ALBERT

Description: The International Cometary Explorer (ICE) encounter with Comet Giacobini-Zinner took place 7 years after the spacecraft's original launch on 12 August 1978 as the International Sun Earth Explorer 3 (ISEE-3), part of a three-spacecraft project to study the interaction between the solar wind and the Earth's magnetosphere. Transfer to an interplanetary trajectory was performed via a 119-km-altitute, gravity-assist, lunar swingby on December 1983. Navigation support during interplanetary cruise and comet encounter was provided by orbit determination utilizing radio metric data from the DSN 64-meter antennas in Goldstone, California and Madrid, Spain. Orbit solutions yielding predictions of 50-km geocentric delivery accuracy in the target aim plane were achieved during interplanetary cruise and at comet encounter using 6-to-12-week data arcs between periodic attitude-change maneuvers. One-sigma two-way range and range rate residuals were consistently 40 meters and 0.2 mm/s or better, respectively. Non-gravitational forces affected the comet's motion during late August and early September 1985 and caused a 2300-km shift in the orbit of the comet relative to the spacecraft. This necessitated a final ICE orbit trim maneuver 3 days prior to encounter. Near-real-time assessment of two-way 2-GHz (S-band) Doppler pseudo-residuals during the June and July 1985 trajectory change maneuvers aided in calibration of the spacecraft's thrusters in preparation for this final critical maneuver. Post-flight analysis indicates tail centerline passage was achieved within 10 seconds of the predicted time and geocentric position uncertainty at encounter was less than 40 km.

Description: The second guide star catalog (GSC-2) is a project that aims to create a complete catalog of stars and galaxies to about the 18th magnitude, and would contain colors, magnitudes, positions and proper motions. The catalog would provide an object list for the construction of an input catalog for possible future astrometric satellites, such as the global astrometric interferometer for astrophysics (GAIA) satellite. With a schedule that is compatible with the projected timeframe of GAIA, the GSC-2 could be available in time to support the preparatory astrophysical observations for an input catalog. The availability of the digitalized images for the preparation of finding charts would improve the efficiency of this task.

Description: We present radio observations of the gravitational lens PKS 1830-211 at 8.4 and 15 GHz acquired using the Very Large Array. The observations were made over a 13 month period. Significant flux density changes over this period provide strong constraints on the time delay between the two lensed images and suffest a value of 44 +/- 9 days. This offers new direct evidence that this source is indeed a gravitational lens. The lens distance is dependent upon the model chosen, but reasonable limits on the mass of the lensing galaxy suggest that it is unlikely to be at a redshift less than a few tenths, and may well be significantly more distant.

Description: The power laws are approximately f(exp -1.9), f(exp -1.9), and f(exp -2.1) respectively for the Grigg-Shjellerup (GS), Giacobini-Zinner (GZ), and Halley (H) comets. Other than similarities in the power spectra, the magnetic field turbulence is considerably different at the three comets. Phase steepening is demonstrated to occur at the trailing edges of the GS waves. This is probably due to nonlinear steepening plus dispersion of the left-hand mode components, i.e., the turbulence is whistler-mode. This too can be explained by nonlinear steepening plus dispersion of the magnetosonic waves. At the level of GS and GZ turbulence development when the spacecraft measurements were made, classical three-wave processes, such as the decay or modulation instabilities do not appear to play important roles. It is most likely that the nonlinear steepening and dispersive time scales are more rapid than three-wave processes, and the latter had not had time to develop for the relatively new turbulence. The wave turbulence at Halley is linearly polarized. The exact nature of this turbulence is still not well understood. Several possibilities are suggested, based on a preliminary analyses.

Description: A study of X-ray emission from five short-period Algol-type binaries based on observations with Advanced Satellite for Cosmology and Astrophysics (ASCA) and ROSAT is presented. We have observed RZ Cas with both satellites, and beta Per, U Cep, delta Lib, and TW Dra with ROSAT. Significant intensity variations are seen in the X-ray emission from RZ Cas, U Cep, TW Dra, and delta Lib. These variations seem unrelated to the eclipsing behavior of these systems and are probably due to either rotational modulation of compact active regions on the surfaces of the chromospherically active secondary components or to flaring activity in the systems. The spectra of all but one of the systems require the presence of at least two discrete plasma components with different temperatures (0.6 - 0.7 keV, and approximately 2 keV) and the abundances of the medium-Z elements 20% - 50% of the solar photospheric values. The high resolving power and signal-to-noise ratio of the ASCA spectra allow us to individually constrain the coronal abundances of O, Ne, Mg, Si, S, and Fe in RZ Cas. We demonstrate that, if we use the elemental abundances and temperatures obtained from the analysis of their ASCA spectra as (fixed) inputs, to fit the ROSAT PSPC spectra well requires the presence of a third component (kT approximately 0.2 - 0.3 keV) in RZ Cas and beta Per. A continuous emission measure model of the power-law type (EM(T) variesas (T/T(sub max)(sup alpha)) generally gives a poor fit to the ASCA and ROSAT data on most sources. Circumstellar or circumbinary absorbing matter seems to be present in some of these systems, as indicated by the variable total column density needed to fit their X-ray spectra.

Description: The 183-GHz water vapor line was tentatively detected on Mars in January 1991, with the IRAM 30-m millimeter antenna, under extremely dry atmospheric conditions. The measurement refers to the whole disk. The spectral line, although marginally detected, can be fit with a constant H2O mixing ratio of 1.0 x 10(exp -5), which corresponds to a water abundance of 1 pr-microns; in any case, an upper limit of 3 pr-microns is inferred. This value is comparable to the very small abundances measured by Clancy (1992) 5 weeks before our observation and seems to imply both seasonal and long-term variations in the martian water cycle.

Description: Titan's large free eccentricity results in significant tidal dissipation. This can be used to constrain the existence and depth of hydrocarbon oceans. A hydrodynamical-numerical 2 deg ocean tide model has been constructed to investigate this connection. The model allows some simple land configurations. The results indicate that existence of such an ocean over the age of the solar system is hard to explain, as is the existence of the large eccentricity itself. If such an ocean exists, it is likely to be more than 500 m deep, ignoring the influence of land masses.

Description: A number of planetary objects exhibit large radar reflectivity and polarization ratios, and more recently, a similar behavior has been observed over a vast portion of the Earth's surface: the percolation facies of the Greenland Ice Sheet. Surface-based ranging radar data and snow stratigraphy studies demonstrated that the radar properties of that portion of Greenland are caused by enhanced scattering from massive, large, solid-ice bodies buried in the top few meters of the dry, cold, clean snowy surface of the ice sheet and created by seasonal melting and refreezing events. Here, we model the icy inclusions as randomly oriented, discrete, noninteracting, dielectric cylinders embedded in a transparent snow medium. An exact analytical solution is used to compute the scattered field from the cylinders. Using this model, we correctly predict the polarimetric radar observations gathered by an airborne imaging system at three wavelengths (5.6, 24, and 68 cm), between 19 deg and 65 deg incidence angle. The diameter and number density of the cylinders that are inferred from the radar data using the model are consistent with in situ observations of the icy inclusions. The large radar reflectivity and polarization ratios are interpreted as arising internal reflections of the radar signals in the icy inclusions that first-order external reflection models fail to predict. The results compare favorably with predictions from the coherent backscatter or weak localization theory and may provide a complementary framework for interpreting exotic radar echoes from other planetary objects.

