GOES dynamic propagation of attitude

The spacecraft in the next series of Geostationary Operational Environmental Satellites (GOES-Next) are Earth pointing and have 5-year mission lifetimes. Because gyros can be depended on only for a few years of continuous use, they will be turned off during routine operations. This means attitude must, at times, be determined without benefit of gyros and, often, using only Earth sensor data. To minimize the interruption caused by dumping angular momentum, these spacecraft have been designed to reduce the environmental torque acting on them and incorporate an adjustable solar trim tab for fine adjustment. A new support requirement for GOES-Next is that of setting the solar trim tab. Optimizing its setting requires an estimate of the unbalanced torque on the spacecraft. These two requirements, determining attitude without gyros and estimating the external torque, are addressed by replacing or supplementing the gyro propagation with a dynamic one, that is, one that integrates the rigid body equations of motion. By processing quarter-orbit or longer batches, this approach takes advantage of roll-yaw coupling to observe attitude completely without Sun sensor data. Telemetered momentum wheel speeds are used as observations of the unbalanced external torques. GOES-Next provides a unique opportunity to study dynamic attitude propagation. The geosynchronous altitude and adjustable trim tab minimize the external torque and its uncertainty, making long-term dynamic propagation feasible. This paper presents the equations for dynamic propagation, an analysis of the environmental torques, and an estimate of the accuracies obtainable with the proposed method

Attitude Estimation for Large Field-of-View Sensors

The QUEST measurement noise model for unit vector observations has been widely used in spacecraft attitude estimation for more than twenty years. It was derived under the approximation that the noise lies in the tangent plane of the respective unit vector and is axially symmetrically distributed about the vector. For large field-of-view sensors, however, this approximation may be poor, especially when the measurement falls near the edge of the field of view. In this paper a new measurement noise model is derived based on a realistic noise distribution in the focal-plane of a large field-of-view sensor, which shows significant differences from the QUEST model for unit vector observations far away from the sensor boresight. An extended Kalman filter for attitude estimation is then designed with the new measurement noise model. Simulation results show that with the new measurement model the extended Kalman filter achieves better estimation performance using large field-of-view sensor observations

Quaternion Averaging

Many applications require an algorithm that averages quaternions in an optimal manner. For example, when combining the quaternion outputs of multiple star trackers having this output capability, it is desirable to properly average the quaternions without recomputing the attitude from the the raw star tracker data. Other applications requiring some sort of optimal quaternion averaging include particle filtering and multiple-model adaptive estimation, where weighted quaternions are used to determine the quaternion estimate. For spacecraft attitude estimation applications, derives an optimal averaging scheme to compute the average of a set of weighted attitude matrices using the singular value decomposition method. Focusing on a 4-dimensional quaternion Gaussian distribution on the unit hypersphere, provides an approach to computing the average quaternion by minimizing a quaternion cost function that is equivalent to the attitude matrix cost function Motivated by and extending its results, this Note derives an algorithm that deterniines an optimal average quaternion from a set of scalar- or matrix-weighted quaternions. Rirthermore, a sufficient condition for the uniqueness of the average quaternion, and the equivalence of the mininiization problem, stated herein, to maximum likelihood estimation, are shown

Christian Higher Education and Participation in the Redemptive Work of God

This history of distinctively Christian institutions of higher education in America signals the importance of missional vigilance for stakeholders. This article proposes a framework for Christian faculty to approach their work of educating students in a distinctively Christian way, by orienting each discipline and field of study to the main points of redemptive history as defined by Christian theology. When we train students at a Christian institution, we should be training them to become participants in the redemptive work of God. By taking an intentional approach to this (i.e., orienting our disciplines and the subject-matter to redemptive history), we help our students to realize the opportunity that presents itself with the acquisition of learning and credentials. We aren’t just training them to be job-ready graduates, research-ready graduates, informed citizens, or ministry-ready graduates. We aren’t just training them for thriving lives of obedience to God. Nor are we just training them to go into the workplace and share the gospel. In addition to these, we are training them to be participants in the redemptive work of God who use their knowledge and skills to mitigate the reign of death and dysfunction in creation, and who instantiate aspects of new creation now – catalysts of redemptive change in all spheres of society. This is a distinctively Christian approach to higher education in all academic disciplines, all of which is possible because of what God has done for us, and will do through us, in Christ and for His glory

