In 1992 Honeywell began development of Earth Reference Attitude Determination System (ERADS), a v... more In 1992 Honeywell began development of Earth Reference Attitude Determination System (ERADS), a very small low cost/power/weight attitude reference system designed for small satellite applications. We undertook this development because it appeared to us that small satellites require significantly smaller, lighter, and lower cost attitude reference systems than are currently available. ERADS was conceived as a single, strapdown, three axis sensor that would image the entire Earth's limb in the ultraviolet. The spectral band was selected because it provided feature stability comparable to what is seen in the infrared along with sensor cost and weight characteristic of visible sensors. Although an Earth reference sensor was
: The fundamental objectives of the capstone design project in the Department of Astronautics at ... more : The fundamental objectives of the capstone design project in the Department of Astronautics at the United States Air Force Academy are for cadets to learn important engineering lessons by executing a real space mission on a Department of Defense-funded satellite project. FalconSAT-5 is a 153 kg, three-axis stabilized spacecraft being designed and built by cadets and scheduled for launch in December 2009 on a Minotaur-IV from Kodiak, Alaska. The satellite has a space science mission to measure the local state of the ionosphere at ambient conditions with the intelligent Miniaturized Electrostatic Analyzer (iMESA) instrument and higher energy ions with the Wafer Integrated Spectrometers (WISPERS) instrument. There is also an RF receiver that can tune in the VHF and UHF bands in order to measure RF scintillation and correlate large scale ionospheric variations with the local iMESA and WISPERS measurements. One additional science objective is to understand and measure the interaction o...
Abstract : The fundamental objectives of the capstone design project in the Department of Astrona... more Abstract : The fundamental objectives of the capstone design project in the Department of Astronautics at the United States Air Force Academy are for cadets to learn important engineering lessons by executing a real space mission on a Department of Defense-funded satellite project. FalconSAT-5 is a 153 kg, three-axis stabilized spacecraft being designed and built by cadets and scheduled for launch in December 2009 on a Minotaur-IV from Kodiak, Alaska. The satellite has a space science mission to measure the local state of the ionosphere at ambient conditions with the intelligent Miniaturized Electrostatic Analyzer (iMESA) instrument and higher energy ions with the Wafer Integrated Spectrometers (WISPERS) instrument. There is also an RF receiver that can tune in the VHF and UHF bands in order to measure RF scintillation and correlate large scale ionospheric variations with the local iMESA and WISPERS measurements. One additional science objective is to understand and measure the interaction of generated plasmas with the body of a satellite and the local magnetic fields.
The fundamental objectives of the capstone design project in the Department of Astronautics at th... more The fundamental objectives of the capstone design project in the Department of Astronautics at the United States Air Force Academy (USAFA) are for cadets to learn important engineering lessons by executing a real space mission on a Department of Defense-funded satellite project. FalconSAT-3 is a 50 kg, gravity gradient-stabilized designed and built by cadets and launched March 2007 on the first ESPA (Enhanced extended launch vehicle Satellite Payload Adapter) mission. FalconSAT-3 was one of six satellites integrated onto the launch vehicle and the nature of the mission made it that the satellite was subject to the full formality of testing requirements. Two successive gravity gradient booms failed either design requirements or environmental testing; design requirements grew dramatically during the design phase; ambiguous thermal vacuum test results led to uncertainty at launch; and after launch it was not possible to contact the satellite for several weeks.
The Space Systems Research Center at the United States Air Force Academy is building a cadre of s... more The Space Systems Research Center at the United States Air Force Academy is building a cadre of satellite space professionals "one cadet at a time." Its motto and aim is for cadets to "Learn Space by Doing Space." Approximately one half of the cadets majoring in astronautical engineering perform a one year long capstone program of the design, fabrication, testing, launching and operation of a satellite in space (the FalconSAT program). FalconSAT-2 is a 19.5-kg satellite, which was launced on the SpaceX Falcon I launch vehicle in March 2006 from Kwajalien Island in the South Pacific. The cadets are currently working on FalconSAT-3, a 50-kg satellite due for launch on 7 December 2006 on an Atlas V ESPA. Both missions have payloads approved by the Department of Defense Space Experiments Review Board to conduct space-weather experiments and Air Force Research Laboratory avionics and propulsion experiments. This program works just like any Air Force program, with the ...
