Results of fusion of LRI based attitude data in the attitude Kalman filter

2020 ◽  
Author(s):  
Sujata Goswami ◽  
Tamara Bandikova ◽  
Dah-Ning Yuan ◽  
Samuel Francis ◽  
Bob Spero
Keyword(s):  
Kalman Filter ◽  
Gravity Field ◽  
Beam Steering ◽  
Line Of Sight ◽  
Laser Ranging ◽  
First Results ◽  
Gravity Field Determination ◽  
Gravity Recovery ◽  
The Impact ◽  
Technology Demonstrator

<p>Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) carries the Laser Ranging Interferometer (LRI) as a technology demonstrator that measures the inter-satellite range with nanometer precision. For the precise laser beam pointing, LRI uses the beam steering method where the fast steering mirror is actuated to correct for the misalignment between the incoming and outgoing laser beams. From the fast steering mirror commands, we can compute the inter-satellite pitch and yaw angles. These angles are provided as LSM1B product and represent spacecraft's relative orientation with respect to line-of-sight (LOS). The SCA1B data, which is computed by combining the data of three star cameras and IMU in the Kalman filter, represents the absolute orientation of the spacecrafts. Currently, this SCA1B product is used in the gravity field determination.  </p> <p>Here we present first results of a new attitude product which is computed by the combination of fast steering mirror data with the star cameras and IMU in the attitude kalman filter.  We also present the impact of this new combined attitude data on the gravity field solutions.</p>

Preliminary GRACE-FO gravity field solutions from Tongji University

2020 ◽  
Author(s):  
Qiujie Chen ◽  
Yunzhong Shen ◽  
Xingfu Zhang ◽  
Jürgen Kusche
Keyword(s):  
Mass Transport ◽  
Gravity Field ◽  
Sampling Rate ◽  
Laser Ranging ◽  
University Of Technology ◽  
Gravity Field Determination ◽  
New Feature ◽  
Gravity Recovery ◽  
Grace Mission ◽  
Tongji University

<p>Due to the battery issue, the Gravity Recovery and Climate Experiment (GRACE) mission unfortunately came to an end in October 2017 after providing more than 15 years of mass transport information of our changing planet. To continue to monitoring the mass transport in the Earth system, the GRACE Follow-On (GRACE-FO) was launched in May 2018. As a new feature of GRACE-FO, a Laser Ranging Interferometer (LRI) was equipped to measure the inter-satellite range at a nanometer level. Since May 2019, GRACE-FO Level-1B observations have been made available to our community. Using the GRACE-FO Level-1B observations without laser ranging information, preliminary GRACE-FO gravity field solutions from Center for Space Research (CSR), GeoForschungsZentrum (GFZ), Jet Propulsion Laboratory (JPL) and Graz University of Technology have been released. Incorporating laser ranging observations into gravity field determination, a preliminary time series of GRACE-FO gravity field solutions has been derived from Tongji University in collaboration with University of Bonn. In this paper, the signal and noise of our gravity field solutions are analyzed and compared to those from other research groups. Our results show that the laser ranging observations with a sampling rate of 2s are able to improve gravity field solutions by about 7% in terms of geoid degree variances up to degree and order 96 as compared to the K-Band ranging data with a sampling rate of 5s.</p>

Performance of 4G-LTE Communication and Navigation System in Blended Wing-Body UAS

2019 ◽  
Vol 8 (4) ◽  
pp. 9538-9542
Keyword(s):  
Satellite Communication ◽  
Line Of Sight ◽  
Multiple Factors ◽  
The World ◽  
New Type ◽  
Blended Wing Body ◽  
4G Lte ◽  
The Right ◽  
And Control ◽  
Technology Demonstrator