Description: 24 years of Lunar Laser Ranging (LLR) observations and 16 years of Very Long Baseline Interferometry (VLBI) observations are combined in a global analysis to yield improved estimates of the Earth's precession and nutation. The correction to the International Astronomical Union (IAU) (1976) precession constant inferred from this joint VLBI/LLR analysis is -3.00 +/- 0.20 milliarcsec/yr (mas/yr). A significant obliquity rate correction of -0.20 +/- 0.08 mas/yr is also found. In all, 32 forced nutation coefficients are estimated. These coefficients confirm that the IAU (1980) nutation theory is in error by several mas. The estimated nutation coeficients are found to vary by as much as several tenths of mas, depending on the a priori nutation model used to analyze the VLBI and LLR data. Forced circular nutations derived from this analysis agree with the ZMOA-1990-2 nutation theory at the 0.2 mas level for the 18.6 yr terms, and at the 0.05 mas level for the other terms (periods less than or = 1 yr). A retrograde free core nutation with an amplitude of 0.20 mas is also detected. Its phase is found to be very sensitive to the precise value of the free core nutation period used in the solution. Separate analyses of four independent subsets of the LVBI data indicate no significant variations of the free core nutation since 1988. The pre-1988 estimates of the free core nutation are consistent with the post-1988 estimates but are not accurate enough to rule out possible variations of the free core nutation at these earlier epochs.

Description: The Ulysses spacecraft has gathered data from within flows from the Sun's southern polar coronal hole, the first in situ measurement of this region. We present a brief analysis of the heliospheric magnetic field data from this region, using a fractal method. As is the case near the ecliptic, estimated spectral exponents are near 5/3 on spacecraft scales of seconds to minutes. On longer time scales, however, there appears to be a significantly different population in polar flows, which is similar to that found by the Helios spacecraft in fast solar wind flows at 0.3 AU.

Description: A calculation, employing a detailed model of neutral oxygen, is carried out to give fluorescent line intensities expected in a long-proposed photoexcitation by accidental resonance (PAR) process in which hydrogen Lyman-beta photoexcites the oxygen spectrum. The results pertain to the optically thin case but provide an upper limit to the fluorescent intensities which can be attained. They are applied to analyze line ratios involving the strong 8446 A line observed in classical novae during the diffusion-enhanced and Orion phases. Operation of the PAR process in the novae is verified. It is found that photoexcitation rates in the ejecta reach values greater than 0.1/sec, corresponding to hydrogen Lyman-beta radiation field intensities greater than 1250 ergs/cm/sec/sr.

Description: We have investigated the properties of the OMC-2 and OMC-3 cores in the Orion giant molecular cloud using high spatial spectral resolution observations of several transitions of the (13)CO, C(18)O, C(S-32) and C(S-34) molecules taken with the SEST telescope. The OMC-2 core consists of one clump (22 solar mass) with a radius of 0.11 pc surrounded by a cluster of 11 discrete infrared sources. The H2 column density and volume density in the center of this clump are 2 x 10(exp 22)/sq cm and 9 x 10(exp 5)/cu cm respectively. From a comparison between physical parameters derived from C(18)O and C(S-32) observations we conclude that the molecular envelope around the core has been completely removed by these sources and that only the very dense gas is left. OMC-3 shows a more complex elongated structure in C(18)O and CS than OMC-2. The C(S-32) and C(S-34) maps show that the denser region can be separated into at least sub-cores of roughly equal sizes (radius approximately equals 0.13 pc), with n(H2) = 6 x 10(exp 5)/cu cm, and a mass of 10 solar mass (from C(S-32)). The very different masses obtained for the central core from C(18)O and C(S-32) (55 and 12 solar mass respectively) indicate that a massive envelope is still present around the very dense sub-cores. We report the first detection of several molecular outflows in OMC-3. The presence of an IRAS source and the first detection of these outflows confirm that star formation is going on in OMC-3. Based on the different physical properties of these regions compared with OMC-1, OMC-2 appears to be in an intermediate evolutionary stage between OMC-1 and OMC-3.

Description: The depletion of condensable elements onto grains in gaseous nebulae can provide evidence that dust is well mixed with the ionized gas. Al and CA are two of the most depleted elements in the general interstellar medium, and it is therefore important to measure their abundances within the ionized region of nebulae. We compute a large grid of photoionization models and identify sets of line ratios which are relatively insensitive to stellar and nebular parameters, and are thus excellent diagnostics for determining relative abundances. Based on the absence of the ((Ca II) lambda lambda 291, 7324 doublet and the detection of Al II) lambda lambda 2660, 2669 in the ultraviolet, we determine the extent of aluminum and calcium depletion onto grains in NGC 7027 and the Orion Nebula. Our results show a approximately 0.3 dex depletion for Al, but a depletion of more than two and a half orders of magnitude for Ca. A similar calculation based on Mg II lambda 2798 yields roughly a 0.8 dex depletion for Mg. This reaffirms the discrepancy between depletion determined from high and low ionization Mg lines. We also find evidence for a 'depletion gradient' in Ca in NGC 7027, since the calcium depletion we infer for the outer, more neutral regions using (Ca II) is somewhat higher than that inferred for the inner high-ionization region, using (Ca v). This gradient can test current models of the survival of grains within hot ionized gas.

Description: Synthetic-aperture radar (SAR) interferograms produced from ESA's ERS-1 satellite, provide the first synoptic view of ice flow dynamics of the western sector of the Greenland Ice Sheet. Glacial motion is detected in the radar ranging direction at millimetric scales, across a complete sequence of snow accumulation and melting regimes, despite significant varations in their radar scattering properties. Ice flow evolves from a slow, regular motion at the higher elevations. At lower elevations, motion is strongly convoluted by meter-scale undulations in surface topography, which have a unique interferometric signature that enables a novel approach for retrieving flow direction. Inferred flow directions, combined with surface displacements in the radar ranging direction, yield ice velocity estimates that are within 6% of in-situ measurements gathered along a 40 km survey line. Application of repeat-pass SAR interferometry to the entire Greenland Ice Sheet should enable precise mapping of its ice flow dynamics at an unprecedented level of spatial detail.

Description: The modern scenario of evolution of massive binary systems predicts the existence of a subclass of binary radio pulsars (PSRs) with black holes (BHs). Their Galactic number was evaluated as approximately 1 per 1000 single pulsars (Lipunov et al. 1994b). Distinctive properties of such binaries would be (1) mass of the unseen companion M(sub c) greater than 3-4 solar mass and (2) absence of eclipses of the pulsar radiation with no distinctive variance of the dispersion measure along the pulsar orbit. The pulsars themselves must be similar to standard isolated ones. The recently discovered binary 1 s pulsar PSR B0042-73 = PSR J0045-7319 in the Small Magellanic Cloud (SMC) with a massive companion in a highly elongated (eccentricity e =0.8) 51 day orbit (Kaspi et al. 1994) may be the first such pulsar with a BH. The paradoxical fact that the first pulsar discovered in the SMC proved to be in a binary system can be naturally understood if its companion actually is a 10-30 solar mass black hole. We illustrate this fact by the numerical calculation of evolution of radio pulsars after a star formation burst.

