Attitude Jitter Research Articles

Detection and Estimation of Along-Track Attitude Jitter From Ziyuan-3 Three-Line-Array Images Based on Back-Projection Residuals

High-resolution satellite images (HRSIs) obtained from linear array charge-coupled device sensors always suffer from geometric instability in the presence of attitude jitter. Therefore, detection and compensation of spacecraft attitude jitter in both the cross-track and along-track directions are crucial to improve the geometric accuracy of HRSIs. A number of reports have been made on the detection and estimation of cross-track attitude jitter. However, the detection of the attitude jitter in the along-track direction is more complicated due to the impact of topographic change. This paper presents a novel approach to achieve accurate estimation of the along-track attitude jitter by eliminating the influence of topographic information based on the back-projection residuals of three-line-array (TLA) images. The principle of detection and estimation of along-track attitude jitter is described, and the proposed approach consists of three main components as follows: 1) dense image matching of the TLA images using a comprehensive matching strategy; 2) detection of the back-projection residuals in the line direction caused by attitude jitter; and 3) estimation of the along-track attitude jitter from the back-projection residuals using a genetic algorithm. Experiments were conducted using China’s Ziyuan-3 (ZY-3) TLA images, and the experimental results reveal that the frequency of the attitude jitter in the along-track direction ranges between 0.6 and 0.7 Hz, which is consistent with the frequency in the cross-track direction observed in our previous study. In addition, a comparison of the results of the proposed approach with those from direct attitude observations shows good consistency, with as little as 0.1-pixel disparity, which demonstrates the feasibility and reliability of the proposed approach. Furthermore, the geometric accuracy is further improved from a pixel level to a subpixel level and the periodic trend is removed with the compensation of the estimated attitude jitter in addition to the conventional affine compensation, which validates the potential of the proposed approach for geometric accuracy improvement with ZY-3 TLA images.

Image jitter detection and compensation using a high-frequency angular displacement method for Yaogan-26 remote sensing satellite

Satellite platform jitter is an important factor restricting the imaging quality of high-resolution (HR) optical satellite images. To address the critical issue of compensation for attitude jitter in HR images, this paper proposes a steady-state reimaging model using high-frequency angular displacement data to detect and compensate for the attitude jitter of HR images. The bidirectional Kalman filter and overall weighted smoothing method helps realizing information fusion of star sensor and angular displacement sensor and obtaining the high-frequency attitude for image jitter detection. Then, the steady reimaging model is used to correct the distorted image with geolocation consistency based on a rigorous geometric model. The Yaogan-26 remote sensing satellite’s distorted panchromatic images of airports, targets and calibration fields affected by platform jitter were used to validate the effectiveness and accuracy of the proposed method. The compensation results show that the proposed method can effectively improve the relative geometric quality of images affected by platform jitter, with the images’ jitter distortion being clearly eliminated. Compared to the conventional compensation method that bundle adjustment with GCPs, the absolute geometric accuracy can also be improved.

Calibrating for the satellite attitude jitter in multistatic SAR using a subspace method

With respect to a spaceborne multistatic synthetic aperture radar (SAR) system, satellite attitude jitter, consisting of yaw-, pitch-, and roll-angle components, undermines the coherent cooperation among the satellites and results in degraded imaging performance. In order to calibrate the system to compensate for the jitter, a parametric method is proposed in this study. The approach starts by deriving the echo signal with unknown jitter received by each satellite as a bistatic extended space–time model. Then, the high-order instantaneous moment of the model is obtained, which is in the form of a high-order polynomial phase array signal. Finally, the unknown jitter is estimated using the multiple signal classification method, which is a subspace method. The proposed method can improve the imaging performance by correctly calibrating the system to compensate for the jitter. Furthermore, the authors demonstrate that the proposed method outperforms conventional autofocus algorithms using the simulated raw data of a Cartwheel constellation, which is a typical flying formation of a multistatic SAR system.

