Engineering tests of the C-141 telescope
Data on image quality, chopper performance, and the closed-loop operation of the 91 cm telescope of the Kuiper Airborne Observatory which were obtained in September 1977 are presented.
Erickson, E. F.↗
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Far infrared polarization of the Kleinmann-Low Nebula in Orion
Elongated dust grains aligned by local magnetic fields are though to absorb background radiation and produce linear and circular polarization which exhibit strong wavelength dependence in the near infrared. The NASA Kuiper observatory 91 cm infrared telescope was used to observe polarization characteristics of the Kleinmann-Low nebula in four far infrared wavelength bands in order to detect emission from these same oriented grains at longer wavelengths, and determine whether this radiation shows a direction of polarization perpendicular to that seen in the near infrared. The polarization, if any, that characterized the radiation in the three longest wavelength filter positions (28-48 micron, 44-72 micron, and 70-115 micron) is small. The noisiest measurements were obtained in the 16-33 micron filter position. Possible explanations for the low polarization observed at long wavelengths are explored.
Gull, G. E.↗
Occultation of Epsilon Geminorum by Mars. II - The structure and extinction of the Martian upper atmosphere
The occultation of Epsilon Geminorum by Mars on April 8, 1976, was observed at three wavelengths and 4-ms time resolution with the 91-cm telescope aboard NASA's G. P. Kuiper Airborne Observatory. Temperature, pressure, and number-density profiles of the Martian atmosphere were obtained for both the immersion and emersion events. Within the altitude range 50-80 km above the mean surface, the mean temperature is about 145 K, and the profiles exhibit wavelike structures with a peak-to-peak amplitude of 35 K and a vertical scale of about 20 km. The ratio of the refractivity of the atmosphere at 4500 A and 7500 A is consistent with the atmospheric composition measured by Viking 1. From the 'central flash' - a bright feature in the light curve midway between immersion and emersion - an optical depth at 4500 A of 3.3 + or - 1.7 per km atm (about 0.23 per equivalent Martian air mass) is found for the atmosphere about 25 km above the mean surface near the south polar region. This large value and its weak wavelength dependence rule out Rayleigh scattering as the principal cause of the observed extinction.
Elliot, J. L.↗
The abundances of ammonia in the atmospheres of Jupiter, Saturn, and Titan
An investigation of low-resolution ratio spectra of Jupiter, Saturn, and Titan in the region 5400-6500 A has permitted new evaluations of ammonia absorption bands. The distribution of ammonia over the disk of Jupiter is very inhomogeneous. The carbon-to-nitrogen ratio is distinctly different from the solar value, but this is probably a result of uneven mixing of methane and ammonia, as suggested previously by Kuiper (1952), rather than a compositional anomaly. The abundancy of ammonia on Saturn also shows spatial variations, but appears constant in time over a 3-yr period. Two weak, unidentified absorptions were discovered in the red region of Titan's spectrum, in the absence of any detectable ammonia.
Woodman, J. H.↗
Moon-Mercury - Relative preservation states of secondary craters
Geologic studies including mapping of the Kuiper quadrangle of Mercury suggest that secondary craters are much better preserved than those on the moon. Factors which may account for the apparent differences between lunar and Mercurian secondary crater morphology include: (1) the rapid isostatic adjustment of the parent crater, (2) different impact fluxes of the two planets, (3) the greater concentration of Mercurian secondaries around impact areas, and (4) differences in crater ejection velocities. It has been shown that the ejection velocities on Mercury are about 50% greater than those on the moon at equivalent ranges. This may account for morphologically enhanced secondary craters, and may explain their better preservation with time.
Scott, D. H.↗
Evidence for CO in Jupiter's atmosphere from airborne spectroscopic observations at 5 microns
High-altitude (12.4 km) spectra of Jupiter recorded at the Kuiper Airborne Observatory are analyzed for the presence of CO absorption lines. A line-by-line comparison of Jupiter's spectrum with that of carbon monoxide is presented, as well as a correlation analysis that includes the influence of other gases present in Jupiter's atmosphere (CH4, NH3, H2O, PH3, and GeH4). The resulting evidence points strongly to the presence of carbon monoxide in Jupiter's atmosphere, thus strengthening Beer's evidence for it. Possible explanations for the existence and observability of Jovian CO, including convection from hotter, deeper layers or decomposition of organic molecules, are explored. A recent suggestion that the Jovian CO is restricted to stratospheric levels is not supported by the observations.
