Terms Of RMS Research Articles

High-resolution tropospheric refractivity fields by combining machine learning and collocation methods to correct earth observation data

Signals used for Earth observation, when travelling through the atmosphere, are sensitive to refractivity; especially high spatio-temporal variations of water vapor are difficult to model and correct. Remaining unmodeled tropospheric delays deteriorate the positioning solution and therefore limit the accuracy of sensing and navigation applications. These delays are usually computed with empirical models based on ground meteorological parameters (pressure, temperature and water vapor partial pressure). However, existing models are not accurate enough for high-precision applications such as GNSS, where in consequence the so-called zenith total delay (ZTD) has to be estimated together with other unknown parameters (coordinates etc.).For decades, the Institute of Geodesy and Photogrammetry at ETH Zurich has been studying collocation methods for the modeling of tropospheric delays using meteorological parameters, successfully interpolating pointwise or integral atmospheric observations. Meanwhile, machine learning has become a widely used and valuable alternative, when big datasets are available for the training process. Indeed, we have already successfully predicted ZTDs based on meteorological parameters with an accuracy of 1–2 cm for locations (GNSS stations) already used in the training phase. However, difficulties arise to predict delays at new locations.In this work, we take a step forward in investigating the combination of machine learning algorithms and physical models used in a collocation approach to derive atmospheric delay fields at a very high resolution. Thus, without processing any GNSS data we can predict tropospheric delay fields everywhere in the area of investigation. In this paper, we firstly describe the designed architecture of the neural network, secondly, the combination of least-squares collocation and artificial neural networks for high-resolution prediction of tropospheric delays. We benefit from the complementary characteristics of these algorithms. While machine learning is capable of successfully predicting the variation of time series for given points, empirical models based on collocation are well suited for describing spatial variations within the area of investigation. Finally, we report the achieved performance for the entire territory of Switzerland (1–2 cm in terms of RMS), showing that the synergic combination of these algorithms can overcome the individual drawbacks of each method and provide more accurate delay estimates than either method individually.Datasets of 11 years, covering the territory of Switzerland, consisting of GNSS ZTDs from 72 permanent AGNES/COGEAR (swisstopo, ETHZ) stations and meteorological data from MeteoSwiss were used for this research.

Maximal growth rate of the ascending phase of a sunspot cycle for predicting its amplitude

Context. Forecasting the solar cycle amplitude is important for a better understanding of the solar dynamo as well as for many space weather applications. Different empirical relations of solar cycle parameters with the peak amplitude of the upcoming solar cycle have been established and used for solar cycle forecasts, as, for instance, the Waldmeier rule relating the cycle rise time with its amplitude, the polar fields at previous minimum, and so on. Recently, a separate consideration of the evolution of the two hemispheres revealed even tighter relations. Aims. We aim to introduce the maximal growth rate of sunspot activity in the ascending phase of a cycle as a new and reliable precursor of a subsequent solar cycle amplitude. We also intend to investigate whether the suggested precursor provides benefits for the prediction of the solar cycle amplitude when using the sunspot indices (sunspot numbers, sunspot areas) derived separately for the two hemispheres compared to the total sunspot indices describing the entire solar disc. Methods. We investigated the relationship between the maximal growth rate of sunspot activity in the ascending phase of a cycle and the subsequent cycle amplitude on the basis of four data sets of solar activity indices: total sunspot numbers, hemispheric sunspot numbers from the new catalogue from 1874 onwards, total sunspot areas, and hemispheric sunspot areas. Results. For all the data sets, a linear regression based on the maximal growth rate precursor shows a significant correlation. Validation of predictions for cycles 1–24 shows high correlations between the true and predicted cycle amplitudes reaching r = 0.93 for the total sunspot numbers. The lead time of the predictions varies from 2 to 49 months, with a mean value of 21 months. Furthermore, we demonstrated that the sum of maximal growth rate indicators determined separately for the north and the south hemispheric sunspot numbers provides more accurate predictions than that using total sunspot numbers. The advantages reach 27% and 11% on average in terms of rms and correlation coefficient, respectively. The superior performance is also confirmed with hemispheric sunspot areas with respect to total sunspot areas. Conclusions. The maximal growth rate of sunspot activity in the ascending phase of a solar cycle serves as a reliable precursor of the subsequent cycle amplitude. Furthermore, our findings provide a strong foundation for supporting regular monitoring, recording, and predictions of solar activity with hemispheric sunspot data, which capture the asymmetric behaviour of the solar activity and solar magnetic field and enhance solar cycle prediction methods.

