Search NASA⌕ Search

SEARCH · Search NASA

Results for “steerable”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Daytime three-dimensional drifts at Millstone Hill Observatory

Vertical drift measurements in the topside F region at midlatitudes have confirmed the importance of dynamical processes, but it has been difficult isolating those processes due to E X B drifts from those due to neutral winds. To remove this ambiguity, three-dimensional drift measurements were made at Millstone Hill Observatory with the steerable L-band radar in conjunction with the vertical UHF antenna. The geometry of the experiment is discussed and daytime drifts are presented. Unusual lifting of the F-layer peak was observed on two occasions. A reversal in the deduced meridional neutral wind is observed in one case and an enhanced eastward electric field in the other.

Carpenter, L. A.↗
NASA NTRS1974

The imaging experiment on Pioneer 10

In the period plus or minus 4 days from Jovian pericenter, Pioneer 10 returned data from 153 imaging sequences. Data were obtained with the imaging photopolarimeter, a 2.54-cm-diam and 8.6-cm-focal-length steerable telescope configured as a narrow beam (0.5-mrad) photometer in a spin scan mode of operation. Images were obtained in two spectral bands (390 to 500 nm and 595 to 720 nm), and seven of the most interesting pictures are shown and discussed.

Swindell, W.↗
NASA NTRS1974

Airoscope telemetry system

The AIROscope (Ames Infrared Observatory telescope) telemetry system is described from signal conditioning on the gondola to display and storage at the ground station. All analog and digital data from the systems and experiments on the gondola go to a PCM encoder which formats the data into 10-bit words. Therefore, 0.1-percent resolution is inherently available for experimental data. The coded bit stream directly modulates the carrier of the FM transmitter. To insure reliable transmission over a 650-km range an 11-watt FM transmitter operating at 1483.5 MHz is used on the gondola. Modulation is narrow band FM with a maximum deviation of plus or minus 500 kHz. The maximum modulation frequency is determined by the data bit rate which could be as high as 500 kbps. Presently, a rate of 20.48 kbps is used. The ground station receiving system includes a steerable antenna (19-db gain), preamplifier (21-db gain) and receiver. All data are recorded on a tape recorder. The recorded signal then can be played back through the PCM decommutator unit at a later time for detailed data analysis by the experimenter.

Pitts, K. J.↗
NASA NTRS1975

Space Tug Avionics Definition Study. Volume 5: Cost and Programmatics

The baseline avionics system features a central digital computer that integrates the functions of all the space tug subsystems by means of a redundant digital data bus. The central computer consists of dual central processor units, dual input/output processors, and a fault tolerant memory, utilizing internal redundancy and error checking. Three electronically steerable phased arrays provide downlink transmission from any tug attitude directly to ground or via TDRS. Six laser gyros and six accelerometers in a dodecahedron configuration make up the inertial measurement unit. Both a scanning laser radar and a TV system, employing strobe lamps, are required as acquisition and docking sensors. Primary dc power at a nominal 28 volts is supplied from dual lightweight, thermally integrated fuel cells which operate from propellant grade reactants out of the main tanks.

Source record↗
NASA NTRS1975

A decametric wavelength radio telescope for interplanetary scintillation observations

A phased array, electrically steerable radio telescope (with a total collecting area of 18 acres), constructed for the purpose of remotely sensing electron density irregularity structure in the solar wind, is presented. The radio telescope is able to locate, map, and track large scale features of the solar wind, such as streams and blast waves, by monitoring a large grid of natural radio sources subject to rapid intensity fluctuation (interplanetary scintillation) caused by the irregularity structure. Observations verify the performance of the array, the receiver, and the scintillation signal processing circuitry of the telescope.

Cronyn, W. M.↗
NASA NTRS1974

Data handling and control of the Mariner Venus Mercury '73 spacecraft

Data handling and control subsystems are described for the MVM73 spacecraft, which demonstrated the feasibility of multiple-planet gravity-assist missions. In spite of strict budgetary constraints, MVM73 carried out experiments utilizing television, an IR radiometer, a UV spectrometer, a fluxgate magnetometer, a charged particle telescope, a modulation-demodulation unit, an X-band and S-band dual frequency communications system, a steerable high-gain antenna, a time-sharing digital articulation and pointing system, and moveable solar panels. The trajectory design and flight data system are described, and the systems governing articulation and pointing and attitude control are discussed.

