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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
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NASA NTRS1980

Far infrared measurement of stratospheric HCl

Thermal emission from three rotational lines of H(Cl-35) and H(Cl-37) was observed with a Fourier transform spectrometer from a balloon platform at 28.9 km. The measured HCl line-of-sight density at 1.9 deg elevation above 28.9 km is 4.7 + or - 1.3 x 10 to the 15th/sq cm, implying an average volume mixing ratio of 0.8 + or - 0.2 x 10 to the -9th at the mean sampling altitude of 32.5 km. For a uniform mixing ratio model, this corresponds to a vertical column density of 2.4 + or - 0.6 x 10 to the 14th/sq cm. This result is in reasonable agreement with near infrared spectroscopic determinations and an abundance from a chemical sampling technique of HCl at this altitude; a pressure modulator radiometer measurement yields a significantly higher amount of HCl.

Chance, K. V.↗
NASA NTRS1981

Simulation of the magnetic structure of the inner heliosphere by means of non-spherical source surface

A new method for mapping the Sun's magnetic field B from the photosphere through the corona and interplanetary space is presented. The method entails the derivation of B from a scalar potential within a current-free annular volume bounded inside by photosphere and outside by a prescribed nonspherical source surface to which B is made (as nearly as possible) perpendicular. As usual we obtain the potential for the part of B that arises from currents inside the Sun by fitting an expansion to the observed line-of-sight component of B at the photosphere. A second least-squares fit is introduced to obtain the part of B that arises from currents outside the source surface. Comparisons are made between this model and observed coronal and interplanetary structures. There is evidence that observation data underestimate the strength of photospheric polar magnetic fields.

Levine, R. H.↗
NASA NTRS1981

Molecular hydrogen emission from W51

The detection of emission from the v = 1 approaches 0 S(1) quadrupole transition of H2 toward the cluster of intense infrared and H2O maser sources in W51 (north) is reported. The apparent luminosity of this line in W51 (north) is only about 4% of the luminosity of the same line toward the Kleinmann-Low infrared cluster in Orion; however, additional line-of-sight extinction and spatial extent of the source may account for the lower apparent power in W51. Similarity in the infrared and H2O properties of these clusters is addressed. The implications of the H2 emission for mass loss in the W51 region is discussed and some proposed models of radiation-driven mass outflow from pre-main sequence stars are briefly considered.

Beckwith, S.↗
NASA NTRS1980

Steady flows in the chromosphere and transition-zone above active regions as observed by OSO-8

Two years of data from the University of Colorado ultraviolet spectrometer aboard OSO-8 were searched for steady line-of-sight flows in the chromosphere and transition-zone above active regions. The most conspicuous pattern that emerges from this data set is that many sunspots show persistent blueshifts of transition-zone lines indicating velocities of about 20 km/s with respect to the surrounding plage areas. The data show much smaller shifts in ultraviolet emission lines arising from the chromosphere: the shifts are frequently to the blue, but sometimes redshifts do occur. Plage areas often show a redshift of the transition-zone lines relative to the surrounding quiet areas, and a strong gradient of the vertical component of the velocity is evident in many plages. One area of persistent blueshift was observed in the transition-zone above an active region filament. The energy requirement of these steady flows over sunspots is discussed.

Lites, B. W.↗
NASA NTRS1981

The gravity field in the central Pacific from satellite-to-satellite tracking

Satellite-to-satellite Doppler tracking between the ATS 6 and the GEOS 3 spacecraft was used to measure the high-degree and high-order gravity field over an 80-deg region in the central Pacific Ocean. Forty passes of GEOS 3/ATS 6 Doppler data have been analyzed. The precision of these range rate data is about 0.3 mm/s, and the line-of-sight gravity anomalies recovered from these data have a precision of about 0.2 mGal at the GEOS 3 altitude of about 840 km. In general, the agreement between the SST-derived map and the conventional GEM method and an altimeter-derived geoid is good. Eight significant positive gravity anomalies were exposed in the central Pacific. Generally speaking, the anomalies form a roughly east-west pattern of alternating sign in the central region, and near the East Pacific they strike about north and south.