Evaluation of wavefront aberrations induced by overlay errors in stitching computer-generated holograms

The emergence of large-aperture telescopes has fueled the need for testing and assisted alignment of large-scale optical systems. Computer-generated holograms (CGHs) have proven to be a useful method for aspheric optical testing and assisted alignment, and large-sized CGHs are required for large-scale aspherical systems. However, the maximum size of CGH is generally in the range of 6 to 9 inches owing to its current lithography capability. Stitching technology is a promising method for realizing larger-sized CGHs. As a proof of concept, a CGH with an aperture of 80 mm is fabricated using multistep lithography to investigate the overlay errors in stitching. Theoretical derivations reveal that additional tip/tilt aberrations are introduced owing to the overlay errors, which commonly couple with aberrations from adjustment errors. Therefore, to budget the effects of overlay errors, an evaluation method is proposed in this study. The evaluation results guide the separation and compensation of coupling aberrations in measurement. It is verified that the accuracy of a stitching CGH is considerably improved from 0.156λ to 0.017λ in terms of RMS after compensation. The findings obtained in this study during the development of stitching method and error evaluation are expected to promote the technology development and improvement of testing accuracy in stitching CGHs.

Improving Discrimination in Color Vision Deficiency by Image Re-Coloring.

People with color vision deficiency (CVD) cannot observe the colorful world due to the damage of color reception nerves. In this work, we present an image enhancement approach to assist colorblind people to identify the colors they are not able to distinguish naturally. An image re-coloring algorithm based on eigenvector processing is proposed for robust color separation under color deficiency transformation. It is shown that the eigenvector of color vision deficiency is distorted by an angle in the , Y-B, R-G color space. The experimental results show that our approach is useful for the recognition and separation of the CVD confusing colors in natural scene images. Compared to the existing techniques, our results of natural images with CVD simulation work very well in terms of RMS, HDR-VDP-2 and an IRB-approved human test. Both the objective comparison with previous works and the subjective evaluation on human tests validate the effectiveness of the proposed method.

IRG2018: A regional geoid model in Iran using Least Squares Collocation

The aim of this study is to determine an accurate geoid model for Iran based on the Least Squares Collocation method in the framework of the Remove — Compute — Restore technique. In areas suffering from a lack of homogeneous and accurate gravity anomaly data, as is the case of Iran, the choice of the most compatible global gravity model has a significant impact on the estimated form of the geoid. Different combined and satellite-only global gravity models were therefore analyzed for Iran, and EIGEN6C4 was selected as the best one. The Shuttle Radar Topography Mission height model was used for the residual terrain correction. The covariance modeling, a crucial step in the Least Squares Collocation method, was based on two strategies. In the first, the study area was divided into four sub-areas, and then an individual empirical covariance was computed and a covariance model fitted to each of them. In the second, an empirical covariance was computed using all terrestrial gravity data, and a unique covariance model was fitted to it. Despite some border effects, the former strategy showed slightly better performance according to the resulting statistics, and therefore it was preferred for the estimation of the geoid model called IRG2018. To remove the offset of IRG2018 with respect to GNSS/Leveling-derived geoid heights, two alternative approaches were tested: subtracting a fitting polynomial surface or directly using the GNSS/Leveling data as an input to the IRG2018 computation process. Evaluation of the results, based on an independent control set of approximately half of available GNSS/Leveling points, showed an advantage of the latter approach, with an estimated accuracy of about 20 cm in terms of RMS.

