Applications Technology Satellite Research Articles

A Sight for Sore Eyes: The Return of True Color to Geostationary Satellites

Abstract In 1967, at the dawn of the satellite era, the Applications Technology Satellite 3 (ATS-3) provided the first full-disk “true color” images of Earth. With its depiction of blue oceans, golden deserts, and green forestlands beneath white clouds, the imagery captured the iconic Blue Marble in a way that resonates strongly with human perception. After ATS-3, the standard fare of geostationary satellites entailed a single visible band with additional infrared spectral channels. While single-band visible satisfied the basic user requirements of daytime imagery, the loss of true-color capability and its inherent capability to distinguish myriad atmospheric and surface features via coloration left a notable void. Nearly half a century later, with the launch of Japan’s Himawari-8 in October 2014, there is once again a geostationary sensor—the Advanced Himawari Imager (AHI)—containing the multispectral visible bands required notionally for true color. However, it soon became apparent that AHI’s “green” band, centered at 0.51 μm, was not aligned with the chlorophyll reflectance signature near 0.55 μm. As a result, vegetation appears browner and deserts appear redder than legacy true-color imagery. Here, we describe a technique that attempts to mitigate these issues by blending information from a ref lective-infrared band at 0.86 μm to form a “hybrid” green band. When combining this method with Rayleigh corrections, AHI’s true-color performance is found to be consistent with that of the optimal 0.55-μm band, offering a stopgap solution adaptable to future satellites of similar design.

A dynamic global model of the plasmasphere

The three-dimensional Global Plasmasphere Ionosphere Density (GPID) model simulates the global-scale dynamics of the magnetic field-aligned ion and electron densities within the plasmasphere and plasmatrough ( L⩽9) by simultaneously modeling the field-aligned plasma density distributions of several thousand magnetic flux tubes distributed uniformly about the Earth. GPID uses a dynamical diffusive equilibrium approach within each magnetic flux tube that allows it to model the temporal variations in H + and O + densities, the dominant ions in the topside ionosphere and plasmasphere. Using the International Reference Ionosphere (IRI) to model the ionosphere and a simple electron density profile above the ionosphere in the polar regions ( L>9), GPID is able to simulate electron densities globally from ground level to an altitude of ∼50,000 km . Comparisons of GPID predictions with (1) direct plasmaspheric observations obtained from Low Earth Orbit (LEO) satellites equipped with Global Position System (GPS) receivers, (2) ground-based radio beacon measurements using the Applications Technology Satellite 6 (ATS-6) satellite and (3) several empirical plasmasphere models, show good agreement. This good agreement indicates the value of the GPID model as a tool for investigating the physics of the inner magnetopshere.

Ion Propulsion Development Projects in U.S.: Space Electric Rocket Test I to Deep Space 1

The historical background and characteristics of the experimental flights of ion propulsion systems and the major ground-based technology demonstrations are reviewed. The results of the first successful ion engine flight in 1964, Space Electric Rocket Test (SERT) I, which demonstrated ion beam neutralization, are discussed along with the extended operation of SERT II starting in 1970. These results together with the technologies employed on the early cesium engine flights, the applications technology satellite series, and the ground-test demonstrations, have provided the evolutionary path for the development of xenon ion thruster component technologies, control systems, and power circuit implementations. In the 1997-1999 period, the communication satellite flights using ion engine systems and the Deep Space 1 flight confirmed that these auxiliary and primary propulsion systems have advanced to a high level of flight readiness.

Ghost stories

Occasionally, peculiar features show up in otherwise reliable data sets. These features can almost invariably be explained as the result of adverse effects on spacecraft and instrumentation by the environment external to the sensor itself. For example, within weeks after the Applications Technology Satellite 5 (ATS 5) was launched into geosynchronous orbit in August 1969, a strange pattern was observed in the behavior of the 50‐eV to 50‐keV particles near local midnight (see the article “Spacecraft Charging at Synchronous Orbit,” by S. E. DeForest, Journal of Geophysical Research, vol. 77, p. 651, 1972). After careful analysis, it was found that ATS 5 was charging to potentials as high as 10,000 volts during spacecraft eclipse. DeForest notes that the effects of local charging near particle detectors could “snarl the particle optics in an indecipherable manner that probably would resemble interesting new physical phenomena.” Other diverse reasons for unusual effects in data and systems are cosmic ray hits on imaging electronics, “glinting” from adjacent spacecraft, physical contamination from spacecraft outgassing or debris, offsets caused by improperly shielded electronics, and simple instrument degradation caused by age and/or radiation dose.