In vision of searching for the right Unmanned Aerial System (UAS) for a specific mission, there are multiple factors to be considered by the operator such as mission, endurance, type of payload and range of the telemetry and control. This research is focusing on extending control range of the UAS by using 4G-LTE network to enable beyond-line-of-sight flying for the commercial UAS. Major UAS such Global Hawk, Predator MQ-1 are able to fly thousands of kilometers by the use of satellite communication. However, the satellite communication annual license subscription can be very expensive. With this situation in mind, a new type of flight controller with 4G-LTE communication has been developed and tested. Throughout the research, blended-wing-body (BWB) Baseline B2S is used as the platform for technology demonstrator. Result from this analysis has proven that the proposed system is capable to control a UAS from as far as United Kingdom, with a latency less than 881 ms in average. The new added capability can potentially give the commercial UAS community a new horizon to be able to control their UAS from anywhere around the world with the availability of 4G-LTE connection

scholarly journals Mixed NNLO QCD×electroweak corrections of $$ \mathcal{O} $$(Nfαsα) to single-W/Z production at the LHC

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Stefan Dittmaier ◽  
Timo Schmidt ◽  
Jan Schwarz
Keyword(s):  
Z Bosons ◽  
Leading Order ◽  
Current Standard ◽  
Gauge Invariant ◽  
Mass Distributions ◽  
Self Energy ◽  
Electroweak Gauge Boson ◽  
First Results ◽  
Invariant Part ◽  
The Impact

Abstract First results on the radiative corrections of order $$ \mathcal{O} $$ O (Nfαsα) are presented for the off-shell production of W or Z bosons at the LHC, where Nf is the number of fermion flavours. These corrections comprise all diagrams at $$ \mathcal{O} $$ O (αsα) with closed fermion loops, form a gauge-invariant part of the next-to-next-to-leading-order corrections of mixed QCD×electroweak type, and are the ones that concern the issue of mass renormalization of the W and Z resonances. The occurring irreducible two-loop diagrams, which involve only self-energy insertions, are calculated with current standard techniques, and explicit analytical results on the electroweak gauge-boson self-energies at $$ \mathcal{O} $$ O (αsα) are given. Moreover, the generalization of the complex-mass scheme for a gauge-invariant treatment of the W/Z resonances is described for the order $$ \mathcal{O} $$ O (αsα). While the corrections, which are implemented in the Monte Carlo program Rady, are negligible for observables that are dominated by resonant W/Z bosons, they affect invariant-mass distributions at the level of up to 2% for invariant masses of ≳ 500 GeV and are, thus, phenomenologically relevant. The impact on transverse-momentum distributions is similar, taking into account that leading-order predictions to those distributions underestimate the spectrum.

scholarly journals Out of sight, out of mind? The impact of correlated clustering in substructure lensing

2021 ◽  
Author(s):  
Alexandres Lazar ◽  
James S Bullock ◽  
Michael Boylan-Kolchin ◽  
Robert Feldmann ◽  
Onur Çatmabacak ◽  
...  
Keyword(s):  
Dark Matter ◽  
Principal Axis ◽  
Major Axis ◽  
Line Of Sight ◽  
Gravitational Lenses ◽  
Local Clustering ◽  
Analytic Expression ◽  
Halo Masses ◽  
The Impact

Abstract A promising route for revealing the existence of dark matter structures on mass scales smaller than the faintest galaxies is through their effect on strong gravitational lenses. We examine the role of local, lens-proximate clustering in boosting the lensing probability relative to contributions from substructure and unclustered line-of-sight (LOS) haloes. Using two cosmological simulations that can resolve halo masses of Mhalo ≃ 109 M⊙ (in a simulation box of length Lbox ∼ 100 Mpc) and 107 M⊙ (Lbox ∼ 20 Mpc), we demonstrate that clustering in the vicinity of the lens host produces a clear enhancement relative to an assumption of unclustered haloes that persists to >20 Rvir. This enhancement exceeds estimates that use a two-halo term to account for clustering, particularly within 2 − 5 Rvir. We provide an analytic expression for this excess, clustered contribution. We find that local clustering boosts the expected count of 109 M⊙ perturbing haloes by ${\sim }35{{\ \rm per\ cent}}$ compared to substructure alone, a result that will significantly enhance expected signals for low-redshift (zl ≃ 0.2) lenses, where substructure contributes substantially compared to LOS haloes. We also find that the orientation of the lens with respect to the line of sight (e.g. whether the line of sight passes through the major axis of the lens) can also have a significant effect on the lensing signal, boosting counts by an additional $\sim 50{{\ \rm per\ cent}}$ compared to a random orientations. This could be important if discovered lenses are biased to be oriented along their principal axis.

