An Accurate GEO SAR Range Model for Ultralong Integration Time Based on mth-Order Taylor Expansion

As the Geosynchronous Earth Orbital Synthetic Aperture Radar (GEO SAR) allows a wide area viewing combined with a short revisit cycle, it is suitable for many applications that require high timeliness, such as natural disaster monitoring, weather supervision, and military reconnaissance. However, the ultralong integration time and the invalidation of “stop-and-go” assumption caused by the raise of orbital height also greatly increase the difficulty of signal processing. In this paper, a generalized method for calculating the accurate propagation distance between a GEO satellite and a target with ultralong integration time is proposed. This range model is mainly composed of an accurate pulse transmitting distance and an error compensation term for “stop-and-go” assumption failure. The transmitting distance is obtained by Taylor expansion, and the specific derivation process of the general formula of the mth-order expansion is given, in this paper. As for the compensation term, this is achieved by approximately calculating the pulse receiving distance based on twice Taylor expansion, the first expansion is for fast-time and the other is for slow-time. Finally, a series of simulation experiments were conducted to verify the effectiveness and superiority of this new range model for an ultralong integration time.

Morphometric analysis of the orbit in dry human skulls in Northeast Brazil

Introduction: The orbit is a bone cavity in the skull. Its morphological and anthropological knowledge is essential, as it is a region subjected to several surgical procedures. Objective: To analyze the morphology of orbits in the skulls of two populations in Northeastern Brazil Methods: 115 skulls belonging to Federal University of Paraíba (UFPB) and Federal University of Ceará (UFC) were analyzed. The skulls were categorized into three types: Megaseme, Mesoseme and Microseme. Quantitative analysis included these measurements: orbital height (OH), Orbital Breadth (OB) and index orbital (OI). Data were prepared for statistical analysis using IBM SPSS 23 software, with a significance level of 5%. Results: 58 skulls (50.4%) were female and 57 (49.6%) were male. The sample consisted of 91 (79.1%) skulls from UFPB and 24 (20.9%) from UFC. At UFPB, 85.16% of the orbits were Microseme, 12.64%, Mesoseme and 2.2%, Megaseme. In the UFC, 58.3% were Microseme, 25%, Mesoseme and 16.7%, Megaseme. Considering both populations, 79.6% of the orbits were microseme, 15.2%, mesoseme and 5.2%, megaseme. There were no differences in morphometric parameters between the orbits (p> 0.05). When comparing the two populations studied, there were significant differences in the variables OI and OB (p <0.05). Conclusions: Orbits were of the Microseme type. No difference between the height of the UFC and UFPB orbits was found, however, there was a difference in OI and OB. These regional differences corroborate the clinical and surgical importance of the morphological study of the orbit, as it undergoes changes depending on the population.

Influence of Orbital Parameters on SEU Rate of Low-Energy Proton in Nano-SRAM Device

The on-orbit single-event upset (SEU) rate of nanodevices is closely related to the orbital parameters. In this paper, the on-orbit SEU rate (OOSR) induced by a heavy ion (HI), high-energy proton (HEP) and low-energy proton (LEP) for a 65 nm SRAM device is calculated by using the software SPACE RADIATION under different orbits based on the experimental data. The results indicate that the OOSR induced by the HI, HEP and LEP varies with the orbital parameters. In particular, the orbital height, inclination and shieling thickness are the key parameters that affect the contribution of the LEP to the total OOSR. Our results provide guidance for the selection of nanodevices on different orbits.

First observations and magnitude measurement of Starlink’s Darksat

Aims. We measured the Sloan g′ magnitudes of the Starlink’s STARLINK-1130 (Darksat) and 1113 low Earth orbit (LEO) communication satellites to determine the effectiveness of the Darksat darkening treatment at 475.4 nm. Methods. Two observations of the Starlink’s Darksat LEO communication satellite were conducted on 2020/02/08 and 2020/03/06 using Sloan r′ and g′ filters, respectively. A second satellite, STARLINK-1113, was observed on 2020/03/06 using a Sloan g′ filter. The initial observation on 2020/02/08 was a test observation conducted when Darksat was still in the process of manoeuvring to its nominal orbit and orientation. Based on the successful test observation, the first main observation took place on 2020/03/06, along with an observation of the second Starlink satellite. Results. The calibration, image processing, and analysis of the Darksat Sloan g′ image gives an estimated Sloan g′ magnitude of 7.46 ± 0.04 at a range of 976.50 km. For STARLINK-1113, an estimated Sloan g′ magnitude of 6.59 ± 0.05 at a range of 941.62 km was found. When scaled to a range of 550 km and corrected for the solar and observer phase angles, a reduction by a factor of two is seen in the reflected solar flux between Darksat and STARLINK-1113. Conclusions. The data and results presented in this work demonstrate that the special darkening coating used by Starlink for Darksat has darkened the Sloan g’ magnitude by 0.77 ± 0.05 mag when the range is equal to a nominal orbital height (550 km). This result will serve members of the astronomical community who are actively modelling the satellite mega-constellations to ascertain their actual impact on both amateur and professional astronomical observations. Both concurrent and subsequent observations are planned to cover the full optical and NIR spectrum using an ensemble of instruments, telescopes, and observatories.

