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The Development Of The Northern Satellite Service, Rolf Skatteboe Sep 1992

The Development Of The Northern Satellite Service, Rolf Skatteboe

Small Satellite Conference

Launch- and operational cost have been prohibiting factors for small satellite systems. and it is becoming clearer that a new philosophy must be adopted to accommodate the reduced budgets of such systems. This paper discusses the design of an integrated launch facility for small polar orbiting satellites and sounding rockets. It focuses on the development of a cost-effective total service for integration, launch, operation and TT&C for micro-satellites, called the Northern Satellite Service (NSS). The goal is to create a flexible service, and offer this service to the international market The proposed launch facility is based on the existing infrastructure …

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Resistance To Satellite Failures Of Leo Communication Systems, Thomas Wolf, Jean-Jacques De Ridder Sep 1992

Resistance To Satellite Failures Of Leo Communication Systems, Thomas Wolf, Jean-Jacques De Ridder

Small Satellite Conference

This paper presents a satellite failure analysis for Low Earth Orbit (LEO) constellations with continuous global coverage. Worst case failure configurations are identified for polar orbit constellations and the coverage performance deterioration 'is evaluated by computer simulations. Then, the probability of having a number of satellite failures in a given constellation is evaluated as a function of satellite reliability. It is shown that the probability of occurrence of a worst case failure configuration is very low, and that the most probable configuration is a uniform distribution of the defective satellites. As a consequence, the maximum tolerable number of satellite failures …

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High-Data-Rate Communication Techniques For Small Satellites, Robert Bokulic Sep 1992

High-Data-Rate Communication Techniques For Small Satellites, Robert Bokulic

Small Satellite Conference

Modulation and coding techniques that are both power and bandwidth-efficient are examined at the system level in this paper. Such techniques include convolutional encoding with QPSK modulation and the relatively new trellis-coded modulation. Power and bandwidth trade-offs are discussed, a sample link calculation is given, and hardware implementation is considered.

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A Unique New Antenna Technology For Small (And Large) Satellites, Bernard Raab, Larry Sikora Sep 1992

A Unique New Antenna Technology For Small (And Large) Satellites, Bernard Raab, Larry Sikora

Small Satellite Conference

The application of large antennas in spacecraft is often limited by available volume, as well as by the more usual mass limitation. Shroud dimensions usually determine the maximum aperture which can be carried without resorting to complex and potentially unreliable unfurling mechanisms. This applies all the more in a small-satellite environment with the smaller available launch volumes and severe mass limits of this species. FLAPS (Flat Parabolic Surface) is a newly developed technology for RF reflector surfaces which frees the spacecraft designer from the packaging rigidity of the common parabolic dish. It offers the ability to essentially duplicate the capability …

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Downlink Signal Level And Error Measurements For Pacsat-1, Robert Diersing Sep 1992

Downlink Signal Level And Error Measurements For Pacsat-1, Robert Diersing

Small Satellite Conference

The PACSAT-l store-and-forward amateur radio satellite was placed into low earth orbit (LEO) on January 22, 1990 using the Ariane Structure for Auxiliary Payloads (ASAP). Most of the first year of operation was spent on application software development with full time operation of file server and file broadcast services beginning in late 1990. During 1991, both ground station and satellite-based software matured and stabilized such that the satellite sees a high volume of daily use both by individual amateur radio station operators and stations acting as gateways for terrestrial packet radio networks operating in the Amateur Radio Service. The purpose …

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Using Digital Signal Processors On Small Satellites, Don Lefevre, Daniel Mulally, Mark Heiberger Sep 1992

Using Digital Signal Processors On Small Satellites, Don Lefevre, Daniel Mulally, Mark Heiberger

Small Satellite Conference

Digital Signal Processing integrated circuits (DSPs) have improved terrestrial communications systems by allowing the implementation of greatly improved transmitters and receivers. In applications from dial-up modems, to echo-free conference phones, to customer-specific hearing aids, DSPs have allowed the implementation of functions that would be impractical without them. However, DSPs have had limited use in small satellites due to lower available data rates and relatively high power consumption. Also, most of the existing DSPs have not been space qualified. Improvements in semiconductor processes are allowing the construction of integrated circuits (ICs) with much smaller features. In fact, 0.6 micron processes are …

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A Laser Downlink For Small Satellites Using An Optically Modulating Retroreflector, Gary Jensen, Charles Swenson Sep 1992

A Laser Downlink For Small Satellites Using An Optically Modulating Retroreflector, Gary Jensen, Charles Swenson

Small Satellite Conference

This paper presents an earthsatellite-earth laser downlink system which is compact, simple, and low-power enough to be considered for use on very small satellites. Presented here is the design, feasibility study, and results from preliminary "proof of concept" testing of the critical components.