Cooling Efficiencies of a NiTi-Based Cooling Process

2013 ◽  
Author(s):  
Marvin Schmidt ◽  
Andreas Schütze ◽  
Stefan Seelecke
Keyword(s):  
Solid State ◽  
Thermodynamic Analysis ◽  
Cooling System ◽  
Analysis Method ◽  
Efficiency Ratio ◽  
Cooling Process ◽  
First Results ◽  
Work Input ◽  
Underlying Mechanisms ◽  
The Impact

Energy saving and environmental protection are topics of growing interest. In the light of these aspects alternative refrigeration principles become increasingly important. Shape memory alloys (SMA), especially NiTi alloys, generate a large amount of latent heat during solid state phase transformations, which can lead to a significant cooling effect in the material. These materials do not only provide the potential for an energy-efficient cooling process, they also minimize the impact on the environment by reducing the need for conventional ozone-depleting refrigerants. Our paper, presenting first results obtained in a project within the DFG Priority Program SPP 1599 “Ferroic Cooling”, focuses on the thermodynamic analysis of a NiTi-based cooling system. We first introduce a suitable cooling process and subsequently illustrate the underlying mechanisms of the process in comparison with the conventional compression refrigeration system. We further introduce a graphical solution to calculate the energy efficiency ratio of the system. This thermodynamic analysis method shows the necessary work input and the heat absorption of the SMA in stress/strain- or temperature/entropy-diagrams, respectively. The results of the calculations underline the high potential of this solid-state cooling methodology.

High-Frequency and Passive Radar Designs for Homeland Security Applications

2011 ◽  
Vol 45 (3) ◽  
pp. 111-119 ◽  
Author(s):  
Magdy F. Iskander ◽  
Zhengqing Yun ◽  
Nuri Celik ◽  
Hyoungsun Youn ◽  
Nobutaka Omaki ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Homeland Security ◽  
High Frequency ◽  
Beam Steering ◽  
Antenna System ◽  
Hf Radar ◽  
Passive Radar ◽  
High Definition ◽  
Security Applications ◽  
The Impact

AbstractEmerging homeland security applications require low-cost and fast, deployable, high-frequency (HF) radar systems and the ability to operate in challenging terrain environments. With the need to cover as many border and coastal areas as possible, taking advantages of available transmitter resources to track targets using passive radar technologies is yet another area of research of considerable interest. In this paper, we describe the development of an HF radar system that meets these operational challenges, and we also highlight some recent implementation of the passive radar technology for homeland security applications. Specifically, we describe the design of a novel, electrically small HF antenna system consisting of three helical elements, one connected to the feed port while the other two are folded arms terminated with switchable loads. The antenna is 0.90-m (<3 feet) high with a small ground disk of 0.60 m (∼2 feet) diameter. The antenna is self-resonant at multiple frequencies (5.7, 16, 20.5, and 27.7 MHz) and with input impedance values that can be easily matched to a 50-Ω coaxial feed. Values of the electrical size ka range from 0.44 at 30 MHz down to 0.08 at 5.7 MHz. The achieved bandwidths range from 1.4% up to 12% and associated efficiencies range from 66.2% to 76% within the HF band (3‐30 MHz). As for the operational requirement in challenging terrain environments, a setup in a hilltop-type environment with a slope terrain and surface roughness was considered. A propagation modeling and ray-tracing approach was used to evaluate the impact of such terrain conditions on the effective interelement spacing of an HF radar antenna array and the subsequent impact on its beamforming and beam steering performance. It is shown that while the effect of the slope on the effective interelement spacing of the array could be very significant, diffraction effects from surface roughness resulted in a much smaller, but significant, error of about 18°. Results from some initial work on the implementation of passive radar technology, with focus on addressing the bandwidth requirement to ensure practical resolution values, are also described. It is shown that signals from wide-band transmitters (e.g., High Definition Television [HDTV] signals) rather than those from radio stations are required to provide acceptable range resolution. These as well as simulation and experimental results of the antenna design, and results from beamforming simulations illustrating the effect of a rough hilltop terrain on the HF radar performance are described.

