTEP’s Variability of the Sun and Its Terrestrial Impact (VarSITI) program which supported research into the terrestrial component of this system. The four themes supported under ROSMIC are solar influence on climate, coupling by dynamics, trends in the mesosphere lower thermosphere, and trends and solar influence in the thermosphere. Over the course of the VarSITI program, scientific advances were made in all four themes. This included improvements in understanding (1) the transport of photochemically produced species from the thermosphere into the lower atmosphere; (2) the manner in which waves produced in the lower atmosphere propagate upward and influence the winds, dynamical variability, and transport of constituents in the mesosphere, ionosphere, and thermosphere; (3) the character of the long-term trends in the mesosphere and lower thermosphere; and (4) the trends and structural changes taking place in the thermosphere. This paper reviews the progress made in these four areas over the past 5 years and summarizes the anticipated research directions in these areas in the future. It also provides a physical context of the elements which maintain the structure of the terrestrial component of this system. The effects that changes to the atmosphere (such as those currently occurring as a result of anthropogenic influences) as well as plausible variations in solar activity may have on the solar terrestrial system need to be understood to support and guide future human activities on Earth.

China’s Mars exploration mission has stimulated tremendous interest in planetary science exploration recently. To propose potential scientific research projects, this study presents a concept simulation for the measurement of Martian atmospheric winds using the Doppler Michelson interferometry technique. The simulation is based on the satellite instrument initially designed for the Dynamic Atmosphere Mars Observer(DYNAMO) project to measure vertical profiles of winds from the 1.27 μm airglow observations in the Martian atmosphere. A comprehensive DYNAMO measurement simulation forward model based on an orbit submodel, an atmospheric background field submodel, and an instrument submodel is developed using the Michelson equation. The simulated interferogram signal over the field of view(FOV) calculated by the forward model is associated with the filter transmittance function, column emission rate of airglow, wind velocity, temperature, and the Michelson phase. The agreement between the derived atmospheric signals from the simulated interferogram without altitude inversion and the input parameters used to initiate the forward model confirms the validity of the forward model.

For the first time, a generalized bin-by-bin analysis approach developed to characterize the visibility, phase, and brightness from Doppler Michelson interferometry (DMI) fringe images is presented. This approach allows for significant advances to the spatial/temporal resolution and sensitivity of DMI utilized for measuring upper atmospheric motions. Expressions for the sensitivity that depend only on the instrument parameters are derived. A unique calibration approach, developed to take full advantage of the DMI imaging capability, is described. The usefulness and validity of this approach is demonstrated using observations from two field-widened interferometers implemented in the field (E-Region Wind Interferometer (ERWIN-II) and the Michelson Interferometer for Airglow Dynamics Imaging (MIADI)). Incorporating the imaging capability into the DMI approach enhances the spatial/temporal information that can be extracted from geophysical observations.

This work focuses on determining the optimal design for field widening, and thermal and achromatic compensating a static Mars wind imaging Michelson interferometer (MWIMI). The target lines of MWIMI are emission lines in the 1.27 mu m band of the O-2((1)Delta(g)) airglow. These emissions allow the dynamics of the Martian atmosphere from similar to 5 km to similar to 60 km to be observed. Two designs, a three-layer (consisting of two arm glasses and an air gap) and a four-layer (consisting of three arm glasses and an air gap) are examined for a path difference of 10 cm. All possible glass combinations from the SCHOTT glass catalog for these two designs are considered using a computer matching program to determine the optimal ones. The optimal glass combinations are listed and their properties are discussed. The error caused by the misalignment/tilt of optical surface, the homogeneity of glass, the variation of ambient temperature, the glass thickness error and the refractive index error is analyzed. The limits of the tilt angle of optical surface and the homogeneity for MWIMI are provided. The optical path difference varies by less than 0.1 wavelengths over the 5 degrees angular range passing through the interferometer when the variation of ambient temperature and the thickness and refractive index uncertainties are considered. The wind velocity error, the primary factor for characterizing a field-widened Michelson interferometer, is analyzed. Calculations show that the wind speed uncertainty can be better than 1 m s(-1) for an altitude range of 0 - 90 km during daytime and is better than 6 m s(-1) for an altitude range of 0 - 75 km during nighttime.