Description: We calculate the structure of an effectively optically thin and geometrically thin accretion disk in the Kerr geometry, including electron-positron pairs. We show that the properties of the disk solutions are strongly dependent on the angular momentum of the central black hole. We find that close to a rapidly rotating hole there can be an appreciable pair density even for modest accretion rates. Pair critical accretion rates recently discovered in Newtonian disk models are also shown to be present in the general relativistic models, and we show that the geometrically thin disk approximations easily break down for rapidly rotating holes.

Description: We examine the hydrodynamic origin of relativistic outflows in active galactic nuclei (AGN). Specifically, we propose that the presence of a population of relativistic hadrons in the AGN 'central engine' and the associated neutron production suffices to produce outflows which under rather general conditions could be relativistic. The main such condition is that the size of the neutron production region be larger than the neutron flight path tau(sub n) approximately 3 x 10(exp 13) cm. This condition guarantees that the mean energy per particle in the proton fluid, resulting from the decay of the neutrons outside their production region, be greater than the proton rest mass. The expansion of this fluid can then lead naturally to a relativistic outflow by conversion of its internal energy to directed motion. We follow the development of such flows by solving the mass, energy as well as the kinetic equation for the proton gas in steady state, taking into account the source terms due to compute accurately the adiabatic index of the expanding gas, and in conjunction with Bernoulli's equation the detailed evolution of the bulk Lorentz factor. We further examine the role of large-scale magnetic fields in confining these outflows to produce the jets observed at larger scales.

Description: The topology of the magnetic field in the heliosheath is illustrated using plots of the field lines. It is shown that the Archimedean spiral inside the terminal shock is rotated back in the heliosheath into nested spirals that are advected in the direction of the interstellar wind. The 22-year solar magnetic cycle is imprinted onto these field lines in the form of unipolar magnetic envelopes surrounded by volumes of strongly mixed polarity. Each envelope is defined by the changing tilt of the heliospheric current sheet, which is in turn defined by the boundary of unipolar high-latitude regions on the Sun that shrink to the pole at solar maximum and expand to the equator at solar minimum. The detailed shape of the envelopes is regulated by the solar wind velocity structure in the heliosheath.

Description: SN 1987A hard X-ray continuum spectra obtained on 1987 October 29, 1988 April 9-10, and 1988 November 11 from balloon-flight measurments are presented. The spectra, spanning the energy range from 25 keV to 300 keV, have been analyzed using a detector response matrix inversion technique that converts the spectra form counts/s/sq cm keV to photons/s/sq cm keV allowing direct comparison with theoretical models. The results indicate that the bulk of the (56)Co is mixed moderately through the inner regions of the supernova envelope but they do not preclude the mixing of a small amount of the (56)Co farther out into the envelope necessary to account for the observed (56)Co line fluxes. The effect of the ratio (57)Co to (56)Co on the 1988 November 11 continuum spectrum is discussed.

Description: The UV line profile structure of high-ionization resonance lines found with the International Ultraviolet Explorer (IUE) in the brightest of four multiply imaged sources (images-A) in the candidate gravitational lens UM 425 = QSO 1120+019 indicates broad absorption line (BAL) structure. The deep-broad trough associated with the O IV line extends to velocities approiximately -12,000 km/s, and contains disrete features that suggest multicomponent velocity structure. This structure may include contributions from C IV absorption from the early-type galaxy that is believed to lens UM 425. A strong absorption feature in the blue wing of the Lyman-alpha lambda 1216 emission line may be a Lyman alpha absorption system at a Z(sub Ly alpha) = 1.437 +/- 0.003, or it may be formed by the superposition of the broad N V lambda lambda 1238, 1242 absorption trough on the extended blue emission wing of the QSO Lyman-alpha line. We obtained a redshift of Z(sub QSO) = 1.471 +/- 0.003 from Lyman-alpha lambda 1215, consistent with the redshift found by Meylan and Djorgovski in the optical. The Lyman-alpha line appears unusally weak due to the presence of N V lambda 1240 BAL absorption. A Lyman-limit absorption system at lambda 912 was not observed in the QSO rest frame. The detection of BAL structure in the other weaker ground-state resonance lines of N II (l) and S IV (l) was not found, suggesting these lines are formed in a region that is distinct from the BAL component. Detection of BAL structure in the other fainter images in this system with Hubble Space Telescope (HST) instrumentation, similar to structure observed here in image A, could provide evidence that UM 425 is a gravitational lens.

Description: We investigate the physical basis for the timescale of impulsive-phase, redshifted Lyman-alpha emission in stellar flares on the assumption that it is determined by energy losses in a nonthermal proton beam that is penetrating the chromosphere from above. The temporal evolution of ionization and heating in representative model chromospheres subjected to such beams is calculated. The treatment of 'stopping' of beam protons takes into account their interactions with (1) electrons bound in neutral hydrogen, (2) nuclei of neutral hydrogen, (3) free electrons, and (4) ambient thermal protons. We find that, for constant incident beam flux, the system attains an equilibrium with the beam energy input to the chromosphere balanced by radiative losses. In equilibrium, the beam penetration depth is constant, and erosion of the chromosphere ceases. If the redshifted, impulsive-phase stellar flare Lyman-alpha emission is produced by downstreaming hydrogen formed through charge exchange between beam protons and ambient hydrogen, then the emission should end when the beam no longer reaches neutral hydrogen. The durations of representative emission events calculated on this assumption range from 0.1 to 14 s. The stronger the beam, the shorter the timescale over which the redshifted Lyman-alpha emission can be observed.

Description: Through analysis of available optical spectrophotometric data and radio flux density measurements in the literature, it is demonstrated that a good correlation exists between the radio power and bolometric luminosity of the optically-selected OSOs in the Bright Quasar Sample (BOS) of Schmidt and Green (1983). We have recently used VLBI measurements of a sample of ultraluminous infrared galaxies to infer the likely existence of radio-quiet Active Galactic Nuclei (AGNs) deeply enshrouded in dust within their nuclei (Lonsdale, Smith, and Lonsdale 1993). We employ the radio-bolometric luminosity correlation for the BQS quasars to test whether these hypothetical buried AGNs can be energetically responsible for the observed far-infrared luminosities of the ultraluminous infrared galaxies. The ultraluminous infrared galaxies are shown to follow the same relation between radio core power and bolometric luminosity as the radio-quiet QSOs, suggesting that buried AGNs can account for essentially all the observed infrared luminosity, and raising the possibility that any starburst which may be in progress may not be energetically dominant. The broader implications of the radio-optical correlation in quasars for AGNs and luminous infrared galaxy models and the use of radio astronomy as a probe of the central powerhouse in radio quiet AGNs and luminous infrared galaxies are briefly discussed.

Description: The proposed design and construction of the Fizeau astrometric mapping explorer (FAME), a small astrometric instrument for use on an artificial satellite, is reported on. The instrument and spacecraft are designed to slowly spin and will repeatedly scan great circles on the sky so that, over a period of time, it will cover the complete sky and repeat in a manner similar to that of the Hipparcos satellite. The instrument will use the two fixed dilute aperture telescopes to measure a fixed angle between stars and detect the positions, magnitude and color of all stars crossing its field of view to a visual magnitude of approximately 15 mag. The aim of the instrument is to obtain a catalog of positions, proper motions and parallaxes of all stars down to about 15 mag, with a magnitude dependent accuracy of positions of 20 to 800 micro arcsec, proper motions of 20 to 800 micro arcsec per year and parallaxes of 20 to 800 micro arcsec.