Attitude Jitter Detection Based on Remotely Sensed Images and Dense Ground Controls: A Case Study for Chinese ZY-3 Satellite

Satellite platform vibration induced by the onboard dynamic components and exterior perturbation deteriorates platform stability and causes attitude jitter, resulting in image distortion and geometric accuracy degradation. This paper presents an attitude jitter detection method based on images and dense ground controls, which requires neither high-performance attitude measurement devices nor specific sensor configuration like parallax observation. Attitude variations will result in image space discrepancies at control points, from which the attitude jitter can be retrieved. The method was validated by a case study with ZY-3 satellite, which is the first civilian high-resolution stereo mapping satellite in China. The experimental results show that an almost constant jitter frequency of about 0.65 Hz was detected, which was consistent with the direct attitude observations. The photogrammetric method is theoretically capable of detecting attitude jitter up to half of the image line scanning rate according to Shannon's sampling theorem, which is far beyond the detectable range by direct attitude observations at a frequency usually not higher than 4 Hz. Currently, the attitude jitter of the roll angle and the pitch angle can be effectively detected and accurately estimated for the nadir camera. The pitch angle jitter is also well estimable for the forward and the backward cameras. With approximation, the roll angle jitter for the two off-nadir cameras can also be estimated, though with some deviation caused by the influence of the yaw angle jitter.

GLACIER VOLUME CHANGE ESTIMATION USING TIME SERIES OF IMPROVED ASTER DEMS

Abstract. Volume change data is critical to the understanding of glacier response to climate change. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system embarked on the Terra (EOS AM-1) satellite has been a unique source of systematic stereoscopic images covering the whole globe at 15m resolution and at a consistent quality for over 15 years. While satellite stereo sensors with significantly improved radiometric and spatial resolution are available to date, the potential of ASTER data lies in its long consistent time series that is unrivaled, though not fully exploited for change analysis due to lack of data accuracy and precision. Here, we developed an improved method for ASTER DEM generation and implemented it in the open source photogrammetric library and software suite MicMac. The method relies on the computation of a rational polynomial coefficients (RPC) model and the detection and correction of cross-track sensor jitter in order to compute DEMs. ASTER data are strongly affected by attitude jitter, mainly of approximately 4 km and 30 km wavelength, and improving the generation of ASTER DEMs requires removal of this effect. Our sensor modeling does not require ground control points and allows thus potentially for the automatic processing of large data volumes. As a proof of concept, we chose a set of glaciers with reference DEMs available to assess the quality of our measurements. We use time series of ASTER scenes from which we extracted DEMs with a ground sampling distance of 15m. Our method directly measures and accounts for the cross-track component of jitter so that the resulting DEMs are not contaminated by this process. Since the along-track component of jitter has the same direction as the stereo parallaxes, the two cannot be separated and the elevations extracted are thus contaminated by along-track jitter. Initial tests reveal no clear relation between the cross-track and along-track components so that the latter seems not to be easily modeled analytically from the first one. We thus remove the remaining along-track jitter effects in the DEMs statistically through temporal DEM stacks to finally compute the glacier volume changes over time. Our method yields cleaner and spatially more complete elevation data, which also proved to be more in accordance to reference DEMs, compared to NASA’s AST14DMO DEM standard products. The quality of the demonstrated measurements promises to further unlock the underused potential of ASTER DEMs for glacier volume change time series on a global scale. The data produced by our method will help to better understand the response of glaciers to climate change and their influence on runoff and sea level.

