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At least 829 records · Page 46

Satellite broadcasting - Capabilities for public service

Satellite broadcast services to support health-care and educational transmissions must work with small, low-cost terminals in allocated radio-frequency bands. The ATS-6 spacecraft has successfully demonstrated such capability in the bands of non-technical users. It supports interactive television broadcasting to simple, low-cost terminals in a nationwide series of experiments in the delivery of health-care and educational services. ATS-6 achieves this capability with a very large antenna and moderate transmitter power. The coverage limitations inherent in this approach will be overcome by the joint U.S.-Canadian Communications Technology Satellite to be launched in December 1975. The CTS will demonstrate broadcast capability with new, high-power technology in a newly-allocated radio-frequency band. This will make it possible to use smaller antennas, greatly enlarging the area coverage available to the many nontechnical experimenters using CTS for their own needs. A practical application of these technologies is now in development for operational broadcasting services in Japan.

Marsten, R. B.↗

Apollo 14 and 15 missions: Intermittent steerable antenna operation

An attempt was made to determine the cause of antenna tracking interruptions during Apollo 14 and Apollo 15 missions prior to powered descent, and after ascent from the lunar surface but before rendezvous. Probable causes examined include: (1) amplitude modulation on the uplink radio frequency carrier, (2) noise capacitively or inductively coupled into the track error line, and (3) hardware problems resulting in tracking loop instabilities. It was determined that amplitude modulation caused the antenna oscillations. The corrective procedures taken are given.

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The high-resolution structure of the Centaurus A nucleus at 2.3 and 8.4 GHz

VLBI observations of the nucleus of Centaurus A have been made at two frequencies with an array of five Australian radio telescopes as part of the Southern Hemisphere VLBI Experiment. Observations were made at 2.3 GHz with all five antennas, while only two were employed at 8.4 GHz. At 2.3 GHz seven tracks in the (u,v) plane with coverage of 6-8 hr each were obtained, yielding significant information on the structure of the nuclear jet. At 8.4 GHz a compact unresolved core was detected as well. It is found that the source consists of the compact self-absorbed core, a jet containing a set of three knots extending from 100 to 160 mas from the core, and a very long, narrow component elongated along the same position angle as the knots. The allowable range for the position angle of the jet is 51 + or - 3 deg, in agreement with that of the radio and X-ray structure on arcsecond and arcminute scales. The jet has brightened at 2.3 GHz by about 4 Jy, a factor of nearly 3, since the early 1970s, 1.8 Jy of which has occurred in the last 2 yr with no discernable changes in structure.

Meier, David L.↗

New results and techniques in space radio astronomy.

The methods and results of early space radioastronomy experiments are reviewed, with emphasis on the RAE 1 spacecraft which was designed specifically and exclusively for radio astronomical studies. The RAE 1 carries two gravity-gradient-stabilized 229-m traveling-wave V-antennas, a 37-m dipole antenna, and a number of radiometer systems to provide measurements over the 0.2 to 9.2 MHz frequency range with a time resolution of 0.5 sec and an absolute accuracy of plus or minus 25%. Observations of solar bursts at frequencies down to 0.2 MHz provide new information on the density, plasma velocity, and dynamics of coronal streamers out to distances greater than 50 solar radii. New information on the distribution of the ionized component of the interstellar medium is being obtained from galactic continuum background maps at frequencies around 4 MHz. Cosmic noise background spectra measured down to 0.5 MHz produce new estimates on the interstellar flux of cosmic rays, on magnetic fields in the galactic halo, and on distant extragalactic radio sources.

Alexander, J. K.↗

Helicopter Rotor Antenna

This effort was directed toward demonstration of the efficacy of a concept for mitigation of the rotor blade modulation problem in helicopter communications. An antenna is envisioned with radiating elements mounted on the rotor and rotating with it. The rf signals are coupled to the radio stationary with respect to the airframe via a coupler of unique design. The coupler has an rf cavity within which a mode is established and the field distribution of this mode is sampled by probes rotating with the radiating elements. In this manner the radiated pattern is "despun" with respect to the rotor. Theoretical analysis has indicated that this arrangement will be less susceptible to rotor blade modulation that would be a conventional fixed mounted antenna. A small coupler operating at S-band was designed, fabricated, and mounted on a mockup representative of a helicopter body. A small electric motor was installed to rotate the rotor portion of the coupler along with a set of radiating elements during testing. This test article was be evaluated using the JPL Mesa Antenna Measurement Facility to establish its ability to mitigate rotor blade modulation. It was found that indeed such a coupler will result in a despun pattern and that such a pattern can be effective in mitigation of rotor blade modulation.