Analysis of Solid Contamination in Ball Bearing Through Acoustic Emission Signals

AbstractAcoustic emission is one of the effective techniques used for the condition monitoring of rolling element bearings. Contamination is one of the major reasons for bearing early failure due to presence of solid particle in lubricant grease. In most cases, outer race is stationary and the inner race is attached to the rotating assembly. The lubrication is very essential for the bearing to perform under various demanding conditions. The main aim of this project is to analyze the effect of contamination of lubricant by solid particles on the dynamic behavior of rolling bearing. Green sand at three concentration levels 5%, 15%, 25% and different particle sizes 75 μm, 106 μm and 150μm is used to contaminate the lubricant. Experimental tests have been performed for different load and speed condition in good and contaminated ball bearings lubricated with grease. The trends in the amount of AE waves affected by the contamination of the grease were determined. Acoustic emission signals were analyzed in terms of RMS, kurtosis, and peak-peak.

Statistically optimal estimation of degree-1 and C20 coefficients based on GRACE data and an ocean bottom pressure model

In this study, we develop a methodology to estimate monthly variations in degree-1 andC20 coefficients by combing Gravity Recovery and Climate Experiment (GRACE) data withoceanic mass anomalies (combination approach).With respect to the method by Swenson et al.,the proposed approach exploits noise covariance information of both input data sets and thusproduces stochastically optimal solutions supplied with realistic error information. Numericalsimulations show that the quality of degree-1 and -2 coefficients may be increased in this wayby about 30 per cent in terms of RMS error.We also proved that the proposed approach can bereduced to the approach of Sun et al. provided that the GRACE data are noise-free and noise inoceanic data is white. Subsequently, we evaluate the quality of the resulting degree-1 and C20coefficients by estimating mass anomaly time-series within carefully selected validation areas,where mass transport is small. Our validation shows that, compared to selected Satellite LaserRanging (SLR) and joint inversion degree-1 solutions, the proposed combination approachbetter complementsGRACE solutions. The annual amplitude of the SLR-based C10 is probablyoverestimated by about 1 mm. The performance of the C20 coefficients, on the other hand, issimilar to that of traditionally used solution from the SLR technique.

An improved troposphere tomographic approach considering the signals coming from the side face of the tomographic area

Abstract. The spatio-temporal distribution of atmospheric water vapour information plays a crucial role in the establishment of modern numerical weather forecast models and description of the different weather variations. A troposphere tomographic method has been proposed considering the signal rays penetrating from the side of the area of interest to solve the problem of the low utilisation rate of global navigation satellite system (GNSS) observations. Given the method above needs the establishment of a unit scale factor model using the radiosonde data at only one location in the research area, an improved approach is proposed by considering the reasonability of modelling data and the diversity of the modelling parameters for building a more accurate unit scale factor model. The new established model is established using grid point data derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) and evenly distributed in the tomographic area, which can enhance the number of calculated initial water vapour density values with high accuracy. We validated the improved method with respect to the previous methods, as well as the result from a radiosonde using data from 12 stations from the Hong Kong Satellite Positioning Reference Station Network. The obtained result shows that the number of initial values estimated by the new model is increased by 6.83 %, while the internal and external accuracies are 0.08 and 0.24 g m−3, respectively. Integrated water vapour (IWV) and water vapour density profile comparisons show that the improved method is superior to previous studies in terms of RMS, MAE, and bias, which suggests higher accuracy and reliability.

