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Geosynchronous communications satellites provide a wide variety of services. They carry wideband signals, such as television, and narrowband signals, such as business data networks. This paper describes a signal recognition system for the narrowband signals found on Ku-band satellites. Using readily available equipment, it saves observed signals which are later processed into an observation report. Observed signals are labeled using a decision tree, which is a pattern recognition technique. Each observation report also includes center frequency, bandwidth, and carrier-to-noise ratio. This paper presents the design and implementation of the signal recognition system. Results from the system are included. / Master of Science

Thesis (PhD)--Stellenbosch University, 1995. / ENGLISH ABSTRACT: New advanced control techniques for attitude determination and control of small (micro) satellites are presented. The attitude sensors and actuators on small satellites are limited in accuracy and performance due to physical limitations, e.g. volume, mass and power. To enhance the application of sophisticated payloads such as high resolution imagers within these confinements, a multi-mode control approach is proposed, whereby various optimized controller functions are utilized during the orbital life of the satellite. To keep the satellite's imager and antennas earth pointing with the minimum amount of control effort, a passive gravity gradient boom, active magnetic torquers and a magnetometer are used. A "cross-product" detumbling controller and a robust Kalman filter angular rate estimator are presented for the preboom deployment phase. A fuzzy controller and magnetometer full state extended Kalman filter are presented for libration damping and Z-spin rate control during inactive imager periods. During imaging, when high performance is required, additional fine resolution earth horizon, sun and star sensors plus 3-axis reaction wheels are employed. Full state attitude, rate and disturbance estimation is obtained from a horizon/sun extended Kalman filter. A quaternion feedback reaction wheel controller is presented to point or track a reference attitude during imaging. A near-minimum time, eigenaxis rotational reaction wheel controller for large angular maneuvers. Optimal linear quadratic and minimum energy algorithms to do momentum dumping using magnetic torquers, are presented. A new recursive magnetometer calibration method is designed to enhance the magnetic in-flight measurements. Finally, a software structure is proposed for the future onboard implementation of the multi-mode attitude control system. / AFRIKAANSE OPSOMMING: Nuwe gevorderde beheertegnieke vir die oriëntasiebepaling en -beheer van klein (mikro-) satelliete word behandel. Die oriëntasiesensors en -aktueerders op klein satelliete het 'n beperkte akkuraatheid en werkverrigting as gevolg van fisiese volume, massa en kragleweringbeperkings. Om gesofistikeerde loonvragte soos hoë resolusie kameras binne hierdie tekortkominge te kan hanteer, word 'n multimode beheerbenadering voorgestel. Hiermee kan 'n verskeidenheid van optimale beheerfunksies gedurende die wentelleeftyd van die satelliet gebruik word. Om die satellietkamera en -antennas aardwysend te rig met 'n minimale beheerpoging, word 'n passiewe graviteitsgradiëntstang, aktiewe magneetspoele en 'n magnetometer gebruik. 'n "Kruisproduk" onttuimellings beheerder en 'n robuuste hoektempo Kalmanfilter afskatter is ontwikkel vir die periode voordat die graviteitsgradiëntstang ontplooi word. 'n Wasige beheerder en 'n volledige toestand, uitgebreide Kalmanfilter afskatter is ontwikkel om librasiedemping en Z-rotasietempo beheer te doen gedurende tydperke wanneer die kamera onaktief is. Gedurende kamera-opnames word hoë werkverrigting verlang. Fyn resolusie aardhorison, son en stersensors met 3-as reaksiewiele kan dan gebruik word. 'n Volledige oriëntasie, hoektempo en steurdraaimoment Kalmanfilter afskatter wat inligting van bogenoemde sensors gebruik, is ontwikkel. 'n “Quaternion” reaksiewiel terugvoerbeheerder waarmee die satelliet na verwysings oriëntasiehoeke gerig kan word of waarmee oriëntasiehoektempos gevolg kan word, word behandel. 'n Naby minimumtyd, "eigen"-as reaksiewielbeheerder vir groothoek rotasies is ontwikkel. Optimale algoritmes om momentumontlading van reaksiewiele met lineêre kwadratiese en minimumenergie metodes te doen, word afgelei en aangebied. 'n Nuwe rekursiewe kalibrasietegniek waarmee 'n magnetometer outomaties gedurende vlug ingestel kan word, is ontwikkel. Ten slotte, word 'n programstruktuur voorgestel vir aanboord implementering van die nuwe multimode beheerstelsel.