Pogorzelski, Ronald J.↗

Indoor Occupant Counting by RF Backscattering

Building HVAC (heating, ventilation and air conditioning) consumes approximately 13% of all energy consumption in USA. Motion detectors, cameras and user programmable thermostats have been shown to be ineffective for HVAC controls to save energy, mostly due to the user concerns of comfort, reliability and privacy. A new HVAC control system based on real-time occupant counting that is fully automated, highly accurate, economically sensible and preserving privacy and aesthetics can thus bring forth a disruptive impact to this large energy sector. Our indoor occupant monitoring technology is based on the radio-frequency identification system (RFID), deployed in the room, not on the occupants. One reader with four antennas can be deployed on the ceiling or behind the ceiling panels for every thousand square feet in home, office and assisted living, with or without room partitions. The sticker-like passive tag, 10 cents each and maintenance-free, are profusely hidden on the wall or inside the furniture at arbitrary position, preserving privacy and aesthetics. The large number of tags can realize diverse observation points to accommodate arbitrary room layouts, which is impractical by other active units of camera, infrared, radar or lidar. With 20 tags, the system can reliably detect the number of occupants. For 100 tags, occupant posture and location can be known. The technology has been verified in the research labs and test buildings with very high accuracy. When the real-time occupant number can be accurately known without assuming devices on occupants or occupant motion, the building HVAC system can be automated to achieve building energy saving without sacrificing occupant comfort. According to our limited testing in a few types of building models and the simplified cost calculation, the RFID system has low overall cost in production, deployment, operation and maintenance. The signal processing algorithm based on machine learning requires very small number of training cases as most learning is transferrable for various layouts, and very low computational needs during operation, according to our testing in four different room sizes and layouts. In our preliminary estimate from HVAC saving alone, the RFID system can potentially pay for itself within 1.5 years, in addition to the other enhancement in building automation systems (BAS). Our commercialization strategy and business pitch deck focus on venturing this Cornell occupant monitoring technology into BAS and energy management markets. We have identified three broad BAS market segments of senior living, residential buildings, and office buildings. We have put together the minimum viable product characteristics for these identified segments, including analyses on total cost and competing technologies, as well as the fit and technical gaps for these market segments. We intend to bring the technology to market by licensing or partnering with existing BAS vendors. A list of potential collaborators and licensing partner candidates was assembled for different aspects of integrating our technology into a potential product that can be used with BAS.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Multiband Photonic Phased-Array Antenna

A multiband phased-array antenna (PAA) can reduce the number of antennas on shipboard platforms while offering significantly improved performance. Crystal Research, Inc., has developed a multiband photonic antenna that is based on a high-speed, optical, true-time-delay beamformer. It is capable of simultaneously steering multiple independent radio frequency (RF) beams in less than 1,000 nanoseconds. This high steering speed is 3 orders of magnitude faster than any existing optical beamformer. Unlike other approaches, this technology uses a single controlling device per operation band, eliminating the need for massive optical switches, laser diodes, and fiber Bragg gratings. More importantly, only one beamformer is needed for all antenna elements.

Tang, Suning↗

NASA Tech Briefs, June 2007

Topics covered include: High-Accuracy, High-Dynamic-Range Phase-Measurement System; Simple, Compact, Safe Impact Tester; Multi-Antenna Radar Systems for Doppler Rain Measurements; 600-GHz Electronically Tunable Vector Measurement System; Modular Architecture for the Measurement of Space Radiation; VLSI Design of a Turbo Decoder; Architecture of an Autonomous Radio Receiver; Improved On-Chip Measurement of Delay in an FPGA or ASIC; Resource Selection and Ranking; Accident/Mishap Investigation System; Simplified Identification of mRNA or DNA in Whole Cells; Printed Multi-Turn Loop Antennas for RF Biotelemetry; Making Ternary Quantum Dots From Single-Source Precursors; Improved Single-Source Precursors for Solar-Cell Absorbers; Spray CVD for Making Solar-Cell Absorber Layers; Glass/BNNT Composite for Sealing Solid Oxide Fuel Cells; A Method of Assembling Compact Coherent Fiber-Optic Bundles; Manufacturing Diamond Under Very High Pressure; Ring-Resonator/Sol-Gel Interferometric Immunosensor; Compact Fuel-Cell System Would Consume Neat Methanol; Algorithm Would Enable Robots to Solve Problems Creatively; Hypothetical Scenario Generator for Fault-Tolerant Diagnosis; Smart Data Node in the Sky; Pseudo-Waypoint Guidance for Proximity Spacecraft Maneuvers; Update on Controlling Herds of Cooperative Robots; and Simulation and Testing of Maneuvering of a Planetary Rover.