Regional gravity field modelling from GOCE observables

In this article we discuss a regional recovery of gravity disturbances at the mean geocentric sphere approximating the Earth over the area of Central Europe from satellite gravitational gradients. For this purpose, we derive integral formulas which allow converting the gravity disturbances onto the disturbing gravitational gradients in the local north-oriented frame (LNOF). The derived formulas are free of singularities in case of r≠R. We then investigate three numerical approaches for solving their inverses. In the initial approach, the integral formulas are firstly modified for solving individually the near- and distant-zone contributions. While the effect of the near-zone gravitational gradients is solved as an inverse problem, the effect of the distant-zone gravitational gradients is computed by numerical integration from the global gravitational model (GGM) TIM-r4. In the second approach, we further elaborate the first scenario by reducing measured gravitational gradients for gravitational effects of topographic masses. In the third approach, we apply additional modification by reducing gravitational gradients for the reference GGM. In all approaches we determine the gravity disturbances from each of the four accurately measured gravitational gradients separately as well as from their combination. Our regional gravitational field solutions are based on the GOCE EGG_TRF_2 gravitational gradients collected within the period from November 1 2009 until January 11 2010. Obtained results are compared with EGM2008, DIR-r1, TIM-r1 and SPW-r1. The best fit, in terms of RMS (2.9mGal), is achieved for EGM2008 while using the third approach which combine all four well-measured gravitational gradients. This is explained by the fact that a-priori information about the Earth’s gravitational field up to the degree and order 180 was used.

COMPARISON OF MAGNETIC PROPERTIES IN A MAGNETIC CLOUD AND ITS SOLAR SOURCE ON 2013 APRIL 11–14

ABSTRACT In the context of the Sun–Earth connection of coronal mass ejections and magnetic flux ropes (MFRs), we studied the solar active region (AR) and the magnetic properties of magnetic cloud (MC) event during 2013 April 14–15. We use in situ observations from the Advanced Composition Explorer and source AR measurements from the Solar Dynamics Observatory. The MCs magnetic structure is reconstructed from the Grad–Shafranov method, which reveals a northern component of the axial field with left handed helicity. The MC invariant axis is highly inclined to the ecliptic plane pointing northward and is rotated by 117° with respect to the source region PIL. The net axial flux and current in the MC are comparatively higher than from the source region. Linear force-free alpha distribution (10−7–10−6 m−1) at the sigmoid leg matches the range of twist number in the MC of 1–2 au MFR. The MFR is nonlinear force-free with decreasing twist from the axis (9 turns/au) toward the edge. Therefore, a Gold–Hoyle (GH) configuration, assuming a constant twist, is more consistent with the MC structure than the Lundquist configuration of increasing twist from the axis to boundary. As an indication of that, the GH configuration yields a better fitting to the global trend of in situ magnetic field components, in terms of rms, than the Lundquist model. These cylindrical configurations improved the MC fitting results when the effect of self-similar expansion of MFR was considered. For such twisting behavior, this study suggests an alternative fitting procedure to better characterize the MC magnetic structure and its source region links.

Rationality optimization of tool path spacing based on dwell time calculation algorithm

With the aim to achieve the dwell time calculation and the optimization of tool path planning in optical figuring, an improved algorithm is proposed and experimentally validated. Firstly, the principle of the algorithm is introduced, of which tool path planning is added. After that, a two-part simulation is conducted. In the first part, the high convergence accuracy of the proposed algorithm is verified. And it also reveals that although the convergence accuracy of the algorithm without tool path planning is higher, the surface grid size changes with the tool path spacing (TPS) would affect the initial surface error and make the algorithm unpractical. In the second part, the optimization of tool path planning using the proposed algorithm is investigated, in terms of RMS, polishing time, and polishing track. The result reveals that the proposed algorithm can be used to find out the optimal TPS. Finally, polishing experiment is carried out, by using the optimal TPS obtained from the optimization process. Considering the instability of the removal functions in the polishing process and the gradient of the initial surface, the experimental result has shown an acceptable convergence ratio. Therefore, the accuracy and practicality of the presented algorithm are proven.

