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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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NASA NTRSDate not supplied

Preliminary JPSS-3 VIIRS Polarization Sensitivity and Comparison with S-NPP, JPSS-1 and -2

The Visible-Infrared Imaging Radiometer Suite (VIIRS) was first launched on-board the Suomi National Polar-orbiting Partnership (S-NPP) spacecraft in October of 2011. There have been three subsequent builds of the VIIRS sensor for the Joint Polar Satellite System (JPSS) program with JPSS-1, -2 and -3 having launch dates of November 2017, March 2022 and 2026 respectively. There is also a JPSS-4 VIIRS, that is in hardware integration during 2020, with a launch date of 2031. VIIRS has 22 bands: 7 thermal emissive bands (TEBs), 14 reflective solar bands (RSBs) and a Day Night Band (DNB). Ocean Color/Chlorophyll (OCC) products use calibrated Science Data Records (SDRs) for bands M1-M7 (0.412-0.865μm) to compute their ocean chemistry products. These bands require accurate polarization sensitivity characterization to compensate for polarized upwelling Rayleigh scatter and produce accurate OCC Environment Data Products (EDRs). VIIRS polarization sensitivity requirement failures have driven hardware modifications to the bandpass filters and dichroic beam splitter over the program. This paper will discuss the preliminary JPSS-3 polarization results and how these hardware modifications, as the JPSS program progresses, have affected the sensor performance. Comparisons of the polarization sensitivities between sensor builds will be discussed along with the hardware modifications that contributed to their differences.

VIIRS↗
NASA NTRS2014

Performance Characterization of UV Science Cameras Developed for the Chromospheric Lyman-Alpha Spectro-Polarimeter

The NASA Marshall Space Flight Center (MSFC) has developed a science camera suitable for sub-orbital missions for observations in the UV, EUV and soft X-ray. Six cameras will be built and tested for flight with the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), a joint National Astronomical Observatory of Japan (NAOJ) and MSFC sounding rocket mission. The goal of the CLASP mission is to observe the scattering polarization in Lyman-alpha and to detect the Hanle effect in the line core. Due to the nature of Lyman-alpha polarization in the chromosphere, strict measurement sensitivity requirements are imposed on the CLASP polarimeter and spectrograph systems; science requirements for polarization measurements of Q/I and U/I are 0.1 percent in the line core. CLASP is a dual-beam spectro- polarimeter, which uses a continuously rotating waveplate as a polarization modulator, while the waveplate motor driver outputs trigger pulses to synchronize the exposures. The CCDs are operated in frame-transfer mode; the trigger pulse initiates the frame transfer, effectively ending the ongoing exposure and starting the next. The strict requirement of 0.1 percent polarization accuracy is met by using frame-transfer cameras to maximize the duty cycle in order to minimize photon noise. Coating the e2v CCD57-10 512x512 detectors with Lumogen-E coating allows for a relatively high (30 percent) quantum efficiency at the Lyman-alpha line. The CLASP cameras were designed to operate with a gain of 2.0 +/- 0.5, less than or equal to 25 e- readout noise, less than or equal to 10 e-/second/pixel dark current, and less than 0.1percent residual non-linearity. We present the results of the performance characterization study performed on the CLASP prototype camera; system gain, dark current, read noise, and residual non-linearity.

Champey, Patrick↗
NASA NTRS1985

The San Fernando Observatory video Stokes polarimeter

A study was conducted to determine the suitability of the San Fernando Observatory's 61 cm (24 inch) aperture vacuum solar telescope and 3 m (118 inch) focal length vacuum spectroheliograph for Stokes Polarimetry measurements. The polarization characteristics of these two instruments was measured by determining their Mueller matrices as a function of telescope orientation, field angle, wavelength, grating type, and position of the measuring beam in the telescope entrance window. In general, the polarizing and depolarizing properties are small so that inversion of the system Mueller matrix will permit the accurate measurement of Stokes profiles for vector magnetic field determination. A proposed polarimeter design based on the use of a TV camera system to simultaneously scan six different polarization components of a given line profile is described. This design, which uses no rotating optics or electronic modulators and makes efficient use of the available irradiance, promises to yield high quality vector magnetograms.