Analysis of Swarm Electric Field Data in View of Tsunami Events and related Earthquakes

&lt;p&gt;Three Swarm satellites are equipped with Langmuir Probes (LP) measuring in-situ electron density of Earth electric field and POD GNSS receivers determining topside total electron content (TEC) in the upper ionosphere. It is proved that different events on the Earth and in its atmopshere have their own impact on Earth electric field, and the earthquakes are in this group. Many strong earthquakes induce tsunamis, which are also suspected as contributing to the gravity waves having an impact on the ionospheric TEC. These reasons encourage to the study on the sensitivity of Swarm LP and POD GNSS data to the abovementioned phenomena. Referring to the sensitivity of TEC data derived from GNSS stations to Earthquakes, sensitivity of GNSS and LP data at around 500 km high orbit is analyzed here. A similar orbital height can be found in case of many LEO missions equipped at least with GNSS POD receivers, which makes Swarm especially interesting data acquisition platforms.&lt;/p&gt;&lt;p&gt;The investigation of Swarm data in view of Tsunamis and earthquakes is difficult due to several factors. There are only three satellites, the two of which fly almost together, which gives in fact only two points of the survey. The orbital repetition period is long, which seriously limits the number of comparable observations in terms of the location and time of the day. Finally, the number of large earthquakes and tsunami events in time of Swarm science mission is low, and many Earthquakes do not coincide sufficiently with Swarm passes in time and space. All these factors, however, doesn&amp;#8217;t exclude an opportunity of analyzing of Swarm data passes above the earthquakes of magnitude nearby 8, linked with the tsunamis reaching several decimeters.&lt;/p&gt;&lt;p&gt;Swarm LP data is detrended and analyzed before the earthquakes and also during the earthquakes and resulting tsunami events. The GNSS POD topside TEC from Swarm is analyzed together as a background for LP data. In-situ electron density disturbances occurring during a pass close to the earthquake is compared to selected STEC measurements between LEO and GNSS satellites. Additionally absolute STEC values from selected nearby ground stations are analyzed in order to&amp;#160; find existing correlations for detected disturbances in the electric and magnetic fields. All the observations are sparse in time and space, and therefore, leave some unanswered questions and uncertainties. However, several interesting perturbations over earthquake/tsunami events are observable in both Swarm LP data and GNSS TEC data.&lt;/p&gt;

Orbital proportion indices and microlipografting for correction of secondary post-traumatic enophthalmos

Aim. Aesthetic rehabilitation of patients with secondary post-traumatic enophthalmos. Methods. From 2013 to 2018, 14 patients with secondary post-traumatic enophthalmos were treated at the maxillofacial surgery clinic of the Azerbaijan Medical University. All patients underwent reconstruction of the damaged orbital wall, so its bone volume was restored. However, in the postoperative period, a deficiency of the orbital soft tissue was noted. In preparation for the surgery, all patients underwent the following types of examination: three-dimensional computed tomography, photographic, anthropometric measurements with the determination of proportional indices and computer simulation. Based on the data obtained, the orbital proportion indices were calculated: intercanthal index (en-en)100/(ex-ex); orbital protrusion index (ex-ex)100/(ex-en,rl)+(en-en); orbital width index (ex-en,l)100/(en-en); eye fissure (palpebral) index (ps-pi, l)100/(ex-en,l); orbital index (os-or,l)100/(ex-en,l); eyebrow orbital height index (os-or,l)100/(sci-or,l); index of vertical orbital contour (os-or,l)100/(ps-os+pi-or)+(ps-pi); eyelid height index (pi-or,l)100/(ps-os,l). Microlipografting was performed according to the Coleman method with modification by T. Marten. Fat aspiration was performed with a blunt cannula with a diameter of 2.12.4 mm and a 10 ml syringe, without anesthetic administration. Prior to microlipografting, fibrotic cords between the skin and underlying tissues were dissected using a sharp needle and a V-shaped cannula. Microlipografting was performed using microcannulas of 0.71.1 mm. The fat microtransplant was introduced in two layers: under the circular muscle of the eye and subperiostally in the orbit. Results. In 11 cases, with an unexpressed form of secondary post-traumatic enophthalmos, a good aesthetic result was recorded. In 3 patients with a pronounced form of enophthalmos, a satisfactory aesthetic result was obtained; in these cases, repeated microlipografting was carried out. Conclusion. Microlipografting based on the calculation of the orbit proportions indices during rehabilitation of patients with secondary post-traumatic enophthalmos is a minimally invasive and effective procedure.