Optimization Design for Car Suspension Elastic Elements

To realize an efficient car suspension control (for instance in technical inspection) it is important to use easy measurable variables. This is the reason for developing optimization techniques in order to simplify and improve the engineering design process. The paper presents an optimization process of a torsion bar spring included in the car suspension involving the following steps: modeling and analyzing the torsion bar spring behaviour, definition of the optimization objective and the specifications for the proposed solution choosing an appropriate methodology to satisfy the design objectives. It has been used a Min-Max optimization method to highlight the vibration response (in terms of RMS) of the system. CAD analysis and MatLAB optimization are performed on the car suspension elastic element and the obtained results provide an optimum vibrational response and constructive design. This combination of these analyses can be considered an efficient tool in order to ensure the driver and passengers comfort according to the standards.

Benefit of the NeQuick Galileo Version in GNSS Single-Point Positioning

The GNSS measurements are strongly affected by ionospheric effects, due to the signal propagation through ionosphere; these effects could severely degrade the position; hence, a model to limit or remove the ionospheric error is necessary. The use of several techniques (DGPS, SBAS, and GBAS) reduces the ionospheric effect, but implies the use of expensive devices and/or complex architectures necessary to meet strong requirements in terms of accuracy and reliability for safety critical application. The cheapest and most widespread GNSS devices are single frequency stand-alone receivers able to partially correct this kind of error using suitable models. These algorithms compute the ionospheric delay starting from ionospheric model, which uses parameters broadcast within the navigation messages. NeQuick is a three-dimensional and time-dependent ionospheric model adopted by Galileo, the European GNSS, and developed by International Centre for Theoretical Physics (ICTP) together with Institute for Geophysics, Astrophysics, and Meteorology of the University of Graz. The aim of this paper is the performance assessment in single point positioning of the NeQuick Galileo version provided by ESA and the comparison with respect to the Klobuchar model used for GPS; the analysis is performed in position domain and the errors are examined in terms of RMS and maximum error for the horizontal and vertical components. A deep analysis is also provided for the application of the exanimated model in the first possible Galileo only position fix.

GNSS Reliability Testing in Signal-Degraded Scenario

Multiconstellation satellite navigation is critical in signal-degraded environments where signals are strongly corrupted. In this case, the use of a single GNSS system does not guarantee an accurate and continuous positioning. A possible approach to solve this problem is the use of multiconstellation receivers that provide additional measurements and allows robust reliability testing; in this work, a GPS/GLONASS combination is considered. In urban scenario, a modification of the classical RAIM technique is necessary taking into account frequent multiple blunders. The FDE schemes analysed are the “Observation Subset Testing,” “Forward-Backward Method,” and “Danish Method”; they are obtained by combining different basic statistical tests. The considered FDE methods are modified to optimize their behaviour in urban scenario. Specifically a preliminary check is implemented to screen out bad geometries. Moreover, a large blunder could cause multiple test failures; hence, a separability index is implemented to avoid the incorrect exclusion of blunder-free measurements. Testing the RAIM algorithms of GPS/GLONASS combination to verify the benefits relative to GPS only case is a main target of this work too. The performance of these methods is compared in terms of RMS and maximum error for the horizontal and vertical components of position and velocity.

Self-Organized Nanostructures on GaSb(001) Surfaces Due to Low-Energy Ion Irradiation

Surface modification of GaSb(001) induced by low energy (2 to 4.5 keV) Ar ion beam irradiation has been investigated by means of atomic force microscopy (C-AFM). It has been found, that depending on the ion beam parameters, i.e. energy and fluence, narrow size distribution of nanostructure patterns have been developed on the irradiated surfaces. Particularly, at incidence angle of 80o with respect to the surface normal, remarkably ordered ripple like structures are formed. The wave vector of the ripple pattern is oriented perpendicular to the direction of the ion beam projection on the irradiated surface. It has been also found, that the surface roughness, in terms of RMS, is initially a decreasing function of the ion fluence, but above medium fluence (of 1×1016 ions/cm2) it increases with the irradiation time. The results are discussed in terms of ballistic processes of sputtering and existing theories describing the ion beam induced surface modification.

