Comparison of PM2.5 in Seoul, Korea Estimated from the Various Ground-Based and Satellite AOD

Based on multiple linear regression (MLR) models, we estimated the PM2.5 at Seoul using a number of aerosol optical depth (AOD) values obtained from ground-based and satellite remote sensing observations. To construct the MLR model, we consider various parameters related to the ambient meteorology and air quality. In general, all AOD values resulted in the high quality of PM2.5 estimation through the MLR method: mostly correlation coefficients >~0.8. Among various polar-orbit satellite AODs, AOD values from the MODIS measurement contribute to better PM2.5 estimation. We also found that the quality of estimated PM2.5 shows some seasonal variation; the estimated PM2.5 values consistently have the highest correlation with in situ PM2.5 in autumn, but are not well established in winter, probably due to the difficulty of AOD retrieval in the winter condition. MLR modeling using spectral AOD values from the ground-based measurements revealed that the accuracy of PM2.5 estimation does not depend on the selected wavelength. Although all AOD values used in this study resulted in a reasonable accuracy range of PM2.5 estimation, our analyses of the difference in estimated PM2.5 reveal the importance of utilizing the proper AOD for the best quality of PM2.5 estimation.

Studies of the atmosphere of ultra-hot Jupiter TOI-1431b/MASCARA-5b

<p>Ultra-hot Jupiters are defined as giant planets with equilibrium temperatures larger than 2000 K. Most of them are found orbiting bright A-F stars, making them extremely suitable object to study their atmospheres using high-resolution spectroscopy.</p> <p>TOI-1431b, also known as MASCARA-5b, a newly discovered planet with the temperature of 2375 K is a prefect example of ultra-hot Jupiter. We studied this object using three transit observations obtained with high-resolution spectrographs HARPS-N and EXPRES. Analysis of Rossiter-McLaughlin effect shows that the planet is in the polar orbit, which speaks about an interesting dynamical history, and perhaps indicating the presence of more than one planet in the early history of this system. Applying the cross-correlation and transmission spectroscopy method, we find no evidence of atoms and molecules in this planet. There results are at odds with the other studies of similar UHJs orbiting bright stars, where various species have been found.</p>

Zonal Profiles of Jupiter's Tropospheric Abundances from Near-Infrared Juno JIRAM Spectroscopy

<p>The polar orbit of the Juno spacecraft provides an unprecedented view of Jupiter's atmosphere as it passes above the cloud tops every 53 days. The spectrum in the near infrared is dominated by reflected sunlight from aerosols (both condensate clouds and hazes) in the troposphere, as well as absorptions by the molecular species present. In addition, thermal emission longward of 4.5 µm provides access to the gaseous composition and aerosols below the top-most clouds.  Of particular importance in shaping the spectra are ammonia, phosphine and water, in addition to minor contributions from species such as arsine, germane and carbon monoxide. These regions also include emissions by ionospheric H<sub>3</sub><sup>+</sup>. Here, we produce meridionally averaged zonal profiles from the Juno-JIRAM observations obtained during PJ3, which provide almost complete latitude coverage. To analyse the observations, we use the radiative transfer and retrieval code NEMESIS (Irwin et al., 2008), which has been updated to cover this wavelength with the latest line-data from HITRAN. Our aim is to analyse both the reflected-sunlight region (2-4 µm) and the thermal emission region (4-5 µm) simultaneously for the first time, building on the work of Grassi et al. (2019) and Grassi et al. (2020).  We investigate the appropriate set of aerosol and haze layers, starting with NH4SH at 1.3 bars, NH3 and 0.7 bars and two grey hazes: one in the troposphere and one in the stratosphere.  The optical properties of these aerosols are tested to find the optimal cloud structure to reproduce the full JIRAM spectrum. From the retrievals of the zonally-averaged spectra we investigate whether spatial variations of tropospheric composition are truly required to fit the data, comparing gaseous contrasts to the expected circulation patterns associated with Jupiter’s belts and zones.</p>

Cruise and flyby operations of BepiColombo – first results and planned activities

<p>BepiColombo was launched on 20 October 2018 from the European spaceport Kourou in French Guyana and is now on route to Mercury to unveil Mercury’s secrets. BepiColombo with its state of the art and very comprehensive payload will perform measurements to increase our knowledge on the fundamental questions about Mercury’s evolution, composition, interior, magnetosphere, and exosphere. BepiColombo is a joint project between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) and consists of two orbiters, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio). </p> <p>On its way BepiColombo will travel 18 times around the Sun until the spacecraft will be put into an polar orbit around Mercury. During its long way through the inner solar system, BepiColombo will perform nine flybys (one at Earth, two at Venus and six at Mercury). However, since the spacecraft is in a stacked configuration during the flybys only some of the instruments on both spacecraft will perform scientific observations. In addition there are plenty of opportunities for further science operations (testing Einstein’s theory during solar conjunctions, listening to gamma ray bursts, or investigation of the solar environment).</p> <p>A status of the mission and instruments, science operations plans during cruise, and first results of measurements taken in the first three years since launch will be given.</p>

The BepiColombo Planetary Magnetometer MPO-MAG: What Can We Learn from the Hermean Magnetic Field?

The magnetometer instrument MPO-MAG on-board the Mercury Planetary Orbiter (MPO) of the BepiColombo mission en-route to Mercury is introduced, with its instrument design, its calibration and scientific targets. The instrument is comprised of two tri-axial fluxgate magnetometers mounted on a 2.9 m boom and are 0.8 m apart. They monitor the magnetic field with up to 128 Hz in a $\pm 2048$ ± 2048 nT range. The MPO will be injected into an initial $480 \times 1500$ 480 × 1500 km polar orbit (2.3 h orbital period). At Mercury, we will map the planetary magnetic field and determine the dynamo generated field and constrain the secular variation. In this paper, we also discuss the effect of the instrument calibration on the ability to improve the knowledge on the internal field. Furthermore, the study of induced magnetic fields and field-aligned currents will help to constrain the interior structure in concert with other geophysical instruments. The orbit is also well-suited to study dynamical phenomena at the Hermean magnetopause and magnetospheric cusps. Together with its sister instrument Mio-MGF on-board the second satellite of the BepiColombo mission, the magnetometers at Mercury will study the reaction of the highly dynamic magnetosphere to changes in the solar wind. In the extreme case, the solar wind might even collapse the entire dayside magnetosphere. During cruise, MPO-MAG will contribute to studies of solar wind turbulence and transient phenomena.