The United States Air Force Academy uses Space Physics as the scientific rational for an undergra... more The United States Air Force Academy uses Space Physics as the scientific rational for an undergraduate course which has cadets design, build, test and operate small satellites that fly real Academy and third-party space weather payloads. While the course description emphasizes the engineering aspects of small satellite design, this interdisciplinary course has cadets and faculty participating from across the engineering,
In 1992 Honeywell began development of Earth Reference Attitude Determination System (ERADS), a v... more In 1992 Honeywell began development of Earth Reference Attitude Determination System (ERADS), a very small low cost/power/weight attitude reference system designed for small satellite applications. We undertook this development because it appeared to us that small satellites require significantly smaller, lighter, and lower cost attitude reference systems than are currently available. ERADS was conceived as a single, strapdown, three axis sensor that would image the entire Earth\u27s limb in the ultraviolet. The spectral band was selected because it provided feature stability comparable to what is seen in the infrared along with sensor cost and weight characteristic of visible sensors. Although an Earth reference sensor was originally envisioned, it became evident that the ultraviolet was an excellent spectral band to observe stars as well, providing a providing a combined star/sun/Earth sensing capability in a single package. As a result, the current system can provide both three a...
It is becoming increasingly obvious that satellite bus technologies, which have been developed fo... more It is becoming increasingly obvious that satellite bus technologies, which have been developed for traditional larger satellite platforms, are not always suitable for use with smallsats. This is due to the intrisic limitations in size, weight, available power, and cost associated with the latter. The problem is particularly obvious for attitude reference sensors of both the earth and star viewing
Journal of Parallel and Distributed Computing, 2006
An ad hoc grid is a heterogeneous computing and communication system that allows a group of mobil... more An ad hoc grid is a heterogeneous computing and communication system that allows a group of mobile devices to accomplish a mission, often in a hostile environment. Energy management is a major concern in ad hoc grids. The problem studied here focuses on statically assigning resources in an ad hoc grid to an application composed of communicating subtasks. The goal of the allocation is to minimize the average percentage of energy consumed by the application to execute across the machines in the ad hoc grid, while meeting an application execution time constraint. This pre-computed allocation is then used when the application is deployed in a mission. Six different heuristic approaches of varying time complexities have been designed and compared via simulations to solve this ad hoc grid allocation problem. Also, a lower bound based on the performance metric has been designed to compare the performance of the heuristics developed.
18th International Parallel and Distributed Processing Symposium, 2004. Proceedings.
An ad hoc computing grid is characterized not only by constraints on the available energy and com... more An ad hoc computing grid is characterized not only by constraints on the available energy and communications bandwidth associated with each participating device, but also by the dynamic nature of the grid itself. This is caused by the mobile nature of the assets connected to the grid (computing devices, sensors, and users), plus the fragility of interconnecting communication links. The challenge, therefore, is to efficiently and robustly manage both computational and communication resources in this dynamic, unpredictable environment. This paper reports on one potential solution that combines Lagrangian techniques with the receding horizon concept used in modern robust control systems.
Small Satellite Technology and Applications III, 1993
It is becoming increasingly obvious that satellite bus technologies that have been developed for ... more It is becoming increasingly obvious that satellite bus technologies that have been developed for traditional larger satellite platforms are not always suitable for use with smallsats. This is due to the intrinsic smallsat limitations in size, weight, available power, and cost. The problem is particularly obvious for attitude reference sensors of both the earth and star viewing type. In response to the lack of suitable sensors for this purpose, Honeywell and Los Alamos National Laboratory are developing a system that determines three axis attitude through ultraviolet imaging of the earth's limb and adjacent stars. A nonconventional wide angle optics assembly and intensified CCD array are utilized for this purpose. Because of the stability and predictability of the features being observed and the large number of pixels on which the scene is imaged, it should be possible to obtain accuracies on the order of .02 degrees with a very small and lightweight sensor configuration. A prototype sensor has been fabricated and tested, and has met all performance objectives. A more advanced version is now being developed, and a flight prototype should be completed by the end of 1993.
