EOS: Atmospheric Radiative Transfer in Habitable Worlds with HELIOS

We present EOS, a procedure for determining the outgoing longwave radiation (OLR) and top-of-atmosphere (TOA) albedo for a wide range of conditions expected to be present in the atmospheres of rocky planets with temperate conditions. EOS is based on HELIOS and HELIOS-K, which are novel and publicly available atmospheric radiative transfer (RT) codes optimized for fast calculations with GPU processors. These codes were originally developed for the study of giant planets. In this paper we present an adaptation for applications to terrestrial-type, habitable planets, adding specific physical recipes for the gas opacity and vertical structure of the atmosphere. To test the reliability of the procedure, we assessed the impact of changing line opacity profile, continuum opacity model, atmospheric lapse rate, and tropopause position prescriptions on the OLR and the TOA albedo. The results obtained with EOS are in line with those of other RT codes running on traditional CPU processors, while being at least one order of magnitude faster. The adoption of OLR and TOA albedo data generated with EOS in a zonal and seasonal climate model correctly reproduces the fluxes of the present-day Earth measured by the CERES spacecraft. The results of this study disclose the possibility to incorporate fast RT calculations in climate models aimed at characterizing the atmospheres of habitable exoplanets

Dynamics of non-spherical dust in the coma of 67P/Churyumov- Gerasimenko constrained by GIADA and ROSINA data

Among the comet 67P/Churyumov-Gerasimenko (67P/C-G) in situ measurements, the closest that have ever been performed at a comet nucleus, are also those of speed, mass, and cross-section of cometary grains performed by the Grain Impact Analyser and Dust Accumulator (GIADA) instrument. To interpret GIADA data, we performed dust dynamical numerical simulations with both spherical and non-spherical (spheroids) shapes. This allowed us to analyse how the grain non-sphericity affects the data interpretation. We find that some measured dust speeds are unlikely reproducible when a spherical shape is considered. We considered two GIADA observational periods, 2015 February 19-27 and 2015 March 13-28. Gas parameters calibrated with the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) measurements have been used to retrieve the gas conditions to set up the dust particle motion. The dust grains are assumed to be out of the near nucleus coma, i.e. where the gas velocity is radial and constant, therefore they are either aligned or have random but constant orientation with respect to the gas drag. We reproduced the GIADA dust speeds, using spheres and two different spheroidal shapes. We find that the particle shapes that reproduce best the GIADA dust speeds are consistent with the particle shape constrained by the GIADA data. We obtain different terminal velocities for spherical and non-spherical particles of the same mass. The shape, which reproduces the GIADA data, is oblate rather than prolate spheroid. We obtain rotational frequencies of the spheroidal particles that best fit the GIADA measurements in these periods

GIADA microbalance measurements on board Rosetta: submicrometer- to micrometer-sized dust particle flux in the coma of comet 67P/Churyumov-Gerasimenko

Context. From August 2014 to September 2016, Rosetta escorted comet 67P/Churyumov-Gerasimenko (67P) during its journey around the Sun. One of the aims of Rosetta was to characterize cometary activity and the consequent formation of dust flux structures in cometary comae. Aims: We characterize and quantify the submicrometer- to micrometer-sized dust flux that may be shaped in privileged directions within the coma of 67P inbound to and outbound from perihelion. Methods: The in situ dust-measuring instrument GIADA, part of the Rosetta/ESA payload, consisted of three subsystems, one of which was the Micro Balance Subsystem (MBS), composed of five quartz crystal microbalances. From May 2014 to September 2016, MBS measured the submicrometer- to micrometer-sized deposited dust mass every 5 min. Results: We characterized the submicrometer- to micrometer-sized dust mass flux in the coma of 67P. The anti-sunward and the radial direction are preferred, and the flux is higher in the anti-sunward direction. The measured cumulative dust mass in the anti-sunward direction is 2.38 ± 0.04 × 10-7 kg, and in the radial direction, it is 1.18 ± 0.02 × 10-7 kg. We explain the anti-sunward dust flux as the effect of nonuniform gas emission between the night- and dayside of the nucleus, which acts in combination with the solar radiation pressure. We compared the cumulated dust mass of particles ≤5 μm with particles ≥100 μm. The retrieved ratio of ≈2% implies a differential size distribution index of ≈-3.0, which confirms that particles of size ≥0.1 mm dominate the dust coma cross-section of 67P during the entire orbit. Conclusions: Submicrometer- to micrometer-sized dust mass flux measurements were made for the first time from the arising of cometary activity until its extinction. They indicate that these particles do not provide a substantial optical scattering in the coma of 67P with respect to the scattering caused by millimeter-sized particles. In addition, MBS data reveal that the measured dust flux is highly anisotropic: anti-sunward plus radial

