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Papers concerning the development of the Space Telescope which were presented at the Twenty-first Annual Meeting of the American Astronautical Society in August, 1975 are included. Mission planning, telescope performance, optical detectors, mirror construction, pointing and control systems, data management, and maintenance of the telescope are discussed.
Consideration is given to the following types of high energy physics instrumentation: drift chambers, multiwire proportional chambers, calorimeters, optical detectors, ionization and scintillation detectors, solid state detectors, and electronic and digital subsystems. Attention is also paid to reactor instrumentation, nuclear medicine instrumentation, data acquisition systems for nuclear instrumentation, microprocessor applications in nuclear science, environmental instrumentation, control and instrumentation of nuclear power generating stations, and radiation monitoring. Papers are also presented on instrumentation for the High Energy Astronomy Observatory.
Formulas for the response of an optical detector to the transmitted component of a tilted absorbing glass plate are derived in terms of the angle of incidence, the thickness of the plate, and the absorption coefficient and index of refraction of the glass. Numerical results are discussed for detectors of various sizes compared to the width of the incident beam and thickness of the plate.
An overview of the Princeton-M.I.T. second mass-driver is presented. Mass-Driver Two is a 13.1 cm caliber system which uses a two coil superconducting bucket and a two-phase in quadrature drive system. Discrete drive coils are individually energized with timing supplied by position-sensing optical detectors. Intermediate energy storage is provided by sector capacitors which are recharged every half cycle by an external power source. A vacuum environment is provided for the superconducting bucket by a 4 inch ID glass pipe with the drive coils surrounding it. Magnetic flight is generated by eddy current repulsion from six copper guide strips lining the glass pipe. The length is 2.5 meters equally divided between acceleration and deceleration sections. Nominal acceleration is 5000 m/sec per sec giving a maximum bucket velocity of 112 m/sec. Regenerative braking is used to decelerate the bucket. Current densities of 25 sq cm are achieved in the superconducting bucket coils and are maintained by a cryogenic service station.
Presented are the designs used in the construction of the 2.5 m mass driver and the results of the initial testing program. The mass driver consists of equal length sections of acceleration and deceleration each containing 59 drive coils of 13.1 cm caliber. Intermediate energy storage is provided by sector capacitors which are recharged every half cycle by an external power source. The drive coils are individually energized through SCR's with timing supplied by position sensing optical detectors. The drive consists of two phases which operate in quadrature. The initial bucket to be propelled through the mass driver contains two coils of aluminum wire chilled to liquid nitrogen temperatures to momentarily sustain superconducting field intensities. Magnetic flight is generated by eddy current repulsion from six copper guide strips lining the mass driver. Nominal acceleration is 5000 m/sec per sec giving a maximum bucket velocity of 112 m/s.
A ten-channel IR radiometer for the Pioneer Venus orbiter is described. The experimental techniques used and the design of the instrumentation by which they were implemented are considered. Emphasis is placed on temperature sounding, limb sounding, limb darkening, zenith scanning, cloud top temperature, spectral albedo and water vapor measurements. Instrumentation description is also given including optics, detectors, and electronics. Attention is given to data acquisition and handling, calibration, and in-flight performance.
Tools used in the measurement of satellite attitude are described. Attention is given to the elements that characterize an attitude sensor, the references employed (stars, moon, Sun, Earth, magnetic fields, etc.), and the detectors (optical, magnetic, and inertial). Several examples of attitude sensors are described, including sun sensors, star sensors, earth sensors, triaxial magnetometers, and gyrometers. Finally, sensor combinations that make it possible to determine a complete attitude are considered; the SPOT attitude measurement system and a combined CCD star sensor-gyrometer system are discussed.
This paper presents a new wide field of view laser beacon system for measurement, in three dimensions, of aircraft or other remote objects. The system is developed for aircraft collision hazard warning independent of ground-based hardware, as well as for flight research, helicopter-assisted construction and rescue, and robotic manipulation applications. Accurate information describing the relative range, elevation, and azimuth of the aircraft are generated by the sweep of a low-power fan-shaped rotating laser beacon past an array of optical detectors. The system achieves a wide angle of acceptance of laser beacon light through use of compound parabolic concentrators, which collimate the light for spectral filtering to minimize solar interference. An on-board microprocessor system converts the pulse sequence to aircraft position in real time. System reliability and performance are enhanced through narrow pass filtering of the pulse signals, digital logic design to mask spurious signals, and adaptive modulation of trigger threshold levels.
Dual differential interferometer uses two pairs of orthogonallypolarized optical beams to measure amplitude and orientation of broadband ultrasonic surface acoustic waves. Instrument modular, and sensitivity limited only by optical detector used.