scholarly journals The impact of line-of-sight structures on measuring H0 with strong lensing time delays

2021 ◽  
Vol 504 (2) ◽  
pp. 2224-2234
Author(s):  
Nan Li ◽  
Christoph Becker ◽  
Simon Dye
Keyword(s):  
Time Delays ◽  
Line Of Sight ◽  
Lens Model ◽  
Local Universe ◽  
Significant Discrepancy ◽  
Turn On ◽  
Strong Lensing ◽  
Systematic Effects ◽  
The Impact ◽  
Realistic Line

ABSTRACT Measurements of the Hubble–Lemaitre constant from early- and local-Universe observations show a significant discrepancy. In an attempt to understand the origin of this mismatch, independent techniques to measure H0 are required. One such technique, strong lensing time delays, is set to become a leading contender amongst the myriad methods due to forthcoming large strong lens samples. It is therefore critical to understand the systematic effects inherent in this method. In this paper, we quantify the influence of additional structures along the line of sight by adopting realistic light-cones derived from the cosmoDC2 semi-analytical extragalactic catalogue. Using multiple-lens plane ray tracing to create a set of simulated strong lensing systems, we have investigated the impact of line-of-sight structures on time-delay measurements and in turn, on the inferred value of H0. We have also tested the reliability of existing procedures for correcting for line-of-sight effects. We find that if the integrated contribution of the line-of-sight structures is close to a uniform mass sheet, the bias in H0 can be adequately corrected by including a constant external convergence κext in the lens model. However, for realistic line-of-sight structures comprising many galaxies at different redshifts, this simple correction overestimates the bias by an amount that depends linearly on the median external convergence. We therefore conclude that lens modelling must incorporate multiple-lens planes to account for line-of-sight structures for accurate and precise inference of H0.

GRACE Follow-On Gravity Field Recovery from Combined Laser Ranging Interferometer and Microwave Ranging System Measurements

2021 ◽  
Author(s):  
Saniya Behzadpour ◽  
Andreas Kvas ◽  
Torsten Mayer-Gürr
Keyword(s):  
Gravity Field ◽  
Laser Ranging ◽  
Measurement Technology ◽  
Additional Measurement ◽  
Covariance Functions ◽  
Gravity Field Recovery ◽  
Global Gravity ◽  
Least Squares Adjustment ◽  
Noise Covariance ◽  
Component Estimation

&lt;p&gt;Besides a K-Band Ranging System (KBR), GRACE-FO carries a Laser Ranging Interferometer (LRI) as a technology demonstration to provide measurements of inter-satellite range changes. This additional measurement technology provides supplementary observations, which allow for cross-instrument diagnostics with the KBR system and, to some extent, the separation of ranging noise from other sources such as noise in the on-board accelerometer (ACC) measurements.&lt;/p&gt;&lt;p&gt;The aim of this study is to incorporate the two ranging systems (LRI and KBR) observations in ITSG-Grace2018 gravity field recovery. The two observation groups are combined in an iterative least-squares adjustment with variance component estimation used to determine the unknown noise covariance functions for KBR, LRI, and ACC measurements. We further compare the gravity field solutions obtained from the combined solutions to KBR-only results and discuss the differences with a focus on the global gravity field and LRI calibration parameters.&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document