Scull, J. R.↗
NASA NTRS1975

Observations of Jupiter at 26.3 MHz using a large array

A 640 element phase-steerable dipole array has been used to make highly sensitive observations of the planet Jupiter during the 1973 apparition. The satellite Io is found to have very little influence at the low flux levels, whereas the definition of sources A and B appears to be relatively flux independent. A two-dimensional analysis of the data in the Jupiter-Io plane has revealed considerable source B activity at low intensities which is not influenced by Io.

Desch, M. D.↗
NASA NTRS1976

Adaptive multibeam antennas for spacelab. Phase A: Feasibility study

The feasibility was studied of using adaptive multibeam multi-frequency antennas on the spacelab, and to define the experiment configuration and program plan needed for a demonstration to prove the concept. Three applications missions were selected, and requirements were defined for an L band communications experiment, an L band radiometer experiment, and a Ku band communications experiment. Reflector, passive lens, and phased array antenna systems were considered, and the Adaptive Multibeam Phased Array (AMPA) was chosen. Array configuration and beamforming network tradeoffs resulted in a single 3m x 3m L band array with 576 elements for high radiometer beam efficiency. Separate 0.4m x 0.4 m arrays are used to transmit and receive at Ku band with either 576 elements or thinned apertures. Each array has two independently steerable 5 deg beams, which are adaptively controlled.

Allen, C. C.↗
NASA NTRS1977

Feasibility and systems definition study for microwave multi-application payload (MMAP)

There were three Shuttle/Spacelab experiments: adaptive multibeam phased array antenna (AMPA) experiment, electromagnetic environment experiment (EEE), and millimeter wave communications experiment (MWCE). Work on the AMPA experiment was completed. Results included are definition of operating modes, sequence of operation, radii of operation about several ground stations, signal format, foot prints of typical orbits and preliminary definition of ground and user terminals. Definition of the MOD I EEE included conceptual hardware designs, spacelab interfaces, preliminary data handling methods, experiment tests and verification, and EMC studies. The MWCE was defined conceptually for a steerable high gain antenna.

Horton, J. B.↗
NASA NTRS1977

Feasibility and systems definition study for Microwave Multi-Application Payload (MMAP)

Work completed on three Shuttle/Spacelab experiments is examined: the Adaptive Multibeam Phased Array Antenna (AMPA) Experiment, Electromagnetic Environment Experiment (EEE) and Millimeter Wave Communications Experiment (MWCE). Results included the definition of operating modes, sequence of operation, radii of operation about several ground stations, signal format, foot prints of typical orbits and preliminary definition of ground and user terminals. Conceptual hardware designs, Spacelab interfaces, data handling methods, experiment testing and verification studies were included. The MWCE-MOD I was defined conceptually for a steerable high gain antenna.

Horton, J. B.↗
NASA NTRS1976

The imaging photopolarimeter - The first extraterrestrial spin-scan imager

The paper describes the imaging photopolarimeter used to take close-ups of Jupiter from Pioneers 10 and 11. The instrument operates in a steerable spin-scan mode of operation, contains a 1 in. diameter, f/3.4 Maksutov telescope with a focal plane aperture whose size is selectable. The paper examines those aspects of the design that are substantially influenced by the unusual design constraints, such as choice of detector and method of steering the telescope, and demonstrates the image processing and display techniques used to create the images from the telemetry and correct them for distortion and other defects.

Swindell, W.↗
NASA NTRS1978

A communications satellite system concept based on the AMPA experiment

This paper describes a system employing sophisticated satellites with steerable high gain, multibeam phased array antennas, which serve small low-cost user terminals. Adaptive techniques are used to form, point, and shape the beams. Pseudonoise signaling achieves user access/distress without requiring dedicated access/emergency channels. The L-band array has 32 elements, 34-dB gain; the user terminal has 15W transmitter, 3-dB gain antenna. The pseudonoise code and message structures are described. Approximately 100 users can be simultaneously acquired with success-probability exceeding 99%; system capacity can be increased by providing additional beams. System implementation is feasible in the Shuttle era.