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A Low-Cost Small Satellite Space Radar System, Bernard Raab, Robert Bartlett Sep 1992

A Low-Cost Small Satellite Space Radar System, Bernard Raab, Robert Bartlett

Small Satellite Conference

The advantages of space-based radar have been frequently noted for such applications as environmental monitoring, crop detection, soil-moisture determination, coastal ice measurement, and all-weather surveillance, to name just a few. The FLAPSTM ("Flat Parabolic Surface") antenna technology developed by Malibu Research, enables the conception of a smallsatellite radar system. The design described in this paper is that of a lightweight surveillance satellite capable of being launched on a Pegasus booster. It is capable of detecting small ships and aircraft, such as may be required for drug-interdiction missions and other all-weather surveillance applications. The FLAPSTM antenna has many of the features …

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Precision Quartz Oscillators And Their Use In Small Satellites, J.R. Norton, J.M. Cloeren Sep 1992

Precision Quartz Oscillators And Their Use In Small Satellites, J.R. Norton, J.M. Cloeren

Small Satellite Conference

Space-qualified precision quartz oscillators are ideal instruments for use aboard small satellites as the heart of the spacecraft navigation system as well as for other applications such as radio science experiments, pseudorandom communications, and altimetry. This paper provides information on the history of precision quartz oscillator use aboard small satellites and discusses potential applications and design tradeoffs. The Johns Hopkins University Applied Physics Laboratory pioneered the use of precision quartz oscillators in small satellites in 1958. Current performance parameters of oscillators designed by the Applied Physics Laboratory will be presented along with mass and power considerations.

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Populating The Abyss-Investigating More Efficient Orbits -Or- "Getting More Miles To The Gallon For Your (Space) Vehicle", John Draim, Thomas Kacena Sep 1992

Populating The Abyss-Investigating More Efficient Orbits -Or- "Getting More Miles To The Gallon For Your (Space) Vehicle", John Draim, Thomas Kacena

Small Satellite Conference

Most satellites operating in orbit are spatially distributed in one of the following regions: LEO (below 600 nm and below), MEO (Molniya and GPS), and GEO (synchronous circular). Other than Molniya and a few similar systems, little use has been made of either elliptic orbits or the 'middle-ground' orbits lying between 600 nm and synchronous altitude. This paper explores the potential for exploiting these less populated regions and demonstrates that analyzing system optimization parametrically may in fact, also dictate an increasing interest in this new territory. A non-dimensional coverage parameter is presented which indicates that the 'efficiency' of an orbit …

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The Space Test Program Apex Mission Satellite, Frank Knight Sep 1992

The Space Test Program Apex Mission Satellite, Frank Knight

Small Satellite Conference

An overview is presented of the Air Force Space Test Program's Advanced Photovoltaic and Electronic Experiments (APEX) Mission. APEX will provide spaceflight for three military experiments on the fourth flight of the Pegasus Air-Launched Vehicle in ready 1993. The APEX spacecraft is Orbital Sciences Corporation's "PegaStar" integrated third stage, in which components of the final stage of the launch vehicle are augmented to provide a fully-functional, 3-axis stabilized experiment platform. The spacecraft configuration and capabilities are described. The mission development history to date is outlined, as is the vehicle processing prior to launch. Finally, plans for the distribution of experiment …

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Technologies For Future High Capability Micro-Milsatcom Systems, B. Steele, R.J. Bonometti, A. Wallace, K. Brandt Sep 1992

Technologies For Future High Capability Micro-Milsatcom Systems, B. Steele, R.J. Bonometti, A. Wallace, K. Brandt

Small Satellite Conference

Satellite communications systems are a vitally important component of our Defense infrastructure for both tactical and strategic missions. In particular, satellite communications (whether military or commercial) have become increasingly important to support tactical operations, as was clearly demonstrated during Operations Desert Shield and Desert Storm. In the emerging doctrinal shift to a CONUS-based force structure with capabilities for rapidly responsive lethal power projection to meet global crises, the vital necessity for SATCOM to provide an omnipresent communications infrastructure for immediate support of the developing theater will become a key element in the successful realization of our new warfighting strategy. This …

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Near Earth Asteroid Rendezvous, Edward Reynolds, Robert Farquhar Sep 1992

Near Earth Asteroid Rendezvous, Edward Reynolds, Robert Farquhar

Small Satellite Conference

The Johns Hopkins University Applied Physics Laboratory recently completed a pre-Phase A study to design a spacecraft to rendezvous and go into orbit around a near earth asteroid. The spacecraft would map the asteroid's surface and collect other science data for a one year period. The primary mission would be a rendezvous with either asteroid Anteros or with asteroid 1982XB. Presently, the APL NEAR spacecraft is beginning Phase A study. This paper identifies the science objectives and mission goals, outlines the mission scenario, and concludes with a description of the APL NEAR pre-Phase A spacecraft.