Is cranial multi-detector computed tomography imaging valuable for stature estimation in Egyptian population?

Background and objectives Stature estimation is an initial and essential component of any medico-legal investigations. However, it becomes more challenging when only skull remains are available. So, the goal of this study is to assess stature estimation using cranial multi-detector computed tomography (MDCT) images in a sample of the Egyptian population. Methods This clinical study was conducted on 150 Egyptian subjects underwent cranium MDCT with age ranged from 21 to 60 years. The measurements used were maximum cranial breadth, minimum frontal breadth, upper facial breadth, bizygomatic breadth, orbital height, orbital breadth, parietal chord, bimastoidale, maximum cranial length, basion-bregma height, cranial base length, and basion-prosthion length. Results The results revealed that stature and craniofacial measurements of males were significantly higher than those of females, all measurements were significantly positively correlated with stature in pooled cases, but the correlation coefficient differs in separate sex. Simple linear regression for stature estimation showed that the least standard error of estimate (SEE) values for the regression equations obtained when using bizygomatic breadth in pooled cases (7.9 cm) and in males only (5.7 cm), while in females using parietal chord had the least SEE (6.8 cm). Using multiple and stepwise regression analysis reported lower SEE values than simple linear regression analysis. Conclusion On the basis of this study, it is concluded that the cranial measurements obtained from MDCT images have limited utility in stature estimation among Egyptians, but could be used as an alternative method in cases where the best predictors, such as long bones, are not available.

ORBITAL INDEX OF ADULT BINIS IN EDO STATE, NIGERIA

Context: Each orbital cavity has width usually greater than the height; the relationship between the two is given by orbital index.Aim: The purpose of this study was to determine the orbital index of adult Binis. Settings and Design: The retrospective survey method was used in this study.Methods and Materials: The height and width of the orbit were measured by using the frontal skull x-ray films consisting of 100 (63 males and 37 females) anterio- posterior skull x-ray of subjects aged between 18 and 63 years. The measurement was carried out by choosing four points on the radiograph indicating the upper, lower, medial and lateral margins of the orbital rim and the distance between these points were measured using a digital vernier calliper.Statistical analysis used: The data were analyzed using the Statistical Package for the Social Sciences (SPSS 20). The independent t test was used to determine gender differences in orbital index among the participants.Results: The mean orbital height for the right and left sides were 31.11±0.56mm and 31.02±0.29mm respectively while the orbital widths were 39.97±0.37mm and 39.61±0.30mm respectively. The mean orbital index was 78.54±56 for the total population. Conclusion: The study population belongs to the Microseme category.

Ionospheric conductivity effects on electrostatic field penetration into the ionosphere

The classic approach to calculate the electrostatic field penetration, from the Earth's surface into the ionosphere, is to consider the following equation ∇·(σ·∇Φ)=0 where σ and Φ are the electric conductivity and the potential of the electric field, respectively. The penetration characteristics strongly depend on the conductivities of atmosphere and ionosphere. To estimate the electrostatic field penetration up to the orbital height of DEMETER satellite (about 700 km) the role of the ionosphere must be analyzed. It is done with help of a special upper boundary condition for the atmospheric electric field. In this paper, we investigate the influence of the ionospheric conductivity on the electrostatic field penetration from the Earth's surface into the ionosphere. We show that the magnitude of the ionospheric electric field penetrated from the ground is inverse proportional to the value of the ionospheric Pedersen conductance. So its typical value in day-time is about hundred times less than in night-time.