A Teatro con INAF - Il Portfolio degli spettacoli dell’Istituto Nazionale di Astrofisica

A dicembre 2020, il Gruppo Storie dell’Istituto Nazionale di Astrofisica (INAF) ha pubblicato insieme al magazine di Didattica e Divulgazione dell’Ente, EduINAF, il Portfolio degli spettacoli dell’INAF. Il Portfolio è il risultato di un’accurata ricognizione in collaborazione con i referenti degli stessi ed è unico nel suo genere per un Ente di ricerca. Comprende una trentina di spettacoli, a tema astrofisico o scientifico, prodotti negli anni dal personale INAF in autonomia o in collabora-zione con realtà professionali. Nel Portfolio, ogni spettacolo è descritto in una scheda informativa e la fruizione è resa immediata grazie a filtri appositi. Il Portfolio è man mano aggiornato per meglio rispondere alle esigenze e curiosità del pubblico in cerca di approcci non tradizionali nell’esplorazione dell’astronomia e della ricerca in generale. Ad accompagnare il Portfolio, un breve video per la disseminazione sui canali social e un segnalibro dedicato, in preparazione, da offrire in incontri con scuole e in eventi con il pubblico. Grazie alla visione d’insieme offerta dal Portfolio, nell’Ente sono nate valutazioni per massimizzare la visibilità degli spettacoli tramite l’organizzazione di un ‘Festival INAF diffuso’. In questo report descriviamo il Portfolio, il suo contesto, le criticità riscontrate e i progetti futuri

BepiColombo Science Investigations During Cruise and Flybys at the Earth, Venus and Mercury

The dual spacecraft mission BepiColombo is the first joint mission between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) to explore the planet Mercury. BepiColombo was launched from Kourou (French Guiana) on October 20th, 2018, in its packed configuration including two spacecraft, a transfer module, and a sunshield. BepiColombo cruise trajectory is a long journey into the inner heliosphere, and it includes one flyby of the Earth (in April 2020), two of Venus (in October 2020 and August 2021), and six of Mercury (starting from 2021), before orbit insertion in December 2025. A big part of the mission instruments will be fully operational during the mission cruise phase, allowing unprecedented investigation of the different environments that will encounter during the 7-years long cruise. The present paper reviews all the planetary flybys and some interesting cruise configurations. Additional scientific research that will emerge in the coming years is also discussed, including the instruments that can contribute