GLACIER VOLUME CHANGE ESTIMATION USING TIME SERIES OF IMPROVED ASTER DEMS

Volume change data is critical to the understanding of glacier response to climate change. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system embarked on the Terra (EOS AM-1) satellite has been a unique source of systematic stereoscopic images covering the whole globe at 15m resolution and at a consistent quality for over 15 years. While satellite stereo sensors with significantly improved radiometric and spatial resolution are available to date, the potential of ASTER data lies in its long consistent time series that is unrivaled, though not fully exploited for change analysis due to lack of data accuracy and precision. Here, we developed an improved method for ASTER DEM generation and implemented it in the open source photogrammetric library and software suite MicMac. The method relies on the computation of a rational polynomial coefficients (RPC) model and the detection and correction of cross-track sensor jitter in order to compute DEMs. ASTER data are strongly affected by attitude jitter, mainly of approximately 4 km and 30 km wavelength, and improving the generation of ASTER DEMs requires removal of this effect. Our sensor modeling does not require ground control points and allows thus potentially for the automatic processing of large data volumes. <br><br> As a proof of concept, we chose a set of glaciers with reference DEMs available to assess the quality of our measurements. We use time series of ASTER scenes from which we extracted DEMs with a ground sampling distance of 15m. Our method directly measures and accounts for the cross-track component of jitter so that the resulting DEMs are not contaminated by this process. Since the along-track component of jitter has the same direction as the stereo parallaxes, the two cannot be separated and the elevations extracted are thus contaminated by along-track jitter. Initial tests reveal no clear relation between the cross-track and along-track components so that the latter seems not to be easily modeled analytically from the first one. We thus remove the remaining along-track jitter effects in the DEMs statistically through temporal DEM stacks to finally compute the glacier volume changes over time. Our method yields cleaner and spatially more complete elevation data, which also proved to be more in accordance to reference DEMs, compared to NASA’s AST14DMO DEM standard products. <br><br> The quality of the demonstrated measurements promises to further unlock the underused potential of ASTER DEMs for glacier volume change time series on a global scale. The data produced by our method will help to better understand the response of glaciers to climate change and their influence on runoff and sea level.

Zero-Speed Crossing Avoidance with Three Active Reaction Wheels using Set-Point Angular Momentum Management

Reaction wheels (RW) are common actuators for attitude control of three-axis stabilized satellites. By exchanging momentum with the spacecraft’s body, a set of three non-planar RW is able to ensure the off-nadir fine pointing capabilities of agile high-resolution imaging satellites. Nonetheless, due to stiction, RW can cause considerable attitude jitter when their angular velocity is close to zero. This paper proposes a method to analyze the maximum off-nadir pointing angles that are allowable without causing zero-speed crossing for a spacecraft using only three active RW. In sequence, by applying this method for a sun-synchronous mission, it is shown that angular momentum management can be used to give the satellite an adequate roll slewing margin by placing the reaction wheel momentum set point in an appropriate position. This method can be applied to any mission that relies on three active RW and requires high pointing stability.

Interspacecraft link simulator for the laser ranging interferometer onboard GRACE Follow-On.

Link acquisition strategies are key aspects for interspacecraft laser interferometers. We present an optical fiber-based setup able to simulate the interspacecraft link for the laser ranging interferometer (LRI) on gravity recovery and climate experiment Follow-On. It allows one to accurately recreate the far-field intensity profile depending on the mispointing between the spacecraft, Doppler shifts, and spacecraft attitude jitter. Furthermore, it can be used in late integration stages of the mission, since no physical contact with the spacecraft is required. The setup can also be easily adapted to other similar missions and different acquisition algorithms.

A jitter compensation method for spaceborne line-array imagery using compressive sampling

Attitude jitter is a problem commonly experienced by remote-sensing satellites, and deteriorates the accuracy of geo-positioning and mapping. Therefore, it is important to design a method which can handle this problem. This paper presents a compensation method using compressive sampling. In this method, the influence of attitude jitter in imagery is represented by two fluctuating signals, which are called distortion signals in this paper. Using compressive sampling, the distortion signals in the remote-sensing imagery can be estimated with a small set of ground control points (GCPs). Based on the estimated distortion signals, we can conduct compensation on the remote-sensing imagery affected by attitude jitter. The significant advantage of this method is that it requires only rational function model (RFM) and few GCPs, which makes it easier to be applied than other similar methods. Experiment with image from satellite ALOS (Advanced Land Observing Satellite) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiaometer) showed the feasibility of the proposed method and the effect of the distribution of GCPs.