An evaluation of recent GOCE geopotential models in Brazil

An evaluation of recent GOCE geopotential models in BrazilSeveral global geopotential models based on Gravity field and steady-state Ocean Circulation Explorer (GOCE) data have been published in the last two years. Some of these models use combinations of different satellite missions, while others use only GOCE data. This paper presents the evaluation and analysis of each approach using GOCE data in the Southeast of Brazil. Two assessments have been made. We compared the geoid heights derived from GOCE-based models with the geoidal heights from 176 GPS stations on leveling benchmarks. The findings show an improvement in GOCE-based models TIM_R3 (0.40 m) and DIR_R3 (0.39 m) for degree and order 210 in relation to EGM2008 (0.44 m) in terms of RMS. For the other models the results did not exceed 0.44 m. The second evaluation reports the comparison in terms of gravity disturbances between terrestrial gravity data and the models. The results, in terms of RMS and up to degree and order 210, indicate slightly low GOCO 02S values (10.34 mGal), TIM_R2 (10.37 mGal) and TIM_R3 (10.47 mGal) compared to EGM2008 (10.66 mGal). We also applied the residual terrain model and, as a result, the RMS errors were reduced by ~35% (~6.0 mGal) in the entire area and by ~45% in the mountain region.

Photocatalytic Degradation of Gaseous Acetone by a Self-Prepared Nano-Sized Composite TiO<sub>2</sub>/In<sub>2</sub>O<sub>3</sub>/SnO<sub>2</sub> Film Photocatalyst

The objective of this study is to decompose gaseous acetone ((CH3)2CO) by a self-prepared nano-sized composite TiO2/In2O3/SnO2 film photocatalyst that was prepared by a multi-target vacuum sputter operating at a vacuum pressure of 3 mtorr. The operating parameters investigated for the sputtering process included oxygen to argon ratio (O2/Ar), sputtering temperature, substrate materials, substrate layers, and sputtering duration. The nano-sized composite TiO2/In2O3/SnO2 film photocatalyst was mainly composed of anatase with a few rutile. The surface roughness of the TiO2/In2O3/SnO2 film photocatalyst in terms of RMS ranged from 2.292 to 7.533 nm, while the thickness of the single- and double-layer film photocatalysts were 473.5 and 506.0 nm, respectively. Gaseous acetone was initially injected into and further degraded in a self-designed batch photocatalytic reactor containing the nano-sized composite TiO2/In2O3/SnO2 film photocatalyst. Experimental results indicated that the highest acetone degradation efficiency of 99.9% was obtained at 50°C and 1 atm with the incident of near-UV illuminated by a fluorescent black light lamp. Under the incidence of blue light (430-500 nm), the reaction rates of acetone decomposition were 2.353x10-5 and 3.478x10-5 μmole/cm2-sec for using single- and double-layer TiO2/In2O3/SnO2 film photocatalysts, respectively.

Time of flight measurements over a radio link from Uppsala to Bruntingthorpe and their application to testing predictions methods that approximate the ray tracing technique

Time of flight measurements (TOF) over the radio link between Uppsala (Tx: 59.9°N, 17.6°E) and Bruntingthorpe (Rx: 52.5°N, 1.1°W) have been performed every 2 min at six frequencies (4.637, 6.954, 8.008, 10.391, 11.118, and 14.364 MHz) during the period November 2006–January 2008. Such measurements have been compared with the TOF provided by three prediction methods that approximate the ray tracing technique: IRI-95, SIRM&BR_D, and ICEPAC. The root mean square deviation (rms) between TOF monthly median measurements and TOF monthly median predictions and the differences (DP) between the length of the median and predicted ray path have been calculated. The results, which are presented in terms of rms and DP for different seasons and different time periods, have indicated that the approximate methods are inadequate and that for more accurate predictions ray tracing techniques should be applied.