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Exploration Of Pluto: Search For Applicable Small Satellite Technology, Robert Staehle, John Carraway, Christopher Salvo, Richard Terrile, Stacy Weinstein, Elaine Hansen Sep 1992

Exploration Of Pluto: Search For Applicable Small Satellite Technology, Robert Staehle, John Carraway, Christopher Salvo, Richard Terrile, Stacy Weinstein, Elaine Hansen

Small Satellite Conference

Pluto is the last known planet in our Solar System awaiting spacecraft reconnaissance. In its eccentric orbit taking it 50 AU from the Sun, Pluto presently has a thin atmosphere containing methane, which is projected to "collapse" back to the icy planet's surface in about three decades, following Pluto's 1989 perihelion pass at 30 AU. Based on ground and Earth-orbit-based observing capabilities limited by Pluto's small size and extreme distance, present top-priority scientific questions for the first mission concern Pluto and Charon's surface geology, morphology and composition, and Pluto's neutral atmosphere composition. Budgetary realities preclude a large, many-instrument flyby spacecraft, …

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Copernicus - Lunar Surface Mapper, Frank Redd, Shaun Anderson Sep 1992

Copernicus - Lunar Surface Mapper, Frank Redd, Shaun Anderson

Small Satellite Conference

The Utah State University (USU) 1991-92 Space Systems Design Team has designed a Lunar Surface Mapper (LSM) to parallel the development of the NASA Office of Exploration lunar initiatives. USU students named the LSM "Copernicus" after the 16th Century Polish astronomer, for whom the large lunar crater on the face of the moon was also named. The top level requirements for the Copernicus LSM are to produce a digital map of the lunar surface with an overall resolution of 12 meters (39.4 ft). It will also identify specified local surface features/areas to be mapped at higher resolutions by follow-on missions. …

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The Space System For The High Energy Transient Experiment, Bob Dill, Rick Fleeter, Richard Warner, Francois Martel, George Ricker Sep 1992

The Space System For The High Energy Transient Experiment, Bob Dill, Rick Fleeter, Richard Warner, Francois Martel, George Ricker

Small Satellite Conference

The High Energy Transient Experiment (HETE) is an astrophysics project funded by NASA and led by the Center for Space Research (CSR) at the Massachusetts Institute of Technology (MIT). It has for principal goal the detection and precise localization of the still mysterious sources of gamma ray bursts. The project is original in many respects. HETE will provide simultaneous observations of bursts in the gamma, X-ray and UV ranges from the same small (250 Ibms) space platform. A network of ground stations around the world will diffuse in real time key information derived from HETE observations to many ground observatories, …

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Mapping Of Earth's Magnetic Field With The Ørsted Satellite, W.R. Baron, K. Leschly, P.L. Thomsen Sep 1992

Mapping Of Earth's Magnetic Field With The Ørsted Satellite, W.R. Baron, K. Leschly, P.L. Thomsen

Small Satellite Conference

The Danish Ørsted satellite will carry three science experiments with the objectives of mapping the Earth's magnetic field and measuring the charged particle environment from a 7801an altitude sun-synchronous polar orbit. The science data generated during the planned one year mission will be used to improve geomagnetic models and study the auroral phenomena. Comprehensive and accurate mapping of the geomagnetic field every 5 to 10 years is of particular interest to geophysical studies. As such, the Ørsted science data return will complement the Magsat (1979-80) and Aristoteles (=2000) mission objectives. Two magnetometers will be mounted on an 8 meter long …

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Space Test Program Activities And Lessons Learned, Lt. David Spackman, Elmer Witte Sep 1992

Space Test Program Activities And Lessons Learned, Lt. David Spackman, Elmer Witte

Small Satellite Conference

The Space Test Program (STP) was established in 1966 to provide space flight for Department of Defense (DOD) space experiments which had no other means of space flight. This paper discusses STP's capabilities and achievements as a provider of space services. STP is now part of a new organization with expanded capabilities to include on-orbit support, launch operations and planning, and sub-orbital launches. With extensive experience acquiring, launching, and operating small satellites, lessons learned from recent missions are presented.