The APT on the Polar Orbiting Weather Satellites

The receipt of the Pioneer Award has given me a chance to look back over my professional life and the opportunity to take stock of how I helped shape a small part of the world. While I hope this process entertains my contemporaries, more importantly, I hope it stimulates those that are engaged in actively shaping the present. To describe the need for automatic picture transmission (APT), I must retrace the historical development of meteorological satellites. The idea for weather observations from a satellite originated with a small group of meteorologists at the U.S. Army Signal Corps Research and Development Lab. at Ft. Monmouth, N.J., and resulted in the design of Vanguard II. The Tiros and TOS series of satellites, and the design of Nimbus, followed soon thereafter. However, a faster picture dissemination than was available at that time was needed, and it was this necessity that sparked the development of APT. Nimbus was originally intended to be an operational system, but the advent of simpler, less costly stabilization systems made the Tiros evolution the clear winner. The geosynchronous weather satellites started nearly a decade later and evolved from the NASA Application Technology Satellite (ATS) series. All three systems, existing polar orbiting weather satellites, APT, and geosynchronous weather satellites, have changed meteorology and the reliability of weather forecasting profoundly.

Satellite drifts off station

After more than 18 years of service, the first Applications Technology Satellite (ATS‐1) has failed to respond to commands to correct its eastward drift from geostationary position over the Gilbert Islands in the western Pacific, according to the National Aeronautics and Space Administration (NASA). ATS‐1 provided the first transmission of full‐earth, cloud cover pictures from geosynchronous orbit, the forerunners of the hemispheric weather pictures seen on television today. The satellite also provided the first transmission of real time television pictures from the mid‐Pacific in 1967, when it relayed pictures of the Apollo 4 splashdown.

NASA's revitalized role in satellite communications

The early efforts of NASA in space communications development strengthened the general level of confi. dence in the use of satellite technology for telecommunications. Soon afterward, the formation of organizations such as INTELSAT and the Comsat Corporation and their subsequent progress brought reliable communications via satellite at affordable rates. These capabilities have grown worldwide through new industries that are fostering the principles of the 1958 Space Act to exploit the peaceful benefits of space for the betterment of mankind. As a result of this recognized success arid the pressures of budget cutting, NASA's role in this pioneering effort was slowed in 1973. The flight projects then under development, the Applications Technology Satellite Six (ATS-6) and the Communications Technology Satellite (CTS) were allowed to continue but the research projects were reduced to a small ground-based effort directed toward long-term high-risk components and techniques. Now, as we enter the 1980's, the situation is reversed. The principal NASA spacecrafts are retired, but the program for research and development and flight experiments is revived.

The Use of Communication Satellites for the Delivery of Education and Training Services: A Brief History, and a Look at the Present and Future

The United States began to think seriously about a domestic satellite in the late 60's. Educational interests were one of the first to begin lobbying for the Federal Communications Commission (FCC) to rule that carriers provide special rates. In 1969, Alaskans asked the National Aeronautics and Space Administration (NASA) to use the Applications Technology Satellite Number 1 (ATS-1) for medical and education research. By 1970, the FCC decided to ask for proposals for domestic satellite systems to include provisions for low cost or free public services with special emphasis on education. Eight companies responded. After holding hearings throughout 1972, the FCC decided that sufficient information was not available about the economic viability of satellites to pursue the education topic. The first domestic satellite was provided by Western Union in 1974 followed by Radio Corporation of America (RCA) in 1975 and American Telephone & Telegraph (AT&T) in 1977; Satellite Business Systems (SBS) Corporation will provide another system in 1980. American Satellite Corporation began offering services in 1974 using the Western Union satellite. In addition, a maritime satellite (MARISAT) initiated services in the Atlantic Ocean to the U.S. Navy and Merchant fleets in 1976. While rates for special usage can be negotiated with the satellite common carriers, most of the carriers do not offer the technology that would permit widespread use of communications satellites for education and training unless existing systems are shared by many users. With the continuing proliferation of usage by business, industry and government, education may be able to negotiate the sharing of time and costs with these entities and obtain services which normally would be out of reach in the foreseeable future.