Marsh, J. G.↗
NASA NTRS1981

Mars - Hellas Planitia gravity analysis

Doppler radio tracking data from Viking Orbiter 1 has provided new detailed observations of gravity variations over Hellas Planitia. Line-of-sight Bouguer gravity definitely indicates that isostatic adjustment has occurred. Two theoretical models were tested to obtain fits to the gravity data. Results for a surface deficit model, and a model with a surface deficit and a mass excess at depth are displayed. The mass-at-depth model produced very marked improvement in the data fit as compared to the surface deficit model. The optimum depth for the mass excess is 130 km.

Sjogren, W. L.↗
NASA NTRS1981

Venus gravity fields

Results of Pioneer Venus Orbiter observations concerning the gravity field of Venus are presented. The gravitational data was obtained from reductions of Doppler radio tracking data for the Orbiter, which is in a highly eccentric orbit with periapsis altitude varying from 145 to 180 km and nearly fixed periapsis latitude of 15 deg N. The global gravity field was obtained through the simultaneous estimation of the orbit state parameters and gravity coefficients from long-period variations in orbital element rates. The global field has been described with sixth degree and order spherical harmonic coefficients, which are capable of resolving the three major topographical features on Venus. Local anomalies have been mapped using line-of-sight accelerations derived from the Doppler residuals between 40 deg N and 10 deg S latitude at approximately 300 km spatial resolution. Gravitational data is observed to correspond to topographical data obtained by radar altimeter, with most of the gravitational anomalies about 20-30 milligals. Simulations evaluating the isostatic states of two topographic features indicate that at least partial isostasy prevails, with the possibility of complete compensation.

Sjogren, W. L.↗
NASA NTRS1981

The distribution and morphology of X-ray-emitting gas in the core of the Perseus cluster

An unresolved source has been found coincident with the nucleus of NGC 1275 in a high-resolution X-ray image of the core of the Perseus cluster. Absorption in the optical features at high velocity with respect to NGC 1275, which are thought to be associated with a foreground galaxy, does not produce any detectable X-ray absorption. The emission tends to become asymmetric in the presence of the lower-velocity filaments, but no obvious, detailed correlation is found between X-ray enhancements and individual filaments. Deprojection of surface brightness to yield temperature and density profiles of the intracluster gas shows results consistent with a quasi-hydrostatic radiative accretion flow onto NGC 1275, and the pressure-driven mass inflow onto the central galaxy is then 200-400 solar masses/yr. The possibility of a problem in the relation of line-of-sight velocity dispersion to cluster gravitational mass is confirmed.

Fabian, A. C.↗
NASA NTRS1981

Chatanika radar measurements of the electrical properties of auroral arcs

Ionospheric parameters measured in the presence of auroral arcs by the incoherent scatter Chatanika radar are used to define properties of the arcs. The radar broadcasts at 3-5 MW with a range resolution of 4.5 km along the radar line-of-sight, and has yielded auroral measurements on the variation of electron density, Hall and Pederson conductivity, horizontal electric fields, electrojet currents, precipitating electron energy flux, and the Joule heating rate. Elevation-scan techniques have been utilized to study the latitude and altitude variation of the ionospheric plasma parameters, and fixed-position scans allow determination of ionization conditions, including the electric fields and the acceleration of precipitating auroral electrons. Arcs in the diffuse aurora have been found to be local conductivity enhancements, while discrete arcs correspond to the boundary plasma sheet and have an asymmetric electric field pattern reduced on the northward side.

Vondrak, R. R.↗
NASA NTRS1981

Sodium remote from Io

Measurements of sodium emission lines originating in the middle Jupiter magnetosphere are measured, confirming the wide dispersal of neutral sodium in the Jovian system in at least two distinct manifestations. Candidate neutral transport processes in the context of the observed kinematical signatures are discussed. It is argued that the normal emission feature is produced by sodium atoms on bound elliptical orbits originating in the Io sodium cloud but with apojove in the field of view. Observations of the fast sodium feature indicate that atoms episodically acquire a broad range of line-of-sight velocities above the Jupiter gravitational escape speed and far above the speeds characteristic of surface-sputtered atoms. Three suggested reactions are distinguished according to (1) production rates based on estimated plasmaspheric properties, (2) kinematical signature, and (3) the timing of occurrences of the fast sodium feature.