Description: The concepts related to the operation and design of the global astrometric interferometer for astrophysics (GAIA) bring together solutions chosen for the astrometry satellite and interferometric techniques. Like the Hipparcos satellite, GAIA is a continuously scanning instrument for which the integration time on any observed object is limited by the field of view of the detector. If a final astrometric accuracy of 10 microarcsec is aimed at, a field of 1 deg in diameter is needed. A design is presented for the proposed 2.6 m baseline Fizeau interferometer with two 40 cm apertures and overall dimensions compatible with the size of the Ariane 5 payload shroud. It has a 0.9 deg diffraction limited field of view. The response of the optical system to small perturbations on each optical element is given in terms of the fringe visibility, which is shown to be dependent on the sub-aperture spot separation. The robustness of the design to thermal, mechanical and manufacturing errors is discussed. The unavoidable distortion present in wide field optical systems is analyzed in terms of displacement of the interference fringes.

Description: A direct link to an extragalactic reference system is considered as being a principle aim of the global astrometric interferometer for astrophysics (GAIA) mission. The data available from an extragalactic data base and a quasi stellar object (QSO) catalog were used to obtain an estimation of the number of QSO link candidates. The quality of presently available data and the expected accuracy of the extragalactic link are discussed. It is concluded that at least 150 QSO's must be observed by GAIA in order to guarantee an accuracy of better than 1 microarcsec/year for the link. New observations will be needed before the GAIA launch in order to reduce uncertainties in the positions, magnitudes and redshifts for some known quasars. The variability of QSO's with magnitudes near the GAIA observation limit can raise a potential problem. The motions of nearby QSO's are expected to be much smaller than 2 microarcsec/year, and therefore, will not affect the accuracy of the link in the proposed GAIA mission.

Description: We present interferometric observations of ice-sheet motion in western Greenland based on pairs of ERS-1 synthetic aperture radar (SAR) images. These observations provide the first detailed regional view of ice motion associated with dynamically supported topography near the margin of an ice sheet. The interferograms of this area are much more complicated than other interferograms of ice sheets presented to date. We devote the largest part of this paper to explaining the source of the complexity in these interferograms. A synthetic interferogram based on a simple model helps to illustrate the effects of different components of the ice velocity field in interferometric data and suggests a method for estimating the large-scale ice velocity field from such data.

Description: We report on large-scale ab initio multiconfiguration Hartree-Fock calculations for the UV0.01 multiplet, 2s(sup 2)2p(sup 2)P(sub J) - 2s2p(sup 2 4)P(sub J prime), in N III. The resulting transition probabilities agree very well with recent semiempirical calculations, and the lifetimes for two of the three upper levels agree with experiments. The deviation for the third level is discussed. Comparisons made with the highest quality IUE echelle spectra available -- those of RR Tel and V1016 Cyg (both photoionized sources with electron densities below 10(exp 8)/cu cm) -- show that computed branching ratios of lines sharing a common upper level are in agreement with observations to within uncertainties of +/- 10%. High-quality solar limb data or stellar data from the Hubble Space Telescope (HST) could, in principle, be used to determine whether the theoretical or measured lifetimes for the discrepant level are in error. Unfortunately, stellar data for high-density plasmas (N(sub e) greater than 10(exp 11)/cu cm are needed) do not yet exist, and existing solar data lack the photometric precision to address this problem.

Description: Thermal drag, a variant of the Yarkovsky effect, may act on small asteroids with sizes from a few meters to a few tens of meters. Yarkovsky thermal drag comes from an asteroid's absorbing sunlight in the visible and reradiating it in the infrared. Since the infrared photons have momentum, by action-reaction, they kick the asteroid when they leave its surface. The reradiation, which is asymmetric in latitude over the asteroid, gives a net force along the asteroid's pole. Due to the asteroid's thermal inertia, averaging this force over one orbital period produces a net drag if the spin axis has a component in the orbital plane. Thermal drag tends to circularize orbits. It can increase or decrease orbital inclinations. An object whose spin axis points in random directions over its lifetime displays little change in orbital inclination. Thermal drag appears to have little to do with the delivery of chondrites from the asteroid belt; the thermal drag timescale (10(exp 8) years for meter-sizzed objects) is long compared with their cosmic ray exposure ages, and aphelia in the asteroid belt are not expected for mature thermal drag orbits. However, Yarkovsky thermal drag may act on the recently discovered near-Earth asteroids, which have radii of 10-30 m. Asteroid 1992 DA, for instance, might have its orbit shrunk by 0.1 AU in 3 x 10(exp 7) years, removing it from an Earth-crossing orbit. The near-Earth asteroids also tend to have small to moderate orbital eccentricities, as expected for highly evolved thermal drag objects. However, the time needed to bring them in from the asteroid belt (about 10(exp 9) years) is long compared with the collisonal and dynamical lifetimes (both about 10(exp 8) years) for Earth-crossing objects, arguing against their emplacement by thermal drag.

Description: High-contrast peaks in the cosmic microwave background (CMB) anisotropy can appear as unresolved sources to observers. We fit simluated CMB maps generated with a cold dark matter model to a set of unresolved features at instrumental resolution 0.5 deg-1.5 deg to derive the integral number density per steradian n (greater than absolute value of T) of features brighter than threshold temperature absolute value of T and compare the results to recent experiments. A typical medium-scale experiment observing 0.001 sr at 0.5 deg resolution would expect to observe one feature brighter than 85 micro-K after convolution with the beam profile, with less than 5% probability to observe a source brighter than 150 micro-K. Increasing the power-law index of primordial density perturbations n from 1 to 1.5 raises these temperature limits absolute value of T by a factor of 2. The MSAM features are in agreement with standard cold dark matter models and are not necessarily evidence for processes beyond the standard model.

Description: We have simulated full-sky maps of the cosmic microwave background (CMB) anisotropy expected from cold dark matter (CDM) models at 0.5 deg and 1.0 deg angular resolution. Statistical properties of the maps are presented as a function of sky coverage, angular resolution, and instrument noise, and the implications of these results for observability of the Doppler peak are discussed. The rms fluctuations in a map are not a particularly robust probe of the existence of a Doppler peak; however, a full correlation analysis can provide reasonable sensitivity. We find that sensitivity to the Doppler peak depends primarily on the fraction of sky covered, and only secondarily on the angular resolution and noise level. Color plates of the simulated maps are presented to illustrate the anisotropies.

Description: Soft gamma repeaters are characterized by recurrent activity consisting of short-duration outbursts of high-energy emission that is typically of temperature less than 40 keV. One recent model of repeaters is that they originate in the environs of neutron stars with superstrong magnetic fields, perhaps greater than 10(exp 14) G. In such fields, the exotic process of magnetic photon splitting gamma yields gamma gamma acts very effectively to reprocess gamma-ray radiation down to hard X-ray energies. In this Letter, the action of photon splitting is considered in some detail, via the solution of photon kinetic equations, determining how it limits the hardness of emission in strongly magnetized repeaters, and thereby obtaining observational constraints to the field in SGR 1806-20.

Description: The COMPTEL sky map of the 1.8 MeV line emission from Al-26 shows an extended diffuse distribution along the Galactic plane with a peculiar large scale asymmetry about the Galactic center (GC) and a clumpy structure with several noticeable hot spots. The most prominent hot spot at the GC appears shifted to positive longitude by about 2 deg. Nearby supernova remnants or Wolf-Rayet stars are plausible explanations for individual hot spots such as in the Vela region. We show that the global asymmetry and most hot spots can be understood by a more general model: the Al-26 sources are confined in the spiral arms of our Galaxy, and coagent star formation is responsible for additional clumpiness. The off-centered GC hot spot is probably due to the observed asymmetrically distributed circumnuclear molecular gas interacting with a central stellar bar, whose existence has been inferred from IR observations.

