Eclipse Period Research Articles

Energy Storage for the Next Generation of Robotic Space Exploration

Energy storage technologies play an important role in powering the robotic exploration of space. Batteries can serve as either the primary power source for a mission, or augment power produced by solar arrays or radioisotope thermoelectric generators. Primary batteries have been used to power atmospheric and landed probes, with rechargeable batteries used to provide power to various spacecraft types during launches, to support peak power/load levelling needs, and to provide power during eclipse periods. Further advances in aerospace energy storage technologies are needed, in particular with respect to improving battery safety and reliability, specific energy, and extreme environment capabilities.

Benchmark model for multi‐orbital transient analysis of satellite electrical power subsystem

In this study, an efficient multi-orbital simulation model is presented for satellite Electrical Power Subsystem (EPS) which is integral to the success of the mission. The model integrates converter models, PV array model, DC bus model, and a numerical battery model according to a generalised EPS architecture to form one unified model of the entire EPS. The proposed model reduces simulation complexity, enhances speed, and enables multi-orbit analysis capability. Dynamic interaction among the elements is modelled through a coordinated control containing maximum power point tracking (MPPT), voltage regulation, battery charge/discharge control and management. Practical concerns of digital control implementation for PI controllers and MPPT are also incorporated in the model. Anti-windup is implemented to avoid latency in controller action after the eclipse. Additionally, a robust MPPT algorithm ensures fast immediate action after eclipse. Efficient component models and practical attention-to-detail enable the developed model to simulate multiple orbits with eclipse periods. The superior speed of the model, ability to simulate multiple orbits, and test different control strategies are demonstrated with a practical case study of Mysat-1, an imaging satellite launched by the Khalifa University. The model can be used as a proof-of-concept tool for predicting the operational behaviour of EPS during the development of a satellite.

Soundscape shifts during the 2017 total solar eclipse: an application of dispersed automated recording units to study ephemeral acoustic events

ABSTRACT Shifts in soundscapes often reflect diurnal patterns. In 2017 a total solar eclipse occurred in the US, resulting in a period of 3 h with the sun partially covered by the moon and 2 min of total darkness. We hypothesised this would create yet unmeasured and novel changes in different biophonic events. We placed automated recording units across an urban–rural gradient within the path of the total solar eclipse. We used generalised additive models to model and visualise acoustic shifts as a function of both time and per cent urban development. Biophony, a measure of the average frequency generated from biological sound, increased immediately before the period of the total solar eclipse and following the end of the eclipse, assuming the character of a dusk and dawn chorus. Other unique effects were observed, such as less anthrophony before totality. The total solar eclipse provided novel insight on temporal and spatial variation in soundscapes. Key policy inslights The ecological response to changes in a landscape can be measured over time and space using acoustic technology Landscape context must be considered when studying the biology of astrological events Generalized additive modeling allows a better understanding of non-linear and unique trends and consider the nested effect of location

Homburgvirus LP-018 Has a Unique Ability to Infect Phage-Resistant Listeria monocytogenes.

Listeria phage LP-018 is the only phage from a diverse collection of 120 phages able to form plaques on a phage-resistant Listeria monocytogenes strain lacking rhamnose in its cell wall teichoic acids. The aim of this study was to characterize phage LP-018 and to identify what types of mutations can confer resistance to LP-018. Whole genome sequencing and transmission electron microscopy revealed LP-018 to be a member of the Homburgvirus genus. One-step-growth curve analysis of LP-018 revealed an eclipse period of ~60–90 min and a burst size of ~2 PFU per infected cell. Despite slow growth and small burst size, LP-018 can inhibit the growth of Listeria monocytogenes at a high multiplicity of infection. Ten distinct LP-018-resistant mutants were isolated from infected Listeria monocytogenes 10403S and characterized by whole genome sequencing. In each mutant, a single mutation was identified in either the LMRG_00278 or LMRG_01613 encoding genes. Interesting, LP-018 was able to bind to a representative phage-resistant mutant with a mutation in each gene, suggesting these mutations confer resistance through a mechanism independent of adsorption inhibition. Despite forming plaques on the rhamnose deficient 10403S mutant, LP-018 showed reduced binding efficiency, and we did not observe inhibition of the strain under the conditions tested. Two mutants of LP-018 were also isolated and characterized, one with a single SNP in a gene encoding a BppU domain protein that likely alters its host range. LP-018 is shown to be a unique Listeria phage that, with additional evaluation, may be useful in biocontrol applications that aim to reduce the emergence of phage resistance.