Brown, R. A.↗
NASA NTRS1981

UVSP/SMM observations of transition region oscillations in sunspots

Using Ultraviolet Spectrometer and Polarimeter data obtained in emission lines formed at temperatures of 70,000 K to 130,000 K, transition region oscillations in sunspots have been observed. The frequency of these oscillations lies in the range 5.8 mHz to 7.8 mHz. Their regular appearance in line-of-sight velocity and their frequent occurrence in intensity in phase with maximum blue shift leads to the interpretation of the oscillations as upward-propagating acoustic waves. The presence in two of the C IV wavelength 1548.19 time series of a phase-shifted oscillation in the line width may be caused by the presence of unidentified blends in the line wings. The energy flux carried by the umbral acoustic waves is less than 2000 erg/sq cm/s, some seven orders of magnitude smaller than the missing radiative flux of sunspots.

Gurman, J. B.↗
NASA NTRS1961

Analog Simulation of a Pilot-Controlled Rendezvous

The rendezvous of a pilot-controlled space ferry vehicle with an orbiting space station was simulated in six degrees of freedom. A fixed-base simulator and an analog computer were used. The ferry vehicle was assumed to have a single main thrusting rocket and to be provided with attitude control. Control of the thrust was provided by a rocket throttle quadrant which could provide either proportional or on-off control. The attitude of the vehicle was controlled during the rendezvous with a two-axis, pencil-type side-arm controller and rudder pedals. For the most part rendezvous maneuvers were made with the target satellite in a circular orbit. In addition, an elliptical station orbit was investigated. Tolerable initial conditions, as well as adequate data presentations, were determined. Results of the investigation indicate that a human pilot can rendezvous successfully with the vehicle and instrumentation considered over a wide band of initial conditions. Coplanar conditions are not necessary. Retro-rocket fuel used is not greatly increased by imposing perturbing influences such as rocket-misalignment torques on the rendezvous vehicle. When excessive attitude-control torques are required to maintain the necessary trim attitudes under misalignment influences, the reaction fuel used for this control increases. The time required for a specific rendezvous varies somewhat between pilots. If control of the time for completing the rendezvous is desired, requirements for retrorocket fuel are affected, and an energy-management schedule is required. Continuous variation of the thrust is not necessary. The pilot positions the throttle to obtain a desired level of thrust, and applies bursts of thrust as required. All data were presented on dialed instruments. The quantities required are range and range rate and line-of-sight rates between the vehicle and the station, vehicle attitudes and angular rates, and the angles subtended by the line of sight. For the equipment assumed herein, satellite rendezvous presented no great problem to the pilot.

Brissenden, Roy F.↗
NASA NTRS2026

The Thermal and Kinematic Sunyaev–Zeldovich Effect in Galaxy Clusters and Filaments Using Multifrequency Temperature Maps of the Cosmic Microwave Background A399–A401 Cluster Pair Case Study

We present a multifrequency and multi-instrument methodology to study the physical properties of galaxy clusters and cosmic filaments using cosmic microwave background observations. Our approach enables simultaneous measurement of both the thermal (tSZ) and kinematic Sunyaev–Zeldovich (kSZ) effects, incorporates relativistic corrections, and models astrophysical foregrounds such as thermal dust emission. We do this by jointly fitting a single physical model across multiple maps from multiple instruments at different frequencies, rather than fitting a model to a single Compton-y map. We demonstrate the success of this method by fitting the A399–A401 galaxy cluster pair and filament system using archival data from the Planck satellite and new, targeted deep data from the Atacama Cosmology Telescope, covering 11 different frequencies over 14 maps from 30 GHz to 545 GHz. Our tSZ results are consistent with previous work using Compton-y maps. We measure the line-of-sight peculiar velocities of the cluster–filament system using the kSZ effect and find statistical uncertainties on individual cluster peculiar velocities of ≲600 km s −1 , which are competitive with current state-of-the-art measurements. Additionally, we measure the optical depth of the filament component with a signal-to-noise of 8.5σ and reveal hints of its morphology. This modular approach is well-suited for application to future instruments across a wide range of millimeter and submillimeter wavebands.