Description: Background information and exercises are provided to: (1) establish or expand understanding of the concepts, methods, and terminology of computer processing of image producing data; (2) develop insight into the advantages of computer based image processing compared with the photointerpretation approach for processing, classifying, interpreting, and applying remote sensing data; (3) foster a broad perspective on the principal of the main techniques for image enhancement, pattern recognition, and thematic classification; (4) appreciate the pros and cons of batch and interactive modes of image analysis; (5) examine and evaluate some specific computer generated products for subscenes in Pennsylvania and New Jersey; and (6) interrelate these particular examples of output with more theoretical explanations of computer processing strategies and procedures.

Description: For abstract, see N77-26624.

Description: A discussion is presented on nickel cadmium battery life tests using reconditioning and some comparative tests not using reconditioning. The discussion is aimed at the program application part of the testing. The goals of the program were to get an increased utilization out of the battery system in geosynchronous orbit. An attempt was made to push the depth of discharge operation up around 80 to 85 percent and the intent with the reconditioning program was to extend this type of utilization out towards a 10-year life and attune the voltage regulation.

Description: The mode of operation that is of interest in this discussion is a solar array battery load-sharing mode. The battery is loaded for a fraction of a second and then charged, so the cycle is a 100 millisecond load, followed by a 500 millisecond charge. The purpose of the experiment was to evaluate the charge efficiency and the state of charge. Charge/discharge ratio graphs are presented.

Description: The use of statistical analysis (regression analysis) to determine the data correlation between eight voltage parameters is discussed. The eight parameters correlated include: temperature, depth of discharge; charge rate; discharge rate; percent recharge; concentration of KOH; amount of KOH; and precharge. Graphs are presented which show: (1) starpoint/centerpoint cycles to failure vs. parameters; (2) cycles to failure vs. temperature; and (3) positive and negative plate thickness and weight vs. cycles. An empirical equation derived from cycles to failure vs. temperature graph for cells cycled at 1C charge, 2C discharge, and 14 percent recharge is also presented.

Description: As part of the NASA lightweight battery program, the Lewis Research Center has a number of programs that are being reviewed. A brief and general discussion of these programs is presented.

Description: After using all the instrumentation that is available on a nickel hydrogen battery it will be subjected to the same low earth orbit cycles experienced by the sixty amphere hour nickel cadmium batteries now being flown on some low earth orbit missions. The objective of the test is to demonstrate real differences between the two batteries. In order to simulate flight conditions, the thermal environment and criteria for charge control will vary. The depth of discharge will be increased and testing will continue until some failures or some degradation or spread between cell performances are revealed. Different charge control modes are being considered in order to demonstrate a reasonable life for the nickel hydrogen battery.

Description: An experiment to obtain some flight experience with a nickel-hydrogen battery in low earth orbit is described. The battery was built to be as compatible with the satellite bus as possible because the satellite bus is used for recharge power. The battery is mounted on an experimental pallet on the satellite. It has its own charge control system, a modification of an existing system that is used for nickel-cadmium, which primarily uses temperature compensated voltage as its criteria. Also, on the pallet is a load bank, a resistive load band, which allows switch to various load regimes. There is some other equipment on the satellite such as the nickel-hydrogen battery to power it. Monitors attached to the 21-cell battery are described.

Description: Features of the first operational nickel hydrogen battery are described as well as experiences encountered during its testing and installation. Battery performance since launching of the NTS-2 satellite is discussed.

Description: Test data developed primarily on low earth, but also some accelerated synchronous orbit data are presented for first 40 hour ampere hour boiler plate cells. Graphic data show the following characteristics: charge/discharge voltage; charge/discharge temperature; voltage; pressure; temperature; and discharge voltage.

Description: The effects of overcharge and total cycling rate on one electrochemically impregnated and four chemically impregnated nickel electrodes are examined. Topics discussed include porosity distribution, electrode corrosion, electrolyte absorption and positive electrode involvement in the decrease in the amount of electrolyte in the separator. The electrochemically impregnated electrode is shown to be superior to all types of conventionally impregnated electrodes regardless of the loading level.

Description: A nylon separator was placed in a flooded condition in K0H solution and heated at various high temperatures ranging from 60 C to 110 C. The weight decrease was measured and the molecular weight and decomposition product were analyzed to determine: (1) the effect of K0H concentration on the hydrolysis rate; (2) the effect of K0H concentration on nylon degradation; (3) the activation energy at different K0H concentrations; and (4) the effect of oxygen on nylon degradation. The nylon hydrolysis rate is shown to increase as K0H concentration is decreased 34%, giving a maximum rate at about 16%. Separator hydrolysis is confirmed by molecular weight decrease in age of the batteries, and the reaction of nylon with molecular oxygen is probably negligible, compared to hydrolysis. The extrapolated rate value from the high temperature experiment correlates well with experimental values at 35 degrees.

Description: Nylon separator degradation was examined as a function of temperature. Electrochemically active uncharged excess negative (overcharge protection)was measured by charging a cell venting it until it became fully charged, and continuing to overcharge the vent gas. The gas was analyzed as a function of time. The amount of hydrogen evolved was examined, and the cell voltage was observed as the oxygen and/or hydrogen evolved from the cell.

Description: The modular power system, which is the first intended use for the NASA standard battery, is basically a four foot by four foot by eighteen inch box which can handle a complement of three 20 ampere hour batteries or later on the intended use is for three 50 ampere hour batteries to be the full complement. The system is designed to be used as a plug on component on a multi mission modular spacecraft. It has as a design point a basically 1250 watt orbital average load. The way it breaks up in a near earth orbit it would be somewhere around 1,000 watts for everything except 10 minutes, and during any 10 minute period it may go up to a peak of 3,000 watt load. Features of the battery reviewed include criteria to store electrical energy, the battery package, the covers and cases, and electrolytes. The capacities expected are 90 percent, the average cell capacity for 24 C, 90 percent of the actual battery capacity of 19 C, and 85 percent of the actual 25 degree battery capacity at zero discharge voltage for 50 percent DOD new battery is in the vicinity expected or predicted of 26.4 volts.

Description: A brief description of the ITOS power systems is presented. The descriptions are from viewgraphs shown to the participants of the Workshop. A block diagram of ITOS power supply subsystem is presented along with graphs representing: ITOS voltage limit versus temperature; and battery charge-discharge current profiles over an orbit period.

Description: Photoresponse distribution measurement by scanning a light spot across the surface of a semiconductor device is examined. The technqiue is used for solar cell characterization because the measured quantity is the direct expression of the distribution of the desired performance of the device. An apparatus for measuring the photoresponse distribution was set and used in the development of polysilicon thin film solar cells. A schmeatic diagram of the apparatus and an example of measurement are shown.

Description: The series resistance and diode quality factor are used for evaluation of solar cell performance. These parameters are normally deduced from the terminal I-V characteristics under forward bias. The method produces a smaller series resistance and a larger value for diode quality factor than appropriate for the device when operating as a solar cell. It is suggested that the diode quality factor be determined from measured saturated photocurrent, open circuit voltage characteristics and the series resistance be measured with an r-f bridge or calculated from a measurement of the surface sheet resistance.