GNSS yaw attitude estimation: Results for the Japanese Quasi‐Zenith Satellite System Block‐II satellites using single‐ or triple‐frequency signals from two antennas

The Japanese Quasi-Zenith Satellite System (QZSS) constellation has added three new Block-II satellites, which broadcast ranging signals from their main L-band antenna together with augmentation signals from separate, auxiliary antennas. After determination of the baseline vector between main and auxiliary antenna, differential processing allows for an estimation of the satellite's yaw attitude with an accuracy of less than 1°. Differential carrier-phase center variation maps have been derived. Yaw estimation results are presented for periods of special interest, for example 360° yaw rotations, orbit correction maneuvers and the satellite's eclipse period, where a special pseudo-yaw steering attitude mode is applied. The second part of the paper introduces a new concept using triple-frequency signals from two different antennas for attitude determination. This method is demonstrated with QZSS measurements but is also applicable to other satellite navigation system, like the enhanced GLONASS-M satellites with L3 signal capabilities.

System Level Modelling of Batteries in Spacecraft Power System in Multiple Source and Multiple Load Configuration

AbstractIn present day spacecraft applications, power system uses solar arrays as the primary source of power generation and rechargeable Lithium ion batteries as secondary source of power. In normal orbits, during sunlit period, solar arrays support the power requirement from all the subsystems and payloads along with the charge power requirement of batteries. During eclipse period, entire load should be supported by batteries. In addition to the eclipse support, starting from launch pad to till deployment of solar panels, all loads will be on batteries. Contingency loads should also be taken care by batteries. So, battery sizing is very critical part in designing the power system of spacecraft. In multiple source and multiple load configuration where two or more batteries are connected to same Spacecraft power bus, current sharing between the batteries is expected, which needs to be considered for optimized sizing and designing of batteries. The scenario becomes complex with additional constraints namely some loads can come on one battery and not on others or vice versa. Even in a configuration where potential difference exists between batteries, current sharing will start as soon as this difference vanishes. A system level simulation model is developed, using network equations, to analyze in‐circuit performance of batteries in multiple source and multiple load power system. The simulation model uses actual current sharing and predicts State of Charge (SOC) of each battery from which Open Circuit Voltage (OCV) is derived. This OCV of batteries is used periodically for finding actual current sharing which runs in a loop for analyzing battery performance in multisource system. Currently a configuration in which two batteries are connected to two buses, which are paralleled and having different loads, is simulated. Optimized battery sizing, actual current sharing and SOC of each battery are derived. This model can also be extended to a system where more than two batteries are present. Two different approaches are used for simulation and results are compared. The developed generic model has features to use in multiple battery configuration.

GPS satellite inter-frequency clock bias estimation using triple-frequency raw observations

This study proposes a unified uncombined model to estimate GPS satellite inter-frequency clock bias (IFCB) in both triple-frequency code and carrier-phase observations. In the proposed model, the formulae of both phase-based and code-based IFCBs are rigorously derived. Specifically, satellite phase-based IFCB refers to its time-variant part and it is modeled as a periodic function related to the sun–spacecraft–earth angle. A zero-mean condition of all available GPS satellites that support triple-frequency data is introduced to render satellite code-based IFCB estimable. Three months of data from 40 globally distributed stations of the International GNSS Service Multi-GNSS Experiment are used to test our method. The results show that the four-order periodic function is suitable for eliminating the 12-h, 6-h, 4-h, and 3-h periods that exist in the a posteriori phase residuals when no periodic function is used. For comparison, the geometry-free and ionosphere-free (GFIF) phase combination and differential code bias (DCB) products released by DLR (German Aerospace Center) and IGG (Institute of Geodesy and Geophysics, China) are also used to calculate the satellite phase-based and code-based IFCBs, respectively. The results show that (1) the average root mean square (RMS) of the phase-based IFCB difference between the proposed method and the GFIF phase combination is 4.3 mm; (2) the average RMS in the eclipse period increased by 50% compared with the average RMS in the eclipse-free period; (3) the mean monthly STD for code-based IFCB from the proposed method is 0.09 ns; and (4) the average RMS values of code-based IFCB differences between the proposed method and the DCB products released by DLR and IGG are 0.32 and 0.38 ns. This proposed model also provides a general approach for multi-frequency GNSS applications such as precise orbit and clock determination.