Richter, P. H.↗
NASA NTRS1992

Scanning-Pencil-Beam Radar Scatterometer

SCANSCAT conceptual scanning radar scatterometer placed in nearly polar orbit around Earth at altitude of 705 km aboard Spacecraft B of NASA's Earth Observing System. Measures radar backscattering from surface of ocean. Data processed on ground into normalized radar-backscattering cross sections, then processed into velocities of winds near surface of ocean by use of empirical mathematical model of relationship between normalized backscattering cross section, wind vector at scanned spot, and angle of incidence and azimuth angle of radar beam. Accuracy and coverage exceeds those of fan-beam scatterometer. Modified versions of scanning plan useful in laser inspection of surface finishes on machined parts.

Long, David G.↗
NASA NTRS1973

Light-direction sensor based on birefringency

Optical system consisting of polarizer, analyzer, quarterwave retarder converts incident light beam to one which has an intensity related to the extent the incident beam is off axis.

Johnston, A. R.↗
NASA NTRS1975

Design of an offset fed scanning antenna for the shuttle imaging microwave system

A design study is described for a mechanically scanned offset fed parabolic torus reflector antenna having a 4m x 2m aperture for simultaneous use at eleven frequency channels from UHF to millimeter wavelengths. A design for the antenna is presented utilizing dipole and horn feeds at the low frequencies and a Gregorian aberration correcting subreflector system for feeding the torus at the high frequencies. The results and details of a theroetical study based on geometrical optics performed to evaluate the high frequency design and the results of an experimental study involving a one-tenth scale model for evaluation of the low-frequency behavior are given. Beam efficiencies, antenna patterns, beamwidths and cross polarization levels are presented and these results demonstrate that the antenna concept is viable for the Shuttle Imaging Microwave System requirement.

Gustincic, J. J.↗
NASA NTRS1975

The 1.06 micrometer wideband laser modulator: Fabrication and life testing

The design, fabrication, testing and delivery of an optical modulator which will operate with a mode-locked Nd:YAG laser at 1.06 micrometers were performed. The system transfers data at a nominal rate of 400 Mbps. This wideband laser modulator can transmit either Pulse Gated Binary Modulation (PGBM) or Pulse Polarization Binary Modulation (PPBM) formats. The laser beam enters the modulator and passes through both crystals; approximately 1% of the transmitted beam is split from the main beam and analyzed for the AEC signal; the remaining part of the beam exits the modulator. The delivered modulator when initially aligned and integrated with laser and electronics performed very well. The optical transmission was 69.5%. The static extinction ratio was 69:1. A 1000 hour life test was conducted with the delivered modulator. A 63 bit pseudorandom code signal was used as a driver input. At the conclusion of the life test the modulator optical transmission was 71.5% and the static extinction ratio 65:1.

Teague, J. R.↗
NASA NTRS1978

Experimental studies of the formation/deposition of sodium sulfate in/from combustion gases

Interference in a reflected beam of monochromatic light from a linearly polarized helium-neon laser was used to determine the dew point and deposition rate of B2O3 on a heated platinum target. Preliminary results at different BCl3 seed levels, except for one flow velocity and equivalence ratio (.813) are presented and discussed. Alkali chloride reactions with atomic oxygen were also investigated. Readily detectable Na*(g) and K*(g) - atoms were observed in emission at 589 nm, 766nm, 796nm, respectively.

Rosner, D. E.↗
NASA NTRS1991

Antennas for mobile satellite communications

A NASA sponsored program, called the Mobile Satellite (MSAT) system, has prompted the development of several innovative antennas at L-band frequencies. In the space segment of the MSAT system, an efficient, light weight, circularly polarized microstrip array that uses linearly polarized elements was developed as a multiple beam reflector feed system. In the ground segment, a low-cost, low-profile, and very efficient microstrip Yagi array was developed as a medium-gain mechanically steered vehicle antenna. Circularly shaped microstrip patches excited at higher-order modes were also developed as low-gain vehicle antennas. A more recent effort called for the development of a 20/30 GHz mobile terminal antenna for future-generation mobile satellite communications. To combat the high insertion loss encountered at 20/30 GHz, series-fed Monolithic Microwave Integrated Circuit (MMIC) microstrip array antennas are currently being developed. These MMIC arrays may lead to the development of several small but high-gain Ka-band antennas for the Personal Access Satellite Service planned for the 2000s.