Description: A method is described for testing silicon solar cells in concentrated sunlight and simulated sunlight. Concentrated sunlight is obtained by using an acrylic Fresnel lens; the simulated sunlight source is a short arc Xenon lamp. Average illumination levels during the tests are inferred from an assumed linear relationship between short circuit current and illumination. The linearity assumption is investigated for 0.3 alpha cm base resistivity silicon cells and found to be valid. Some typical results are presented to illustrate the type of information obtained during the testing.

Description: For abstract, see N77-26626.

Description: A review of recommendations for standardizing the performance rating of flat plate terrestrial solar panels is given to develop an international standard code of practice for performance rating. Required data to characterize the performance of a solar panel are listed. Other items discussed are: (1) basic measurement procedures; (2) performance measurement in natural sunlight and simulated sunlight; (3) standard solar cells; (4) the normal incidence method; (5) global method and (6) definition of peak power.

Description: The problems encountered by manufacturers and users of solar modules are summarized. Related measurement of the rated power of the module is included, and a temperature test is suggested to define the actual performance of a module. Other suggestions are given for environmental module and array tests.

Description: For abstract, see N77-26625.

Description: For abstract, see N77-26621.

Description: For abstract, see N77-26623.

Description: For abstract, see N77-26619.

Description: Solar radiation of five typical clear weather days and under a variety of conditions is used to determine the spectral distribution of the photonflux at different planes of a CdS/Cu2S solar cell. The fractions of reflected and absorbed flux are determined at each of the relevant interfaces and active volume elements of the solar cell. The density of absorbed photons is given in respect to spectral and spatial distribution. The variance of the obtained distribution, with changes in insolation and absorption spectra of the active solar cell layers, is indicated. A catalog of typical examples is given in the appendix.

Description: For abstract, see N77-26618.

Description: Spectral measurements of daily, total horizontal radiation were analyzed to determine the magnitude and character of the effects in silicon cell output. Data for different seasons and weather conditions are included. Techniques and results are described.

Description: Observations of cosmic and gamma radiation by SAS-2 satellite are summarized and analyzed to determine processes responsible for producing observed galactic radiation. In addition to the production of gamma rays in discrete galactic objects such as pulsars, there are three main mechanisms by which high-energy (greater than 100 MeV) radiation is produced by high-energy interactions involving cosmic rays in interstellar space. These processes, which produce what may be called diffuse galactic gamma-rays, are: (1) the decay of pi mesons produced by interactions of cosmic ray nucleons with interstellar gas nuclei; (2) the bremsstrahlung radiation produced by cosmic ray electrons interacting in the Coulomb fields of nuclei of interstellar gas atoms; and (3) Compton interactions between cosmic ray electrons and low-energy photons in interstellar space.

Description: Gamma ray astronomy is now beginning to provide a new look at the galactic structure and the distribution of cosmic rays, both electrons and nucleons, within the galaxy. The observations are consistent with a galactic spiral-arm model in which the cosmic rays are linearly coupled to the interstellar gas on the scale of the spiral arms. The agreement between the predictions of the model and the observations for regions of the plane where both 21-cm and 2.6-mm CO surveys exist emphasizes the need to extend these observations to include the entire plane. Future gamma-ray observations with more sensitivity and better angular resolutions, combined with these radio surveys, should shed new light on the distribution of cosmic rays, the nature of the galaxy, and the location and intensity of the spiral arms.

Description: The density distributions of pulsars in luminosity, period, Z-distance, and galactocentric distance were derived, using a uniform sample of pulsars detected during a 408-MHz pulsar survey at Jodrell Bank. There are indications of a fine-scale structure in the spatial distributions and evidence that there is a general correlation with other galactic populations and the overall spiral structure. The electron layer in our galaxy is shown to be wider than the pulsar layer and uniform on a large scale. The number of pulsars in the galaxy has been estimated and used to derive the pulsar birthrate.

Description: Thermal radiation associated with the explosion of supernovae is investigated. High temperature is required to produce copious gamma radiation of this sort. It appears that type 11 supernovae do not release much of their energy as gamma ray continuum radiation.

Description: The degree of saturation characterizing low altitude emission observations of H(I) and the optical depth corrections to the derived column and volume densities are discussed. The amount of fine-scale velocity and spatial structure diluted by the instrumental limitations of the presently available surveys are described. The general problem of detailed mapping of H(I) in the galaxy is explored. Comparison is made between the distribution of H(I) and that of CO and several other galactic tracers. Atomic hydrogen is unique in its distribution, instead of being typical of many Population I constituents. As defined by atomic hydrogen, the galactic disk has a diameter fully twice as large as that defined by the ionized and molecular states of hydrogen, as well as by other molecules, supernova remnants, pulsars, gamma-radiation, synchroton radiation, and the youngest stars. It is also less confined to the galactic equator than most of the other constituents. The degree of small scale structure apparent in the molecular observations is much greater than that in the H(I) observations.

Description: Data from the SAS-2 high-energy gamma-ray experiment reveal the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma-ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields (10 to the 12th power gauss) correspond to many radiation lengths which cause electrons to emit photons by magnetic bremsstrahlung and which cause these photons to pair-produce. The cascade develops until the mean photon energy drops below the pair-production threshold which is in the gamma-ray range; at this stage, the photons break out from the source.

Description: Considerations made in developing a model of pulsars are explored. Observational data seems to support the argument that pulsar magnetospheres may contain large masses of plasma. The cascade process resulting from pair creation enables one to interpret the X-ray emission from the Crab and Vela pulsars as synchrotron radiation. On the other hand, the optical radiation from the Crab pulsar is best understood as coherent curvature radiation. Radio emission is interpreted as curvature radiation produced by charge bunches moving along magnetic-field lines. Certain tests of this model are proposed.

Description: The results of an experiment to test storage effects on electric cells of a battery are presented and discussed. The type of cells were the 20 amp-hour OAO type. The various modes that were tested were the integration type mode, the trickle charge, the discharge shorted and the discharged OCV (open current voltage). Every six months the cells were reconditioned and approximately two weeks of tests were performed. The tests included three capacity checks, two zero-degree overcharge tests and an internal short test (the cells are shunted for 16 hours, the shunt removed and allowed to stand on local circuit recovery for 24 hours). The integration pack was discontinued after three years and the trickle charge shorted packs after five years.

Description: Some possible parameters which could be used to predict failures within packs of electrochemical cells based on measurements that are taken while the cells are cycling are discussed. Discharge and charge curves are presented and fitted to measure the efficiency of the cells in terms of voltage vs. time.

Description: A discussion is presented on the use of statistical analysis to develop a technique that will reliably predict the life of a battery.

Description: Prediction techniques are discussed for the cycle life of nickel cadmium space cells. Equations and graphs which incorporate such parameters as temperature and recharge are presented.

Description: A brief discussion on the accelerated testing of batteries is given. The statistical analysis and the various aspects of the modeling that was done and the results attained from the model are also briefly discussed.

Description: The orbit data for the Intelsat 4 spacecraft is described. The performance and characteristics of the battery used for this spacecraft are discussed. Graphs are presented which relate battery voltage to various eclipse seasons.

Description: The OSO-1 represents a recent vintage satellite, or more recent design satellite. A summary of the battery design used on OSO-1 is presented. The temperature effects on voltage and charging-discharging of the battery system are discussed.