Ajay S Gill↗
DOE OSTI2025

Characterization of Flashback and Flame-Holding in a Jet-in-Crossflow Mixing Configuration with Methane-Hydrogen Fuel Blends

An approach that combines experimental and numerical analyses has been implemented to characterize the fundamentals of flashback events and flame-holding phenomena during high-hydrogen combustion in a jet-in-crossflow (JICF) configuration. Such flame dynamics are visualized experimentally using nanosecond (ns)-based hydroxyl planar laser-induced fluorescence (OH-PLIF) and chemiluminescence diagnostics techniques. The JICF burner has an optically accessible pre-mixing tube allowing the optical diagnostics. The testing was conducted for varied pre-mixer velocities (V) and equivalence ratio (ϕ) for 90%-100% (H2, by mole) H2/CH4 reactant mixtures at atmospheric temperature and pressure conditions. Two distinct flashback events were identified – conventional rich flashback and lean flashback, recorded while increasing ϕ and decreasing ϕ, respectively. The cause of lean flashback was attributed to the lower momentum flux ratio which bends the jet sharply, closer toward the injection plane. The mean OH-PLIF images characterized the flame-holding behavior where the flame was found to be stabilized on the leeward side only or on both windward and leeward sides as a lifted flame near the fuel port. A Large Eddy Simulation (LES) with detailed chemistry combustion modeling approach was implemented along an OH* sub-mechanism, and it showed qualitative agreement with the integrated line-of-sight chemiluminescence results as well as the planar OH-PLIF measurements.

flame holding↗
DOE OSTI2025

Stripline Block Sensor System

The Long Baseline Neutrino Facility requires a secondary sensor system to aid in the installation and replacement of the stripline blocks. These blocks are responsible for delivering large amounts of current to the horn and must be installed with high precision to avoid possible physical damage. There are many constraints due to the modules' surroundings, such as small clearances and a highly radioactive environment. Existing systems have already been implemented within the process; however, these systems offer limited information, leaving much risk during operations. This calls for a sufficiently accurate sensor system, which has a small space requirement and provides valuable information throughout the replacement period. A variety of methods and technologies were explored to provide an applicable approach to the issue. The proposed solution consisted of the use of retroreflective and target, however, it cannot provide positional feedback throughout the entire process. A proposed alternative utilizes a three-dimensional indoor positioning system to provide the operator with real-time positioning and rotational information. Sensors placed on the module and stripline would communicate with fixed receivers surrounding the target hall to provide precise positional feedback. However, this solution may still contain line-of-sight issues as well as installation complications due to the radioactive environment. Future work would consist of finding vendors capable of providing technology that fits our constraints, proof of concept tests for both solutions, implementation planning, and trials within the target hall itself. Due to its ability to provide continuous positional and rotational feedback, the indoor positioning system is the most suitable solution for accurately installing the stripline block.

Espinoza, David [Unlisted, US]↗
DOE OSTI2026

FolpsD: combining EFT and phenomenological approaches for joint power spectrum and bispectrum analyses

We present a theoretical model for the power spectrum and bispectrum of galaxy clustering that exploits the complementarity between small-scale power spectrum information and large-scale bispectrum measurements. We extend the FOLPS code by combining its one-loop EFT galaxy power spectrum with a tree-level galaxy bispectrum projected onto the tripolar spherical harmonics (Sugiyama) basis. To access additional small-scale information, we also consider a line-of-sight damping factor in both statistics, mirroring approaches commonly used in studies of redshift-space distortions. We test the model using DESI DR2 galaxy mocks. Even without damping, the joint analysis of the EFT power spectrum and bispectrum significantly improves constraints and reduces parameter degeneracies relative to power spectrum analyses alone. For LRG-like samples, including the damping further extends the range beyond $k\sim 0.3 \,h \text{Mpc}^{-1}$ in the power spectrum and $k \sim 0.24 \,h \text{Mpc}^{-1}$ in the bispectrum without introducing statistically significant parameter biases. This leads to up to $\sim 30\%$ tighter constraints on $A_s$ and $ω_{cdm}$. For low signal-to-noise tracers such as QSOs, however, the damping parameters are weakly constrained and can absorb noise fluctuations, leading to shifts in inferred parameters. Similar limitations may arise in models where cosmological information is encoded in power-spectrum shape features degenerate with the damping, such as scenarios with massive neutrinos. In contrast, for $w_0w_a$CDM we obtain $15\%$ and $21\%$ tighter constraints on $w_0$ and $w_a$, respectively, yielding a deviation from constant dark energy at slightly more than the $1σ$ level using full-shape information alone. The code is publicly available at https://github.com/cosmodesi/FolpsD