Huang, John↗
NASA NTRS1991

Welding in space and the construction of space vehicles by welding; Proceedings of the Conference, New Carrollton, MD, Sept. 24-26, 1991

The present conference discusses such topics in spacecraft welding as the NASA Long Duration Exposure Facility's evidence on material properties degradation, EVA/telerobotic construction techniques, welding of the superfluid helium on-orbit transfer flight demonstration tanks and hardware, electron-beam welding of aerospace vehicles, variable-polarity plasma arc keyhole welding of Al, aircraft experiments of low-gravity fusion welding, flash-butt welding of Al alloys, and a computer-aided handbook for space welding fabrication. Also discussed are the welded nozzle extension for Ariane launch vehicles, the existence of on-orbit cold-welding, structural materials performance in long-term space service, high-strength lightweight alloys, steels, and heat-resistant alloys for aerospace welded structures, the NASA-Goddard satellite repair program, and the uses of explosion welding and cutting in aerospace engineering.

Source record↗
NASA NTRS2006

Stretched Lens Array (SLA) for Collection and Conversion of Infrared Laser Light: 45% Efficiency Demonstrated for Near-Term 800 W/kg Space Power System

For the past 2% years, our team has been developing a unique photovoltaic concentrator array for collection and conversion of infrared laser light. This laser-receiving array has evolved from the solar-receiving Stretched Lens Array (SLA). The laser-receiving version of SLA is being developed for space power applications when or where sunlight is not available (e.g., the eternally dark lunar polar craters). The laser-receiving SLA can efficiently collect and convert beamed laser power from orbiting spacecraft or other sources (e.g., solar-powered lasers on the permanently illuminated ridges of lunar polar craters). A dual-use version of SLA can produce power from sunlight during sunlit portions of the mission, and from beamed laser light during dark portions of the mission. SLA minimizes the cost and mass of photovoltaic cells by using gossamer-like Fresnel lenses to capture and focus incoming light (solar or laser) by a factor of 8.5X, thereby providing a cost-effective, ultra-light space power system.

O'Neill, Mark↗
NASA NTRS2014

Performance Characterization of UV Science Cameras Developed for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

The NASA Marshall Space Flight Center (MSFC) has developed a science camera suitable for sub-orbital missions for observations in the UV, EUV and soft X-ray. Six cameras will be built and tested for flight with the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), a joint National Astronomical Observatory of Japan (NAOJ) and MSFC sounding rocket mission. The goal of the CLASP mission is to observe the scattering polarization in Lyman-alpha and to detect the Hanle effect in the line core. Due to the nature of Lyman-alpha polarization in the chromosphere, strict measurement sensitivity requirements are imposed on the CLASP polarimeter and spectrograph systems; science requirements for polarization measurements of Q/I and U/I are 0.1% in the line core. CLASP is a dual-beam spectro-polarimeter, which uses a continuously rotating waveplate as a polarization modulator, while the waveplate motor driver outputs trigger pulses to synchronize the exposures. The CCDs are operated in frame-transfer mode; the trigger pulse initiates the frame transfer, effectively ending the ongoing exposure and starting the next. The strict requirement of 0.1% polarization accuracy is met by using frame-transfer cameras to maximize the duty cycle in order to minimize photon noise. Coating the e2v CCD57-10 512x512 detectors with Lumogen-E coating allows for a relatively high (30%) quantum efficiency at the Lyman-$\alpha$ line. The CLASP cameras were designed to operate with ≤10 e- /pixel/second dark current, ≤ 25 e- read noise, a gain of 2.0 and ≤0.1% residual non-linearity. We present the results of the performance characterization study performed on the CLASP prototype camera; dark current, read noise, camera gain and residual non-linearity.