Description: Atmospheric Explorer (AE) is a 1971 power system design, using the heritage of the ITOS system. The system design and its operation are discussed. Problems of charging and discharging the batteries and the effects of temperature on these operations are discussed. A block diagram of the power supply electronics and some graphs related to voltage and temperature for the AE battery design are presented.

Description: A discussion is presented which gives an overview of the research and technological areas on nickel cadmium batteries at the Jet Propulsion Laboratory. Some of the topics covered include: goals; failure modes and mechanisms; factors of degradation and some possible solutions; energy density; and accomplishments for FY 77 and FY 78.

Description: The battery was a three ampere hour nickel cadmium prismatic cell. The battery consists of 20 cells connected in series and there were two batteries per spacecraft. The battery operations (voltage and temperature) that the spacecraft sees during a normal operational day are discussed.

Description: The battery design of OAO-C (OAO-3) is given and consists of three-20 ampere hour 22 series connected cells in the battery. There are three batteries per spacecraft. The packaging configuration is described. The charging-discharging operations and the voltage potential of the battery system are discussed. Graphs are presented for the voltage limits (battery voltage versus temperature) and end of dark voltages (battery voltage versus ampere-hours discharged) of the battery system used on OAO-3. Data tables are also presented which give a summary of the battery performance and a comparison of OAO-3 with OAO A-2.

Description: Progress of four contractors in producing standard 20 AH nickel-cadmium cells meeting a capacity requirement of 24 + or - 2 AH and an envelope requirement listed in NASA/GSFC specification S-711-17 is reported. Among the requirements were 10 burn in cycles 24 C, 0 C, and 35 C capacity tests, charge efficiency tests and precharge verification tests.

Description: Solar array power systems for the space construction base are discussed. Nickel cadmium and nickel hydrogen batteries are equally attractive relative to regenerative fuel cell systems at 5 years life. Further evaluation of energy storage system life (low orbit conditions) is required. Shuttle and solid polymer electrolyte fuel cell technology appears adequate; large units (approximately four times shuttle) are most appropriate and should be studied for a 100 KWe SCB system. A conservative NiH2 battery DOD (18.6%) was elected due to lack of test data and offers considerable improvement potential. Multiorbit load averaging and reserve capacity requirements limit nominal DOD to 30% to 50% maximum, independent of life considerations.

Description: The graphite epoxy cell case and header developed as a means of weight reduction are discussed. Aspects considered include gas permeability, KOH compatibility, pressure and structural dynamic integrity, fiber orientation, fabrication process, cover-to-case sealing, terminal installation and sealing, reproducibility, exposure to the extractable materials that might influence the electrochemical portion of the cell, and electrical conductivity between the terminals.

Description: A summary of the ATS battery design which is onboard the Applications Technology Satellite (ATS) is provided. The 15 ampere hour nickel cadmium cells were manufactured by Gulton, 19 series connected cells per battery, and there are two batteries in each spacecraft. The operating design life was two years in a synchronous orbit, and a maximum depth of discharge of 50 percent. The design temperature for the batteries in the spacecraft was 0 to 25 C, and the charge control consisted of 1 volt versus temperature on a constant percentage voltage. Also, C/10 current limit, and a commandable trickle charge rate, using C/20 or C/60. The undervoltage was sent across a 9 cell and a 10 cell group, and it was set at one volt average per group on either group.

Description: The operation and systems design of a nickel cadmium battery system used on the Nimbus and LANDSAT satellites are discussed. Emphasis is placed on the charging-discharging operation of the battery system.

Description: Three 18 AH Li-CF batteries with a polypropylene separator and using dimethyl sulfite in Li as F6 for the electrolyte will be placed in each shuttle solid rocket booster for range safety and frustrum location aid. Mechanical vibration, acceleration, random and design vibration, and discharge evaluation tests are discussed.

Description: Three lithium SO2 cells, two lithium CF cells, and a vinyl chloride cell, all with crimped seals, and all strictly experimental, were independently discharged on resistors. Three temperatures were used and several different storage temperatures. Discharge rate generally on the nominal discharges were 0.1 amp, 0.5 amp, and 1 amp. Tests results show that the crimp seals are inadequate, especially for the SO2 cells. Normal discharges present no hazards. All cells discharge to zero. The problem of lithium cell explosions, such as occurred during off-limits testing, is discussed.

Description: The long duration exposure facility mission places temperature requirements of from -30 F to +150 F on the batteries to be used. A hermetically sealed lithium sulfur dioxide cell was tested to predict what the temperature of the battery would be over a given spectrum of temperatures of operation. Near the end of cell discharge, as the voltage started collapsing, a very high heat output rise due to chemical reaction took place. However, if the cells were thermally insulated, they vented, ignited, and burned if an attempt was made to discharge them all the way. The cells do not go into reversal. It was determined that the root of the problem was probably the chemical reaction between the lithium and the acetonitrite solvent. A redesigned cell is discussed as well as some alternates.

Description: Experiences with batteries for the Apollo Soyuz Test Project are related and the need for safety criteria for space shuttle orbiter and payload battery handling and design is assessed.

Description: Because of the disintegration of LaNi5 as the lattice expands on absorbing hydrogen, a nickel hydrogen cell similar to a nickel cadmium cell was designed. The positive electrode is wrapped in a microporous separator and the leads are insulated. A negative conducting grid is inserted and welded to the top of the can into an open ended container which is then turned upside down and filled so that LiNa5 powder occupies all the space not used by the rest of the components. The bottom of the can is then welded on. A fill tube is located either on the bottom or on the top of the can. When welded shut, the cell is put into a pressure bomb and the lanthanum nickel is activated at about 1,000 pounds of hydrogen. Electrolytes are added to the cell as well as whatever amount of hydrogen precharge desired, and the cell is sealed. Advantages and disadvantages of the cell are discussed.

Description: Values for the capacity loss with time, naturally on open circuit stand, and information regarding the minimum amount of circuit charge needed to keep the cell charged can be determined from the self-discharge behavior of nickel hydrogen cells. Furthermore, the rate of reaction between hydrogen and a charged nickel electrode is also open for nickel cadmium batteries. In a nickel hydrogen cell, the hydrogen is stored as pressurized gas and the cell stack with the charge that is oxidized nickel-hydroxide electrode is in direct contact with the hydrogen. Therefore, the rate of reaction can be measured easily and precisely by monitoring the charge, the change in hydrogen pressure with time. Measures made on twelve 15 ampere hour nickel hydrogen cells of different stack configurations built for COMSAT are discussed.

Description: Design criteria are discussed for a hermetic seal capable of withstanding the 450 C operating temperature of a lithium-metal sulfide battery system. A mechanical seal consisting of two high strength alloy metal sleeves welded or brazed to a conductor assembly and pressed onto a ceramic is described. The conductor center passes through the ceramic but is not sealed to it. The seal is effected on the outside of the taper where the tubular part is pressed down over and makes contact.

