A New Blind Pointing Model Improves Large Reflector Antennas Precision Pointing at Ka-Band (32 GHz)
NASA Technical Reports Server (NTRS)
Rochblatt, David J.
2009-01-01
The National Aeronautics and Space Administration (NASA), Jet Propulsion Laboratory (JPL)-Deep Space Network (DSN) subnet of 34-m Beam Waveguide (BWG) Antennas was recently upgraded with Ka-Band (32-GHz) frequency feeds for space research and communication. For normal telemetry tracking a Ka-Band monopulse system is used, which typically yields 1.6-mdeg mean radial error (MRE) pointing accuracy on the 34-m diameter antennas. However, for the monopulse to be able to acquire and lock, for special radio science applications where monopulse cannot be used, or as a back-up for the monopulse, high-precision open-loop blind pointing is required. This paper describes a new 4th order pointing model and calibration technique, which was developed and applied to the DSN 34-m BWG antennas yielding 1.8 to 3.0-mdeg MRE pointing accuracy and amplitude stability of 0.2 dB, at Ka-Band, and successfully used for the CASSINI spacecraft occultation experiment at Saturn and Titan. In addition, the new 4th order pointing model was used during a telemetry experiment at Ka-Band (32 GHz) utilizing the Mars Reconnaissance Orbiter (MRO) spacecraft while at a distance of 0.225 astronomical units (AU) from Earth and communicating with a DSN 34-m BWG antenna at a record high rate of 6-megabits per second (Mb/s).
Magnetic field errors tolerances of Nuclotron booster
NASA Astrophysics Data System (ADS)
Butenko, Andrey; Kazinova, Olha; Kostromin, Sergey; Mikhaylov, Vladimir; Tuzikov, Alexey; Khodzhibagiyan, Hamlet
2018-04-01
Generation of magnetic field in units of booster synchrotron for the NICA project is one of the most important conditions for getting the required parameters and qualitative accelerator operation. Research of linear and nonlinear dynamics of ion beam 197Au31+ in the booster have carried out with MADX program. Analytical estimation of magnetic field errors tolerance and numerical computation of dynamic aperture of booster DFO-magnetic lattice are presented. Closed orbit distortion with random errors of magnetic fields and errors in layout of booster units was evaluated.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Santoro, J. P.; McNamara, J.; Yorke, E.
2012-10-15
Purpose: There is increasingly widespread usage of cone-beam CT (CBCT) for guiding radiation treatment in advanced-stage lung tumors, but difficulties associated with daily CBCT in conventionally fractionated treatments include imaging dose to the patient, increased workload and longer treatment times. Respiration-correlated cone-beam CT (RC-CBCT) can improve localization accuracy in mobile lung tumors, but further increases the time and workload for conventionally fractionated treatments. This study investigates whether RC-CBCT-guided correction of systematic tumor deviations in standard fractionated lung tumor radiation treatments is more effective than 2D image-based correction of skeletal deviations alone. A second study goal compares respiration-correlated vs respiration-averaged imagesmore» for determining tumor deviations. Methods: Eleven stage II-IV nonsmall cell lung cancer patients are enrolled in an IRB-approved prospective off-line protocol using RC-CBCT guidance to correct for systematic errors in GTV position. Patients receive a respiration-correlated planning CT (RCCT) at simulation, daily kilovoltage RC-CBCT scans during the first week of treatment and weekly scans thereafter. Four types of correction methods are compared: (1) systematic error in gross tumor volume (GTV) position, (2) systematic error in skeletal anatomy, (3) daily skeletal corrections, and (4) weekly skeletal corrections. The comparison is in terms of weighted average of the residual GTV deviations measured from the RC-CBCT scans and representing the estimated residual deviation over the treatment course. In the second study goal, GTV deviations computed from matching RCCT and RC-CBCT are compared to deviations computed from matching respiration-averaged images consisting of a CBCT reconstructed using all projections and an average-intensity-projection CT computed from the RCCT. Results: Of the eleven patients in the GTV-based systematic correction protocol, two required no
Planck 2013 results. VII. HFI time response and beams
NASA Astrophysics Data System (ADS)
Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bowyer, J. W.; Bridges, M.; Bucher, M.; Burigana, C.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Haissinski, J.; Hansen, F. K.; Hanson, D.; Harrison, D.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hou, Z.; Hovest, W.; Huffenberger, K. M.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leonardi, R.; Leroy, C.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; MacTavish, C. J.; Maffei, B.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matsumura, T.; Matthai, F.; Mazzotta, P.; McGehee, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polegre, A. M.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rusholme, B.; Sandri, M.; Santos, D.; Sauvé, A.; Savini, G.; Scott, D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Yvon, D.; Zacchei, A.; Zonca, A.