Antiviral and virucidal activities against herpes simplex viruses of umesu phenolics extracted from Japanese apricot.

Umesu phenolics were obtained from the salt extracts of Japanese apricot (Nanko-mume cultivar of Prunus mume Sieb. et Zucc.) as purified phenolics. The antiviral activities of umesu phenolics obtained were then examined against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2), enveloped DNA viruses. The phenolics inhibited the multiplication of these viruses when added to the culture media of the infected cells. This inhibition occurred at phenolic concentrations at which they showed no severe cytotoxicity. One-step growth experiments showed that the eclipse period in the HSV-1 multiplication process was extended in the presence of umesu phenolics and that the addition of phenolics after the completion of viral DNA replication did not affect their multiplication. More drastic effects were observed on virucidal activities against HSV-1 and HSV-2; the infectivity decreased to 0.0001 when infected cells were incubated with 3 mg/ml phenolics at 30°C for 5 min. These results demonstrate the antiviral and virucidal activities of umesu phenolics and suggest a potential pharmacological use for these phenolics as a sanitizing or preventive medicine against superficial HSV infections.

Abnormal behaviour of sporadic E-layer during the total solar eclipse of 22 July 2009 near the crest of EIA over India

In this study we present the behaviour of sporadic E-layer during a total solar eclipse (TSE) which occurred during the dawn/sunrise hours over a site located in the path of totality. A Canadian Advanced Digital Ionosonde (CADI) was operated at Allahabad (25.4° N, 81.9° E), a low latitude station located near the crest of equatorial ionization anomaly (EIA) in the Indian subcontinent to study the ionospheric effects of 22 July 2009 TSE. Corresponding to the eclipse period, a gradual increase of ftEs (top frequency of Es layer) in the 4–5 MHz range was seen on the control days. On 22 July (the TSE day), correlated changes in ftEs coinciding with the TSE progression was noted – (i) sharp decrease near first and second contact of TSE, (ii) an increase after first and second contact, and (iii) wavelike fluctuations in ftEs variation during eclipse hours and beyond. Much higher ftEs values were noted during the TSE hours in comparison to that seen on usual days. Strong blanketing Es layer developed during the TSE hours and persisted for slightly longer duration than its usual occurrence time. Near the TSE totality, slight lowering of the base height of Es layer was also noted.

Perturbations in Earth’s Atmosphere over An Indian Region during the Total Solar Eclipse on 22 July 2009

During a total solar eclipse (TSE) on 22 July 2009, atmospheric perturbations were monitored from the surface to thermosphere to understand TSE’s impact on the meteorological (temperature, relative humidity, wind speed, and wind direction) and chemical (O3 and NOx) parameters around Kadapa (14.28°N, 78.42°E), a tropical semi-arid region of India. For this purpose, an experiment was conducted at Yogi Vemana University Campus, Kadapa, India, to measure the temperature, wind speed, wind direction, and concentrations of ozone (O3), NO, NO2, and NOx by using the automatic weather station (AWS) and O3 analyzer. On the eclipse day (22 July 2009), the surface observations at Kadapa showed a reduction in temperature (about 1.1°C) because of the solar insulation. Comparison of the thermal, dynamical (wind), and chemical parameters on the TSE day with control days [preceding (21 July 2009) and succeeding (23 July 2009) the TSE] illustrated the influence of solar eclipse. During the eclipse period, the O3 mixing ratio decreased, while NO2 and NOx increased; however, NO remained unchanged. In addition, radio occultation (RO) temperature profiles from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)/Formosat Satellite Mission (FORMOSAT-3) and Thermosphere, Ionosphere, and Mesosphere Energetics and Dynamics (TIMED) satellites were utilized to understand the impact of TSE on dynamics of the middle and upper atmosphere from tropopause to the thermosphere. High vertical resolution COSMIC observations revealed that during the solar eclipse, tropopause was cooler with twin peaks (double tropopause). The lower thermosphere between 110 and 130 km became warmer during the TSE, which might be caused by the dynamical response of the atmosphere in this region to the solar eclipse. The experimental data have provided very fine-scale variations of the atmospheric parameters both in time and height and also constituted a new set of results on TSE for further research.

