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NASA NTRS1974

Removal of seeing and instrumental blur effects from astronomical scanner observations

The Phillips-Twomey method for solving simultaneous integral equations is applied to the problem of removing blur effects arising from atmospheric and instrumental sources from astronomical observations made with photoelectric area-scanning instruments. Details of the method and the effects of observational errors on the quality of the results are discussed in the context of applications to actual observations of stars and the planet Saturn.

Clements, A. E.↗

NASA NTRS1974

The C-12/C-13 ratio in comet Kohoutek /1973f/

Results are presented for photoelectric scans of the C sub 2 1 to 0 band head at 4737 A at resolutions of 0.14 to 0.50 A in the comet Kohoutek. On the basis of medium-resolution scans and of one high-resolution scan two values are obtained for the C-12/C-13 ratio which are consistent within the experimental errors with the terrestrial values of C-12/C-13 equal to 89. The study also demonstrates the limitations imposed by NH2 blends.

Danks, A. C.↗

NASA NTRS1975

The light curve of Comet Kohoutek

Visual estimates of total coma brightness define the light curve of Comet Kohoutek between Nov. 24, 1974 and Feb. 6, 1974. These data are well fitted by straight lines on the M-log r diagram. The preperihelion value of n is 2.2, and the post perihelion value is 3.8 up to January 16. A standstill in the decline is suspected between January 16 and 19. If the standstill is ignored the postperihelion data can be fitted less precisely by a single line with n equals 3.3. From photoelectric measures on four nights between January 5 and 13 after perihelion, n is found to be 4.1. The average B-V with a 32.4 arc sec diaphragm for those four nights is about 0.79; no clear systematic variation with time is noted.

Angione, R. J.↗

NASA NTRS1975

Narrow band filter photometry of Comet Kohoutek

Narrowband photoelectric measurements of CN (3870), CO(+) (4250), C2 (4700), and C2 (5120) were made on twelve nights in December and January of Comet Kohoutek. CN and C2 appear to be stronger after perihelion, and CO(+) showed a strong post perihelion increase coincident with the first appearance of a strong gas tail and then decreased to a fairly constant level.

Angione, R. J.↗

NASA NTRS1975

Recent developments in density, temperature and momentum fluctuation measurement

Attention is drawn to recent advancements in the fluctuating line-reversal temperature measurement, the development of the two-dimensional drag-sensing probe into a three-dimensional drag-sensing probe, and the fluctuating density gradient cross beam Schlieren technique. An experimental apparatus is explained whereby the temperature fluctuation in a pulsating air-fuel ratio Bunsen burner is measured by means of sodium D-line reversal methods with a new photoelectric circuit to obtain both fluctuating and mean temperature data. The three-D drag probe is made possible by a newly invented differential and total magnetic sensing system that separates signals due to three orthogonal movements so that the vectorial momentum fluctuation can be measured. In the case of the Schlieren technique, the effect of anisotropic density gradients with respect to the angle between the polarization plane and the knife edge of a laser Schlieren system is studied.

Battle, T. M.↗

NASA NTRS1974

Initial results from the EUV spectroheliometer on ATM

The Harvard College Observatory photoelectric spectroheliometer on the Apollo Telescope Mount operated correctly in orbit from May 29, 1973 to Feb. 7, 1974. During this period many thousands of spatial and spectral scans at extreme ultraviolet wavelengths were recorded during observations of a variety of solar features. The construction and modes of operation of the instrument are outlined and the principal scientific results from a preliminary analysis of the data are described.

Reeves, E. M.↗

NASA NTRS1975

A laboratory Atlas of the 5 nu-1 NH3 absorption band at 6475 A with applications to Jupiter and Saturn

A complete atlas of the 5 nu-1 absorption band of NH3 is presented together with measurements of the total band intensity, line intensities, and self-broadening coefficients. The spectrum, which is displayed in the interval from 6418 to 6550 A, was obtained photoelectrically at a pressure of 0.061 atm, and many more lines were seen in this spectrum than in a previous one obtained at a pressure of 0.39 atm. The band intensity is used to derive the NH3 abundance in the atmospheres of Jupiter and Saturn, and the abundances in a single vertical path are found to be about 10 m amagat for Jupiter and 2 m amagat for Saturn. These results are shown to be in agreement with previous results obtained from higher resolution photographic spectra.

Giver, L. P.↗

NASA NTRS1975

The light curve of CV Serpentis, the sometimes-eclipsing Wolf-Rayet star

New photoelectric observations of the B-magnitude of CV Ser made in 1973 and 1974 show no clear evidence of an eclipse, but they establish night-to-night variability of several percent, a systematic brightness change of 0.035 mag during a portion of the single orbit observed in 1973, and irregular flaring in 1974. We made iris photometer measurements of Harvard patrol plates taken between 1905 June and 1953 July, and find no evidence of a very deep eclipse such as observed by Hjellming and Hiltner. We present several new light curves and discuss then in the light of the recent results of Cowley et al.