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Marine Corps Tactical Satellite Communications, Walter Daniel, Gavino Rivas, Robert Bruninga Sep 1992

Marine Corps Tactical Satellite Communications, Walter Daniel, Gavino Rivas, Robert Bruninga

Small Satellite Conference

A tactical satellite communications exercise using the DARPA Microsats was conducted by Naval Academy personnel at the Quantico Marine Corps Base in Virginia. Midshipmen used a military UHF radio, a modified amateur radio transmitter, and scanner receivers while a station in Annapolis communicated with them. Voice communications were clear and understandable even when the tactical teams were in the woods. Amateur radio operators and scanner enthusiasts around the eastern half of the United States and Canada successfully monitored the Microsat downlinks during the demonstration.

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Navy/Marine Corps Demonstrations Of The Darpa Microsats, Walter Daniel, Robert Bruninga Sep 1992

Navy/Marine Corps Demonstrations Of The Darpa Microsats, Walter Daniel, Robert Bruninga

Small Satellite Conference

Demonstrations of the DARPA Microsats with an emphasis on Navy and Marine Corps applications were conducted by personnel at the United States Naval Academy. These satellite communications demonstrations used the analog FM mode of the Microsats. Radios used were military transceivers, transmitters composed of laboratory signal generators with broadband power amplifiers, a modified amateur radio UHF transmitter, and commercially-available scanner receivers. Voice demonstrations included equipment checks with DARPA personnel, a tactical exercise at a Marine Corps base, and communications with a U.S. Navy destroyer. Position and status report data beacons were relayed through the Microsats from training vessels to Annapolis. …

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Restoration And Enhancement Of Earth Images From A Low Cost Sampled Video System, Jay Smith Sep 1992

Restoration And Enhancement Of Earth Images From A Low Cost Sampled Video System, Jay Smith

Small Satellite Conference

The WEBERSAT microsat has been in a 800 Km polar orbit of Earth since January of 1990. During this time an on board, low cost, color CCD camera has logged several dozen video images of Earth and heavens. Each new image has presented a unique challenge in restoration and image enhancement.

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Microsat Constellation Control Techniques, Keith Reiss Sep 1992

Microsat Constellation Control Techniques, Keith Reiss

Small Satellite Conference

The first air-launched constellation of seven small experimental communications satellites into an unexpectedly low earth orbit (246 nmi X 192 nmi) resulted in a set of tough flight control demands. In the abbreviated demonstration mission the flight operations team was challenged in rapidly propelling the spacecraft into a useful uniform distribution about the orbit plane and in maintaining the "stations" under adverse conditions. The constellation was injected in perfect order and began mission operations immediately. However, each spacecraft's attitude control system coupled with the force of heavy atmospheric drag to produce variable in-plane phase drifts that required constant observation and …

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Chemical Release Observation Program Description And Flight Results, Stephen Nichols, Jeffrey Wise, Ian Strong Sep 1992

Chemical Release Observation Program Description And Flight Results, Stephen Nichols, Jeffrey Wise, Ian Strong

Small Satellite Conference

The Chemical Release Observation (CRO) program developed three small satellites that were deployed from the Shuttle on flight STS-39. These were small experimental satellites built with a minimum of paperwork. While meeting all the necessary NASAISTS requirements. Each satellite contained a chemical (either hydrazine or an oxidizer) which was released on ground command. The satellites were approximately 18" diameter and 31" high. and weighed 160 to 195 pounds when loaded. The satellites carried 60 pounds of MMH (MonoMethyl Hydrazine), 52 pounds of UDMH (Unsymmetrical DiMethyl Hydrazine) and 11 pounds of N10 4 (Nitrogen Tetroxide). The satellites were designed and built …

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Integrated Space Experiment Satellite (Ises) Low Cost Stabilization Subsystem Performance, George Sebestyen Sep 1992

Integrated Space Experiment Satellite (Ises) Low Cost Stabilization Subsystem Performance, George Sebestyen

Small Satellite Conference

On June 29, 1991 the ISES satellite was launched into a 450 nm polar orbit. The 183 lbs satellite is a 30 inch diameter, 16 inch high, 16-sided cylinder to provide Nadir-pointing stabilization for a helix antenna associated with the Radiation Experiment (REX) payload of the satellite. The stabilization system uses a 20 ft gravity gradient boom, hysteresis rod damping, a 3-axis magnetometer, a sun sensor and torque coils. Through careful design of the gravity gradient boom and magnetic grooming of the satellite, excellent stability was achieved. The U.S. Air Force commended ISES as the best gravity gradient stabilized satellite. …

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The Effects Of Momentum Bias On A Gravity Gradient Stabilized Spacecraft With Active Magnetic Control, Parimal Pal, Stephen Fox Sep 1992