Distinguishing Polar and Coplanar Circumbinary Exoplanets by Eclipse Timing Variations

Abstract Circumbinary planets (CBPs) can be misaligned with their host binary stars. Orbital dynamics, simulations, and recent observations of protoplanetary disks all suggest that the planet can stably orbit in a plane perpendicular to that of an eccentric host binary star (i.e., a polar orbit). No solid claim of detection of such a configuration has been made; the nine systems detected by the transit technique are nearly coplanar, but their discovery is also biased toward that configuration. Here, we develop eclipse timing variations (ETVs) as a method to detect misaligned CBPs. We find that because the apsidal motion (periastron precession) of the host binary is prograde for a coplanar planet and retrograde for a polar planet, the mean eclipse periods of primary and secondary eclipses differ in a way that distinguishes those configurations. Second, the eclipse duration variations vary in a way that can confirm that inference, over and against a polar model. Third, the relative phasing of primary and secondary ETVs on the planet’s orbital timescale also distinguishes the two configurations, which we explain analytically and quantify through a grid of numerical models. We apply these methods to Kepler-34, a transiting planet known to be nearly coplanar by detailed photodynamic modeling. In this system, we find that the binary eclipse times alone suffice to distinguish these orbital configurations, using the effects introduced here. Our work provides a tool for discovering potential polar CBPs, or misaligned CBPs of milder inclinations, from the existing ETV data set of the Kepler, as well as future observations by TESS or PLATO.

SLR validation and evaluation on BDS precise orbits from 2013 to 2018

The objective of this paper is to validate and evaluate the orbit accuracy of the BeiDou Navigation System (BDS) using satellite laser ranging (SLR) data over a 5-year time series. The microwave-based precise orbits of BDS derived from four Analysis Centers (ACs) are validated from 2013 to 2018, including three Multi-GNSS EXperiment (MGEX) ACs from WHU, CODE and GFZ, as well as a fourth AC, known as ISC in China, with the corresponding products designated as WUM, COM, GBM and ISC. The validated orbits of BDS include the Geostationary Earth Orbit (GEO) satellite of C01, the Inclined Geo-Synchronous Orbit (ISGO) satellites of C08, C10, and C13, as well as the Medium Earth Orbit (MEO) satellite of C11. In addition, the performances of the BDS orbits during noneclipse, eclipse and Yaw Maneuver (YM) period are evaluated. Finally, the dependencies of SLR residuals on the satellite nadir angle and on the Sun elevation angle β are analyzed in detail. The results demonstrated that (1) the optimal orbit accuracies of C01, C08, C10, C11 and C13 are 522.8 mm from WUM, 53.3 mm from ISC, 54.3 mm from ISC, 38.2 mm from ISC and 51.5 mm from COM, respectively. And the orbits derived from ISC have more stable and excellent accuracy than the other ACs due to the advantages of its orbit combination algorithm. (2) Due to the deficiencies of the Solar Radiation Pressure and the YM modeling for BDS satellites from four ACs, the microwave-based orbit accuracy of BDS IGSO and MEO satellites is significantly deteriorated during the eclipse period, especially in the YM period, while the accuracy of GEO C01 during the eclipse period is better than that during the noneclipse period. (3) The dependency of SLR residuals on the satellite nadir angle has been analyzed, but limited by the number and type of all the validated BDS satellites, the nadir-dependency offset of the SLR residuals cannot be well assigned from the characteristics of the SLR detector system, or the Laser Retro-reflector Arrays. (4) By analyzing the dependency of SLR residuals on the Sun elevation angle β, some commonalities of the patterns derived from four ACs have been found for BDS IGSO and MEO satellites, and the patterns are similar to that of the GLONASS, rather than those of GPS and Galileo.

