Vicarious calibration of ASTER thermal infrared bands

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on the Terra satellite has five bands in the thermal infrared (TIR) spectral region between 8-12 /spl mu/m. The TIR bands have been regularly validated in-flight using ground validation targets. Validation results are presented from 79 experiments conducted under clear sky conditions. Validation involved predicting the at-sensor radiance for each band using a radiative transfer model, driven by surface and atmospheric measurements from each experiment, and then comparing the predicted radiance with the ASTER measured radiance. The results indicate the average difference between the predicted and the ASTER measured radiances was no more than 0.5% or 0.4 K in any TIR band, demonstrating that the TIR bands have exceeded the preflight design accuracy of <1 K for an at-sensor brightness temperature range of 270-340 K. The predicted and the ASTER measured radiances were then used to assess how well the onboard calibration accounted for any changes in both the instrument gain and offset over time. The results indicate that the gain and offset were correctly determined using the onboard blackbody, and indicate a responsivity decline over the first 1400 days of the Terra mission.     

Design and preflight performance of ASTER instrument protoflightmodel

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an advanced multispectral imager with high spatial, spectral, and radiometric resolution, built to fly on the EOS-AM1 spacecraft along with four other instruments, which will be launched in 1998. The ASTER instrument covers a wide spectral region, from visible to thermal infrared with 14 spectral bands. To meet the wide spectral coverage, optical sensing units of ASTER are separated into three subsystems: visible and near-infrared (VNIR) subsystem, shortwave infrared (SWIR) subsystem, and thermal infrared (TIR) subsystem. ASTER also has an along-track stereoscopic viewing capability using one of the near-infrared bands. To acquire the stereo data, the VNIR subsystem has two telescopes, one for nadir and another for backward viewing. Several new technologies are adopted as design challenges to realize high performance. Excellent observational performances are obtained by a pushbroom VNIR radiometer with a high spatial resolution of 15 m, a pushbroom SWIR radiometer with high spectral resolution, and a whiskbroom-type TIR radiometer with high spatial, spectral, and radiometric resolutions. The preflight performance is evaluated through a protoflight model (PFM)     

Ozone monitoring instrument calibration

The Ozone Monitoring Instrument (OMI) was launched on July 15, 2004 on the National Aeronautics and Space Administration's Earth Observing System Aura satellite. The OMI instrument is an ultraviolet-visible imaging spectrograph that uses two-dimensional charge-coupled device detectors to register both the spectrum and the swath perpendicular to the flight direction with a 115/spl deg/ wide swath, which enables global daily ground coverage with high spatial resolution. This paper presents the OMI design and discusses the main performance and calibration features and results.     

ASTER preflight and inflight calibration and the validation ofLevel 2 products

Describes the preflight and inflight calibration approaches used for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The system is a multispectral, high-spatial resolution sensor on the Earth Observing System's EOS-AM1 platform. Preflight calibration of ASTER uses well-characterized sources to provide calibration and preflight round-robin exercises to understand biases between the calibration sources of ASTER and other EOS sensors. These round-robins rely on well-characterized, ultra-stable radiometers. An experiment field in Yokohama, Japan, showed that the output from the source used for the visible and near-infrared (VNIR) subsystem of ASTER may be underestimated by 1.5%, but this is still within the 4% specification for the absolute, radiometric calibration of these bands. Inflight calibration will rely on vicarious techniques and onboard blackbodies and lamps. Vicarious techniques include ground-reference methods using desert and water sites. A recent joint field campaign gives confidence that these methods currently provide absolute calibration to better than 5%, and indications are that uncertainties less than the required 4% should be achievable at launch. The EOS-AM1 platform will also provide a spacecraft maneuver that will allow ASTER to see the Moon, allowing further characterization of the sensor. A method for combining the results of these independent calibration results is presented. The paper also describes the plans for validating the Level 2 data products from ASTER. These plans rely heavily upon field campaigns using methods similar to those used for the ground-reference, vicarious calibration methods     

光栅式指示表检定仪的不确定度评定

不确定度作为表征测量结果的一种形式,意味着对测量结果的可信度或有效性的怀疑程度.在实际测量中,由于测量人员、工具或者外界因素的影响,导致测量结果以一定规律分散在特定的区域.不确定度是说明被测量之值分散性的重要参数.本文主要讨论光栅式指示表检定仪的不确定度评定,通过分析其主要误差来源而得到不确定度,从而为指示表类量具的检...     