2014-11-01
This paper characterizes the effective beams, the effective beam window functions and the associated errors for the Planck High Frequency Instrument (HFI) detectors. The effective beam is theangular response including the effect of the optics, detectors, data processing and the scan strategy. The window function is the representation of this beam in the harmonic domain which is required to recover an unbiased measurement of the cosmic microwave background angular power spectrum. The HFI is a scanning instrument and its effective beams are the convolution of: a) the optical response of the telescope and feeds; b) the processing of the time-ordered data and deconvolution of the bolometric and electronic transfer function; and c) the merging of several surveys to produce maps. The time response transfer functions are measured using observations of Jupiter and Saturn and by minimizing survey difference residuals. The scanning beam is the post-deconvolution angular response of the instrument, and is characterized with observations of Mars. The main beam solid angles are determined to better than 0.5% at each HFI frequency band. Observations of Jupiter and Saturn limit near sidelobes (within 5°) to about 0.1% of the total solid angle. Time response residuals remain as long tails in the scanning beams, but contribute less than 0.1% of the total solid angle. The bias and uncertainty in the beam products are estimated using ensembles of simulated planet observations that include the impact of instrumental noise and known systematic effects. The correlation structure of these ensembles is well-described by five error eigenmodes that are sub-dominant to sample variance and instrumental noise in the harmonic domain. A suite of consistency tests provide confidence that the error model represents a sufficient description of the data. The total error in the effective beam window functions is below 1% at 100 GHz up to multipole ℓ ~ 1500, and below 0.5% at 143 and 217 GHz up to
Computerized optimization of multiple isocentres in stereotactic convergent beam irradiation
NASA Astrophysics Data System (ADS)
Treuer, U.; Treuer, H.; Hoevels, M.; Müller, R. P.; Sturm, V.
1998-01-01
A method for the fully computerized determination and optimization of positions of target points and collimator sizes in convergent beam irradiation is presented. In conventional interactive trial and error methods, which are very time consuming, the treatment parameters are chosen according to the operator's experience and improved successively. This time is reduced significantly by the use of a computerized procedure. After the definition of target volume and organs at risk in the CT or MR scans, an initial configuration is created automatically. In the next step the target point positions and collimator diameters are optimized by the program. The aim of the optimization is to find a configuration for which a prescribed dose at the target surface is approximated as close as possible. At the same time dose peaks inside the target volume are minimized and organs at risk and tissue surrounding the target are spared. To enhance the speed of the optimization a fast method for approximate dose calculation in convergent beam irradiation is used. A possible application of the method for calculating the leaf positions when irradiating with a micromultileaf collimator is briefly discussed. The success of the procedure has been demonstrated for several clinical cases with up to six target points.
A method for optical ground station reduce alignment error in satellite-ground quantum experiments
NASA Astrophysics Data System (ADS)
He, Dong; Wang, Qiang; Zhou, Jian-Wei; Song, Zhi-Jun; Zhong, Dai-Jun; Jiang, Yu; Liu, Wan-Sheng; Huang, Yong-Mei
2018-03-01
A satellite dedicated for quantum science experiments, has been developed and successfully launched from Jiuquan, China, on August 16, 2016. Two new optical ground stations (OGSs) were built to cooperate with the satellite to complete satellite-ground quantum experiments. OGS corrected its pointing direction by satellite trajectory error to coarse tracking system and uplink beacon sight, therefore fine tracking CCD and uplink beacon optical axis alignment accuracy was to ensure that beacon could cover the quantum satellite in all time when it passed the OGSs. Unfortunately, when we tested specifications of the OGSs, due to the coarse tracking optical system was commercial telescopes, the change of position of the target in the coarse CCD was up to 600μrad along with the change of elevation angle. In this paper, a method of reduce alignment error between beacon beam and fine tracking CCD is proposed. Firstly, OGS fitted the curve of target positions in coarse CCD along with the change of elevation angle. Secondly, OGS fitted the curve of hexapod secondary mirror positions along with the change of elevation angle. Thirdly, when tracking satellite, the fine tracking error unloaded on the real-time zero point position of coarse CCD which computed by the firstly calibration data. Simultaneously the positions of the hexapod secondary mirror were adjusted by the secondly calibration data. Finally the experiment result is proposed. Results show that the alignment error is less than 50μrad.