Terrestrial-type planetary atmospheres with HELIOS

10siThe next generation of astronomical facilities will be able to retrieve exoplanetary atmospheric spectra in increasing quantity and of increasing quality. Radiative transfer (RT) models of these atmospheres is essential both for interpreting observational data and for linking these data to the planetary physical state with the aid of dedicated climate models. So far, a large effort has been placed in modelling the atmospheres of giant planets, which are the most easily accessible to observations. Now times are ripe to extend these studies to treat the relatively thin atmospheres of terrestrial-type exoplanets, which are the most likely targets for the search of atmospheric biomarkers.Here we present a procedure to perform radiative transfer calculations for terrestrial-type exoplanets with temperate physical conditions (Simonetti et al. in preparation). The procedure is based on HELIOS and HELIOS-K, which are novel, flexible and publicly available codes developed by the University of Bern (Grimm & Heng, 2015; Malik et al., 2017, 2019; Grimm et al., 2021) as a part of the Exoclime Simulation Platform (ESP) repository. These codes make full use of the computing power of Graphics Processing Units (GPUs, colloquially known as graphics cards) being therefore much faster (up to one order of magnitude, see Grimm et al. 2021) than other similar codes and are integrated with a variety of molecular and atomic line repositories such as HITRAN (Gordon et al., 2017), HITEMP (Rothman et al., 2010) and Kurucz. Until now, HELIOS has been mostly applied to study Jupiter-like planets. The main features of the procedure that we have implemented for the treatment of rocky, habitable planets can be summarized as follows.First, we added the treatment of the continuum absorption features of a variety of gases, in particular H2O (Clough et al., 1989; Mlawer et al., 2012) and CO2 (Gruszka & Borysow, 1997; Baranov et al., 2004; Baranov, 2018). These continua strongly contribute to the overall opacity of Earth-like atmospheres and cannot be neglected. Second, we paid special attention to the sub-Lorentzian profile of CO2 absorption lines, testing the effects of different recipes (Perrin & Hartmann, 1989; Tonkov et al., 1996). Third, we considered different hypotheses regarding the convective lapse rate of the troposphere. On these basis we: (i) tested the robustness of HELIOS and HELIOS-K against changes in model variables and (ii) compared them with other codes already published and used in the same context (e.g. LBLRTM Clough et al., 2005), as done by Yang et al. (2016).One of the main goals of this work is to provide a new and fast radiative transfer treatment for the ESTM, an energy balance climate model with upgraded treatment of the vertical and horizontal energy transport Vladilo et al. (2015). The ESTM is extremely flexible and allows for a rapid exploration of the planetary and atmospheric parameter space, providing us the ability to map quantitative indices of habitability on these parameters (Silva et al., 2017). The flexibility of both HELIOS and ESTM will allow us to test a wide variety of atmospheric compositions, which have applications in the study both of exoplanets and of ancient Earth and Mars. Moreover, the HELIOS procedure adapted to terrestrial-type atmospheres can be used to generate synthetic TOA fluxes useful to link the conditions at the planet's surface with quantities that will become observable with future generations of instruments, such as secondary eclipse spectra and direct IR emission spectra from terrestrial-type exoplanets (see e.g. Quanz et al., 2021). Finally, the output of the same procedure can be applied to other codes in the ESP repository, such as the THOR GCM (Mendonca et al., 2016; Deitrick et al., 2020).Figure 1 shows the TOA albedo obtained for three different stellar spectral classes for different values of surface temperature and stellar zenith angle, for an atmosphere of 1 bar of CO2 and a relative H2O humidity of 100%, as obtained by HELIOS using the procedure presented in Simonetti et al. (in preparation). The surface albedo was set to 0.15.Figure 2 shows the relation between OLR and surface temperature for different radiative transfer models for an Earth-like atmosphere composed by N2, O2, 360 ppmv of CO2, 1.8 ppmv of CH4 and a temperature-dependent quantity of H2O (relative humidity equal to 100%). The thick red curve labelled "HELIOS" has been obtained with the novel procedure presented in Simonetti et al. (in preparation). The data relative to the other curves have been taken from Yang et al. (2016). REFERENCES:Baranov, Y. I. 2018, Journal of Molecular Spectroscopy, 345, 11Baranov, Y. I., La erty, W. J., & Fraser, G. T. 2004, Journal of Molecular Spectroscopy, 228, 432Clough, S. A., Kneizys, F. X., & Davies, R. W. 1989, Atmospheric Research, 23, 229Clough, S. A., Shephard, M. W., Mlawer, E. J., et al. 2005, JQSRT, 91, 233Deitrick, R., Mendonca, J. M., Schr...openopenSimonetti, Paolo; Vladilo, Giovanni; Malik, Matej; Silva, Laura; Ivanovski, Stavro; Maris, Michele; Murante, Giuseppe; Biasiotti, Lorenzo; Bisesi, Erica; Monai, SergioSimonetti, Paolo; Vladilo, Giovanni; Malik, Matej; Silva, Laura; Ivanovski, Stavro; Maris, Michele; Murante, Giuseppe; Biasiotti, Lorenzo; Bisesi, Erica; Monai, Sergi

LICIACube: the Light Italian Cubesat for Imaging of Asteroids.