From whaling days to cannery row : a survey of some aspects of the fishing industry at Monterey and vicinity from 1854 to 1920

In the days before there was a Monterey, there were whales in Monterey Bay. We know this because Vizcaino, who dropped anchor in the bay in 1602, kept a diary. And from this diary, Vizcaino\u27s historian, one Venegas who wrote: A History of California in 1758, makes the statement that whales and sea lions swam about in the bay.1 Apparently, the whales kept on swimming in Monterey Bay for about one hundred and fifty years without being molested. Shortly after that, the whales and Monterey fishermen engaged in a long struggle which took place, with periodic cessation, over a span of, roughly, seventy-five years. It is believed that a logical point of termination in this survey has been reached because a certain unity has been attained. It must now be clear that the rise and decline in a certain type of fishing effort has a positive correlation with the rise and decline of certain national groups. The Portuguese were prominent as whalers; the temporary cessation of whaling about 1900 destroyed their dominance at Monterey; there are reports in 1899 and 1901 of Japanese whalers as well as Portuguese. The revival of whaling in 1918 wa not responsible for a Portuguese renaissance because it was not longer an art, but wholesale slaughter by the most destructive weapons. The Chinese lost their prominence in squid and abalone fishing through prohibitory legislation and a fire, which dispersed the Chinese as a fishing colony. The Chinese loss was the Japanese gain, for abalone diving became, after 1900, one of their most effective pursuits. Salmon trolling was another fishing field in which the Japanese proved their worth; after 1916, however, salmon began a slow but steady decline. Consequently, the Japanese turned to albacore trolling in Southern California waters.1 The introduction of the lampara net in 1905 and the phenomenal growth in sardine fishing and canning brought the Italian, or Sicilians, to the fore in this type of fishing effect. Many Orientals found work in the canneries as cutters and packers as did many Occidentals. But the crews and captains of the lampara launches were, by and large, of Italian extraction. Legislation and technical improvements have aided and restricted certain types of fishing. Legislative control during the war was in large part responsible for creating dissatisfaction among fishermen and giving them pretext for strikes. The reasons for the rise and/or decline of a certain type of fishing effort should be clearly understood. Whaling ceased about 100 because of a shortage of whales and inefficient means of securing those whales which remain. Salmon trolling declined in spite of legislation of a restrictive nature, because that legislation was eminently defective. After the legislation of commercial squid fishing in 1913 that fishery has steadily risen to a place of considerable importance. Since 1916, 97% of the California total squid poundage has been loaded at Monterey;3 the lampara note was a decisive factor in this remarkable tally, as it was particularly suited to this small form of marine life. As for sardines, their remarkable rise from bait fish to case goods and meal and oil reduced other types of fishing to a place of secondary importance. In tonnage and in profits, in construction and employment, the sardine fishing by 1920, was supreme in Monterey\u27s fishing industry. There is a logical break in continuity after the year 1919; subsequent years brought a slump in the entire fishing industry and also a diversification in sardine fishing: i.e., reduction of edible fish into meal and oil. As this next period represents an entity in itself due to its technical and legal aspects, this survey is terminated with the year 1919

Guidance and Navigation for Rendezvous and Proximity Operations with a Non-Cooperative Spacecraft at Geosynchronous Orbit