Champey, Patrick↗
NASA NTRS1985

Electromagnetic radiation and nonlinear energy flow in an electron beam-plasma system

It is shown that the unstable electron-plasma waves of a beam-plasma system can generate electromagnetic radiation in a uniform plasma. The generation mechanism is a scattering of the unstable electron plasma waves off ion-acoustic waves, producing electromagnetic waves whose frequency is near the local plasma frequency. The wave vector and frequency matching conditions of the three-wave mode coupling are experimentally verified. The electromagnetic radiation is observed to be polarized with the electric field parallel to the beam direction, and its source region is shown to be localized to the unstable plasma wave region. The frequency spectrum shows negligible intensity near the second harmonic of the plasma frequency. These results suggest that the observed electromagnetic radiation of type III solar bursts may be generated near the local plasma frequency and observed downstream where the wave frequency is near the harmonic of the plasma frequency.

Whelan, D. A.↗
NASA NTRS1980

Observations of waves artificially stimulated by an electron beam inside a region with auroral precipitation

Observations of waves stimulated by artificial injection inside an auroral arc by an electron accelerator mounted on the POLAR 5 sounding rocket are presented. The accelerator produced a pulsed electron beam with currents up to 130 mA and energies up to 10 keV; emissions after the end of beam injection were generated by perturbations in the ambient plasma near the accelerator during beam injection. These emissions were independent of the electron beam direction along the geomagnetic field. The high frequency emission observed after beam injection correlated with the passage through an auroral arc; the low frequency emissions after beam injection were concentrated in two bands below the lower hybrid frequency.

Grandal, B.↗
NASA NTRS1981

Directionality effects in the transfer of X-rays from a magnetized atmosphere: Beam pulse shape

A formalism is presented for radiation transfer in two normal polarization modes in finite and semiinfinite plane parallel uniform atmospheres with a magnetic field perpendicular to the surface and arbitrary propagation angles. This method is based on the coupled integral equations of transfer, including emission, absorption, and scattering. Calculations are performed for atmosphere parameters typical of X-ray pulsars. The directionality of the escaping radiation is investigated for several cases, varying the input distributions. Theoretical pencil beam profiles and X-ray pulse shapes are obtained assuming the radiation is emitted from the polar caps of spinning neutron stars. Implications for realistic models of accreting magnetized X-ray sources are briefly discussed.

Meszaros, P.↗
NASA NTRS1975

The earth as a radio source

The primary characteristics of radio emission from the earth's magnetosphere are summarized, the origins of these missions are considered and similarities to other astronomical radio sources discussed. The auroral kilometric radiation has features very similar to Io-related decametric radiation from Jupiter and from Saturn. The radiation at fp and 2 fp upstream of the bow shock appears to be generated by the same mechanism as type III solar radio bursts. The beaming of the auroral kilometric radiation into a cone shaped region over the polar cap has some similarity to the angular distribution of radiation from Io and to the beaming of radio emission from pulsars.

Gurnett, D. A.↗
NASA NTRS1992

The ACTS multibeam antenna

The Advanced Communications Technology Satellite (ACTS) to be launched in 1993 introduces several new technologies including a multibeam antenna (MBA) operating at Ka-band. The satellite is introduced briefly, and then the MBA, consisting of electrically similar 30 GHz received and 20 GHz transmit offset Cassegrain systems utilizing orthogonal linear polarizations, is described. Dual polarization is achieved by using one feed assembly for each polarization in conjunction with nested front and back subreflectors, the gridded front subreflector acting as a window for one polarization and a reflector for the other. The antennas produce spot beams with approximately 0.3 deg beamwidth and gains of approximately 50 dbi. High surface accuracy and high edge taper produce low sidelobe levels and high cross-polarization isolation. A brief description is given of several Ka-band components fabricated for ACTS. These include multiflare antenna feedhorns, beam-forming networks utilizing latching ferrite waveguide switches, a 30 GHz high mobility electron transmitter (HEMT) low-noise amplifier and a 20 GHz TWT power amplifier.

Regier, Frank A.↗