Asteroid detection at millimetric wavelengths with the Planck survey

The Planck mission, originally devised for cosmological studies, offers the opportunity to observe Solar System objects at millimetric and submillimetric wavelengths. We concentrate in this paper on the asteroids of the Main Belt. We intend to estimate the number of asteroids that can can be detected during the mission and to evaluate the strength of their signal. We have rescaled the instrument sensitivities, calculated by the LFI and HFI teams for sources fixed in the sky, introducing some degradation factors to properly account for moving objects. In this way a detection threshold is derived for asteroidal detection that is related to the diameter of the asteroid and its geocentric distance. We have developed a numerical code that models the detection of asteroids in the LFI and HFI channels during the mission. This code perfoprms a detailed integration of the orbits of the asteroids in the timespan of the mission and identifies those bodies that fall in the beams of Planck and their signal stenght. According to our simulations, a total of 397 objects will be observed by Planck and an asteroidal body will be detected in some beam in 30% of the total sky scan--circles. A significant fraction (in the range from ~50 to 100 objects) of the 397 asteroids will be observed with a high S/N ratio. Flux measurements of a large sample of asteroids in the submillimeter and millimeter range are relevant since they allow to analyze the thermal emission and its relation to the surface and regolith properties. Furthermore, it will be possible to check on a wider base the two standard thermal models, based on a nonrotating or rapidly rotating sphere. Our method can also be used to separate Solar System sources from cosmological sources in the survey. This work is based on Planck LFI activities.Comment: Contact person [email protected]. Accepted for pubblication in New Astronomy (2002). 1 figure in .eps format. Needs elsart.cls style + harvard.st

1999 Quadrantids and the lunar Na atmosphere

Enhancements of the Na emission and temperature from the lunar atmosphere were reported during the Leonids meteor showers of 1995, 1997 and 1998. Here we report a search for similar enhancement during the 1999 Quadrantids, which have the highest mass flux of any of the major streams. No enhancements were detected. We suggest that different chemical-physical properties of the Leonid and Quadrantid streams may be responsible for the difference.Comment: 5 pages, 1 figure, accepted for publication in MNRA

Geometrical Calibration for the Panrover: a Stereo Omnidirectional System for Planetary Rover

Abstract. A novel panoramic stereo imaging system is proposed in this paper. The system is able to carry out a 360° stereoscopic vision, useful for rover autonomous-driving, and capture simultaneously a high-resolution stereo scene. The core of the concept is a novel "bifocal panoramic lens" (BPL) based on hyper hemispheric model (Pernechele et al. 2016). This BPL is able to record a panoramic field of view (FoV) and, simultaneously, an area (belonging to the panoramic FoV) with a given degree of magnification by using a unique image sensor. This strategy makes possible to avoid rotational mechanisms. Using two BPLs settled in a vertical baseline (system called PANROVER) allows the monitoring of the surrounding environment in stereoscopic (3D) mode and, simultaneously, capturing an high-resolution stereoscopic images to analyse scientific cases, making it a new paradigm in the planetary rovers framework.Differently from the majority of the Mars systems which are based on rotational mechanisms for the acquisition of the panoramic images (mosaicked on ground), the PANROVER does not contain any moving components and can rescue a hi-rate stereo images of the context panorama.Scope of this work is the geometric calibration of the panoramic acquisition system by the omnidirectional calibration methods (Scaramuzza et al. 2006) based on Zhang calibration grid. The procedures are applied in order to obtain well rectified synchronized stereo images to be available for 3D reconstruction. We applied a Zhang chess boards based approach even during STC/SIMBIO-SYS stereo camera calibration (Simioni et al. 2014, 2017). In this case the target of the calibration will be the stereo heads (the BPLs) of the PANROVER with the scope of extracting the intrinsic parameters of the optical systems. Differently by previous pipelines, using the same data bench the estimate of the extrinsic parameters is performed

Warming permafrost and active layer variability at Cime Bianche, Western European Alps

The objective of this paper is to provide a first synthesis on the state and recent evolution of permafrost at the monitoring site of Cime Bianche (3100 m a.s.l.) on the Italian side of the Western Alps. The analysis is based on 7 years of ground temperature observations in two boreholes and seven surface points. The analysis aims to quantify the spatial and temporal variability of ground surface temperature in relation to snow cover, the small-scale spatial variability of the active layer thickness and current temperature trends in deep permafrost.Results show that the heterogeneity of snow cover thickness, both in space and time, is the main factor controlling ground surface temperatures and leads to a mean range of spatial variability (2.5 ± 0.1 °C) which far exceeds the mean range of observed inter-annual variability (1.6 ± 0.1 °C). The active layer thickness measured in two boreholes at a distance of 30 m shows a mean difference of 2.0 ± 0.1 m with the active layer of one borehole consistently deeper. As revealed by temperature analysis and geophysical soundings, such a difference is mainly driven by the ice/water content in the sub-surface and not by the snow cover regimes. The analysis of deep temperature time series reveals that permafrost is warming. The detected trends are statistically significant starting from a depth below 8 m with warming rates between 0.1 and 0.01 °C yr⁻¹

Contrasting responses of forest growth and carbon sequestration to heat and drought in the Alps