Several scientific missions exist that require hundreds to thousands of near-simultaneous measure... more Several scientific missions exist that require hundreds to thousands of near-simultaneous measurements at widely distributed locations within the earth's magnetosphere. The current paradigm of individually building, designing, launching, and operating satellites is not capable of performing these missions. An autonomous constellation of smallsats and nanosats, developed as an ad hoc network of distributed wireless sensors will enable real-time, distributed, multi-point sensing of relevant phenomena. A low-cost and mass-producible solution to support this new class of space missions has been designed [1] and this paper addresses the significant system issues driven by this revolutionary technology. The constellation uses smallsats in the ~ 100 kg class as communication and computation nodes and multiple ~5 kg nanosats as distributed sensors to continuously measure plasma parameters in the ionosphere as part of a global space weather monitoring system. The constellation is comprised of separate orbital rings that consist of one or two nodes and between ten and fifty nanosats. Each of the nanosats is a distributed sensor and routing device that generates data messages and routs neighboring data to the nodes. The nodes maintain both an instantaneous data map of the entire orbit distribution of sensors and a time history of all measurements. NOMENCLATURE Distributed sensor satellite = DSsat = A single adhoc sensor node. Communication & Computation Node satellite = CCsat = A single hub satellite for one orbit ring in the network. Ad-Hoc Network = A self-configuring network of mobile routers. Platform Design = A design that can be easily modified for different missions.
An ad hoc grid is a heterogeneous computing and communication system without a fixed infrastructu... more An ad hoc grid is a heterogeneous computing and communication system without a fixed infrastructure; all of its components are mobile. Energy management is a major concern in an ad hoc grid. One important aspect of energy management is to minimize the energy consumption during a mission. In an ad hoc grid, communication and computations are deeply intertwined, and any energy optimization must consider both types of activities together rather than separately. The mapping (defined as matching and scheduling) of tasks onto machines with varied computational capabilities has been shown, in general, to be an NP-complete problem. Therefore, heuristic techniques are required to efficiently map tasks to machines in an ad hoc grid so as to minimize the energy consumed due to communication and computation. This research evaluates and compares energy management issues for resource allocation in ad hoc grids using six static heuristics.
In 1992 Honeywell began development of Earth Reference Attitude Determination System (ERADS), a v... more In 1992 Honeywell began development of Earth Reference Attitude Determination System (ERADS), a very small low cost/power/weight attitude reference system designed for small satellite applications. We undertook this development because it appeared to us that small satellites require significantly smaller, lighter, and lower cost attitude reference systems than are currently available. ERADS was conceived as a single, strapdown, three axis sensor that would image the entire Earth's limb in the ultraviolet. The spectral band was selected because it provided feature stability comparable to what is seen in the infrared along with sensor cost and weight characteristic of visible sensors. Although an Earth reference sensor was
: The fundamental objectives of the capstone design project in the Department of Astronautics at ... more : The fundamental objectives of the capstone design project in the Department of Astronautics at the United States Air Force Academy are for cadets to learn important engineering lessons by executing a real space mission on a Department of Defense-funded satellite project. FalconSAT-5 is a 153 kg, three-axis stabilized spacecraft being designed and built by cadets and scheduled for launch in December 2009 on a Minotaur-IV from Kodiak, Alaska. The satellite has a space science mission to measure the local state of the ionosphere at ambient conditions with the intelligent Miniaturized Electrostatic Analyzer (iMESA) instrument and higher energy ions with the Wafer Integrated Spectrometers (WISPERS) instrument. There is also an RF receiver that can tune in the VHF and UHF bands in order to measure RF scintillation and correlate large scale ionospheric variations with the local iMESA and WISPERS measurements. One additional science objective is to understand and measure the interaction o...
Abstract : The fundamental objectives of the capstone design project in the Department of Astrona... more Abstract : The fundamental objectives of the capstone design project in the Department of Astronautics at the United States Air Force Academy are for cadets to learn important engineering lessons by executing a real space mission on a Department of Defense-funded satellite project. FalconSAT-5 is a 153 kg, three-axis stabilized spacecraft being designed and built by cadets and scheduled for launch in December 2009 on a Minotaur-IV from Kodiak, Alaska. The satellite has a space science mission to measure the local state of the ionosphere at ambient conditions with the intelligent Miniaturized Electrostatic Analyzer (iMESA) instrument and higher energy ions with the Wafer Integrated Spectrometers (WISPERS) instrument. There is also an RF receiver that can tune in the VHF and UHF bands in order to measure RF scintillation and correlate large scale ionospheric variations with the local iMESA and WISPERS measurements. One additional science objective is to understand and measure the interaction of generated plasmas with the body of a satellite and the local magnetic fields.
