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At least 217 records · Page 12

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NASA NTRS1972

Azimuth angle dependence of equatorial ultraviolet airglow.

An EUV solar blind photomultiplier was rocket-flown to an altitude of 103 km from Kourou, French Guiana. The rocket was spinning, thus allowing observations in all azimuthal directions within 15 deg from the horizontal plane. The observed radiation is strongly dependent on azimuth angle, the maxima of radiation are located in the southwest direction (the directions of maximum are slightly different when the experiment is looking down or up), and the radiation intensity is independent of elevation angle, suggesting that the glow is located between 75 and 105 km in altitude.

Quessette, J. A.↗

NASA NTRS1972

Development and testing of the ultraviolet spectrometer for the Mariner Mars 1971 spacecraft

The Mariner Mars 1971 ultraviolet spectrometer is an Ebert-Fastie type of the same basic design as the Mariner Mars 1969 instrument. Light enters the instrument and is split into component wavelengths by a scanning reflection diffraction grating. Two monochrometer exit slits allow the use of two independent photomultiplier tube sensors. Channel 1 has a spectral range of 1100 to 1692 A with a fixed gain, while Channel 2 has a spectral range of 1450 to 3528 A with an automatic step gain control, providing a dynamic range over the expected atmosphere and surface brightness of Mars. The scientific objectives, basic operation, design, testing, and calibration for the Mariner Mars 1971 ultraviolet spectrometer are described. The design discussion includes those modifications that were necessary to extend the lifetime of the instrument in order to accomplish the Mariner Mars 1971 mission objectives.

Farrar, J. W.↗

NASA NTRS1973

Evaluation of the electro-optic direction sensor

Evaluation of a no-moving-parts single-axis star tracker called an electro-optic direction sensor (EODS) concept is described and the results are given in detail. The work involved experimental evaluation of a breadboard sensor yielding results which would permit design of a prototype sensor for a specific application. The laboratory work included evaluation of the noise equivalent input angle of the sensor, demonstration of a technique for producing an acquisition signal, constraints on the useful field-of-view, and a qualitative evaluation of the effects of stray light. In addition, the potential of the silicon avalanche-type photodiode for this application was investigated. No benefit in noise figure was found, but the easily adjustable gain of the avalanche device was useful. The use of mechanical tuning of the modulating element to reduce voltage requirements was also explored. The predicted performance of EODS in both photomultiplier and solid state detector configurations was compared to an existing state-of-the-art star tracker.

Johnson, A. R.↗

NASA NTRS1971

Calibration plan for ultraviolet spectrometer experiment S169

The calibration test equipment presented is employed to calibrate completely assembled and flight-ready Apollo Ultraviolet Spectrometers (UVS) consisting of a vacuum system in which the UVS can be installed. In it a premonochromator produces a monochromatic beam at any desired wavelength from a UV source. This beam can be focused by an adjustable transfer mirror to any point on the entrance slit of the UVS. The transfer mirror can also direct the beam to one or both of two absolutely calibrated reference photomultiplier tubes to determine the number of photons which enter the UVS. A movable mirror rhomb is also provided to intermittently monitor the number of photons in the beam when the beam is centered on the entrance slit.

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NASA NTRS1973

Optical filtering for star trackers

The optimization of optical filtering was investigated for tracking faint stars, down to the fifth magnitude. The effective wavelength and bandwidth for tracking pre-selected guide stars are discussed along with the results of an all-electronic tracker with a star tracking photomultiplier, which was tested with a simulated second magnitude star. Tables which give the sum of zodiacal light and galactic background light over the entire sky for intervals of five degrees in declination, and twenty minutes in right ascension are included.

Wilson, R. E.↗

NASA NTRS1972

Cathodochromic cathode ray tube: An operations manual

A cathodochromic (CC) storage and display system capable of storing full TV resolution images has been built. The images are derived from standard TV signals: composite video, composite sync, composite blanking, horizontal drive, and vertical drive. Image storage takes place in the CC CRT; the fixed image is written for several TV frames for the contrast to be usable. Once stored on the CC CRT, the image can be read out in one of three modes: with the eye, a 35-mm camera, or a TV camera. Incoming information may also be stored in a storage tube similar to the CC CRT but with a phosphor layer behind the CC layer. By exciting the phosphor layer with a standard raster scan it is possible to read out an image stored in the CC layer in one of three modes: direct viewing, photography, or flying-spot readout using a photomultiplier.

Heyman, P. M.↗

NASA NTRS1973

Gated high speed optical detector

The design, fabrication, and test of two gated, high speed optical detectors for use in high speed digital laser communication links are discussed. The optical detectors used a dynamic crossed field photomultiplier and electronics including dc bias and RF drive circuits, automatic remote synchronization circuits, automatic gain control circuits, and threshold detection circuits. The equipment is used to detect binary encoded signals from a mode locked neodynium laser.

Green, S. I.↗

NASA NTRS1973

Multispectral scanner (MSS), ERTS-1

The multispectral scanner onboard ERTS-A spacecraft provides simultaneous images in three visible bands and one near infrared band. The instrument employs fiber optics to transfer optical images to the detectors and photomultiplier tubes. Detector outputs are digitized and multiplexed for transmission from the spacecraft by analog to digital processor.

Arlauskas, J.↗

NASA NTRS1973

Methods of photoelectric observations

Photoelectric detectors and their operation are described, with emphasis on photomultipliers, infrared radiation detectors, and photoelectric photometers.