We present a forecast model for the total variability of DW1 and study its prediction accuracy against the actual variability from the extended Canadian Middle Atmospheric Model (eCMAM) simulations and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) observations in the mesosphere and lower thermosphere region. To account for the long‐term variability (periods >30 days), we fit the data with a multi‐linear regression model that contains the solar cycle, El Niño Southern Oscillation, quasi‐biennial oscillation, and the seasonal harmonics at 12, 6, 4, and 3 months. The fitting coefficients/amplitudes from each deterministic variability are examined between the eCMAM and SABER. To predict the short‐term tidal variability, we adopted an auto‐regression (AR) model from Vitharana et al. (2019, https://doi.org/10.1029/2019JD030573 ). The forecast model is a combination of the multi‐linear regression model and the AR model. The forecast model can predict the total tidal variability of DW1 with high accuracy. The prediction accuracy (correlation coefficient) ranges between 0.81 and 0.98 (average 0.93) for eCMAM and 0.76 and 0.92 (average 0.82) for SABER. The prediction accuracy for the short‐term tidal variability is very high for both eCMAM and SABER and shows little variation with correlation coefficients at ∼0.95. The prediction accuracy for the total tidal variability follows that for the long‐term tidal variability. The discrepancy between the forecast model and the actual total tidal variability is mainly because the forecast model cannot capture all the long‐term tidal variability (periods >30 days). Besides the well‐known periods for long‐term variability, the other periods change on a year‐to‐year basis.

Contemporaneous multi-instrument ground-based optical and meteor radar observations of OH and O-2 airglow, temperature and neutral winds during the winter season of November 2018-February 2019 have been used to investigate the dynamics of the mesosphere/lower thermosphere (MLT) (80-100 km) region in the high Arctic at Svalbard, Norway (78 degrees N, 16 degrees E) and at Eureka, Canada (80 degrees N, 274 degrees E). Temperature observations by the MLS Aura satellite over the 20-90 km height range for the same period were also considered. The period is characterized by an unusual major sudden stratospheric warming (SSW) event that began with a displacement of the polar vortex around December 13, 2018 (DoY 347), followed by the vortex split on January 2, 2019 (DoY 367). The MLS Aura temperature observations outlined four periods of interest: 1) late November - early December (DoY 328-335) with cold temperature anomalies in the mesosphere and warm bursts at the stratopause; 2) December 13, 2018-January 2, 2019 (DoY 347-367) when the stratopause rapidly descended to 45 km and broke down, triggering the onset of a SSW; 3) January 3-20, 2019 (DoY 368-385) during the stratopause recovery phase, and 4) from January 21, 2019 (DoY 386) onward, with the formation of the elevated stratopause and gradual return to its pre-SSW height. Both airglow emissions, OH and O-2 Atm, showed simultaneously significant depletion of the integrated emission rates (IER) and temperature decrease of the order of 50-60 K, indicating upwelling, depletion of the atomic oxygen and adiabatic cooling. These cold temperature anomalies were followed by enhancements in the observed airglow IERs on December 13, 2018 (DoY 347) and January 2, 2019 (DoY 367) accompanied by a decrease in the peak altitude of the OH layer suggesting down-welling and influx of atomic oxygen from the lower thermosphere. The observations revealed oscillations with periods of 4.5-7 days, 8-10 days, and 16-21 days consistent with previously reported planetary wave activity in the winter MLT region and during major stratospheric warming events. However, the results presented here show for the first time comparisons of the multi-instrument temperature observations at 78 degrees N - 80 degrees N, providing an indispensable tool in monitoring the dynamics over the polar cap in general, and in describing the regional dynamical response of the MLT region to major large-scale phenomena like stratospheric warmings, in particular.

An efficient approach is presented that allows the field of view sensitivities of a field-widened birefringent interferometer constructed from several stacked birefringent slabs to be examined. The approach utilizes a Jones matrix framework that is valid for birefringent slabs that have their optic axis parallel to the surface of the slab. It neglects Fresnel effects and multiple reflections, but accounts for birefringent splitting and does not neglect higher-order angular effects. The simplified approach allows the angular sensitivity of the optical path difference near the field-widened configuration to be examined in the presence of misalignment and mismatches between the components. Understanding these effects is critical to developing wide-field interferometers that can be utilized for imaging purposes. Here, we present the developed framework and apply it to examine the field of view effects of a three-element field-widened static birefringent interferometer that is being developed for the measurement of upper atmospheric winds. We examine the sensitivity of the device to rotational misalignment, mismatches, and wavelength shifts. Comparisons among the modeled interference fringes, output from Zemax optical design software, and lab observations are used to validate the approach. It is also shown that the approach accurately simulates parasitic fringes associated with unwanted coupling between extraordinary and ordinary waves at the interfaces.