Bansal, P. [Michigan U., MCTP; Michigan U.] (ORCID↗
DOE OSTI2026

Characterizing the GD-1 Stream with DESI DR2 Data: Thin Stream and Hot Cocoon

GD-1 is among the longest, coldest stellar streams in the Milky Way, making it an ideal target for probing dark matter substructure through dynamical heating. We present a catalog of 608 spectroscopically confirmed GD-1 members from the first three years of Dark Energy Spectroscopic Instrument (DESI) observations. This constitutes the largest homogeneous spectroscopic sample of GD-1, doubling the number of members previously available only through heterogeneous compilations combining multiple surveys with different systematics. Using these data, we derive updated stream tracks in sky position, proper motion, and radial velocity that extend over $100^\circ$ of the stream. We apply a Gaussian mixture model to decompose the stream into a dynamically cold thin component ($σ_V = 2.49\pm 0.28$ km s$^{-1}$, width $= 0.23\pm0.01^\circ$) and a kinematically hot cocoon ($σ_V = 6.13\pm0.75$ km s$^{-1}$, width $= 2.18\pm0.17^\circ$). The cocoon contains $\sim30\%$ of members and its velocity dispersion is consistent with $\sim11$ Gyr of heating by cold dark matter subhalos. We also detect a large proper motion dispersion ($41.36\pm4.98$ km s$^{-1}$) along the stream direction in the cocoon component. This feature indicates a significant line-of-sight distance spread in the cocoon, and its origin will be further explored in a forthcoming paper. These measurements demonstrate the power of DESI spectroscopy for characterizing the multi-component phase-space structure of stellar streams and constraining small-scale dark matter substructure.

Jarvis, Emma [Toronto U.] (ORCID:0009000656127336)↗
DOE OSTI2026

Precision Kinematic Sunyaev--Zel'dovich Measurements Across Halo Mass and Redshift with DESI DR2 and ACT DR6: Part II. Bright Galaxy Survey and Emission-Line Galaxies

We present the first high-significance spectroscopic stacked kinetic Sunyaev-Zel'dovich (kSZ) measurements of circumgalactic gas profiles for both Bright Galaxy Survey (BGS) and Emission Line Galaxy (ELG) tracers, combining DESI Data Release 2 with ACT Data Release 6. Using reconstructed line-of-sight velocities from the DESI galaxies and high-resolution ACT temperature maps, we detect the kSZ signal at high significance, reaching signal-to-noise ratios of up to $\sim$9 for BGS and $\sim$7.5 for ELGs in optimal stellar-mass selections. Together with the LRG measurements presented in Paper I, these constitute the most significant kSZ detections from any spectroscopic survey to date. We perform the analysis in both real and harmonic space, obtaining consistent results. By splitting both tracers into stellar-mass bins, we study the scaling of the kSZ amplitude with galaxy properties. Combining the kSZ measurements with ACT Data Release 6 (DR6) CMB lensing maps enables a joint calibration of the galaxy-halo connection and the gas fractions of host halos. For the BGS galaxies, we observe low gas fractions around the virial radius relative to standard expectations, likely attributable to active galactic nuclei (AGN) activity. We find some evidence for higher-mass halos retaining a larger fraction of their baryons, consistent with more efficient feedback in lower-mass systems. For the ELG sample, dominated by blue, star-forming galaxies, we provide the first detection of the gas distribution in ELG host halos. The ELGs appear to exhibit relatively high gas fractions, which points to the possibility of weaker feedback (due to e.g. low AGN and supernova feedback activity) at their mass scale. Finally, we present generalized Navarro-Frenk-White (GNFW) fits to the harmonic-space measurements, providing a compact parametrization of gas profiles for forward modeling in large-scale structure analyses.

Hadzhiyska, B. [Cambridge U.; Cambridge U., Inst. ↗