Chugaynov, P. F.↗

NASA NTRS1973

Tape Cassette Bacteria Detection System

The design, fabrication, and testing of an automatic bacteria detection system with a zero-g capability and based on the filter-capsule approach is described. This system is intended for monitoring the sterility of regenerated water in a spacecraft. The principle of detection is based on measuring the increase in chemiluminescence produced by the action of bacterial porphyrins (i.e., catalase, cytochromes, etc.) on a luminol-hydrogen peroxide mixture. Since viable as well as nonviable organisms initiate this luminescence, viable organisms are detected by comparing the signal of an incubated water sample with an unincubated control. Higher signals for the former indicate the presence of viable organisms. System features include disposable sealed sterile capsules, each containing a filter membrane, for processing discrete water samples and a tape transport for moving these capsules through a processing sequence which involves sample concentration, nutrient addition, incubation, a 4 Molar Urea wash and reaction with luminol-hydrogen peroxide in front of a photomultiplier tube. Liquids are introduced by means of a syringe needle which pierces a rubber septum contained in the wall of the capsule. Detection thresholds obtained with this unit towards E. coli and S. marcescens assuming a 400 ml water sample are indicated.

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NASA NTRS1973

Skylab experiments. Volume 1: Physical science, solar astronomy

The basic subject of this volume is the solar astronomy program conducted on Skylab. In addition to descriptions of the individual experiments and the principles involved in their performance, a brief description is included of the sun and the energy characteristics associated with each zone. Wherever possible, related classroom activities have been identified and discussed in some detail. It will be apparent that the relationships rest not only in the field of solar astronomy, but also in the following subjects: (1) physics - optics, electromagnetic spectrum, atomic structure, etc.; (2) chemistry - emission spectra, kinetic theory, X-ray absorption, etc.; (3) biology - radiation and dependence on the sun; (4) electronics - cathode ray tubes, detectors, photomultipliers, etc.; (5) photography; (6) astronomy; and (7) industrial arts.

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NASA NTRS1972

Single photon detection and timing - Experiments and techniques.

Single photon detection and timing means essentially the detection and timing of a single photoelectron released by light from a photosensitive surface of a photomultiplier, channel multiplier, avalanche multiplier photodiode, or other photodevice. Necessary photodevice gain and detection circuits, mechanisms and statistics of photodevice gain, photodevice and background noise and their reduction, and practical photodevice techniques and photon detection performance tests are discussed. Fast timing with single photons, and single photon detection with moderate timing requirements are considered.

Poultney, S. K.↗

NASA NTRS1972

A dynamic polariscope for stress wave analysis.

A polariscope for the study of the propagation of stress waves in birefringent sheets is described. Sensitive, fast-responding photomultiplier tubes, a laser light source, and a multiple channel oscilloscope were used for the simultaneous recording of the stress-optic data at several points of the target following impact. A method of separation of stresses and the computation of displacement, strain, and stress is given.

Kinslow, R.↗

NASA NTRS1972

Circular polarization of twilight.

Review of observations of circular polarization of twilight performed with a polarimeter which uses an electronically switched Pockels cell operated as a reversible quarter-wave plate to convert circular into linear polarization. The latter was then analyzed by a Wollaston prism followed by two gallium-arsenide photomultipliers. The discovery of a definite natural circular polarization at twilight does suggest that, with increased observation precision, measurements of the small daylight component are possible. These could give useful information about particles in the atmosphere and be valuable in studies of meteorology and air pollution.

Angel, J. R. P.↗

NASA NTRS1973

Millisecond time scale atmospheric light pulses associated with solar and magnetospheric activity.

By using a wide-angle photomultiplier system a class of millisecond time scale diffuse atmospheric light emission of terrestrial origin has been discovered. These fast atmospheric pulsation events also show damped oscillations around 10-kHz frequency, which distinguishes them from ordinary lightning-type events. Evidence is presented for the enhancement in the rate of these events induced by solar flare activity.

Ogelman, H.↗

NASA NTRS1973

Photometer for detection of sodium day airglow.

Description of a photometer for daytime ground-based measurements of sodium airglow emission. The photometer described can be characterized by the following principal features: (1) a narrow (4.5-A) interference filter for initial discrimination; (2) cooled photomultiplier detector to reduce noise from dark current fluctuations and chopping to eliminate the average dark current; (3) a sodium vapor resonance cell to provide an effective bandpass comparable to the Doppler line width; (4) separate detection of all light transmitted by the interference filter to evaluate the Rayleigh and Mie components within the Doppler width of the resonance cell; and (5) temperature quenching of the resonance cell to evaluate and account for instrumental imperfections.

Mcmahon, D. J.↗

NASA NTRS1973

3 nu sub 3 band of C-12H4 at 1.1 micron.

The 3 nu sub 3 absorption band of C-12H4 has been measured using a high-resolution vacuum infrared spectrometer. A technique is described which allows an extension of the use of the absorption standards available at 4.7 microns to the photomultiplier region of the spectrum. The new measurements indicate a shift of about 0.18 per cm from the most recently published measurements of this band.

Pugh, L. A.↗

NASA NTRS1974

Digital multichannel photometer

System was developed for use in astronomy and other research areas concerned with detection of faint-light images. Photometer system is comparable in performance to good photomultiplier tube array except that digital electronics are used instead of analog.

Beaver, E. A.↗