The Use of Poly(Sodium N-Undecanoyl-l-Leucylvalinate), Poly(Sodium N-Undecanoyl-l-Leucinate) and Poly(Sodium N-Undecanoyl-l-Valinate) Surfactants as Chiral Selectors for Determination of Enantiomeric Composition of Samples by Multivariate Regression Modeling of Fluorescence Spectral Data

Steady-state fluorescence spectroscopy was employed to investigate the use of chiral polymeric surfactants as chiral selectors in chiral analysis by multivariate regression modeling of spectral data. Partial-least-squares regression modeling (PLS-1) was used to correlate changes in the fluorescence spectral data of 1,1'-bi-2-naphthol (BOH), 1,1'-binaphthyl-2,2'-diamine (BNA), or 2,2,2-trifluoroanthrylethanol (TFA) in the presence of poly(sodium N-undecanoyl-L-leucylvalinate), poly(sodium N-undecanoyl-L-leucinate) or poly(sodium N-undecanoyl-L-valinate) as the enantiomeric composition of the chiral analytes was varied. The regression models produced from the spectral data were validated by determining the enantiomeric composition of independently prepared test solutions. The ability of the model to correctly predict the enantiomeric composition of future samples was evaluated using the root-mean-square percent-relative error (RMS%RE) of prediction. In terms of RMS%RE, the ability of the model to accurately predict the enantiomeric composition of future samples was dependent on the chiral analyte, the polymeric surfactant used, and the surfactant medium, and ranged between 1.57 and 6.10%. Chiral analyte concentrations as low as 5 x 10(-6) M were found to give regression models with good predictability.

Trade-off between angular resolution and straylight contamination in the PLANCK Low Frequency Instrument

The last generation of CMB anisotropy experiments operating either from space, like the WMAP and PLANCK satellite, from the atmosphere, such as balloons, or from the ground, like interferometers, make use of complex multi-frequency instruments at the focus of meter class telescopes to allow the joint study of CMB and foreground anisotropies, necessary to achieve an accurate component separation. Between ∼70 GHz and ∼300 GHz, where foreground contamination is minimum, it is extremely important to reach the best trade-off between the improvement of the angular resolution, necessary for measuring the high order acoustic peaks of CMB anisotropy, and the minimization of the straylight contamination mainly due to the Galactic emission. This is one ol the most critical systematic effects at large and intermediate angular scales (i.e. at multipoles f less than 100) and consists in unwanted radiation entering the beam at large angles from the direction of the antenna boresight direction. We consider here the 30 and 100 GHz channels of the PLANCK Low Frequency Instrument (LFI). Assuming the nominal PLANCK scanning strategy, we evaluate the straylight contamination introduced by the most relevant Galactic foreground components for a reference set of optical configurations, accurately simulated as described in Sandri et al. (2004, A&A, 428, 299) (hereafter Paper 1). Given the overall constraints to the LFI optical design, we show that it is possible to improve the angular resolution by 5-7% by keeping the overall peak-to-peak signal of the Galaxy straylight contamination (GSC) below the level of few μK (and about 10 times smaller in terms of rms). A comparison between the level of straylight introduced by the different Galactic components for different beam regions (intermediate and far beam) is presented. We provide approximate relations, both for the intermediate and the far beam, for the rms and the peak-to-peak levels of the GSC as functions of the corresponding contributions to the integrated beam or of the spillover. For some reference cases we compare the results based on Galactic foreground maps derived from radio, IR, and Hα templates with those based on WMAP maps including CMB and extragalactic source fluctuations. The implications for the GSC in the PLANCK LFI polarization data are discussed. Finally, we compare the results obtained at 100 GHz with those at 30 GHz, where the GSC is more critical.