Geometric correction method to correct the influence of attitude jitter on remote sensing imagery using compressive sampling

Attitude jitter occurs widely in the applications of high-resolution satellites. It is a vital factor that deteriorates the accuracy of geopositioning and mapping. However, the normal geometric correction methods cannot eliminate the influence of jitter on remote sensing images. Therefore, it is important to design a method that can handle this problem. This paper presents a geometric correction method using a rational function model (RFM) and compressive sampling called RFM-CS. This method is divided into two modules: precorrection and compensation. In the precorrection part, the original image is geometrically corrected with an RFM. However, when raw images contain distortion caused by attitude jitter, the rational polynomial coefficients (RPCs) don’t approximate the real imaging process well, and there are significant residual distortions in precorrected images. In the compensation part, we propose a new idea by which the residual distortions of images can be expressed as two-dimensional signals, which are called distortion signals. Using the new idea and CS, distortion signals, even those containing the influence of attitude jitter, are exactly reconstructed with a small set of ground control points. Based on the reconstructed distortion signals, the residual geometric error in the remote sensing images can be compensated by resampling. The experiments with images from Advanced Spaceborne Thermal Emission and Reflection Radiometer, Advanced Land Observing Satellite, and simulation demonstrate the promising performance and feasibility of the proposed method.

Application of attitude jitter detection based on short-time asynchronous images and compensation methods for Chinese mapping satellite-1.

Given the recent development in high-resolution (HR) optical satellites, the study of both attitude jitter (AJ) detection and compensation has become increasingly essential to improving the radiometric and geometric quality of HR images. A group of HR optical stereo mapping satellites in China, mapping satellite-1 (MS-1) has launched two satellites and will launch one satellite to build a satellite network. The geometric accuracy of the launched MS-1 satellites is greater than 80 m because of the AJ caused by the instability of the platform. AJ detection and compensation are critical issues that must be addressed to improve the accuracy of geo-positioning and mapping before launching a new satellite. The present study employs a method of jitter detection based on short-time asynchronous images to detect MS-1 jitter. The adjacent overlapping areas of an original panchromatic image are used as detection images instead of the traditional multispectral images, and a differential recursion optimal estimation filter is proposed for the optimal estimation and elimination of the gross errors of the registration data procedure, thereby increasing the detection accuracy. The space variant blurring model and viewing angles correction method are employed for the radiometric and geometric jitter compensation of images, respectively. The methods of radiometric objective evaluation indices and geometric checkpoint are then utilised to evaluate the quality of jitter compensation. Finally, the DeZhou regional image (ShanDong province, China) from MS-1 is used as the experimental data. Results for the AJ of MS-1 are analysed and reported for the first time. The assessment results obtained show that both radiometric and geometric qualities greatly increase after the jitter compensation procedure. Thus, the work of this study for jitter detection and compensation effectively addresses the jitter of MS-1 HR optical satellites.

Laser beam steering for GRACE Follow-On intersatellite interferometry.

The GRACE Follow-On satellites will use, for the first time, a Laser Ranging Interferometer to measure intersatellite distance changes from which fluctuations in Earth's geoid can be inferred. We have investigated the beam steering method that is required to maintain the laser link between the satellites. Although developed for the specific needs of the GRACE Follow-On mission, the beam steering method could also be applied to other intersatellite laser ranging applications where major difficulties are common: large spacecraft separation and large spacecraft attitude jitter. The beam steering method simultaneously coaligns local oscillator beam and transmitted beam with the laser beam received from the distant spacecraft using Differential Wavefront Sensing. We demonstrate the operation of the beam steering method on breadboard level using GRACE satellite attitude jitter data to command a hexapod, a six-degree-of-freedom rotation and translation stage. We verify coalignment of local oscillator beam/ transmitted beam and received beam of better than 10 μrad with a stability of 10 μrad/ √Hz in the GRACE Follow-On measurement band of 0.002...0.1 Hz. Additionally, important characteristics of the beam steering setup such as Differential Wavefront Sensing signals, heterodyne efficiency, and suppression of rotation-to-pathlength coupling are investigated and compared with analysis results.