Multi-beam and single-chip LIDAR with discrete beam steering by digital micromirror device
NASA Astrophysics Data System (ADS)
Rodriguez, Joshua; Smith, Braden; Hellman, Brandon; Gin, Adley; Espinoza, Alonzo; Takashima, Yuzuru
2018-02-01
A novel Digital Micromirror Device (DMD) based beam steering enables a single chip Light Detection and Ranging (LIDAR) system for discrete scanning points. We present increasing number of scanning point by using multiple laser diodes for Multi-beam and Single-chip DMD-based LIDAR.
NASA Astrophysics Data System (ADS)
Gourdji, S. M.; Yadav, V.; Karion, A.; Mueller, K. L.; Conley, S.; Ryerson, T.; Nehrkorn, T.; Kort, E. A.
2018-04-01
Urban greenhouse gas (GHG) flux estimation with atmospheric measurements and modeling, i.e. the ‘top-down’ approach, can potentially support GHG emission reduction policies by assessing trends in surface fluxes and detecting anomalies from bottom-up inventories. Aircraft-collected GHG observations also have the potential to help quantify point-source emissions that may not be adequately sampled by fixed surface tower-based atmospheric observing systems. Here, we estimate CH4 emissions from a known point source, the Aliso Canyon natural gas leak in Los Angeles, CA from October 2015–February 2016, using atmospheric inverse models with airborne CH4 observations from twelve flights ≈4 km downwind of the leak and surface sensitivities from a mesoscale atmospheric transport model. This leak event has been well-quantified previously using various methods by the California Air Resources Board, thereby providing high confidence in the mass-balance leak rate estimates of (Conley et al 2016), used here for comparison to inversion results. Inversions with an optimal setup are shown to provide estimates of the leak magnitude, on average, within a third of the mass balance values, with remaining errors in estimated leak rates predominantly explained by modeled wind speed errors of up to 10 m s‑1, quantified by comparing airborne meteorological observations with modeled values along the flight track. An inversion setup using scaled observational wind speed errors in the model-data mismatch covariance matrix is shown to significantly reduce the influence of transport model errors on spatial patterns and estimated leak rates from the inversions. In sum, this study takes advantage of a natural tracer release experiment (i.e. the Aliso Canyon natural gas leak) to identify effective approaches for reducing the influence of transport model error on atmospheric inversions of point-source emissions, while suggesting future potential for integrating surface tower and
QUEST FOR A NEW WORKING POINT IN RHIC.
DOE Office of Scientific and Technical Information (OSTI.GOV)
TOMAS,R.BAI,M.FISCHER,W.PTITSYN,V.SATOGATA,T.ROSER,T.
2004-07-05
The beam-beam interaction is a limiting factor in RHIC's performance, particularly in proton operation. Changing the working point is a strategy to alleviate the beam-beam effect and improve the performance of the machine. Experiments at injection energy and simulations have been performed for a set of working points to determine the best candidates.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Velec, Michael; Waldron, John N.; O'Sullivan, Brian
2010-03-01
Purpose: To prospectively compare setup error in standard thermoplastic masks and skin-sparing masks (SSMs) modified with low neck cutouts for head-and-neck intensity-modulated radiation therapy (IMRT) patients. Methods and Materials: Twenty head-and-neck IMRT patients were randomized to be treated in a standard mask (SM) or SSM. Cone-beam computed tomography (CBCT) scans, acquired daily after both initial setup and any repositioning, were used for initial and residual interfraction evaluation, respectively. Weekly, post-IMRT CBCT scans were acquired for intrafraction setup evaluation. The population random (sigma) and systematic (SIGMA) errors were compared for SMs and SSMs. Skin toxicity was recorded weekly by use ofmore» Radiation Therapy Oncology Group criteria. Results: We evaluated 762 CBCT scans in 11 patients randomized to the SM and 9 to the SSM. Initial interfraction sigma was 1.6 mm or less or 1.1 deg. or less for SM and 2.0 mm or less and 0.8 deg. for SSM. Initial interfraction SIGMA was 1.0 mm or less or 1.4 deg. or less for SM and 1.1 mm or less or 0.9 deg. or less for SSM. These errors were reduced before IMRT with CBCT image guidance with no significant differences in residual interfraction or intrafraction uncertainties between SMs and SSMs. Intrafraction sigma and SIGMA were less than 1 mm and less than 1 deg. for both masks. Less severe skin reactions were observed in the cutout regions of the SSM compared with non-cutout regions. Conclusions: Interfraction and intrafraction setup error is not significantly different for SSMs and conventional masks in head-and-neck radiation therapy. Mask cutouts should be considered for these patients in an effort to reduce skin toxicity.«less
Definition of Beam Diameter for Electron Beam Welding
DOE Office of Scientific and Technical Information (OSTI.GOV)
Burgardt, Paul; Pierce, Stanley W.; Dvornak, Matthew John
It is useful to characterize the dimensions of the electron beam during process development for electron beam welding applications. Analysis of the behavior of electron beam welds is simplest when a single number can be assigned to the beam properties that describes the size of the beam spot; this value we generically call the “beam diameter”. This approach has worked well for most applications and electron beam welding machines with the weld dimensions (width and depth) correlating well with the beam diameter. However, in recent weld development for a refractory alloy, Ta-10W, welded with a low voltage electron beam machinemore» (LVEB), it was found that the weld dimensions (weld penetration and weld width) did not correlate well with the beam diameter and especially with the experimentally determined sharp focus point. These data suggest that the presently used definition of beam diameter may not be optimal for all applications. The possible reasons for this discrepancy and a suggested possible alternative diameter definition is the subject of this paper.«less
NASA Astrophysics Data System (ADS)
Balaji, K. A.; Prabu, K.