Solar-eclipse-induced perturbations at mid-latitude during the 21 August 2017 event

Abstract. A study of the response of some ionospheric parameters and their relationship in describing the behaviour of ionospheric mechanisms during the solar eclipse of 21 August 2017 is presented. Mid-latitude stations located along the eclipse path and with data available from the Global Ionospheric radio Observatory (GIRO) database were selected. The percentage of obscuration at these stations ranges between 63 % and 100 %. A decrease in electron density during the eclipse is attributed to a reduction in solar radiation and natural gas heating. The maximum magnitude of the eclipse consistently coincided with a hmF2 increase and with a lagged maximum decrease in NmF2 at the stations investigated. The results revealed that the horizontal neutral wind flow is as a consequence of the changes in the thermospheric and diffusion processes. The unusual increase and decrease in the shape and thickness parameters during the eclipse period relative to the control days points to the perturbation caused by the solar eclipse. The relationships of the bottomside ionosphere and the F2 layer parameters with respect to the scale height are shown in the present work as viable parameters for probing the topside ionosphere during the eclipse. Furthermore, this study shows that in addition to traditional ways of analysing the thermospheric composition and neutral wind flow, proper relation of standardized NmF2 and hmF2 can be conveniently used to describe the mechanisms.

Valuation of some viral kinetics of Lytic Bacteriophages Infecting Methicillin Resistant Staphylococcus aureus (MRSA)

Background:
 Bacteriophages represent important groups of viruses that drive the bacterial populations in the ecosystems directly and control their numbers, unlike antibiotics they can kill the bacterial host without damaging or any harm to the normal microbial flora, so bacterial resistance to antibiotics is no more valuable problem if the use of phages becomes more efficient in use.
 Aim:
 The purpose of this study was to isolate and characterizing the phages that able to infect methicillin resistant Staphylococcus aureus (MRSA) and determination of phages kinetics.
 Methods:
 Different techniques were used to isolate and propagate the MRSA phages, then phage kinetics were determined such as adsorption rate, eclipse period, burst size , phage host range, phage sensitivity to pH and temperature and the determination of phage nucleic acids.
 Results:
 Two types of anti-staphylococcal lytic bacteriophages primarily named Phage 1 and Phage 2 were isolated from sewage water. Phage 1 exhibited broad host spectrum it was lytic against all S. aureus isolates included for the study. Conversely, phage 2 have narrow host range as they could inhibit only 30 isolates, None of these phages inhibited a bacterium other than staphylococci species. The adsorption rate of Phage 1 was 2.1×10-10 ml min-1 while Phage 2 was 1.5×10-10 ml min-1. Eclipse and Latent periods of Phage 1 were 6, 13 minutes and for phage 2 were 8, 16 minutes respectively, the burst size of Phage 1 and Phage 2 were 83±15 pfu\cell and 37±10 pfu\cell respectively. Complete lysis time of Phage 1 particles was 4 hours while the complete lysis time of Phage 2 particles was 5 hours. Phages passaging results showed a remarkable increment in plaque forming unit (pfu) which were reached its maximal elevation at six passage in Phage 1 and fourth passage in Phage 2. Fitness of Phage 1 and Phage 2 were 22 ± 5 pfu\cell and 20 ± 2 pfu\cell respectively through six generations. The Phage 1 and Phage 2 particles were stabled at a wide range of pH (6-10) and temperatures (30-50°C), the optimal temperature of two phages were 37°C.
 Conclusion:
 Overall findings suggested that MRSA phages are well distributed in the environment and represent a good and promising tool to control the infections result by this bacteria in which antibiotic resistance will be overwhelmed successfully especially in external infections such as burns and skins infections, which are safe and very specific with less side effects than antibiotic.