The fundamental objectives of the capstone design project in the Department of Astronautics at th... more The fundamental objectives of the capstone design project in the Department of Astronautics at the United States Air Force Academy (USAFA) are for cadets to learn important engineering lessons by executing a real space mission on a Department of Defense-funded satellite project. FalconSAT-3 is a 50 kg, gravity gradient-stabilized designed and built by cadets and launched March 2007 on the first ESPA (Enhanced extended launch vehicle Satellite Payload Adapter) mission. FalconSAT-3 was one of six satellites integrated onto the launch vehicle and the nature of the mission made it that the satellite was subject to the full formality of testing requirements. Two successive gravity gradient booms failed either design requirements or environmental testing; design requirements grew dramatically during the design phase; ambiguous thermal vacuum test results led to uncertainty at launch; and after launch it was not possible to contact the satellite for several weeks.
The Space Systems Research Center at the United States Air Force Academy is building a cadre of s... more The Space Systems Research Center at the United States Air Force Academy is building a cadre of satellite space professionals "one cadet at a time." Its motto and aim is for cadets to "Learn Space by Doing Space." Approximately one half of the cadets majoring in astronautical engineering perform a one year long capstone program of the design, fabrication, testing, launching and operation of a satellite in space (the FalconSAT program). FalconSAT-2 is a 19.5-kg satellite, which was launced on the SpaceX Falcon I launch vehicle in March 2006 from Kwajalien Island in the South Pacific. The cadets are currently working on FalconSAT-3, a 50-kg satellite due for launch on 7 December 2006 on an Atlas V ESPA. Both missions have payloads approved by the Department of Defense Space Experiments Review Board to conduct space-weather experiments and Air Force Research Laboratory avionics and propulsion experiments. This program works just like any Air Force program, with the ...
The United States Air Force Academy uses Space Physics as the scientific rational for an undergra... more The United States Air Force Academy uses Space Physics as the scientific rational for an undergraduate course which has cadets design, build, test and operate small satellites that fly real Academy and third-party space weather payloads. While the course description emphasizes the engineering aspects of small satellite design, this interdisciplinary course has cadets and faculty participating from across the engineering,
In 1992 Honeywell began development of Earth Reference Attitude Determination System (ERADS), a v... more In 1992 Honeywell began development of Earth Reference Attitude Determination System (ERADS), a very small low cost/power/weight attitude reference system designed for small satellite applications. We undertook this development because it appeared to us that small satellites require significantly smaller, lighter, and lower cost attitude reference systems than are currently available. ERADS was conceived as a single, strapdown, three axis sensor that would image the entire Earth\u27s limb in the ultraviolet. The spectral band was selected because it provided feature stability comparable to what is seen in the infrared along with sensor cost and weight characteristic of visible sensors. Although an Earth reference sensor was originally envisioned, it became evident that the ultraviolet was an excellent spectral band to observe stars as well, providing a providing a combined star/sun/Earth sensing capability in a single package. As a result, the current system can provide both three a...
It is becoming increasingly obvious that satellite bus technologies, which have been developed fo... more It is becoming increasingly obvious that satellite bus technologies, which have been developed for traditional larger satellite platforms, are not always suitable for use with smallsats. This is due to the intrisic limitations in size, weight, available power, and cost associated with the latter. The problem is particularly obvious for attitude reference sensors of both the earth and star viewing
Journal of Parallel and Distributed Computing, 2006
An ad hoc grid is a heterogeneous computing and communication system that allows a group of mobil... more An ad hoc grid is a heterogeneous computing and communication system that allows a group of mobile devices to accomplish a mission, often in a hostile environment. Energy management is a major concern in ad hoc grids. The problem studied here focuses on statically assigning resources in an ad hoc grid to an application composed of communicating subtasks. The goal of the allocation is to minimize the average percentage of energy consumed by the application to execute across the machines in the ad hoc grid, while meeting an application execution time constraint. This pre-computed allocation is then used when the application is deployed in a mission. Six different heuristic approaches of varying time complexities have been designed and compared via simulations to solve this ad hoc grid allocation problem. Also, a lower bound based on the performance metric has been designed to compare the performance of the heuristics developed.