Larson, H. P.↗
The occultation of Epsilon Geminorum by Mars as observed at Princeton
Results are reported for two-color (red and blue) high-speed photometric observations of the April 8, 1976, occultation of Epsilon Gem by Mars. The observing system is briefly described, fits to an isothermal atmospheric model of the event are presented, and the blue data are used to derive temperature profiles of the Martian atmosphere in the manner of Wasserman and Veverka (1973). The results are compared with those of Elliot et al. (1977), which were obtained from the NASA Kuiper Airborne Observatory.
Groth, E. J.↗
Upper limits to trace constituents in Jupiter's atmosphere from an analysis of its 5 micrometer spectrum
A high-resolution spectrum of Jupiter at 5 micrometers recorded at the Kuiper Airborne Observatory is used to determine upper limits to the column density of 19 molecules. The upper limits to the mixing ratios of SiH4, H2S, HCN, and simple hydrocarbons are discussed with respect to current models of Jupiter's atmosphere. These upper limits are compared to expectations based upon the solar abundance of the elements. This analysis permits upper limit measurements (SiH4), or actual detections (GeH4) of molecules with mixing ratios with hydrogen as low as 10 to the minus 9th power. In future observations at 5 micrometers the sensitivity of remote spectroscopic analyses should permit the study of constituents with mixing ratios as low as 10 to the minus 10th power, which would include the hydrides of such elements as Sn and As as well as numerous organic molecules.
Treffers, R. R.↗
Germane in the atmosphere of Jupiter
Germane, GeH4, is a tetrahedral molecule like methane. The nu 3 fundamental mode of GeH4 falls in the middle of the 5-micrometer Jupiter window. Jupiter observations were made in December 1975 during three flights with the 0.9-m telescope of the Kuiper Airborne Observatory. The spectrometer is a rapid-scanning Michelson interferometer having InSb detectors at each of the two outputs. The germane identification procedure is based on a comparison of the obtained Jupiter spectrum with that of laboratory germane. It appears that the detection of GeH4 in Jupiter's atmosphere with a mixing ratio of 0.6 ppb is the smallest concentration of a trace constituent yet detected in a nonterrestrial planetary atmosphere. It is pointed out that a strict interpretation of thermochemical equilibrium predictions for the spectral line forming regions of Jupiter's atmosphere does not explain the observation of GeH4.
Fink, U.↗
C3 and infrared spectrophotometry of Y Canum Venaticorum
The 1.2- to 5.6-micron spectrum of the carbon star Y CVn is presented and discussed. The observations were made from the Kuiper Airborne Observatory at an altitude of 12.5 km, thereby avoiding most of the absorption due to terrestrial water vapor. Comparison of Y CVn near 5 microns with laboratory spectra provides possible evidence for the presence of the linear triatomic molecule C3. For the first time in a carbon star the clearly formed band heads of the CN red system between 1.2 and 2.3 microns are observed. Corroborative evidence for the presence of the molecules HCN and C2H2 is presented, and the relative contributions of C3, HCN, and C2H2 to the 3.1-micron absorption band are discussed. Spectra of two other carbon stars, TX Psc and S Cep, are presented for comparison.
Goebel, J. H.↗
16-38 micron spectroscopy of NGC 7027
Medium-resolution spectroscopy of the planetary nebula NGC 7027 over the wavelength range from 16 to 38 microns is reported which was performed from NASA's Kuiper Airborne Observatory. It is found that within the errors, the spectrum is smooth and has the shape of a dilute 130-K blackbody but falls below that curve at the longer wavelengths. The absence of two theoretically predicted features in the 16-40-micron band, a forbidden fine-structure line of O IV at 25.91 microns and a broad emission feature in the 22-35-micron region due to carbonate materials, is discussed; a lower limit of 25,000 per cu cm is placed on the electron density in the ionized region. A simple model involving small graphite grains at a temperature around 90 K is proposed to explain the observed featureless continuum. This model is shown to require a dust mass of about 0.025 solar mass and a gas mass of approximately 1 solar mass, which imply that most of this mass would be associated with the molecular cloud surrounding the ionized region.
Mccarthy, J. F.↗
Airborne infrared and submillimeter astronomical polarization measurements at different wavelengths
Because observations of the Kleinmann-Low region of the Orion Nebula reveal significant polarization in the wavelength range from 1 to 13 micron m, polarization at wavelengths greater than 15 micron were investigated. Far infrared polarization measurements were made of a number of sources using an instrument mounted at the bent cassegrain focus of the Kuiper Airborne Observatory's 90 cm telescope. About two hours of data were obtained on the Orion Nebula on each of two flights, and more careful calibration on Jupiter (assumed to be unpolarized) were obtained on both nights. The data on Orion and Jupiter for three filters are presented. Possible explanations are suggested for reconciling the high polarization observed by others in 1974 with the lower values obtained in this study.