Schild, R.↗

NASA NTRS1975

Spectroradiometric calibration techniques in the far ultraviolet - A stable emission source for the Lyman bands of molecular hydrogen

The problems associated with making accurate spectroradiometric measurements in the far UV region are sketched briefly. The equipment and methods that were developed for providing absolute sensitivity calibration of an Apollo 17 far UV spectrometer are described. The absolute reference standards were photoelectric diodes calibrated at the National Bureau of Standards. A complete vacuum optical facility, which included a premonochromator and stable UV light sources, was developed to calibrate the Apollo 17 instrument, and it has been used for a number of other tasks. Absolute radiometric calibrations between about 1200 and 1700 A were performed with an absolute accuracy of + or - 10%. The light source, which was designed to provide a very stable light output, is a low-pressure molecular hydrogen lamp in which the pressure is stabilized by thermal control of uranium hydride powder.-

Fastie, W. G.↗

NASA NTRS1975

Short-term variability of gamma-2 Velorum

Photoelectric spectrum scans of gamma-2 Velorum in the spectral range 4600-4720 A were analyzed to study the short-term variability of brightness and of emission line strengths. The emission strengths of He II (4686 A) and C III-IV (4650 A) show rms variations of 3 and 2 per cent, respectively. These variations have time scales of 1 minute and longer. Night-to-night variations were also found. The continuum radiation also shows small-amplitude variations. No periodic variations attributable to this star were detected on any of the nights on which these observations were made.

Bahng, J. D. R.↗

NASA NTRS1975

Interstellar K I and Na I absorption lines near rho Ophiuchi

Results are reported for photoelectric interferometric scans of the interstellar K I (7699 A) and Na I D1 absorption lines toward rho Oph AB and omicron Sco in the complex of dark clouds near rho Oph. The scans are found to reveal a well-marked line multiplicity toward both stars. It is shown that the resolved components of the line profiles can provide a natural explanation for the difference between the radial velocity of the strongest atomic lines of Na I and Ca II and that of the much weaker molecular lines of CH(+), CH, and CN that was previously observed toward rho Oph. The less saturated 7699-A lines toward both stars yield K I column densities roughly consistent with the calculated interstellar reddening.

Hobbs, L. M.↗

NASA NTRS1976

Laser extensometer

Drift-compensated and intensity-averaged laser-based system uses optical and photoelectric effects for precise measurement of small thermally-induced size changes. Final output signal is directly proportional to size of sample shadow and independent of laser intensity, detector dark current, and lateral motion of sample.

Stocker, P. L.↗

NASA NTRS1976

Microchannel detector array for X-rays and UV

Device employs sensitive photoelectric electrodes and solid-state memory, can be used at visible UV and X ray wavelengths, includes nonmagnetic proximity focusing, and is immune to high energy charged-particle background.

Timothy, J. G.↗

NASA NTRS1975

Mass loss in red giants and supergiants

The circumstellar envelopes surrounding late-type giants and supergiants were studied using high resolution, photoelectric scans of strong optical resonance lines. A method for extracting the circumstellar from the stellar components of the lines allowed a quantitative determination of the physical conditions in the envelopes and the rates of mass loss at various positions in the red giant region of the HR diagram. The observed strengthening of the circumstellar spectrum with increasing luminosity and later spectral type is probably caused by an increase in the mass of the envelopes. The mass loss rate for individual stars is proportional to the visual luminosity; high rates for the supergiants suggest that mass loss is important in their evolution. The bulk of the mass return to the interstellar medium in the red giant region comes from the normal giants, at a rate comparable to that of planetary nebulae.

Sanner, F.↗

NASA NTRS1975

Engineering studies of vectorcardiographs in blood pressure measuring systems, appendix 2

The development of a cardiovascular monitoring system to noninvasively monitor the blood pressure and heart rate using pulse wave velocity was described. The following topics were covered: (1) pulse wave velocity as a measure of arterial blood pressure, (2) diastolic blood pressure and pulse wave velocity in humans, (3) transducer development for blood pressure measuring device, and (4) cardiovascular monitoring system. It was found, in experiments on dogs, that the pulse wave velocity is linearly related to diastolic blood pressure over a wide range of blood pressure and in the presence of many physiological perturbations. A similar relationship was observed in normal, young human males over a moderate range of pressures. Past methods for monitoring blood pressure and a new method based on pulse wave velocity determination were described. Two systems were tested: a Doppler ultrasonic transducer and a photoelectric plethysmograph. A cardiovascular monitoring system was described, including operating instructions.

Mark, R. G.↗

NASA NTRS1975

Study of the true performance limits of the Astrometric Multiplexing Area Scanner (AMAS)

The Astrometric Multiplexing Area Scanner (AMAS) is an instrument designed to perform photoelectric long focus astrometry of small fields. Modulation of a telescope focal plane with a rotating Ronchi ruling produces a frequency modulated signal from which relative positions and magnitudes can be extracted. Evaluation instrumental precision, accuracy and resolution characteristics with respect to a variety of instrumental and cosmical parameters indicates 1.5 micron precision and accuracy for single stars under specific conditions. This value decreases for increased number of field stars, particularly for fainter stars.

Frederick, L. W.↗

NASA NTRS1975

Enhanced effects of starlight on the interstellar medium

The photodesorption of molecules and atoms from the surfaces of interstellar grains can be an important source of heating for the interstellar medium and the origin of instabilities which may separate grains and gas. For low densities, the force exerted on the grains is proportional to the gas density and independent of the radiation intensity; for high densities, it is proportional to the radiative flux and independent of the gas density. This force may act differently on grains of different sizes. The photoelectric effect may also be an efficient mechanism for the separation of gas and dust in diffuse clouds.

Gerola, H.↗

NASA NTRS1976

Laboratory 15 kV high voltage solar array facility

The laboratory high voltage solar array facility is a photoelectric power generating system. Consisting of nine modules with over 23,000 solar cells, the facility is capable of delivering more than a kilowatt of power. The physical and electrical characteristics of the facility are described.

Kolecki, J. C.↗