Attitude Sensor from Ellipsoid Observations: A Numerical and Experimental Validation.

The preliminary design and validation of a novel, high accuracy horizon-sensor for small satellites is presented, which is based on the theory of attitude determination from ellipsoid observations. The concept consists of a multi-head infrared sensor capturing images of the Earth limb. By fitting an ellipse to the imaged limb arcs, and exploiting some analytical results available from projective geometry, a closed form solution for computing the attitude matrix is provided. The algorithm is developed in a dimensionless framework, requiring the knowledge of the shape of the imaged target, but not of its size. As a result, the solution is less sensitive to the limb shift caused by the atmospheric own radiance. To evaluate the performance of the proposed method, a numerical simulator is developed, which generates images captured in low Earth orbit, including also the presence of the atmosphere. In addition, experimental validation is provided due to a dedicated testbed, making use of a miniature infrared camera. Results show that our sensor concept returns rms errors of few hundredths of a degree or less in determining the local nadir direction.

Geologic Constraints on the Formation and Evolution of Saturn's Mid-Sized Moons.

Saturn's mid-sized icy moons have complex relationships with Saturn's interior, the rings, and with each other, which can be expressed in their shapes, interiors, and geology. Observations of their physical states can, thus, provide important constraints on the ages and formation mechanism(s) of the moons, which in turn informs our understanding of the formation and evolution of Saturn and its rings. Here, we describe the cratering records of the mid-sized moons and the value and limitations of their use for constraining the histories of the moons. We also discuss observational constraints on the interior structures of the moons and geologically-derived inferences on their thermal budgets through time. Overall, the geologic records of the moons (with the exception of Mimas) include evidence of epochs of high heat flows, short- and long-lived subsurface oceans, extensional tectonics, and considerable cratering. Curiously, Mimas presents no clear evidence of an ocean within its surface geology, but its rotation and orbit indicate a present-day ocean. While the moons need not be primordial to produce the observed levels of interior evolution and geologic activity, there is likely a minimum age associated with their development that has yet to be determined. Uncertainties in the populations impacting the moons makes it challenging to further constrain their formation timeframes using craters, whereas the characteristics of their cores and other geologic inferences of their thermal evolutions may help narrow down their potential histories. Disruptive collisions may have also played an important role in the formation and evolution of Saturn's mid-sized moons, and even the rings of Saturn, although more sophisticated modeling is needed to determine the collision conditions that produce rings and moons that fit the observational constraints. Overall, the existence and physical characteristics of Saturn's mid-sized moons provide critical benchmarks for the development of formation theories.

Surface properties of the seas of Titan as revealed by Cassini mission bistatic radar experiments.

Saturn's moon Titan was explored by the Cassini spacecraft from 2004 to 2017. While Cassini revealed a lot about this Earth-like world, its radar observations could only provide limited information about Titan's liquid hydrocarbons seas Kraken, Ligeia and Punga Mare. Here, we show the results of the analysis of the Cassini mission bistatic radar experiments data of Titan's polar seas. The dual-polarized nature of bistatic radar observations allow independent estimates of effective relative dielectric constant and small-scale roughness of sea surface, which were not possible via monostatic radar data. We find statistically significant variations in effective dielectric constant (i.e., liquid composition), consistent with a latitudinal dependence in the methane-ethane mixing-ratio. The results on estuaries suggest lower values than the open seas, compatible with methane-rich rivers entering seas with higher ethane content. We estimate small-scale roughness of a few millimeters from the almost purely coherent scattering from the sea surface, hinting at the presence of capillary waves. This roughness is concentrated near estuaries and inter-basin straits, perhaps indicating active tidal currents.

Characterization of the Surfaces and Near-Surface Atmospheres of Ganymede, Europa and Callisto by JUICE.

We present the state of the art on the study of surfaces and tenuous atmospheres of the icy Galilean satellites Ganymede, Europa and Callisto, from past and ongoing space exploration conducted with several spacecraft to recent telescopic observations, and we show how the ESA JUICE mission plans to explore these surfaces and atmospheres in detail with its scientific payload. The surface geology of the moons is the main evidence of their evolution and reflects the internal heating provided by tidal interactions. Surface composition is the result of endogenous and exogenous processes, with the former providing valuable information about the potential composition of shallow subsurface liquid pockets, possibly connected to deeper oceans. Finally, the icy Galilean moons have tenuous atmospheres that arise from charged particle sputtering affecting their surfaces. In the case of Europa, plumes of water vapour have also been reported, whose phenomenology at present is poorly understood and requires future close exploration. In the three main sections of the article, we discuss these topics, highlighting the key scientific objectives and investigations to be achieved by JUICE. Based on a recent predicted trajectory, we also show potential coverage maps and other examples of reference measurements. The scientific discussion and observation planning presented here are the outcome of the JUICE Working Group 2 (WG2): "Surfaces and Near-surface Exospheres of the Satellites, dust and rings".