2018-03-01
There is an immense demand for high bandwidth and high data rate systems, which is fulfilled by wireless optical communication or free space optics (FSO). Hence FSO gained a pivotal role in research which has a added advantage of both cost-effective and licence free huge bandwidth. Unfortunately the optical signal in free space suffers from irradiance and phase fluctuations due to atmospheric turbulence and pointing errors which deteriorates the signal and degrades the performance of communication system over longer distance which is undesirable. In this paper, we have considered polarization shift keying (POLSK) system applied with wavelength and time diversity technique over Malaga(M)distribution to mitigate turbulence induced fading. We derived closed form mathematical expressions for estimating the systems outage probability and average bit error rate (BER). Ultimately from the results we can infer that wavelength and time diversity schemes enhances these systems performance.
Electron Beam Propagation Through a Magnetic Wiggler with Random Field Errors
1989-08-21
Another quantity of interest is the vector potential 6.A,.(:) associated with the field error 6B,,,(:). Defining the normalized vector potentials ba = ebA...then follows that the correlation of the normalized vector potential errors is given by 1 . 12 (-a.(zj)a.,(z2)) = a,k,, dz’ , dz" (bBE(z’)bB , (z")) a2...Throughout the following, terms of order O(z:/z) will be neglected. Similarly, for the y-component of the normalized vector potential errors, one
Pointing and Jitter Control for the USNA Multi-Beam Combining System
2013-05-10
previous work, an adaptive H-infinity optimal controller has been developed to control a single beam using a beam position detector for feedback... turbulence and airborne particles, platform jitter, lack of feedback from the target , and current laser technology represent just a few of these...lasers. Solid state lasers, however, cannot currently provide high enough power levels to destroy a target using a single beam. On solid-state
Multimodal assessment of visual attention using the Bethesda Eye & Attention Measure (BEAM).
Ettenhofer, Mark L; Hershaw, Jamie N; Barry, David M
2016-01-01
Computerized cognitive tests measuring manual response time (RT) and errors are often used in the assessment of visual attention. Evidence suggests that saccadic RT and errors may also provide valuable information about attention. This study was conducted to examine a novel approach to multimodal assessment of visual attention incorporating concurrent measurements of saccadic eye movements and manual responses. A computerized cognitive task, the Bethesda Eye & Attention Measure (BEAM) v.34, was designed to evaluate key attention networks through concurrent measurement of saccadic and manual RT and inhibition errors. Results from a community sample of n = 54 adults were analyzed to examine effects of BEAM attention cues on manual and saccadic RT and inhibition errors, internal reliability of BEAM metrics, relationships between parallel saccadic and manual metrics, and relationships of BEAM metrics to demographic characteristics. Effects of BEAM attention cues (alerting, orienting, interference, gap, and no-go signals) were consistent with previous literature examining key attention processes. However, corresponding saccadic and manual measurements were weakly related to each other, and only manual measurements were related to estimated verbal intelligence or years of education. This study provides preliminary support for the feasibility of multimodal assessment of visual attention using the BEAM. Results suggest that BEAM saccadic and manual metrics provide divergent measurements. Additional research will be needed to obtain comprehensive normative data, to cross-validate BEAM measurements with other indicators of neural and cognitive function, and to evaluate the utility of these metrics within clinical populations of interest.
