Pseudo-Stochastic Orbit Modeling Techniques for Low-Earth Orbiters

The Earth's non-spherical mass distribution and atmospheric drag cause the strongest perturbations on very low-Earth orbiting satellites (LEOs). Models of gravitational and non-gravitational accelerations are utilized in dynamic precise orbit determination (POD) with GPS data, but it is also possible to derive LEO positions based on GPS precise point positioning without dynamical information. We use the reduced-dynamic technique for LEO POD, which combines the geometric strength of the GPS observations with the force models, and investigate the performance of different pseudo-stochastic orbit parametrizations, such as instantaneous velocity changes (pulses), piecewise constant accelerations, and continuous piecewise linear accelerations. The estimation of such empirical orbit parameters in a standard least-squares adjustment process of GPS observations, together with other relevant parameters, strives for the highest precision in the computation of LEO trajectories. We used the procedures for the CHAMP satellite and found that the orbits may be validated by means of independent SLR measurements at the level of 3.2cm RMS. Validations with independent accelerometer data revealed correlations at the level of 95% in the along-track direction. As expected, the empirical parameters compensate to a certain extent for deficiencies in the dynamic models. We analyzed the capability of pseudo-stochastic parameters for deriving information about the mismodeled part of the force field and found evidence that the resulting orbits may be used to recover force field parameters, if the number of pseudo-stochastic parameters is large enough. Results based on simulations showed a significantly better performance of acceleration-based orbits for gravity field recovery than for pulse-based orbits, with a quality comparable to a direct estimation if unconstrained accelerations are set up every 30

Pasture and Grazing Land Price Information

Pasture and grazing land is a valuable resource in South Dakota, as it accounts for 53% of total land use. The price of land is determined by productivity and market forces. Various sources of land price information are available; they are given here to improve your awareness of prices that are available, when prices are released, and what factors influence them. • Knowledge of land values is useful when deciding between utilizing grazing land and renting it to others. • Knowledge of current returns to land is useful for determining the value of livestock that utilize forage. • Finally, the knowledge is useful for those buying or selling land

Gait retraining as part of the treatment programme for soldiers with exercise-related leg pain: preliminary clinical experiences and retention

Background: Gait retraining as part of a treatment programme for exercise-related leg pain (ERLP) was introduced in the sports medicine department of the Royal Netherlands Army in 2013.Objectives: To describe clinical experiences and retention of gait retraining in a military setting.Methods: Sixty-one cases from the year 2015 were available for analysis of gait and gait retraining. In 2016, 32 of these patients were available for a follow-up survey, 28 of them also for the follow-up measurement of running biomechanics in running shoes.Results: Soldiers received an outpatient treatment programme that lasted on average 129 days (SD 76). On average they received 2.4 gait retraining sessions, leading to significant and lasting changes in running biomechanics; in particular, reduction in maximal force (N) and maximal pressure (N/cm2) on the heels at 317 days follow-up (average, SD 108). Most soldiers were satisfied with gait retraining. At follow-up, 27 soldiers (84%) contributed some, the majority or all reduction of symptoms to it. Seventy percent reported that they had mastered the new running technique within two months. The Single Assessment Numeric Evaluation score increased from 55% to 78% for males and from 44% to 75% for females.Discussion: This is the first study to report on gait retraining for Medial Tibial Stress Syndrome. In future, prospective studies in the military running in shoes and running in boots respectively should be investigated.Conclusion: Soldiers with exercise-related leg pain (ERLP), among them patients with Medial Tibial Stress Syndrome, respond well to a treatment programme that included gait retraining. Ten months post-gait retraining, their running biomechanics still showed these positive changes from their time of intake.Keywords: medial tibial stress syndrome, chronic exertional compartment syndrome, militar

Primordial feature constraints from BOSS+eBOSS

Understanding the universe in its pristine epoch is crucial in order to obtain a concise comprehension of the late-time universe. Although current data in cosmology are compatible with Gaussian primordial perturbations whose power spectrum follows a nearly scale-invariant power law, this need not be the case when a fundamental theoretical construction is assumed. These extended models lead to sharp features in the primordial power spectrum, breaking its scale invariance. In this work, we obtain combined constraints on four primordial feature models by using the final data release of the BOSS galaxies and eBOSS quasars. By pushing towards the fundamental mode of these surveys and using the larger eBOSS volume, we were able to extend the feature parameter space (i.e. the feature frequency $\omega$) by a factor of four compared to previous analyses using BOSS. While we did not detect any significant features, we show that next-generation galaxy surveys such as DESI will improve the sensitivity to features by a factor of 7, and will also extend the parameter space by a factor of 2.5.Comment: 28 + 4 pages, 16 figure

Propagation of atmospheric model errors to gravity potential harmonics—impact on GRACE de-aliasing