An Investigation of Surface Albedo Variations during the Recent Sahel Drought

Applications Technology Satellite (ATS) 3 green sensor data are used to measure surface reflectance variations in the Sahara/Sahel during the recent drought period 1967–74. The magnitude of the seasonal reflectance change is shown to be as much as 80% for years of normal precipitation and less than 50% for drought years. Year-to-year comparisons during both wet and dry seasons reveal the existence of a surface reflectance cycle coincident with the drought intensity. The relationship between the green reflectance and solar albedo is examined and estimated to be about 0.6 times the reflectance change observed by the green channel.

Applications technology satellite program

The Applications Technology Satellite (ATS) program evolved from Project SYNCOM and the Advanced SYNCOM program to develop geosynchronous spacecraft technology made possible by the increased capability of the Atlas-Agena launch vehicle. The ATS-1-5 program developed spin stabilized and gravity gradient stabilized spacecraft for geosynchronous orbit; Earth-oriented antennas for increased antenna gain; Earth-scanning meteorological experiments for continuous weather monitoring; and made possible satellite communications to mobile terminals. The ATS-6 program developed a space-deployed, high-gain antenna for color television broadcast to low-cost ground terminals and precise spacecraft attitude control for pointing, slewing, and tracking applications. All of the ATS program objectives were successfully met, except for the gravity gradient experiments. ATS-1, -3, -5, and -6 are in orbit and operational.

The antenna system of a distress buoy for use in a maritime satellite communication system (MARSAT)

Two different types of antenna systems for a distress buoy for use in the maritime satellite communication system (MARSAT) are described. The buoy radiates signals alternately on the frequencies 2182 kHz (medium frequency (MF) beacon) and 1.65 GHz ( L band beacon). The L band antennas had to be combined with the MF antenna of a commercial buoy. The antenna systems have been tested with success during the application technology satellite (ATS-6) experiments and during a previous European Space Research Organization (ESRO) balloon communication experiment [1].

ATS-6 Satellite Instructional Television Experiment

The Satellite Instructional Television Experiment (SITE) is scheduled for the second year of satellite operation. Applications Technology Satellite (ATS-6) will receive C-band video signals frorn Abmedabad and Delhi, India, and will retransmitt the video and two audio sub-carriers at 860 MHz to 6 clusters of 400 direct-receive stations for a total of 2400 direct-receive stations. Morning programs of 1.5 hours per day are designed for classroom use, and evening programs of 2.5 hours duration are designed for village adult education. Indian production antennas and television sets have been tested and found to meet specifications, and a successful experiment is anticipated.

ATS-6 Millimeter Wave Propagation and Communications Experiments at 20 and 30 GHz

The Applications Technology Satellite (ATS-6) Millimeter Wave Experiment, developed and implemented by the NASA Goddard Space Flight Center, has provided the first direct measurements of 20-and 30-GHz Earth-space links from an orbiting satellite. Studies at eleven locations in the continental United States were directed at an evaluation of rain attenuation effects, scintillations, depolarization, site diversity, coherence bandwidth, and analog and digital communications techniques In addition to direct measurements on the 20-and 30-GHz links, methods of attenuation prediction with radars, rain gauges, and radiometers were developed and compared with the directly measured attenuation. This paper presents a review of the major results of the first year of measurements with ATS-6, with emphasis on the impact of the measurements on millimeter wave space systems design.

ATS-6 Experiment Summary

The ATS-6 is the most advanced experimental satellite that has evolved from the Application Technology Satellite Program conducted and implemented by NASA Goddard Space Flight Center (NASA/GSFC). This project utilizes a state-of-the-art spacecraft and ground terminal network to perform advance studies and to conduct technological demonstrations in a large number of scientific areas. The design and implementation of this unique spacecraft permitted multiple experimentation simultaneously. The control of the spacecraft is performed at ATS Operational Control Center (ATSOCC) located at NASA/GSFC. Experimentation which was performed covered a wide spectrum of communications, technological, meterorological, and scientific subjects. Three principal ground terminals are utilized to assist the experimenters to acquire data. Data reduction and analysis are performed by the many facilities at NASA/GSFC in support of the experimenters.