Estimating IMU heading error from SAR images.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Doerry, Armin Walter
Angular orientation errors of the real antenna for Synthetic Aperture Radar (SAR) will manifest as undesired illumination gradients in SAR images. These gradients can be measured, and the pointing error can be calculated. This can be done for single images, but done more robustly using multi-image methods. Several methods are provided in this report. The pointing error can then be fed back to the navigation Kalman filter to correct for problematic heading (yaw) error drift. This can mitigate the need for uncomfortable and undesired IMU alignment maneuvers such as S-turns.
Holistic approach for overlay and edge placement error to meet the 5nm technology node requirements
NASA Astrophysics Data System (ADS)
Mulkens, Jan; Slachter, Bram; Kubis, Michael; Tel, Wim; Hinnen, Paul; Maslow, Mark; Dillen, Harm; Ma, Eric; Chou, Kevin; Liu, Xuedong; Ren, Weiming; Hu, Xuerang; Wang, Fei; Liu, Kevin
2018-03-01
In this paper, we discuss the metrology methods and error budget that describe the edge placement error (EPE). EPE quantifies the pattern fidelity of a device structure made in a multi-patterning scheme. Here the pattern is the result of a sequence of lithography and etching steps, and consequently the contour of the final pattern contains error sources of the different process steps. EPE is computed by combining optical and ebeam metrology data. We show that high NA optical scatterometer can be used to densely measure in device CD and overlay errors. Large field e-beam system enables massive CD metrology which is used to characterize the local CD error. Local CD distribution needs to be characterized beyond 6 sigma, and requires high throughput e-beam system. We present in this paper the first images of a multi-beam e-beam inspection system. We discuss our holistic patterning optimization approach to understand and minimize the EPE of the final pattern. As a use case, we evaluated a 5-nm logic patterning process based on Self-Aligned-QuadruplePatterning (SAQP) using ArF lithography, combined with line cut exposures using EUV lithography.
Online beam energy measurement of Beijing electron positron collider II linear accelerator
NASA Astrophysics Data System (ADS)
Wang, S.; Iqbal, M.; Liu, R.; Chi, Y.
2016-02-01
This paper describes online beam energy measurement of Beijing Electron Positron Collider upgraded version II linear accelerator (linac) adequately. It presents the calculation formula, gives the error analysis in detail, discusses the realization in practice, and makes some verification. The method mentioned here measures the beam energy by acquiring the horizontal beam position with three beam position monitors (BPMs), which eliminates the effect of orbit fluctuation, and is much better than the one using the single BPM. The error analysis indicates that this online measurement has further potential usage such as a part of beam energy feedback system. The reliability of this method is also discussed and demonstrated in this paper.
Online beam energy measurement of Beijing electron positron collider II linear accelerator.
Wang, S; Iqbal, M; Liu, R; Chi, Y
2016-02-01
This paper describes online beam energy measurement of Beijing Electron Positron Collider upgraded version II linear accelerator (linac) adequately. It presents the calculation formula, gives the error analysis in detail, discusses the realization in practice, and makes some verification. The method mentioned here measures the beam energy by acquiring the horizontal beam position with three beam position monitors (BPMs), which eliminates the effect of orbit fluctuation, and is much better than the one using the single BPM. The error analysis indicates that this online measurement has further potential usage such as a part of beam energy feedback system. The reliability of this method is also discussed and demonstrated in this paper.
Instrument Pointing Capabilities: Past, Present, and Future
NASA Technical Reports Server (NTRS)
Blackmore, Lars; Murray, Emmanuell; Scharf, Daniel P.; Aung, Mimi; Bayard, David; Brugarolas, Paul; Hadaegh, Fred; Lee, Allan; Milman, Mark; Sirlin, Sam;
2011-01-01
This paper surveys the instrument pointing capabilities of past, present and future space telescopes and interferometers. As an important aspect of this survey, we present a taxonomy for "apples-to-apples" comparisons of pointing performances. First, pointing errors are defined relative to either an inertial frame or a celestial target. Pointing error can then be further sub-divided into DC, that is, steady state, and AC components. We refer to the magnitude of the DC error relative to the inertial frame as absolute pointing accuracy, and we refer to the magnitude of the DC error relative to a celestial target as relative pointing accuracy. The magnitude of the AC error is referred to as pointing stability. While an AC/DC partition is not new, we leverage previous work by some of the authors to quantitatively clarify and compare varying definitions of jitter and time window averages. With this taxonomy and for sixteen past, present, and future missions, pointing accuracies and stabilities, both required and achieved, are presented. In addition, we describe the attitude control technologies used to and, for future missions, planned to achieve these pointing performances.