Durrani, S. H.↗
NASA NTRS1979

Voyager telecommunications - The broadcast from Jupiter

The means by which the data collected by the Voyager 1 mission to Jupiter were returned to earth are presented. Radio links between the earth and the spacecraft are used for the transmission of both imaging and nonimaging telemetry from the spacecraft and commands from the earth and for radiometric observations of the spacecraft and its environment. Features which have lead to vast improvements in the capability of the Voyager telecommunications system over that of previous space probes include the use of X-band rather than S-band telemetry, a dual power X-band traveling wave tube amplifier, a 3.7 m spacecraft antenna and a single channel telemetry system with concatenated coding. Communications equipment at the three ground complexes of the Deep Space Network for telemetry reception includes 64 m steerable antennas, cryogenic maser preamplifiers and a phase-lock loop receiver. Voyager 1 has met or exceeded all of its telecommunications requirements, providing a 98% data return and a total of 2 x 10 to the 11th data bits during the Jupiter encounter.

Edelson, R. E.↗
NASA NTRS1980

Internal image motion compensation system for the Shuttle Infrared Telescope Facility

The Shuttle Infrared Telescope Facility (SIRTF) is being designed as a 1-m, cryogenically cooled telescope capable of a thirty-fold improvement over currently available infrared instruments. The SIRTF, mounted in the Orbiter bay on the Instrument Pointing System (IPS), requires that the image at the focal plane be stabilized to better than 0.1 arcsec with an absolute accuracy of 1 arcsec in order to attain this goal. Current estimates of IPS performance for both stability and accuracy indicate that additional stabilization will be necessary to meet the SIRTF requirements. An Image Motion Compensation (IMC) system, utilizing a Charge Coupled Device (CCD) star tracker located at the focal plane and a steerable mirror in the SIRTF optical path, has been designed to work in conjunction with the IPS.

Lorell, K. R.↗
NASA NTRS1981

Advanced solar concentrator: Executive summary

The preliminary design of a point-focusing solar concentrator, consisting of a steerable space frame structure supporting a paraboloidal mirror glass reflector, is described. A mass production, operation, and maintenance cost assessment is presented. A conceptual evaluation of a modified concentrator design is included. The detailed design of one of the lightweight, structurally efficient reflective elements comprising the paraboloidal reflective surface is given.

Source record↗
NASA NTRS1981

Design definition of a microwave power reception and conversion system for use on a high altitude powered platform

The design definition of a microwave power reception and conversion system for use on high altitude powered platform is presented. The study includes an initial design, construction and test effort on a thin film, printed circuit rectenna. A study of a low altitude demonstration of an airborne rectenna was made starting with the assumption that a fifty foot mechanically steerable parabolic reflector at the Wallops Flight Center would be retrofitted with a low microwave power source consisting of a five kilowatt commercially available magnetron and that a small blimp would be used to support the rectenna.

W. C. Brown↗
NASA NTRS1981

Shuttle infrared telescope facility pointing and control system

The Shuttle Infrared Telescope Facility (SIRTF) is being designed as a 0.85 m cryogenically cooled telescope capable of a three order of magnitude improvement over currently available infrared instruments. The SIRTF requires that the image at the focal plane be stabilized to better than 0.25 arcsec with an absolute accuracy of 1.0 arcsec. Current pointing-mount performance simulations indicate that neither of these requirements can be met without additional stabilization. The SIRTF pointing and control system will utilize gyro outputs, star field position measurements from a focal plane fine guidance sensor, and a steerable secondary mirror to provide the necessary stabilization and pointing control. The charge coupled device fine guidance sensor tracks multiple stars simultaneously and, through the use of multistar processing algorithms in a high performance microcomputer, generates three-axis attitude errors and gyro-drift estimates to correct the pointing-mount gyros. A high-bandwidth feedforward loop, driven directly from the pointing-mount gyro package, controls the steering mirror in order to correct disturbances not compensated for by the pointing-mount control system. A prototype design for the SIRTF pointing and control system is described in detail. Performance analyses made using a digital simulation of the pointing and control system as well as experimental data obtained in laboratory and field test measurements are presented.

Lorell, K. R.↗
NASA NTRS1982

Feed system design and experimental results in the uhf model study for the proposed Urbana phased array

The effects of atmospheric turbulence and the basis for the coherent scatter radar techniques are discussed. The reasons are given for upgrading the Radar system to a larger steerable array. Phase array theory pertinent to the system design is reviewed, along with approximations for maximum directive gain and blind angles due to mutual coupling. The methods and construction techniques employed in the UHF model study are explained. The antenna range is described, with a block diagram for the mode of operation used.

Loane, J. T.↗