Introduction"LICIACube - the Light Italian Cubesat for Imaging of Asteroids"[1] is a CubeSat managed by the Italian Space Agency (ASI), that will be part of the NASA Double Asteroid Redirection Test (DART) mission [2].DART will be the first mission demonstrating the applicability of the kinetic impactor to change to motion of an asteroid in space and prevent the impact of Earth with a hazardous object.After being launched in summer 2021, the DART spacecraft will impact in autumn 2022 Dimorphos, the secondary member of the (65803) Didymos binary asteroid. With a mass of 650 kg and an impact velocity of about 6.6 km/s, DART is expected to change the binary orbital period of the 160-m Dimorphos by about 10 minutes, an effect that can be easily measured by ground-based telescopes.The design, integration and test of the CubeSat have been assigned by ASI to the aerospace company Argotec, while the LICIACube Ground Segment has a complex architecture based on the Argotec Mission Control Centre, antennas of the NASA Deep Space Network and data archiving and processing, managed at the ASI Space Science Data Center. The LICIACube team includes a wide scientific community, involved in the definition of all the aspects of the mission: trajectory design; navigation analysis (and real-time orbit determination during operations); impact, plume and imaging simulation and modelling, in preparation of a suitable framework for the analysis and interpretation of in-situ data. The scientific team is led by National Institute of Astrophysics (OAR, IAPS, OAA, OAPd, OATs) with the support of IFAC-CNR and University Parthenope of Naples. The team is enriched by University of Bologna, for orbit determination and satellite navigation, and Polytechnic of Milan, for mission analysis and optimization.The major technological mission challenge, i.e. the autonomous targeting and imaging of such a small body during a fast fly-by, to be accomplished with the limited resources of a CubeSat, is affordable thanks to a strong synergy of all the mentioned teams in support of the engineering tasks.Nominal missionDART probe will be launched in mid-2021 and LICIACube will be hosted as piggyback during the 15 months of interplanetary cruise, then released 10 days before the impact and autonomously guided along its fly-by trajectory. In Figure 1 the nominal mission is shown. LICIACube downlinks images direct to Earth after the target fly-by.Figure 1- The LICIACube nominal mission.Scientific ObjectivesLICIACube has the aim to testify the main probe impact on Dimorphos, the secondary member of the (65803) Didymos binary asteroid system, and to perform dedicated scientific investigations.Several unique images of the effects of the DART impact on the asteroid, such as the formation and the development of the plume potentially determined by the impact will be collected and transmitted to Earth.The scientific objectives of LICIACube are:Testify and characterize the DART impact; Obtain multiple (at least 3) images of the ejecta plume taken over a span of time and phase angle, that, with reasonable expectations concerning the ejecta mass and particle size distribution, can potentially: Allow measurement of the motion of the slow (< 5 m/s) ejecta: this requirement is intended as the possibility to acquire images at spatial scale better than 5 m/pixel, with the possibility to distinguish the movements of the slowest particles of the plume by the sequence of images. Allow estimation of the structure of the plume, measuring the evolution of the dust distribution; Obtain multiple (at least 3) images of the DART impact site with a sufficient resolution to allow measurements of the size and morphology of the crater. These images will be taken sufficiently late after the impact that the plume can be reasonably expected to have cleared; Obtain multiple (at least 3) images of Dimorphos showing the non-impact hemisphere, hence increasing the accuracy of the shape and volume determination. The whole project and its present status-of-the-art will be presented and discussed together with the in situ observing strategy and the expected performances

Before the DART impact: LICIACube - The Light Italian Cubesat for Imaging of Asteroids

Introduction: In late September 2022 the NASA mission DART will perform the first test of the kinetic impactor technique conceived to deflect an asteroid en route to Earth. With a mass of 650 kg and an impact velocity of about 6.6 km/s, DART is expected to change the binary orbital period of Dimorphos, the 160-m moon of Didymos Near-Earth Asteroid (NEA), by about 10 min, an effect that can be easily measured by ground-based telescopes [1] [2].LICIACube: LICIACube (Light Italian Cubesat for Imaging of Asteroids) is the first purely Italian spacecraft to be operated in deep space. It is a 6U cubesat platform developed by the Argotec company and managed by the Italian Space Agengy (ASI) with the aim to contribute in the NASA DART Planetary Defence objective and to perform autonomous science at the asteroid [3]. LICIACube has been launched together with DART on November 2021: after a 10-months interplanetary cruise it will be released 10 days before the foreseen DART impact on Dimorphos and it will be guided along its fly-by trajectory with a closest approach (CA) of around 55 km from the Dimorphos' surface (Fig. 1). Figure 1 - The nominal LICIACube missionLICIACube is equipped with two different payloads named LEIA (Liciacube Explorer Imaging for Asteroid) and LUKE (Liciacube Unit Key Explorer) (Fig. 2). High-resolution images, obtained by LEIA at the CA (up to 1.5 m/px) will allow us to study the surface morphology of Dimorphos and the presence of boulders/large blocks on its surface. The LUKE data (up to 8 m/px at CA, with a RGB filter system) will give us also the opportunity to investigate the composition of Dimorphos throughout spectrophotometric analyses. It will then be possible to map the surface composition of the object and to derive the surface heterogeneity at the observed scale.After imaging the DART impact, during the fly-by the two instruments will allow us to investigate the nature of the target, explore the difference between the impact and non-impact regions, and to study the nature and the evolution of the produced plume, in order to deeply investigate the composition and the structure of the material composing a small double NEA.Figure 2 - LICIACube and its payload After the Dimorphos fly-by, LICIACube will download the obtained images directly to Earth: the LICIACube Ground Segment has a complex architecture based on the Argotec Mission Control Centre, antennas of the NASA Deep Space Network and data archiving and processing, managed at the ASI Space Science Data Center.Acknowledgements: The LICIACube team acknowledges financial support from Agenzia Spaziale Italiana (ASI, contract No. 2019-31-HH.0 CUP F84I190012600).References: [1] Rivkin A.S. et al., (2021) PSJ, in press. [2] Cheng A. F., et al. (2018) PSS, 157, 104. [3] Dotto E., et al. (2021) PSS 199, 105185