18th International Parallel and Distributed Processing Symposium, 2004. Proceedings.
An ad hoc computing grid is characterized not only by constraints on the available energy and com... more An ad hoc computing grid is characterized not only by constraints on the available energy and communications bandwidth associated with each participating device, but also by the dynamic nature of the grid itself. This is caused by the mobile nature of the assets connected to the grid (computing devices, sensors, and users), plus the fragility of interconnecting communication links. The challenge, therefore, is to efficiently and robustly manage both computational and communication resources in this dynamic, unpredictable environment. This paper reports on one potential solution that combines Lagrangian techniques with the receding horizon concept used in modern robust control systems.
Small Satellite Technology and Applications III, 1993
It is becoming increasingly obvious that satellite bus technologies that have been developed for ... more It is becoming increasingly obvious that satellite bus technologies that have been developed for traditional larger satellite platforms are not always suitable for use with smallsats. This is due to the intrinsic smallsat limitations in size, weight, available power, and cost. The problem is particularly obvious for attitude reference sensors of both the earth and star viewing type. In response to the lack of suitable sensors for this purpose, Honeywell and Los Alamos National Laboratory are developing a system that determines three axis attitude through ultraviolet imaging of the earth's limb and adjacent stars. A nonconventional wide angle optics assembly and intensified CCD array are utilized for this purpose. Because of the stability and predictability of the features being observed and the large number of pixels on which the scene is imaged, it should be possible to obtain accuracies on the order of .02 degrees with a very small and lightweight sensor configuration. A prototype sensor has been fabricated and tested, and has met all performance objectives. A more advanced version is now being developed, and a flight prototype should be completed by the end of 1993.
Several scientific missions exist that require hundreds to thousands of near-simultaneous measure... more Several scientific missions exist that require hundreds to thousands of near-simultaneous measurements at widely distributed locations within the earth's magnetosphere. The current paradigm of individually building, designing, launching, and operating satellites is not capable of performing these missions. An autonomous constellation of smallsats and nanosats, developed as an ad hoc network of distributed wireless sensors will enable real-time, distributed, multi-point sensing of relevant phenomena. A low-cost and mass-producible solution to support this new class of space missions has been designed [1] and this paper addresses the significant system issues driven by this revolutionary technology. The constellation uses smallsats in the ~ 100 kg class as communication and computation nodes and multiple ~5 kg nanosats as distributed sensors to continuously measure plasma parameters in the ionosphere as part of a global space weather monitoring system. The constellation is comprised of separate orbital rings that consist of one or two nodes and between ten and fifty nanosats. Each of the nanosats is a distributed sensor and routing device that generates data messages and routs neighboring data to the nodes. The nodes maintain both an instantaneous data map of the entire orbit distribution of sensors and a time history of all measurements. NOMENCLATURE Distributed sensor satellite = DSsat = A single adhoc sensor node. Communication & Computation Node satellite = CCsat = A single hub satellite for one orbit ring in the network. Ad-Hoc Network = A self-configuring network of mobile routers. Platform Design = A design that can be easily modified for different missions.
An ad hoc grid is a heterogeneous computing and communication system without a fixed infrastructu... more An ad hoc grid is a heterogeneous computing and communication system without a fixed infrastructure; all of its components are mobile. Energy management is a major concern in an ad hoc grid. One important aspect of energy management is to minimize the energy consumption during a mission. In an ad hoc grid, communication and computations are deeply intertwined, and any energy optimization must consider both types of activities together rather than separately. The mapping (defined as matching and scheduling) of tasks onto machines with varied computational capabilities has been shown, in general, to be an NP-complete problem. Therefore, heuristic techniques are required to efficiently map tasks to machines in an ad hoc grid so as to minimize the energy consumed due to communication and computation. This research evaluates and compares energy management issues for resource allocation in ad hoc grids using six static heuristics.
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Papers by William Saylor