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Accurate determination of atmospheric effects is crucial to earth-based inflight radiometric calibration of existing satellite systems. Such calibration work relies on computer codes which compute atmospheric transmittance due to both scattering and absorption processes. Two solar radiometers were used for atmospheric data collection. Results obtained from the two instruments in the visible are compared. Modifications to the autotracking instrument are discussed. The accuracy of existing methods for determining the amounts of key atmospheric constituents actually present at a given time is examined. Computation of integrated water vapor content based on solar radiometer data is discussed. Calculations to account for the effects of gaseous absorption in the near infrared spectral bands of a solar radiometer are outlined. Such corrections will facilitate calibration of these spectral bands. In conclusion, the effects of the uncertainties in the current determination of crucial atmospheric parameters on radiance at the satellite level are examined.

This thesis details the development and validation procedures of the experiment control software to be used on the NPSAT1. The software developed for a standard Linux kernel instead of an expensive proprietary space computer system includes functions for satellite orbit prediction, precise satellite location, and adaptive experiment scheduling using inputs from the electrical power system, sub-satellite position, and sub-satellite local time.

Shallow water bathymetry is important for both safe navigation and natural resource management purposes. Extracting depth information from spectral imagery allows identification of benthic features and characterization of coral reef habitats, especially in remote islands. Techniques have been developed to extract water depth from multispectral imagery (Lyzenga, 1978; Philpot, 1989). These techniques can be difficult to apply in optically shallow waters with heterogeneous bottom types and varying albedo, and require tuning of multiple parameters. An improved algorithm to extract water depth from multispectral satellite imagery was proposed by Stumpf et al. (2003) to generate bathymetric maps with limited a priori information. The algorithm is based on the ratios of transformed reflectance values in the visible bands, retrieving greater depths than previous algorithms and compensating for variable bottom type and albedo. This method requires fewer tunable parameters and can be applied to low-albedo features. Although Stumpf et al. (2003) conclude that the method is robust and works well over variable bottom types, recent studies have pointed out limitations, mostly attributable to varying albedo (Clark, 2005; Densham, 2005). This research attempts to quantify the contribution of variable benthic substrates to the algorithmâ s accuracy by classifying the scene into its main bottom types and tuning the coefficients separately. The algorithm is evaluated using a QuickBird high resolution multispectral image of the remote Midway Atoll, in the Northwestern Hawaiian Islands. Classifying the image into two main bottom types and tuning the coefficients separately produced a small improvement in the accuracy of the bathymetric estimates when bottom reflectance is included as a factor. This result indicates that Stumpf et al. (2003)â s ratio method is not insensitive to variable bottom type, and that knowledge of the distribution and extent of different benthic substrates in optically shallow waters has the potential to improve bathymetric derivation in remote coastal areas such as coral reef environments in the Pacific.