Framework of Jitter Detection and Compensation for High Resolution Satellites

Attitude jitter is a common phenomenon in the application of high resolution satellites, which may result in large errors of geo-positioning and mapping accuracy. Therefore, it is critical to detect and compensate attitude jitter to explore the full geometric potential of high resolution satellites. In this paper, a framework of jitter detection and compensation for high resolution satellites is proposed and some preliminary investigation is performed. Three methods for jitter detection are presented as follows. (1) The first one is based on multispectral images using parallax between two different bands in the image; (2) The second is based on stereo images using rational polynomial coefficients (RPCs); (3) The third is based on panchromatic images employing orthorectification processing. Based on the calculated parallax maps, the frequency and amplitude of the detected jitter are obtained. Subsequently, two approaches for jitter compensation are conducted. (1) The first one is to conduct the compensation on image, which uses the derived parallax observations for resampling; (2) The second is to conduct the compensation on attitude data, which treats the influence of jitter on attitude as correction of charge-coupled device (CCD) viewing angles. Experiments with images from several satellites, such as ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiaometer), LRO (Lunar Reconnaissance Orbiter) and ZY-3 (ZiYuan-3) demonstrate the promising performance and feasibility of the proposed framework.

Astrometric meaning and interpretation of high-precision time delay integration CCD data

We investigate the astrometric content of CCD charge images of stars collected in time delay integration (TDI) mode with a scanning (rotating) telescope. We focus on the ESA astrometric space mission Gaia, but the results are valid for other scanning telescopes too. The physical attitude of the telescope is shown to be unobservable. Instead, an effective astrometric attitude is observed which represents an average over the TDI exposure time. The effective astrometric attitudes seen by different instruments (in case of Gaia: Astro, Spectro, Astro with gates) differ in a non-trivial way. If e.g. the high-precision Astro attitude would be used for the astrometric exploitation of the Spectro data, the Spectro CCDs would be seen to float around on the focal plane by several milli-arcseconds. In addition we find that the TDI mode produces an attitude jitter with the period of TDI clocking. We prove that this is negligibly small in the case of Gaia. We point out that the effective instant of observation is not the instant of charge read-out from the CCDs, but about half an exposure time (i.e. up to a few seconds) earlier. This is particularly important for the astrometry of solar-system objects and for the photometry of rapidly varying objects. It is also relevant for all other objects because of the time dependence of aberration. It is not clear whether the differences between the astrometric attitudes of different instruments require separate attitude reconstructions, but an approximate transformation from Astro to Spectro probably will be sufficient.

Measured spacecraft dynamic effects on atmospheric science instruments

In September 1991, NASA launched the Upper Atmosphere Research Satellite (UARS). In addition to its atmospheric science mission, spacecraft dynamic effects on science measurements were analyzed. The investigation included two in-flight experiments to determine how each onboard instrument, subsystem, and environmental disturbance contributed to the spacecraft dynamic response and how these disturbances affected science measurements. Three case studies are presented that show the impact of spacecraft dynamic response on science measurements. The case studies have demonstrated that the influence of spacecraft dynamic response needs to be examined in most remote-sensing spacecraft that have attitude jitter levels commensurate to instrument pointing requirements. In the first case, correlation of independent atmospheric meridional wind measurements taken by two instruments with the spacecraft dynamic response demonstrated that excessive vibration (exceeding instrument pointing requirements) resulted in wind measurement disagreement. In the second case, solar array disturbances produced a spacecraft response signature on radiometer measurements. The signature explicitly demonstrated that if an instrument has sufficient spatial and temporal resolution, spacecraft dynamic response could impact measurements. In the final case, correlation of an instruments fine Sun-sensor data and CO/sub 2/ measurements demonstrated the effect of temporal and spatial sampling resolution and active pointing control on science measurements. The Sun sensor had a frequency modulated characteristic, due to spacecraft vibration and the periodic scanning of another instrument, which was not present on the CO/sub 2/ measurements.

High-bandwidth attitude jitter determination for pointing and tracking systems

For many reasons smaller spacecraft are becoming more ap- pealing. Because of their lower inertias, these spacecraft are more sen- sitive to disturbances and likely to have more attitude jitter than the larger units. These jitter levels are unacceptable for some scientific instruments and need to be compensated. In the case of line-of-sight type instru- ments, the attitude jitter can be mitigated by incorporating a fast steering mirror into the system. To take full advantage of these devices, the spacecraft attitude must be measured at sufficiently high bandwidth, well beyond what is commonly provided by inertial reference units. Various ways to obtain higher bandwidth attitude measurements for the purpose of jitter control are explored and a practical solution to the problem is proposed. © 1997 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(97)02807-9)