>Climate change is expected to increase both the frequency and the intensity of climate extremes, consequently increasing the risk of forest role transition from carbon sequestration to carbon emission. These changes are occurring more rapidly in the Alps, with important consequences for tree species adapted to strong climate seasonality and short growing season. In this study, we aimed at investigating the responses of a high-altitude Larix decidua Mill. forest to heat and drought, by coupling ecosystem- and tree-level measurements. From 2012 to 2018, ecosystem carbon and water fluxes (i.e., gross primary production, net ecosystem exchange, and evapotranspiration) were measured by means of the eddy covariance technique, together with the monitoring of canopy development (i.e., larch phenology and normalized difference vegetation index). From 2015 to 2017 we carried out additional observations at the tree level, including stem growth and its duration, direct phenological observations, sap flow, and tree water deficit. Results showed that the warm spells in 2015 and 2017 caused an advance of the phenological development and, thus, of the seasonal trajectories of many processes, at both tree and ecosystem level. However, we did not observe any significant quantitative changes regarding ecosystem gas exchanges during extreme years. In contrast, in 2017 we found a reduction of 17% in larch stem growth and a contraction of 45% of the stem growth period. The growing season in 2017 was indeed characterized by different drought events and by the highest water deficit during the study years. Due to its multi-level approach, our study provided evidence of the independence between C-source (i.e., photosynthesis) and C-sink (i.e., tree stem growth) processes in a subalpine larch forest

Photometric observations of comet 81P/Wild 2 during the 2010 perihelion passage

Context. The Jupiter-family comet 81P/Wild 2, target of the NASA Stardust mission, is very important in the context of the studies of pristine objects in the solar system. First, it was only recently deflected into the present orbit, having spent at least 300 yr at higher heliocentric distance prior to the orbital change in 1974. It is therefore likely that the comet experienced a recent activation with consequent low alteration of its original material. Second, it is the only comet whose coma material was brought back to Earth for laboratory analysis. We observed the object between 2010 February 9 and September 9 for a total of 11 nights during the 2010 perihelion passage. Aims. The goals of the campaign were the characterization of the comet's dust activity and the comparison with previous apparitions to derive hints on the secular behavior of the object. Methods. Broadband R-and I-images were acquired using three instruments: ALFOSC, CAMELOT, and TCP. The first one is mounted at the Nordic Optical Telescope on La Palma, while the second and the third are mounted at the Instituto de Astrofisica de Canarias 0.82-m telescope on Tenerife. We analyzed the presence and variability of dust structures in the coma with image-enhancing techniques, the radial profile of the dust brightness, and we measured the dust production rate and the dust reddening. Results. We found evidence of a long-lasting sunward fan and anti-solar tail activity throughout all our observations up to a heliocentric distance of 2.42 AU. Afρ measurements suggest a pre-perihelion peak of the activity, caused by a seasonal effect, plus two post-perihelion outbursts. Both spatial and Afρ radial profiles indicate a steady-state coma at nucleocentric distances greater than ~1000-2000 km. The color analysis reveals a moderately reddened dust with a 6-9%/1000 reddening, consistent with the current picture of cometary dust. The second outburst emitted dust with lower reddening. Conclusions. The comparison with previous perihelion passages points toward a recurrent main activity always driven by the same areas on the nucleus, producing dust with similar characteristics and in similar coma structures in different years. Our Afρ measurement at the longest heliocentric distance suggests the comet was less dust-productive in 2010, pointing toward a possible secular aging of the object and its activity. The change of dust colors during the unusual second outburst suggests that an internal part of the nucleus has different physical properties compared with those that produce the recurrent main activity, pointing toward a heterogeneous comet. © ESO, 2012

The Cratering History of Asteroid (2867) Steins

The cratering history of main belt asteroid (2867) Steins has been investigated using OSIRIS imagery acquired during the Rosetta flyby that took place on the 5th of September 2008. For this purpose, we applied current models describing the formation and evolution of main belt asteroids, that provide the rate and velocity distributions of impactors. These models coupled with appropriate crater scaling laws, allow the cratering history to be estimated. Hence, we derive Steins' cratering retention age, namely the time lapsed since its formation or global surface reset. We also investigate the influence of various factors -like bulk structure and crater erasing- on the estimated age, which spans from a few hundred Myrs to more than 1Gyr, depending on the adopted scaling law and asteroid physical parameters. Moreover, a marked lack of craters smaller than about 0.6km has been found and interpreted as a result of a peculiar evolution of Steins cratering record, possibly related either to the formation of the 2.1km wide impact crater near the south pole or to YORP reshaping.Comment: Accepted by Planetary and Space Scienc

A PHOTOGRAMMETRIC PIPELINE FOR THE 3D RECONSTRUCTION OF CASSIS IMAGES ON BOARD EXOMARS TGO

CaSSIS (Colour and Stereo Surface Imaging System) is the stereo imaging system onboard the European Space Agency and ROSCOSMOS ExoMars Trace Gas Orbiter (TGO) that has been launched on 14 March 2016 and entered a Mars elliptical orbit on 19 October 2016. During the first bounded orbits, CaSSIS returned its first multiband images taken on 22 and 26 November 2016. The telescope acquired 11 images, each composed by 30 framelets, of the Martian surface near Hebes Chasma and Noctis Labyrithus regions reaching at closest approach at a distance of 250 km from the surface. Despite of the eccentricity of this first orbit, CaSSIS has provided one stereo pair with a mean ground resolution of 6 m from a mean distance of 520 km. The team at the Astronomical Observatory of Padova (OAPD-INAF) is involved into different stereo oriented missions and it is realizing a software for the generation of Digital Terrain Models from the CaSSIS images. The SW will be then adapted also for other projects involving stereo camera systems. To compute accurate 3D models, several sequential methods and tools have been developed. The preliminary pipeline provides: the generation of rectified images from the CaSSIS framelets, a matching core and post-processing methods. The software includes in particular: an automatic tie points detection by the Speeded Up Robust Features (SURF) operator, an initial search for the correspondences through Normalize Cross Correlation (NCC) algorithm and the Adaptive Least Square Matching (LSM) algorithm in a hierarchical approach. This work will show a preliminary DTM generated by the first CaSSIS stereo images