Description: Isolated knobs that are erosional remnants of central volcanoes or of folded rocks occur in several areas of the Altiplano are visible on both optical and images. The optically visible streaks occur in the immediate lee of the knobs, whereas the radar visible streaks occur in the zone downwind between the knobs. Aerial reconnaissance and field studies showed that the optically visible streaks consist of a series of small ( 100 m wide) barchan and barchanoid dunes, intradune sand sheets, and sand hummocks (large shrub coppice dunes) up to 15 m across and 5 m high. On LANDSAT images these features are poorly resolved but combine to form a bright streak. On the radar image, this area also appears brighter than the zone of the radar dark streak; evidently, the dunes and hummocks serve as radar reflectors. The radar dark streak consists of a relatively flat, smooth sand sheet which lacks organized aerolian bedforms, other than occasional ripples. Wind velocity profiles show a greater U value in the optically bright streak zone than in the radar dark streak.

Description: The diversity of proposed origins for large Martian outflow channels results from the differing interpretations given to the landforms associated with the outflow channels. In an attempt to help limit the possible mechanisms of channel erosion, detailed studies of three of the channel features were done; the streamlined islands, longitudinal grooves and scour marks. This examination involved a comparison of the martian streamlined islands with various streamlined landforms on Earth including those found in the Channel Scabland in large rivers, glacial drumlins, and desert yardangs. The comparisons included statistical analyses of the landform lengths versus widths and positions of maximum width, and an examination of the degree of shape agreement with the geometric lemniscate which was in turn demonstrated to correspond closely with true airfoil shapes. The analyses showed that the shapes of the martian islands correspond closely to the streamlined islands in rivers and the Channel Scabland land. Drumlins show a much smaller correlation. Erosional rock islands formed by glaciers are very much different in shape.

Description: Final revisions were made in the study of continuum spectrophotometry of 17 comets done at Lick Observatory. Changes based upon this study were introduced into the Divine-Newburn cometary modelling paradigm. Work was begun on modifications to all of the theory based upon the direct nucleus and coma observations made by the Halley space missions.

Description: An Atlas of Comet Halley 1910 II photographs and spectra is being prepared. The major section consists of 838 photographic observations from fifteen observatories around the world. Multiple images of many photographs are reproduced to bring out detail in the near nucleus region, in the coma and in the tail. The Atlas contains a total of 1209 photographic images of the 1910 apparition. In addition there are sections showing drawings from 1935 and 1910. A short section compares 1910 drawings and photographs. The final two sections display digitally processed images from 1910 and 1910 spectra. A three part appendix contains diagrams of various data associated with the 1910 apparition, a set of tables of all 1910 images and a bibliography.

Description: Two innovative thermodynamic power cycles are analytically examined for future engineering feasibility. The power cycles use a hydrogen-oxygen fuel cell for electrical energy production and use the thermal dissociation of water for regeneration of the hydrogen and oxygen. The TDS (thermal dissociation system) uses a thermal energy input at over 2000 K to thermally dissociate the water. The other cycle, the HTE (high temperature electrolyzer) system, dissociates the water using an electrolyzer operating at high temperature (1300 K) which receives its electrical energy from the fuel cell. The primary advantages of these cycles is that they are basically a no moving parts system, thus having the potential for long life and high reliability, and they have the potential for high thermal efficiency. Both cycles are shown to be classical heat engines with ideal efficiency close to Carnot cycle efficiency. The feasibility of constructing actual cycles is investigated by examining process irreversibilities and device efficiencies for the two types of cycles. The results show that while the processes and devices of the 2000 K TDS exceed current technology limits, the high temperature electrolyzer system appears to be a state-of-the-art technology development. The requirements for very high electrolyzer and fuel cell efficiencies are seen as determining the feasbility of the HTE system, and these high efficiency devices are currently being developed. It is concluded that a proof-of-concept HTE system experiment can and should be conducted.

Description: This report discusses and documents the design, development, and verification of a microcomputer-based solar cell math model for simulating the Space Station's solar array Initial Operational Capability (IOC) reference configuration. The array model is developed utilizing a linear solar cell dc math model requiring only five input parameters: short circuit current, open circuit voltage, maximum power voltage, maximum power current, and orbit inclination. The accuracy of this model is investigated using actual solar array on orbit electrical data derived from the Solar Array Flight Experiment/Dynamic Augmentation Experiment (SAFE/DAE), conducted during the STS-41D mission. This simulator provides real-time simulated performance data during the steady state portion of the Space Station orbit (i.e., array fully exposed to sunlight). Eclipse to sunlight transients and shadowing effects are not included in the analysis, but are discussed briefly. Integrating the Solar Array Simulator (SAS) into the Power Management and Distribution (PMAD) subsystem is also discussed.

Description: Multipolarized airborne Synthetic Aperture Radar (SAR) data were acquired over a largely agricultural test site near Macomb, Illinois, in conjunction with the Shuttle Imaging Radar (SIR-B) experiment in October 1984. The NASA/JPL L-band SAR operating at 1.225 GHz made a series of daily overflights with azimuth view angles both parallel and orthogonal to those of SIR-B. The SAR data was digitally recorded in the quadpolarization configuration. An extensive set of ground measurements were obtained throughout the test site and include biophysical and soil measurements of approximately 400 agricultural fields. Preliminary evaluation of some of the airborne SAR imagery indicates a great potential for crop discrimination and assessment of canopy condition. False color composites constructed from the combination of three linear polarizations (HH, VV, and HV) were found to be clearly superior to any single polarization for purposes of crop classification. In addition, an image constructed using the HH return to modulate intensity and the phase difference between HH and VV returns to modulate chroma indicates a clear capability for assessment of canopy height and/or biomass. In particular, corn fields heavily damaged by infestations of corn borer are readily distinguished from noninfested fields.

Description: Multipolarization Synthetic Aperture Radar (SAR) data from the NASA/JPL aircraft SAR were used in conjunction with LANDSAT Thematic Mapper (TM), Thermal Infrared Multispectral Scanner (TIMS), and Airborne Imaging Spectrometer (AIS) data as part of a three-year research program to evaluate the utility of remote sensing measurements for analysis of sedimentary basins. The purpose of this research effort is to construct stratigraphic columns, map variations in the lithology, geometry, and structure of sedimentary rocks in the Wind River/Bighorn Basin area, Wyoming, and to integrate remote sensing data with conventional rain models of basin formation and evolution.

Description: Several digital data processing techniques were evaluated in an effort to identify and map active/abandoned, partially reclaimed, and fully revegetated surface mine areas in the central portion of Logan County. The TM data were first subjected to various enhancement procedures, including a linear contrast stretch, principal components and canonical analysis transformations. At the same time, four general procedures were followed to produce six classifications as a means of comparing the techniques involved. Preliminary results show that various feature extraction/data reduction techniques provide classification results equal or superior to the more straightforward unsupervised clustering technique. Analyst interaction time for labelling clusters is reduced using the canonical analysis and principal components procedures, though the canonical technique has clearly produced better results to date.

Description: The design and operations of a low cost, high rate thermal cycling facility designed for LEO conditions is described. Thermal cycling facilities were constructed with various design criteria. Some were designed to duplicate as closely as possible the conditions a cell or module would encounter while in orbit about the Earth. A typical facility to perform this type of cycling was a large vacuum system with liquid nitrogen cooled walls. The cells were heated by an AMO spectrum solar simulator, then a shutter was closed allowing the cells to give up their heat to the cold walls. This system was good at duplicating the orbital conditions but was slow and very costly to operate. Other systems used a gas atmosphere and heated the cells with radiant heat and cooled the cells by moving them into close proximity to a cold plate. The systems greatly increased the cycle times. Other systems moved the heating and cooling atmosphere into and out of the test areas and achieved reasonable cycle rates. All these systems, however, are expensive to operate.