Yaw attitude modeling for BeiDou I06 and BeiDou-3 satellites

The estimated yaw angles of the BeiDou I06 satellite demonstrated that the satellite experienced midnight- or noon-turn maneuvers when the sun elevation angle above the orbital plane (β angle) was in the range of [− 3°, + 3°] and the orbital angle was in the range of approximately [− 6°, 6°] or [174°, 186°]. The behavior of yaw attitude maneuvers in the vicinity of the midnight and noon points was identical. An alternative yaw attitude model similar to that used for the Galileo Full-Operation-Capacity (FOC) satellites was developed on the basis of the estimated BeiDou I06 yaw angles with an accuracy of approximately 3.4° to reproduce the yaw attitude behaviors. However, a discrepancy in the form of a reversal in yaw direction during the midnight-turn maneuver was observed for BeiDou I06 when the β angle was extremely small (< 0.1°). The derived yaw attitude model was proved to model the yaw attitude of the BeiDou-3 experimental satellites, and reduces the observation residuals in the vicinity of the midnight and noon points to normal levels, and facilitates continuous satellite clock estimation during eclipse periods. Compared to the yaw attitude model developed by the European Space Operations Centre (ESOC), a similar performance has been achieved with maximum yaw differences up to 9.2° when the β angle is close to 0°. The average agreement between the models is about 1°. However, the ESOC model was developed based on a patented eclipsing model, the developed model in this study is open access.

Solar Coronal Jets Extending to High Altitudes Observed during the 2017 August 21 Total Eclipse

Abstract Coronal jets, which extend from the solar surface to beyond 2 R ⊙, were observed in the polar coronal hole regions during the total solar eclipse on 2017 August 21. In a time-series of white-light images of the corona spanning 70 minutes taken with our multi-site observations of this eclipse, six jets were found as narrow structures upwardly ejected with an apparent speed of about 450 km s−1 in polar plumes. On the other hand, extreme-ultraviolet (EUV) images taken with the Atmospheric Image Assembly of the Solar Dynamics Observatory show that all of the eclipse jets were preceded by EUV jets. Conversely, all the EUV jets whose brightnesses are comparable to ordinary soft X-ray jets and that occurred in the polar regions near the eclipse period, were observed as eclipse jets. These results suggest that ordinary polar jets generally reach high altitudes and escape from the Sun as part of the solar wind.

Optical Studies of 15 Hard X-Ray Selected Cataclysmic Binaries

Abstract We conducted time-resolved optical spectroscopy and/or time-series photometry of 15 cataclysmic binaries that were discovered in hard X-ray surveys by the Swift Burst Alert Telescope and the International Gamma-Ray Astrophysics Laboratory, with the goal of measuring their orbital periods and searching for spin periods. Four of the objects in this study are new optical identifications: Swift J0535.2+2830, Swift J2006.4+3645, IGR J21095+4322, and Swift J2116.5+5336. Coherent pulsations are detected from three objects for the first time, Swift J0535.2+2830 (1523 s), 2PBC J1911.4+1412 (747 s), and 1SWXRT J230642.7+550817 (464 s), indicating that they are intermediate polars (IPs). We find two new eclipsing systems in time-series photometry: 2PBC J0658.0−1746, a polar with a period of 2.38 hr, and Swift J2116.5+5336, a disk system that has an eclipse period of 6.56 hr. Exact or approximate spectroscopic orbital periods are found for six additional targets. Of note is the long 4.637-day orbit for Swift J0623.9−0939, which is revealed by the radial velocities of the photospheric absorption lines of the secondary star. We also discover a 12.76 hr orbital period for RX J2015.6+3711, which confirms that the previously detected 2.00 hr X-ray period from this star is the spin period of an IP, as inferred by Coti Zelati et al. These results support the conclusion that hard X-ray selection favors magnetic CVs, with IPs outnumbering polars.