Juno spacecraft gravity measurements provide evidence for normal modes of Jupiter.

The Juno spacecraft has been collecting data to shed light on the planet's origin and characterize its interior structure. The onboard gravity science experiment based on X-band and Ka-band dual-frequency Doppler tracking precisely measured Jupiter's zonal gravitational field. Here, we analyze 22 Juno's gravity passes to investigate the gravity field. Our analysis provides evidence of new gravity field features, which perturb its otherwise axially symmetric structure with a time-variable component. We show that normal modes of the planet could explain the anomalous signatures present in the Doppler data better than other alternative explanations, such as localized density anomalies and non-axisymmetric components of the static gravity field. We explain Juno data by p-modes having an amplitude spectrum with a peak radial velocity of 10-50 cm/s at 900-1200 µHz (compatible with ground-based observations) and provide upper bounds on lower frequency f-modes (radial velocity smaller than 1 cm/s). The new Juno results could open the possibility of exploring the interior structure of the gas giants through measurements of the time-variable gravity or with onboard instrumentation devoted to the observation of normal modes, which could drive spacecraft operations of future missions.

[A video-aided minilaparocholecystectomy]. / Una tecnica di minilaparocolecistectomia video-assistita.

AIM: The main objective is to prospectively evaluate the therapeutic efficacy of minilaparocholecystectomy combined with videolaparoscopic view in cases of complicated gallstones where VLC was risky. MATERIAL OF STUDY: We carried out minilaparotomic video-aided cholecystectomy on 110 patients (32 males and 78 females) with preoperative diagnosis of intraabdominal adhesions or biliary severe inflammation. RESULT: No significant intra or postoperative complications was reported and in all cases pain was never greater than that reported after VLC. In all these cases the anesthetists reported an easier intra-operative management of the vital parameters than with VLC procedures. DISCUSSION: Minilaparocholecystectomy appears a type of alternative procedure able to combine mini-invasiveness with as low a number as possible of intra- and post-operative complications, in cases where VLC have risk. No significant postoperative pain was reported, and in any case pain was never greater than that reported after VLC. Recovery times were similar to those after VLC; patients were able to return to their normal social and working life within a mean 3 days. The procedure carried out by us is a low-cost one: it does not require disposable instruments From the esthetic viewpoint, video-aided minicholecystectomy minimal scars in our cases, wound ranged from 4 to 6 cm. in length. CONCLUSIONS: In patients in whom VLC have risks, video-aided minilaparocholecystectomy represents an easy-to-perform and low-cost alternative. VMC can also be proposed as a procedure of choice in cases of complicated gallstones instead of the traditional open cholecystectomy technique.

Gastric metastasis from breast carcinoma. Report of three cases, diagnostic-therapeutic critical close examination and literature review.

Gastric metastases of breast cancer represent a not so rare event in patients affected. In fact, it occurs in 0.3% of cases. Although the introduction of new adjuvant therapies has given rise to an increase in disease free survival and overall survival rates, it has also led to more frequent occurrences of breast cancer metastatic lesions localized in bone, lung/pleura and liver, but above all in the stomach. The authors present three cases of patients suffering from breast cancer with secondary gastric neoplastic lesions from lobular and infiltrating ductal breast cancer. Lobular breast cancer is the histological type mostly involved in disseminated disease, with an incidence of 85% of cases. A review of the literature reveals that authors address the clinical and diagnostic problems of differentiating between a breast cancer metastasis to the stomach and a primary gastric cancer using recent diagnostic strategies to make an early diagnosis. Today practitioners have specific tests to detect early gastric cancer metastases of breast cancer such as endoscopic ultrasound, which provides a better endoscopic definition of the lesions, and immunohistochemical markers, able to distinguish the primary lobular histological type from ductal cancer. Besides, an early diagnosis associated with the latest adjuvant systemic therapies and hormonal treatment, alone or in combination, may grant affected patients a remission with a survival rate of 10-28 months, and a reasonable quality of life. At present the surgical approach should be reserved for selected cases and/or complications.

A translocation t(4; 13)(q21;q14) as single clonal chromosomal abnormality in a parathyroid adenoma.

Most of the information about the genetic composition of parathyroid tumors has been obtained by comparative genomic hybridization (CGH) and loss of heterozygosity (LOH) studies, whereas only few conventional cytogenetic investigation results are available. We have performed cytogenetic analysis of short-term cultures from 3 parathyroid adenoma tissue samples. Two cases showed a normal karyotype in all the metaphases obtained from independent primary cultures. In one case 5 metaphases (in a total of 25) from 2 independent cultures showed a nonrandom translocation t(4;13)(q21;q14), which was therefore accepted as clonal. To our knowledge this is the second clonal translocation described in this tumor type. Further conventional cytogenetic analysis of more parathyroid tumor specimens would be necessary to identify other specific abnormalities and the involved genes with a potential important role in the diagnosis, prognosis and pathogenesis of parathyroid tumors.