仪表检定实训室建设研究

仪表检定实训室是辽宁机电职业技术学院自动化专业的重要实训基地。文章主要阐述了仪表检定实训室的构成、建成后的应用前景以及为教学承担的实践任务,论述了仪表检定实训室对辽宁机电职业技术学院自动化专业学生所具有的重要意义以及为推进理实一体化改革所起的作用。     

激光标线仪校准项目和方法探索

激光标线仪是一种可以提供水平基准和铅垂基准的激光仪器,在木材、纸张加工行业,装修装潢行业有广泛的应用,本文针对激光标线仪无国家规范的情况,根据仪器的用途,基于日常工作经验,提出了几点仪器校准的项目及其校准方法,并分析了其不确定度.     

一种直线位移通用校准装置的设计与实现

为了实现直线位移的量值溯源,设计并实现一种能对直线位移进行校准的通用装置。该装置采用光学玻璃的KA-300型直线光栅尺作为测量基准,由光栅尺、测量基座、固定附件、读数滑台、读数头靠尺、导轨和数显表等组成;为了实现校准与被校准装置同时工作在同一基座平台上,设计了用圆柱的轴向切线与被测件的基准端面进行动态接触式联接的耦合方式;分析测量误差来源,建立了安装被测件引起的误差分析模型。结果表明:该装置能延长直线光栅尺的寿命5倍以上,提高工作效率300%,用于长度测量时最大测量误差仅为-0.000 7%。     

基于FPGA的电机转速测量仪实时校准方法

为提高电机转速测量仪的测量精度,解决传统测量仪校准方法中校准效果不明显的问题,提出基于FPGA的电机转速测量仪实时校准方法.利用电机转速的监测电路,实时收集电机转速信号,并以此作为电机转速的实际值.根据测量仪的测量原理,得出电机转速的测量值.分析测量仪的测量误差,并结合实际值与测量值之间的差值确定测量仪的实时校准值.在...     

基于虚拟仪器的多通道DC传感器校验平台设计

为了提高DC传感器的校验效率,提出一种基于虚拟仪器的多通道DC传感器校验平台设计方案,并搭建了具体的校验平台。该校验平台由虚拟仪器控制及处理模块、多通道数据采集模块和RS 485总线通信模块三部分组成,具有多通道校验、数据处理和分析功能强大等特点。结合DC传感器的校验需求,进行了DC传感器的校验实验。实验结果表明,所设计的校验平台能准确有效地实现多路DC传感器的校验,提高了传感器校验的效率和自动化水平。     

Atmospheric correction of ASTER

An atmospheric correction algorithm for operational use for the high-spatial resolution, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is presented. The correction is a straightforward approach relying on inputs from other satellite sensors to determine the atmospheric characteristics of the scene to be corrected. Methods for the solar reflective and thermal infrared (TIR) are presented separately. The solar-reflective approach uses a lookup table (LUT) based on output from a Gauss-Seidel iteration radiative transfer code. A method to handle adjacency effects is included that relies on model output, assuming a checkerboard surface. An example of a numerical simulation shows that the effect of a land surface on the radiance over the ocean is stronger just off the coastal zone and decreases exponentially with increasing distance from the land. A typical numerical simulation is performed over the Tsukuba lake area in Japan. The TIR approach relies on the radiative transfer code Moderate Resolution Atmospheric Radiance and Transmittance Model (MODTRAN). The code is run for a given set of atmospheric conditions for multiple locations in the scene for several representative elevations. Pixel-by-pixel radiances are then found using spatial interpolation. Sensitivity analysis of the methods indicate that the results of the atmospheric correction will be limited by the accuracies of the input parameters     

ASTER geometric performance

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system acquires multispectral images ranging from the visible to thermal infrared region. The ASTER system consists of three subsystems: visible and near-infrared (VNIR), short-wave infrared (SWIR) and thermal infrared (TIR) radiometers. The VNIR subsystem has a backward-viewing telescope as well as a nadir one. To deliver data products of high quality from the viewpoint of geolocation and band-to-band registration performance, a fundamental program, called Level-1 data processing, has been developed for images obtained using four telescopes with a cross-track pointing function. In this work, the methodology of the geometric validation is first described. Next, the image quality of ASTER data products is evaluated in view of the geometric performance over a period of four years. The band-to-band registration accuracy in the subsystem is better than 0.1 pixels and that between subsystems is better than 0.2 pixels. This means that the geometric database is determined accurately and the image matching method based on a cross-correlation function is effective in the operational usage.     