Harwit, M.↗
Far-infrared polarization of the Kleinmann-Low Nebula in Orion
Polarization observed in the Kleinmann-Low Nebula is described. The observations were obtained by the Kuiper Airborne Observatory at an altitude of 12 km and in wavelength ranges 16-26, 28-48, 44-72, and 71-115 microns. Beyond 28 microns, the 2% polarization detected is consistent with zero polarization, while the upper limit in the 16-26 micron range is 7% polarization. It is suggested that the smallness of the detected polarization restricts nebula models for explaining the observations.
Gull, G. E.↗
Comparison between stability limits for satellite motion
Three methods of obtaining stability information on satellite motion are compared by means of numerical and analytical computations. The model of the restricted problem of three bodies is used to describe the motion. Kuiper's (1961) approximate results, Szebehely's (1978) approximate results, and computer solutions obtained by successive iterations show close agreement regarding the maximum values of the orbital radii for stability. The lowest value, i.e., the most conservative estimate, is provided by the simplified form of Szebehely's formula.
Szebehely, V.↗
Near-infrared spectra of the Galilean satellites - Observations and compositional implications
Reflectivity spectra of the trailing and leading sides of Io, Europa, Callisto, and Ganymede are analyzed which were obtained at an altitude of 41,000 ft from the Kuiper Airborne Observatory with circular variable filter-wheel spectrometers in the spectral region from 0.7 to 5.5 microns. The data are compared with laboratory spectrum and with synthetic spectra constructed on the basis of simple multiscattering theory. The 2.9-micron feature in Callisto's spectra is attributed primarily to bound water; the fractional amounts of water-ice cover on the trailing and leading sides of Ganymede and on the leading side of Europa are estimated. The bare-ground areas on Ganymede are shown to have reflectivity properties comparable to those of Callisto's surface in the studied spectral region, and the surfaces of both satellites are found to contain significant quantities of bound water. It is suggested that minor but significant amounts of ferrous-bearing material (either ferrous salts or alkali feldspars) can account for the 1.35-micron feature of Io.
Pollack, J. B.↗
The 12- to 20-micron spectrum of Venus - Implications for temperature and cloud structure
The spectrum of Venus was measured between approximately 500 and 800 kaysers (12 to 20 microns) at a resolution of 3.12 kaysers from the NASA C141 G. P. Kuiper Airborne Observatory on 22 and 24 February 1977. The spectrum clearly shows the detailed structure of CO2 absorption in the vicinity of the nu-2 fundamental band at 667 kaysers. In addition, details of model fitting demonstrate the possibility for a cold and thin haze of sulfuric acid droplets along with an optically opaque cloud top near 250 K. Such clouds represent major differences from other H2SO4 main cloud deck models in the recent literature and may be indicative of changes in the vertical distribution of aerosols on a global scale. The temperatures retrieved for pressures at or below 10 mbar are largely independent of the cloud model assumed and they are some 16 to 20 K warmer than the 1972 NASA model. All retrieved temperatures lie within the range of Mariner 5 and Mariner 10 radio occultation inversion results.
Aumann, H. H.↗
Temperature structure of the Uranian upper atmosphere
The temperature structure of the upper atmosphere of Uranus at two locations on the planet was determined from observations of the occultation of the star SAO158687 by Uranus on 10 March 1977, carried out at the Kuiper Airborne Observatory. The temperature-pressure relationships obtained from the immersion and emersion data for 7280 A channel show peak-to-peak variations of 45 K for immersion and 35 K for emersion. The mean temperature for both immersion and emersion profiles is about 100 K, which shows that Uranus has a temperature inversion between 0.001 mbar and the 100 mbar level probed by IR measurements. Both profiles show wavelike temperature variations, which may be due to dynamical or photochemical processes.
Elliot, J. L.↗
Airborne stellar spectrophotometry from 1.2 to 5.5 microns - Absolute calibration and spectra of stars earlier than M3
Airborne infrared spectrophotometry (1.2-5.5 microns, 1.5% resolution) is presented for 13 stars which have been extensively used as infrared calibration objects: alpha Lyr, alpha CMA, alpha UMi, beta Dra, and mu Her; the K giants beta Gem, alpha UMa, alpha Boo, gamma-1 And, and alpha Tau; and the M giants beta And, beta Peg, and alpha Cet. These spectra, obtained using NASA's Kuiper Airborne Observatory and Lear Jet Observatory, are virtually free of the interfering effects of terrestrial absorptions. Absolute calibration of the spectrophotometry was based on the theoretical model of alpha Lyr by Schild, Peterson, and Oke (1971), which fits photometric measurements at shorter wavelengths. The resulting flux densities are compared with previous ground-based photometry.
Strecker, D. W.↗