Approved for public release; distribution is unlimited / Design requirements for a small satellite (NPSAT-1) Attitude Determination and Control Subsystem (ADCS) is a three-axis stabilized spacecraft which requires a control attitude of +/- 1.0 degrees and knowledge attitude of +/- 0.1 degree. Several design aspects are considered in development of attitude control systems for a small satellite, such as: spacecraft dynamics, space environment, disturbance torques, orbit type, and spacecraft complexity. The ideal spacecraft's attitude sensor is a rate gyroscope, which provides rate information to the attitude control system. In the case of NPSAT-1, due to budget constraints alternative sensors will be utilized, such as: a three-axis magnetometer, earth sensors, and a Global Positioning System (GPS). A small satellite designed to have a three-axis stabilized, biased momentum system, must have a robust control system and requires a momentum wheel to provide stiffness to maintain attitude, and magnetic torque rods on each axis. The current design of NPSAT-1 uses all of these sensors to provide rate information for damping and stability to the control system that requires a complicated attitude control design. The purpose of this attitude control design simulation is to investigate and propose a control law utilizing a single pitch momentum wheel and three magnetic torque rods. A further proposal is to utilize a constant speed momentum wheel to avoid momentum damping and over speed, replace the pitch control with magnetic torquers, and develop a Kalman filter estimator to provide all the required angular rates. / Lieutenant Commander, United States Navy

Approved for public release; distribution is unlimited / Design Center of the Naval Postgraduate School. The objective of this simulator is to provide on-the-ground simulation of the dynamics and control of spacecraft for high precision Acquisition, Tracking and Pointing applications associated with space based laser relay. The required initial attitude determination accuracy for the Bifocal Relay Mirror test-bed is 10 æ-radians. Normally, in laboratories where very high initial attitude knowledge is required, actual (space qualified) star trackers are incorporated into the testbed design. This is not possible at NPS as the laboratory does not have a skylight to allow visual access to the stars, and the photosensitive nature of many of the experiments would make such an opening inconvenient. Since it is critical to the operation of the testbed to provide accurate attitude knowledge, a substitute system was required. The present thesis documents the development of a new attitude sensor capable of providing attitude information within the required 10æ-radians (within a field of view of the order of 1 deg). The concepts leading up to the final design, the testing and selection of the equipment used in the final configuration, and a detailed explanation of how the final system calibration was performed are discussed in detail. / Lieutenant, United States Navy

Tsz-Shing Tam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 84-87). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgments --- p.ii / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Literature Review --- p.6 / Chapter 3 --- System Model --- p.12 / Chapter 3.1 --- Static Architecture --- p.12 / Chapter 3.2 --- Dynamics --- p.15 / Chapter 3.3 --- Communication Paradigm --- p.16 / Chapter 3.4 --- Metric --- p.17 / Chapter 4 --- Routing Algorithms --- p.19 / Chapter 4.1 --- Minimum Hops Algorithm (MHA) --- p.20 / Chapter 4.2 --- Minimum Cost Algorithm (MCA) --- p.21 / Chapter 4.3 --- Mesh Algorithm (MA) --- p.24 / Chapter 4.3.1 --- Construction of the Set of Min-hop Paths --- p.24 / Chapter 4.3.2 --- Choosing a Path in S0 --- p.29 / Chapter 4.4 --- k-mesh Algorithm (KMA) --- p.29 / Chapter 4.4.1 --- Finding Sk --- p.30 / Chapter 4.4.2 --- Choosing a path in Sk --- p.34 / Chapter 4.5 --- Revised Mesh Algorithm (RMA) --- p.34 / Chapter 5 --- Reservation Strategies --- p.36 / Chapter 5.1 --- Introduction --- p.36 / Chapter 5.2 --- Notations --- p.38 / Chapter 5.3 --- Basic Reservation Strategy (BRS) --- p.39 / Chapter 5.4 --- Enhanced Reservation Strategy (ERS) --- p.41 / Chapter 5.5 --- Successor Reservation Strategy (SRS) --- p.43 / Chapter 6 --- Experiment --- p.45 / Chapter 6.1 --- Comparison on Routing Algorithms --- p.47 / Chapter 6.2 --- Comparison on Reservation Strategies --- p.64 / Chapter 7 --- Conclusion --- p.72 / Chapter A --- Existence of paths in Sk --- p.75 / Chapter B --- Estimation of basic reservation strategy guaranteed time --- p.79 / Chapter B.1 --- Basic reservation strategy --- p.79 / Chapter B.2 --- Estimation on Guaranteed Duration --- p.80 / Bibliography --- p.83