High-frequency, time-varying mass redistributions in the ocean and atmosphere have an impact on GRACE gravity field solutions due to the space-time sampling characteristics of signal and orbit. Consequently, aliasing of these signals into the GRACE observations is present and needs to be taken into account during data analysis by applying atmospheric and oceanic model data (de-aliasing). As the accuracy predicted prior to launch could not yet be achieved in the analysis of real GRACE data, the de-aliasing process and related geophysical model uncertainties are regarded as a potential error source in GRACE gravity field determination. Therefore, this study aims to improve the de-aliasing process in order to obtain a more accurate GRACE gravity field time-series. As these time-series provide estimates for the integrated mass transport in the Earth system, like the global water cycle and solid Earth geophysical processes, any increase in accuracy will lead to improvements in the geophysical interpretation of the results. So in conclusion, improving the de-aliasing is of relevance for a better understanding of geophysical processes. By no longer regarding the atmosphere and ocean model output as error-free, deeper insight into the impact of such uncertainties on the de-aliasing and on the resulting GRACE gravity field models can be obtained. For this purpose, in a first step, a full error propagation of the atmospheric and oceanic model parameters up to the de-aliasing gravity field coefficients is performed and the GRACE K-Band-Satellite-to-Satellite Tracking (KBR-SST) residuals, as an intermediate gravity field result, are analysed. The paper reviews the standard GRACE de-aliasing process and presents the mathematical model applied for the error propagation. Specifically, the effect of uncertainties in the atmospheric input parameters (temperature, surface pressure, specific humidity, geopotential) on the gravity field potential coefficients used for de-aliasing is shown in several scenarios. Finally, the impact of de-aliasing products (with and without error propagation) on a GRACE gravity field solution is investigated on the level of observation residuals. From the results obtained in this study it can be concluded that with respect to the current GRACE error budget, atmospheric model uncertainties do not play a prominent role in the error budget of current GRACE gravity field solutions. Nevertheless, in order to fully exploit the GRACE measurements towards the baseline accuracy, an optimized de-aliasing is needed. In this case, GRACE gravity field solutions are sensitive to uncertainties in atmospheric and oceanic models. Thus, the associated geophysical model errors shall be taken into account in the de-aliasing proces

High-rate GPS clock corrections from CODE: support of 1Hz applications

GPS zero-difference applications with a sampling rate up to 1Hz require corresponding high-rate GPS clock corrections. The determination of the clock corrections in a full network solution is a time-consuming task. The Center for Orbit Determination in Europe (CODE) has developed an efficient algorithm based on epoch-differenced phase observations, which allows to generate high-rate clock corrections within reasonably short time (<2h) and with sufficient accuracy (on the same level as the CODE rapid or final clock corrections, respectively). The clock determination procedure at CODE and the new algorithm is described in detail. It is shown that the simplifications to speed up the processing are not causing a significant loss of accuracy for the clock corrections. The high-rate clock corrections have in essence the same quality as clock corrections determined in a full network solution. In order to support 1Hz applications 1-s clock corrections would be needed. The computation time, even for the efficient algorithm, is not negligible, however. Therefore, we studied whether a reduced sampling is sufficient for the GPS satellite clock corrections to reach the same or only slightly inferior level of accuracy as for the full 1-s clock correction set. We show that high-rate satellite clock corrections with a spacing of 5s may be linearly interpolated resulting in less than 2% degradation of accurac

Clinical efficacy, radiographic and safety findings through 2 years of golimumab treatment in patients with active psoriatic arthritis: results from a long-term extension of the randomised, placebo-controlled GO-REVEAL study

Objectives: To assess long-term golimumab efficacy/safety in patients with active psoriatic arthritis (PsA).&lt;p&gt;&lt;/p&gt; Methods Adult PsA patients (&#8805;3 swollen, &#8805;3 tender joints, active psoriasis) were randomly assigned to subcutaneous injections of placebo, golimumab 50 mg or 100 mg every 4 weeks (q4wks) through week 20. All patients received golimumab 50 or 100 mg beginning week 24. Findings through 2 years are reported. Efficacy evaluations included &#8805;20% improvement in American College of Rheumatology (ACR20) response, good/moderate response in Disease Activity Scores incorporating 28 joints and C-reactive protein (DAS28-CRP), &#8805;75% improvement in Psoriasis Area and Severity Index (PASI75) and changes in PsA-modified Sharp/van der Heijde scores (SHS).&lt;p&gt;&lt;/p&gt; Results: Golimumab treatment through 2 years was effective in maintaining clinical response (response rates: ACR20 63%–70%, DAS28-CRP 77%–86%, PASI75 56%–72%) and inhibiting radiographic progression (mean change in PsA-modified SHS in golimumab-treated patients: −0.36), with no clear difference between doses. No new safety signals were identified through 2 years. With the study's tuberculosis screening and prophylactic measures, no patient developed active tuberculosis through 2 years.&lt;p&gt;&lt;/p&gt; Conclusions: Golimumab 50 and 100 mg for up to 2 years yielded sustained clinical and radiographic efficacy when administered to patients with active PsA. Increasing the golimumab dose from 50 to 100 mg q4wks added limited benefit. Golimumab safety through up to 2 years was consistent with other antitumour necrosis factor α agents used to treat PsA. Treatment of patients with latent tuberculosis identified at baseline appeared to be effective in inhibiting the development of active tuberculosis.&lt;p&gt;&lt;/p&gt

Assessing non-linear models for galaxy clustering II: model validation and forecasts for Stage IV surveys

Accurate modelling of non-linear scales in galaxy clustering will be crucial for data analysis of Stage IV galaxy surveys. A selection of competing non-linear models must be made based on validation studies. We provide a comprehensive set of forecasts of two different models for the halo redshift space power spectrum, namely the commonly applied TNS model and an effective field theory of large scale structure (EFTofLSS) inspired model. Using simulation data and a least-χ2 analysis, we determine ranges of validity for the models. We then conduct an exploratory Fisher analysis using the full anisotropic power spectrum to investigate parameter degeneracies. We proceed to perform an MCMC analysis utilising the monopole, quadrupole, and hexadecapole spectra, with a restricted range of scales for the latter in order to avoid biasing our growth rate, f, constraint. We find that the TNS model with a Lorentzian damping and standard Eulerian perturbative modelling outperforms other variants of the TNS model. Our MCMC analysis finds that the EFTofLSS-based model may provide tighter marginalised constraints on f at z = 0.5 and z = 1 than the TNS model, despite having additional nuisance parameters. However this depends on the range of scales used as well as the fiducial values and priors on the EFT nuisance parameters. Finally, we extend previous work to provide a consistent comparison between the Fisher matrix and MCMC forecasts using the multipole expansion formalism, and find good agreement between them