The feasibility and benefits of various spacecraft servicing concepts are currently being assessed, and all require that the servicer spacecraft perform rendezvous, proximity, and capture operations with the target spacecraft to be serviced. Many high-value spacecraft, which would be logical targets for servicing from an economic point of view, are located in geosynchronous orbit, a regime in which autonomous rendezvous and capture operations are not commonplace. Furthermore, existing GEO spacecraft were not designed to be serviced. Most do not have cooperative relative navigation sensors or docking features, and some servicing applications, such as de-orbiting of a non-functional spacecraft, entail rendezvous and capture with a spacecraft that may be non-functional or un-controlled. Several of these challenges have been explored via the design of a notional mission in which a nonfunctional satellite in geosynchronous orbit is captured by a servicer spacecraft and boosted into super-synchronous orbit for safe disposal. A strategy for autonomous rendezvous, proximity operations, and capture is developed, and the Orbit Determination Toolbox (ODTBX) is used to perform a relative navigation simulation to assess the feasibility of performing the rendezvous using a combination of angles-only and range measurements. Additionally, a method for designing efficient orbital rendezvous sequences for multiple target spacecraft is utilized to examine the capabilities of a servicer spacecraft to service multiple targets during the course of a single mission

Plant cell wall profiling by fast maximum likelihood reconstruction (FMLR) and region-of-interest (ROI) segmentation of solution-state 2D 1H–13C NMR spectra

BACKGROUND: Interest in the detailed lignin and polysaccharide composition of plant cell walls has surged within the past decade partly as a result of biotechnology research aimed at converting biomass to biofuels. High-resolution, solution-state 2D (1)H–(13)C HSQC NMR spectroscopy has proven to be an effective tool for rapid and reproducible fingerprinting of the numerous polysaccharides and lignin components in unfractionated plant cell wall materials, and is therefore a powerful tool for cell wall profiling based on our ability to simultaneously identify and comparatively quantify numerous components within spectra generated in a relatively short time. However, assigning peaks in new spectra, integrating them to provide relative component distributions, and producing color-assigned spectra, are all current bottlenecks to the routine use of such NMR profiling methods. RESULTS: We have assembled a high-throughput software platform for plant cell wall profiling that uses spectral deconvolution by Fast Maximum Likelihood Reconstruction (FMLR) to construct a mathematical model of the signals present in a set of related NMR spectra. Combined with a simple region of interest (ROI) table that maps spectral regions to NMR chemical shift assignments of chemical entities, the reconstructions can provide rapid and reproducible fingerprinting of numerous polysaccharide and lignin components in unfractionated cell wall material, including derivation of lignin monomer unit (S:G:H) ratios or the so-called SGH profile. Evidence is presented that ROI-based amplitudes derived from FMLR provide a robust feature set for subsequent multivariate analysis. The utility of this approach is demonstrated on a large transgenic study of Arabidopsis requiring concerted analysis of 91 ROIs (including both assigned and unassigned regions) in the lignin and polysaccharide regions of almost 100 related 2D (1)H–(13)C HSQC spectra. CONCLUSIONS: We show that when a suitable number of replicates are obtained per sample group, the correlated patterns of enriched and depleted cell wall components can be reliably and objectively detected even prior to multivariate analysis. The analysis methodology has been implemented in a publicly-available, cross-platform (Windows/Mac/Linux), web-enabled software application that enables researchers to view and publish detailed annotated spectra in addition to summary reports in simple spreadsheet data formats. The analysis methodology is not limited to studies of plant cell walls but is amenable to any NMR study where ROI segmentation techniques generate meaningful results. Please see Research Article: http://www.biotechnologyforbiofuels.com/content/6/1/46/

Ursinus College Bulletin Vol. 17, No. 9, June 15, 1901

A digitized copy of the June 15, 1901 Ursinus College Bulletin.https://digitalcommons.ursinus.edu/ucbulletin/1190/thumbnail.jp

An MME-based attitude estimator using vector observations

In this paper, an optimal batch estimator and filter based on the Minimum Model Error (MME) approach is developed for three-axis stabilized spacecraft. Three different MME algorithms are developed. The first algorithm estimates the attitude of a spacecraft using rate measurements. The second algorithm estimates the attitude without using rate measurements. The absence of rate data may be a result of intentional design or from unexpected failure of existing gyros. The third algorithm determines input-torque modeling error trajectories. All of the algorithms developed in this paper use attitude sensors (e.g., three-axis magnetometers, sun sensors, star trackers, etc.). Results using these new algorithms indicate that an MME-based approach accurately estimates the attitude, rate, and input torque trajectories of an actual spacecraft