工业仪表自动化校验方法与智能化管理的实施策略浅议

随着市场经济的飞速发展,电力能源的需求不断增加。相应地,在自动化技术方面,仪表自动化技术逐渐应用到工业的各个方面。在新时代下,对于工业生产来说,仪表自动化校验以及智能化管理是其不可或缺的一部分,发挥着关键性的作用。因此,本文作者对此进行了相关的分析。     

ASTER DEM performance

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument onboard the National Aeronautics and Space Administration's Terra spacecraft has an along-track stereoscopic capability using its a near-infrared spectral band to acquire the stereo data. ASTER has two telescopes, one for nadir-viewing and another for backward-viewing, with a base-to-height ratio of 0.6. The spatial resolution is 15 m in the horizontal plane. Parameters such as the line-of-sight vectors and the pointing axis were adjusted during the initial operation period to generate Level-1 data products with a high-quality stereo system performance. The evaluation of the digital elevation model (DEM) data was carried out both by Japanese and U.S. science teams separately using different DEM generation software and reference databases. The vertical accuracy of the DEM data generated from the Level-1A data is 20 m with 95% confidence without ground control point (GCP) correction for individual scenes. Geolocation accuracy that is important for the DEM datasets is better than 50 m. This appears to be limited by the spacecraft position accuracy. In addition, a slight increase in accuracy is observed by using GCPs to generate the stereo data.     

基于相机标定和最大连通区域算法的指针式仪表读数识别

针对现有指针式仪表判读技术很少利用摄像机标定参数,自动判读准确度较低,无法满足工业生产实际需求的现状,提出将摄像机标定技术应用于圆形指针式仪表的自动判读,极大地减少了摄像机自身在图像采集过程中产生的误差;提出基于最大连通区域的仪表轮廓识别方法,提高了圆形仪表轮廓检测速度。利用SIFT算法进行仪表图像的关键点提取,利用模板匹配的方式实现图像中仪表的倾斜校正。实验结果表明,该方法的检测精确度可以达到95%以上,检测效率较传统方法提高了30%左右。     

ASTER Level-1 data processing algorithm

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an advanced multispectral imager with high spatial, spectral, and radiometric performance built for the EOS-AM1 polar orbiting spacecraft. ASTER covers a wide spectral region from visible to thermal infrared with 14 spectral bands. To meet this wide spectral coverage, ASTER has three optical-sensing subsystems: visible and near-infrared (VNIR), shortwave infrared (SWIR), and thermal infrared (TIR). In addition, the VNIR subsystem has two telescopes (nadir and backward telescopes) for stereo data acquisition. This ASTER instrument configuration with multitelescopes requires highly refined ground processing for the generation of Level-1 data products that are radiometrically calibrated and geometrically corrected. The algorithm developed for the ASTER Level-1 data processing is described     

基于波束赋形的星载自适应调零技术

针对传统的星载自适应调零系统存在易受干扰影响而大大降低调零效能的问题,提出了一种基于波束赋形的自适应调零方法。星载调零技术以方向信息为调零准则,要求调零系统具有较高测向精度和相干信号处理能力;新方法以波束覆盖区域和相关功率为代价函数,通过自适应迭代处理,在干扰位置处形成零点,从而实现抑制干扰的目的,理论分析和仿真试验均验证了该调零算法的有效性和鲁棒性。     

微型无人侦察机变倍同步聚焦镜头控制

根据微型无人侦察机系统机载摄像机需求,设计了一种用步进电机控制的摄像机镜头快速变倍同步聚焦控制电路.利用无人侦察机飞控系统内置ARM处理器的富余I/O资源,结合SiTI公司的MD127步进电机驱动器,完成了对两相步进电机的驱动,实现了高速飞行状态下平稳快速的变焦与聚焦功能.经过飞行测试,本系统能够安全可靠、精确稳定地工...     

机-机双基地雷达若干关键技术研究

针对机载雷达在作战使用时面临的隐身目标和综合电子干扰,将双基地雷达运用于机栽雷达,提出机-机双基地雷达系统.介绍了该雷达系统的基本组成和原理,结合双基地雷达和机载雷达各自的特点,在双机之间建立高速实时数据链来传输信号,解决空中运动平台信号的传输;采用脉冲追赶法实现空间同步、采用高稳定的原子钟来维持时间同步、采用锁相环加独立频率源综合法实现频率和相位同步;运用合理的作战模式来提高双基地雷达的反隐身和抗干扰能力.最后指出其技术难点和未来的技术发展方向.