Thermal Subsystem Operational Times Analysis for Ubiquitous Small Satellites Relay in LEO

The success of the satellite subsystems engineering depends on the optimal design, modeling, simulation, and validation of the deliverables of the conceptual and mission design objectives. This paper presents the operational times analysis of the thermal control subsystem onboard a 97-kg microsatellite in low-Earth orbit during an eclipse period. Power-storing, communication downlink and uplink, payload processing, and thermal control overpower modes were implemented for a communication mission under worst-case orbital patterns. An embedded digital temperature and lighting controller circuitry was designed and practically validated to effect a desired logic. For an average eclipse period of 34.4 mins, the operational times of the thermal subsystem at altitudes of 400 km, 500 km, and 600 km are 38.6 mins, 38.1 mins, and 37.7 mins respectively. Moreover, the thermal control subsystem simulation reveals that reducing the operational times of non-thermal control subsystems during the eclipse period by 50 % can result in an operational factor of safety of over 1.5. At least 10 dB data link transmission margin can be achieved. The reported findings show that the operational times of spacecraft subsystems overpower modes can be reconfigured in orbit to reliably sustain the operating conditions of the capability-based satellite components for ubiquitous communication.

Isolation and Characterization of Lytic Bacteriophages Infecting Acinetobacter baumannii

This study was carried out during the period from October 2015 to March 2016. It included the isolation of 42 isolates were identified asAcinetobacterbaumannii. All Isolates showed wide range of resistance to antibiotics. Two types of lytic bacteriophages primarily named Phage 1 and Phage 2 were isolated from sewage water. Phage 1 exhibited broad host spectrum it was lytic against all Acinetobacter baumannii isolates included for the study. Conversely,phage 2 have narrow host range as they could inhibit only 30 isolates,None of these phages inhibited a bacterium other than staphylococci species. The adsorption rate of Phage 1 was 3.1×10-10 ml min-1while Phage 2 was 1.7×10-10 ml min-1. Eclipse and Latent periods of Phage 1 were 6,17 minutes and for phage 2 were 7,14 minutes respectively,the burst size of Phage 1 and Phage 2 were 73±16 pfu\cell and 38±11 pfu\cell respectively. Complete lysis time of Phage 1 particles was 4.30 hours while the complete lysis time of Phage 2 particles was 6 hours. Phages passaging results showed a remarkable increment in PFU which were reached its maximal elevation at six passage in Phage 1 and fourth passage in Phage 2. Fitness of Phage 1 and Phage 2 were 24 ±5 pfu\cell and 26 ±4 pfu\cellrespectively through six generations. The Phage 1 and Phage 2 particles were stabled at a wide range of pH (6-10) and temperatures (30-50°C),the optimal temperature of two phages were 37°C.

Orbit and Positioning Accuracy for New Generation Beidou Satellites during the Earth Eclipsing Period

The Beidou System (BDS) started functioning at the end of 2012. The Yaw-Steering (YS) attitude mode for Inclined Geosynchronous Orbit (IGSO) and Medium Earth Orbit (MEO) satellites in BDS ensures that the solar panels face the Sun. The orbit radial accuracies for IGSO/MEO satellites are 0·5 m and the User Equivalent Range Errors (UERE) are 1·5 m in YS mode. BDS-2 satellites adopt Orbit-Normal (ON) mode to meet the power supply and thermal control requirements of the satellite during deep Earth eclipse periods. In ON mode, long-term orbit ephemeris accuracy monitoring in the Operational Control System (OCS) of BDS indicates that the orbit accuracies for IGSO/MEOs are reduced to a few hundreds of metres, seriously affecting the positioning accuracy and navigation service capability of the BDS system. Solar Radiation Pressure (SRP) is difficult to model in ON mode. Continuous Yaw-Steering (CYS) mode is available for new generation Beidou satellites launched since 2015. The orbit accuracies for these new generation Beidou (BDS-3) satellites were estimated based on BDS monitoring station data and SRP models including ECOM 9/5/3. The evaluation method consisted of four steps, namely, orbit internal consistency analysis, UERE calculation, Satellite Laser Ranging (SLR) data fitting Root Mean Square (RMS) determinations and positioning performance analysis; the data gathering period lasted for more than 60 days and included two CYS periods and one ON period. The experiments showed that the orbit accuracy of the radial component in CYS mode for the BDS-3 satellites degrades by 2 to 3 cm and positioning accuracy degrades only by 1 cm over that in YS mode which is just a small reduction in accuracy compared with the decimetre-level BDS orbit accuracy and the metre-level single point positioning accuracy with BDS pseudorange data. This overcomes declining orbit and positioning accuracy issues in ON mode for BDS-2 satellites. Other results also show that the reliability of BDS has been improved.