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A planetary radio astronomy discussion of the 1.55 cm microwave emission of the earth

Using 1.55 cm observations of the earth made by the Electrically Scanned Microwave Radiometer (ESMR) experiment on Nimbus 5, the appearance of the earth from Venus is simulated. A single antenna unable to resolve the earth's disk would give a time-averaged disk temperature of 183 K. In one rotation, the disk temperature would vary from 194 K to 172 K. During the 1973 inferior conjunction, a radio telescope with 1 arc sec resolution would resolve most of the major surface features of the earth.

Webster, W. J., Jr.↗

Characterization and Calibration of the 12-m Antenna in Warkworth, New Zealand

The New Zealand 12-m antenna is scheduled to start participating in regular IVS VLBI sessions from the middle of 2010. Characterization procedures and results of calibration of the New Zealand 12- m radio telescope are presented, including the main reflector surface accuracy measurement, pointing model creation, and the system equivalent flux density (SEFD) determination in both S and X bands. Important issues of network connectivity, co-located geodetic systems, and the use of the antenna in education are also discussed.

Gulyaev, Sergei↗

Collisional quenching of OH radio emission from comet Hale-Bopp

Observations of comets in the 18-cm OH transitions offer a means to probe gas production, kinematics, and OH excitation in comets. We present initial results of OH observations of comet Hale-Bopp obtained with the NRAO 43 m antenna located in Greenbank, WV. Maps of the emission provide strong constraints on the amount of quenching of the inversion of the OH ground state A-doublet in the coma. Analysis of the total radio OH flux and maps of its radial brightness distribution indicate a quenched region on the order of approximately 500,000 km during March and April 1997. This large value is generally consistent with previous observations of radio OH quenching in lower production rate comets when the high production rate of comet Hale-Bopp is considered.

NASA Discipline Exobiology↗

The M.I.T. Ku-band radio interferometer.

The construction of a Ku-band radio interferometer and some preliminary observations are reported. The interferometer was built for the purpose of mapping discrete radio sources like the Crab Nebula, Cassiopeia A, and Cygnus A. It has two 8-ft parabolic antennas operating at 17.128 GHz. The maximum baseline of 100 m corresponds to a resolution of 35 sec of arc. A PDP-8 computer is incorporated in the system and is used for pointing, tracking, delay compensation, and real-time data analysis. The phase stability of the system was better than 10 deg over a period of 2 hours. Consistent fringe components were obtained from the Crab Nebula with a baseline set at 8 m.

Papadopoulos, G. D.↗

Seeing Comet IRAS with a radar eye

IRAS data in April 1983 held evidence for the approach of a comet which would pass close enough to earth to bounce radar signals off the cometary nucleus. The closest pass was calculated to be 450,000 km. Ephemerides were prepared for the object while radio observatory tracking schedules were arranged. S-band observations were selected for the JPL 64 m antenna to obtain 2.7 arcmin resolution. A 400 kW signal was generated. Two 4 hr observational periods were achieved, revealing a rough, faceted surface by using S-band in the first run and the X-band in the second. The comet was concluded irregularly shaped and roughly elliptical, with a 2 d period.

Jurgens, R. F.↗

Environmental projects. Volume 12: Friable asbestos abatement, GDSCC

The Goldstone Deep Space Communications Complex (GDSCC) is part of the NASA Deep Space Network, one of the world's largest and most sensitive scientific telecommunications and radio navigation networks. Activities at the GDSCC are carried out in support of six large parabolic dish antennas. These activities may give rise to a variety of environmental hazards, particularly the danger of exposure of GDSCC personnel to asbestos fibers that have been shown to be responsible for such serious ailments as asbestosis, lung cancer, and mesothelioma. Asbestos-containing materials (ACM's) were used in the construction of many of the approximately 100 buildings and structures that were built at the GDSCC during a 30-year period from the 1950s through 1980s. The friable asbestos-abatement program at the GDSCC is presented which consists of text, illustrations, and tables that describe the friable asbestos abatement carried out at the GDSCC from December 21, 1988 through May 11, 1989.