ATS-6 Spacecraft Attitude Precision Pointing&Slewing Adaptive Control Experiment

The primary objective of the Spacecraft Attitude Precision Pointing and Slewing Adaptive Control (SAPPSAC) Experiment is to establish feasibility and evaluate capabilities of a ground-based spacecraft attitude control system, wherein RF command and telemetry links, together with a ground station on-line minicomputer, perform closed loop attitude control of the Applications Technology Satellite -6 (ATS-6). The ground processor is described, including operational characteristics and the controller software. Attitude maneuvers include precision pointing to fixed targets, slewing between targets, and generation of prescribed ground tracks. Test results show high performance and reliability for over 30 h of on-line control with no serious anomalies. Attitude stabilization relative to a prescribed target has been achieved to better than 0.007° in pitch and roll and 0.020° in yaw for a period of 43 min. Ground tracks were generated which had maximum latitude/longitude deviations less than 0.150 from reference.

ATS-6 Significance

The Applications Technology Satellite (ATS-6), the most powerful, most sophisticated, most versatile communications satellite flown to date, is the last of NASA's experimental satellites intended to demonstrate major advances in communications and spacecraft technology. It is a multipurpose, multidisciplinary spacecraft whose principal objectives were to demonstrate a large, unfurlable antenna structure and precise pointing and attitude control in the synchronous orbit The spacecraft carries 27 different experiments, 3 of which demonstrate users' applications of satellite communications. Significant advances in antenna technology, precise attitude control, materials technology, spacecraft structures, and thermal control have been successfully demonstrated. The most significant accomplishments of the ATS-6 mission are the demonstration of the practicality of satellite broadcasting to small, simple, inexpensive ground stations and the uses of this potential service in the solution of social problems involving education and health care. The success of these initial demonstrations has led ATS-6 experimenters and potential users to incorporate a Public Service Satellite Consortium dedicated to the provision of satellite broadcasting services for educational and health-care applications.

The satellite technology demonstration and health-education telecommunications experiments on ATS-6

The latest in N.A.S.A.’s series of applications technology satellites provides the most powerful space communications capability yet devised. The satellite technology demonstration will explore the feasibility of a satellite-based television system for isolated rural populations and will test and evaluate user acceptance and the cost of various delivery modes using a variety of materials. Television programmes and supporting materials will be devoted primarily to ‘career education’ for junior high school students. Thirty-two schools in six Rocky Mountain states will be equipped with receiving stations. Three schools in each of the six states will have both receive and response capability. In addition, twelve noncommercial television stations will receive the programmes from the satellite and re-transmit them by conventional means.

EOLE Balloon and ATS Cloud Motion Comparisons

Comparisons are made between winds obtained from EOLE balloons and winds determined from cloud motions as observed from the Applications Technology Satellites, ATS-1 and ATS-3. The results show that the mean winds determined from EOLE balloons are greater in speed than mean winds derived from cloud motion observations. Inspection of the total set of comparisons lead one to conclude that the cloud motion winds in the 20–50°S latitude band apply to a level lower than 200 mb. The mean differences become smaller toward the equator and the results further suggest that the cloud motion winds apply to altitudes higher than 200 mb equatorward of 20°S.

A Case Study of Atlantic Cloud Clusters: Part 1. Morphology and Thermodynamic Structure

Abstract Ground based data from the Barbados Oceanographic and Meteorological Experiment (BOMEX) have been combined with satellite data in a study of the time changing cloud and thermodynamic structure of cloud clusters and their environment. Digital images from the third Applications Technology Satellite (ATS-3) were analyzed as “movie loop” sequences on a computer controlled image storage, display, and processing device called McIDAS. Three-to six-hourly soundings from the five BOMEX ships were corrected for radiation and lag errors in moisture, then analyzed in time sections of temperature anomaly, relative humidity, and equivalent potential temperature. The integration of satellite and surface sounding data was accomplished through plexiglas models in which time section strips were treated as space sections. Extended meridional and quasi-zonal space sections of temperature anomaly, relative humidity, and equivalent potential temperature then were constructed from the models. The time sections reveal a...

TV-a challenge and an opportunity

The sixth Applications Technology Satellite (ATS-6), described as the world’s largest and most powerful communications spacecraft, is the first of a new generation of space robots. It is designed to transmit from synchronous orbit with power sufficient for its signals to be received by small and inexpensive ground stations. Educational television programming to isolated regions where terrestrial TV coverage is not feasible is being planned to demonstrate the capabilities of this 1,360 kg. craft. After the first year of operation, the ATS is to be moved over the Indian Ocean to transmit instructional material to some 3,000 community receivers in rural and remote villages in India. The satellite instructional television experiment should answer whether community sets used for direct reception could be maintained in working order; whether the instructional and educational programmes are effective; whether the results are adequate and commensurate with the money spent; and a host of such other questions.