Bolt torque or tension deduced from non contacting measurements. Pulsed Laser induces shockwave in bolthead while continuous-wave acousto-optic detector monitors distortion produced by shock. Shock travel time measured to determine bolt length. Solid-state position detector relatively inexpensive and keeps down cost of extensometer.
A light-activated semiconductor device usable as an optoelectronic switch, pulse generator or optical detector is provided. A semiconductor device is disclosed which provides back-to-back metal-thin oxide-silicon (MTOS) capacitors. Each capacitor includes a thin, light-absorptive aluminum electrode which overlies a thin oxide layer and a lightly doped region implanted in an intrinsic silicon substrate.
The results of an investigation of the performance of three basic precision pointing and tracking control subsystems considered for application to satellite to satellite optical communication missions are discussed. The three-control subsystems include: (1) gyro-stabilized, (2) mass-stabilized and (3) complementary filter. The sources of error included in the analysis included: (1) sensor noise from the optical detector, (2) host satellite baseframe vibrational noise and (3) frictional and bearing noise. The measured vibrational and disturbance data from the LANDSAT satellite was used to generate the power spectral density parameter needed to model the baseframe noise environments of the two satellites used for the evaluation. The results of the study indicate that the 1 microradian rms pointing and tracking accuracy may be achieved with either the gyro-stabilized or the complementary filter approach.
Large-area, HgCdTe MW photovoltaic detectors have been developed for the NASA-HALOE instrument scheduled for operation on the Upper Atmospheric Research Satellite. The photodiodes will be TE-cooled and were designed to operate in the 5.1-5.4 micron band at 185 K to measure nitric oxide concentrations in the atmosphere. The active area required 15 micron thick devices and a full backside common contact. Reflections from the backside contact doubled the effective thickness of the detectors. Optical interference from reflections was eliminated with a dual layer front surface A/R coating. Bakeout reliability was optimized by having Au metallization for both n and p interconnects. Detailed performance data and a model for the optical stack are presented.
The components of the calibration facility at the University of Colorado are described. The system is capable of analyzing the performance of optical components in the wavelength range from 2.7 to 2500 A. The system uses two light sources: a water-cooled hollow cathode gas discharge source and a soft X-ray source. The 2.2-m grazing incidence monochrometer, slits, large chamber, and computer-controlled manipulator are examined. The NBS aluminum oxide photodiode, a flowing gas proportional counter, and an imaging microchannel plate device are employed to detect the light. The optics, detectors, and data acquisition system are computer controlled. The facility is applicable for evaluating the performance of diffraction gratings, multilayer mirrors, reflective coatings, spectrographs, surface roughness scattering, and absolute detector efficiencies. Examples demonstrating the capabilities of the facility and a diagram of the facility are presented.
Receiver for optical communications uses rough reflector instead of diffraction-limited reflector customarily thought necessary for such systems. Rough reflector collects and focuses optical signal. Other receiver components include narrow-passband optical filter to reject out-of-band background radiation, spatial filter to limit receiver field of view, optical-detector array (typically two concentric detectors), and postdetection processor to reconstruct transmitted message.
Proposed random-access-memory (RAM) addressing system, in which memory linked optically to read/write logic circuits, greatly increases computer operating speed. System - comprises addressing circuits including numerous lasers as signal sources, numerous optical gates including optical detectors associated with memory cells, and holographic element to direct light signals to desired memory-cell locations - applied to high-capacity digital systems, supercomputers, and complex microcircuits.
The physical properties of Comet P/Halley are being monitored from the ground using state of the art optical detectors. The long time base (1982-present) of the observations provides a unique record of the development of activity in a single comet. In addition, physical properties of other comets are measured to provide a reference against which Comet Halley may be compared. Results for the past year include: (1) publication of the first results on the surface brightness profiles of dust comets; (2) charge coupled device measurements of Comet Bowell show that the activity of comets can persist at least to heliocentric distances R = 13.6 AU; (3) a study of the back-scattering phase angle dependences of 5 comets (including Halley) shows evidence for small linear phase coefficients in each case; (4) temporal monitoring of P/Halley continues.
Electric and magnetic field measurements have been made in the ionosphere over an active thunderstorm and an optical detector onboard the same rocket yielded an excellent time base for the study of waves radiated into space from the discharge. In addition to detection of intense, but generally well understood whistler mode waves, very unusual electric and magnetic field pulses preceded the 1-10 kHz component of the radiated signal. These pulses lasted several ms and had a significant electric field component parallel to the magnetic field. No known propagating wave mode has this polarization nor a signal propagation velocity as high as those measured here. This study investigated and rejected an explanation based on an anomalous skin depth effect. Although only a hypothesis at this time, a more promising explanation involving the generation of the pulse via a nonlinear decay of whistler mode waves in the frequency range 10-80 kHz is being investigated.