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Environmental projects. Volume 13: Underground storage tanks, removal and replacement. Goldstone Deep Space Communications Complex

The Goldstone Deep Space Communications Complex (GDSCC), located in the Mojave Desert about 40 miles north of Barstow, California, and about 160 miles northeast of Pasadena, is part of the National Aeronautics and Space Administration's (NASA's) Deep Space Network, one of the world's largest and most sensitive scientific telecommunications and radio navigation networks. Activities at the GDSCC are carried out in support of six large parabolic dish antennas. As a large-scale facility located in a remote, isolated desert region, the GDSCC operations require numerous on-site storage facilities for gasoline, diesel oil, hydraulic oil, and waste oil. These fluids are stored in underground storage tanks (USTs). This present volume describes what happened to the 26 USTs that remained at the GDSCC. Twenty-four of these USTs were constructed of carbon steel without any coating for corrosion protection, and without secondary containment or leak detection. Two remaining USTs were constructed of fiberglass-coated carbon steel but without secondary containment or leak protection. Of the 26 USTs that remained at the GDSCC, 23 were cleaned, removed from the ground, cut up, and hauled away from the GDSCC for environmentally acceptable disposal. Three USTs were permanently closed (abandoned in place).

Bengelsdorf, Irv↗

Approximating Effect Of Spherical Radiation Pattern

Time-division multiple-access TDMA multichannels radio communication system implements scheme of temporal and spatial multiplexing of signals to approximate effect of spherical antenna radiation pattern. Signal to be transmitted sped up by factor of n and transmitted in n replicas via n antennas. During reception, incoming signal processed by use of maximum-signal-selection or diversity-reception demodulated-signal-combining technique.

Sickles, Louis, II↗

Video Guidance Sensors Using Remotely Activated Targets

Four updated video guidance sensor (VGS) systems have been proposed. As described in a previous NASA Tech Briefs article, a VGS system is an optoelectronic system that provides guidance for automated docking of two vehicles. The VGS provides relative position and attitude (6-DOF) information between the VGS and its target. In the original intended application, the two vehicles would be spacecraft, but the basic principles of design and operation of the system are applicable to aircraft, robots, objects maneuvered by cranes, or other objects that may be required to be aligned and brought together automatically or under remote control. In the first two of the four VGS systems as now proposed, the tracked vehicle would include active targets that would light up on command from the tracking vehicle, and a video camera on the tracking vehicle would be synchronized with, and would acquire images of, the active targets. The video camera would also acquire background images during the periods between target illuminations. The images would be digitized and the background images would be subtracted from the illuminated-target images. Then the position and orientation of the tracked vehicle relative to the tracking vehicle would be computed from the known geometric relationships among the positions of the targets in the image, the positions of the targets relative to each other and to the rest of the tracked vehicle, and the position and orientation of the video camera relative to the rest of the tracking vehicle. The major difference between the first two proposed systems and prior active-target VGS systems lies in the techniques for synchronizing the flashing of the active targets with the digitization and processing of image data. In the prior active-target VGS systems, synchronization was effected, variously, by use of either a wire connection or the Global Positioning System (GPS). In three of the proposed VGS systems, the synchronizing signal would be generated on, and transmitted from, the tracking vehicle. In the first proposed VGS system, the tracking vehicle would transmit a pulse of light. Upon reception of the pulse, circuitry on the tracked vehicle would activate the target lights. During the pulse, the target image acquired by the camera would be digitized. When the pulse was turned off, the target lights would be turned off and the background video image would be digitized. The second proposed system would function similarly to the first proposed system, except that the transmitted synchronizing signal would be a radio pulse instead of a light pulse. In this system, the signal receptor would be a rectifying antenna. If the signal contained sufficient power, the output of the rectifying antenna could be used to activate the target lights, making it unnecessary to include a battery or other power supply for the targets on the tracked vehicle.

Bryan, Thomas C.↗

System for RFID-Enabled Information Collection

A sensor and system provide for radio frequency identification (RFID)-enabled information collection. The sensor includes a ring-shaped element and an antenna. The ring-shaped element includes a conductive ring and an RFID integrated circuit. The antenna is spaced apart from the ring-shaped element and defines an electrically-conductive path commensurate in size and shape to at least a portion of the conductive ring. The system may include an interrogator for energizing the ring-shaped element and receiving a data transmission from the RFID integrated circuit that has been energized for further processing by a processor.

Fink, Patrick W.↗