The Effects Of Momentum Bias On A Gravity Gradient Stabilized Spacecraft With Active Magnetic Control, Parimal Pal, Stephen Fox

Small Satellite Conference

The improvements achieved by adding a momentum bias wheel to a Gravity Gradient (GG) stabilized spacecraft are evaluated. Mass, power, and computational processing requirements, as well as performance, are compared for three Attitude Determination and Control Subsystem (ADACS) scenarios. Spacecraft which require low mass and power have long Incorporated GG torques as a passive stabilization technique. The spacecraft is oriented in the general direction required by the mission, but the overall attitude and attitude rate errors are not exceptionally tight. In order to improve the spacecraft pointing accuracies the GG stabilized ADACS .can be augmented by an active control technique. …

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Information And Misinformation Regarding Ischemia Of Heart Muscle Tissue. The Cause Of Cell Death During Blood Reperfusion And Reactivation Of Heart Muscle Tissue After Prolonged Ischemia, Fritiof S. Sjöstrand Sep 1992

Information And Misinformation Regarding Ischemia Of Heart Muscle Tissue. The Cause Of Cell Death During Blood Reperfusion And Reactivation Of Heart Muscle Tissue After Prolonged Ischemia, Fritiof S. Sjöstrand

Scanning Microscopy

An electron microscopic study of heart muscle tissue exposed to six hours ischemia and prepared according to the low denaturation embedding technique revealed a structural modification confined to the mitochondrial cristae. The modification consisted of a removal of Krebs cycle enzymes from the cristae. Reperfusion of the ischemic tissue after four hours ischemia led to extensive breakdown of the mitochondrial structure and contractility could not be restored. However, when after six hours ischemia the ischemic tissue was reperfused with blood, the composition of which had been modified to stimulate mitochondrial function, no additional structural changes were observed and contractility was …

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Computer Aided Phase Determination By Electron Probe Microanalysis, P. Nagy Sep 1992

Computer Aided Phase Determination By Electron Probe Microanalysis, P. Nagy

Scanning Microscopy

A measuring procedure and a computer program have been developed for energy dispersive microanalysis to study segregation properties of various bulk, polished samples (alloys and ceramics). A few hundred sampling points were selected at random or regularly forming a grid pattern on the surface of the sample. Energy dispersive spectra were stored and ZAF corrected, and the obtained concentrations were evaluated statistically. An IBM AT compatible computer was used to calculate concentration distribution functions of the elements present in the sample. In addition to the usual statistical values, several types of concentration distribution functions were calculated. The method was tested …

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Microclimates And Tree Growth In Three Urban Spaces, Roger Kjelgren, James R. Clark Sep 1992

Microclimates And Tree Growth In Three Urban Spaces, Roger Kjelgren, James R. Clark

Plants, Soils, and Climate Faculty Publications

Microclimates characteristic of urban park, plaza, and canyon spaces were related to physiology and growth of even-aged sweetgum (Liquidambar styraciflua L.) street trees. Microclimates, tree growth, and physiological responses were characterized diurnally and seasonally. Park and plaza sites received unobstructed sunlight while the canyon was limited to four hours of direct solar radiation in midsummer. Potential seasonal insolation was 44 per cent of the potential maximum at the canyon and over 90 per cent at the park. Heating from paved surfaces at the plaza resulted in cumulative pan evaporation nearly 50 per cent greater than the other sites. Tree growth …

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Publishing Books, Ted Pease Jul 1992

Publishing Books, Ted Pease

Journalism and Communication Faculty Publications

WISE COMMENTATORS have long evaluated books and bookmaking. "Man builds no structure which outlives a book," wrote Eugene Fitch Ware in The Book, and Justin M'Carthy's A Ballade of Book-Making declared, "The critics challenge and defend ... of making books there is no end." Others have written loving odes to the book. Garrison Keillor, for instance: The book is a "great and ancient invention," he marveled, "slow to hatch, as durable as a turtle, light and shapely as befits a descendant of the tree .... A handsome, useful object begotten by the passion for truth ... [books] contain our common …

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Mechanisms Of Ciliary Movement: Contributions From Electron Microscopy, Peter Satir Jun 1992

Mechanisms Of Ciliary Movement: Contributions From Electron Microscopy, Peter Satir

Scanning Microscopy

A brief review of important contributions of electron microscopy to the study of ciliary motility is presented. The electron microscope was used to show the universality of axonemal structure of cilia, and to develop the sliding microtubule model of ciliary motility and later the switch point hypothesis to explain the conversion of sliding into bending. Unexpectedly, insights into the importance of cilia in human health have stemmed from these studies.

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