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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 NTRS2002

STS-111 Flight Day 5 Highlights

On Flight Day 5 of STS-111, the crew of Endeavour (Kenneth Cockrell, Commander; Paul Lockhart, Pilot; Franklin Chang-Diaz, Mission Specialist; Philippe Perrin, Mission Specialist) and the Expedition 5 crew (Valery Korzun, Commander; Peggy Whitson, Flight Engineer; Sergei Treschev, Flight Engineer) and Expedition 4 crew (Yury Onufrienko, Commander; Daniel Bursch, Flight Engineer; Carl Walz, Flight Engineer) are aboard the docked Endeavour and International Space Station (ISS). The ISS cameras show the station in orbit above the North African coast and the Mediterranean Sea, as Chang-Diaz and Perrin prepare for an EVA (extravehicular activity). The Canadarm 2 robotic arm is shown in motion in a wide-angle shot. The Quest Airlock is shown as it opens to allow the astronauts to exit the station. As orbital sunrise approaches, the astronauts are shown already engaged in their EVA activities. Chang-Diaz is shown removing the PDGF (Power and Data Grapple Fixture) from Endeavour's payload bay as Perrin prepares its installation position in the ISS's P6 truss structure; The MPLM is also visible. Following the successful detachment of the PDGF, Chang-Diaz carries it to the installation site as he is transported there by the robotic arm. The astronauts are then shown installing the PDGF, with video provided by helmet-mounted cameras. Following this task, the astronauts are shown preparing the MBS (Mobile Base System) for grappling by the robotic arm. It will be mounted to the Mobile Transporter (MT), which will traverse a railroad-like system along the truss structures of the ISS, and support astronaut activities as well as provide an eventual mobile base for the robotic arm.

Source record↗
NASA NTRS2003

The Surface Roughness of Terrains on Mars

The RMS roughness measurements produced by Neumann et al. from Mars Orbiter Laser Altimeter (MOLA) data provide unique information about surface height variations at an effective length scale of < 75 m. Roughness at this scale is important not only for landing site safety considerations, but also for assessment of landscape evolution, which depends on emplacement mechanisms and erosional/depositional processes. Here we present an examination of the global surface roughness map with discussion of terrain types and potential formation and/or alteration mechanisms. Spatially coherent terrain types were identified based on inspection of the roughness map. These terrains were further characterized through analysis of morphology and geology using MOLA topography, MOC wide-angle, and MOC narrow-angle images as well as the geologic maps produced by Scott & Tanaka and Greeley & Guest. All of these data were used to explore potential formation and modification processes.

K S Deal↗
NASA NTRS2003

Phased Array Antenna Testbed Development at the NASA Glenn Research Center

Ideal phased array antennas offer advantages for communication systems, such as wide-angle scanning and multibeam operation, which can be utilized in certain NASA applications. However, physically realizable, electronically steered, phased array antennas introduce additional system performance parameters, which must be included in the evaluation of the system. The NASA Glenn Research Center (GRC) is currently conducting research to identify these parameters and to develop the tools necessary to measure them. One of these tools is a testbed where phased array antennas may be operated in an environment that simulates their use. This paper describes the development of the testbed and its use in characterizing a particular K-Band, phased array antenna.

Lambert, Kevin M.↗
NASA NTRS2003

The EUSO Mission

The Extreme Universe Space Observatory (EUSO) experiment will use the Earth's atmosphere viewed from space as a detector of extreme energy cosmic rays (EECRs). EUSO s collecting power will exceed previous experiments by more than a factor of 10, making it possible to extend the cosmic ray spectrum beyond 100 EeV with high statistics. This will make it possible to investigate in detail the spectrum beyond the point were the Greisen-Zatsepin-Kuzmin effect is expected to strongly attenuate the proton flux and even beyond the energy where cosmic ray nuclei should be photo-disintegrated by interactions with the universal microwave background. EUSO makes its measurements by detecting the extensive air showers (EASs) that result from the interactions of the EECRs. Looking down from its birth on the International Space Station though wide-angle optics, EUSO records a high-speed movie clip of passage of each EAS though the atmosphere with the light from nitrogen fluorescence and Cherenkov light reflected from the EAS landing point. These movie clips are analyzed to determine the EECR arrival direction and energy. The data also allow neutrino-induced EASs to be discriminated from nuclear-induced showers.

Adams, J. H.↗
NASA NTRS2004

The Extended Parabolic Equation Method and Implication of Results for Atmospheric Millimeter-Wave and Optical Propagation

The extended wide-angle parabolic wave equation applied to electromagnetic wave propagation in random media is considered. A general operator equation is derived which gives the statistical moments of an electric field of a propagating wave. This expression is used to obtain the first and second order moments of the wave field and solutions are found that transcend those which incorporate the full paraxial approximation at the outset. Although these equations can be applied to any propagation scenario that satisfies the conditions of application of the extended parabolic wave equation, the example of propagation through atmospheric turbulence is used. It is shown that in the case of atmospheric wave propagation and under the Markov approximation (i.e., the -correlation of the fluctuations in the direction of propagation), the usual parabolic equation in the paraxial approximation is accurate even at millimeter wavelengths. The methodology developed here can be applied to any qualifying situation involving random propagation through turbid or plasma environments that can be represented by a spectral density of permittivity fluctuations.

Manning, Robert M.↗
NASA NTRS2003

Yearly Comparisons of the Mars North Polar Cap: 1999, 2001, and 2003 MOC Observations

The seasonal cycle of the martian north polar cap has been studied since the time of William Herschel, who published the first quantitative observations of the seasonal recession of the polar caps in 1784. Ground-based observations made after Herschel were summarized by Slipher in 1962. More recent ground-based observations of the north polar cap have been done by Iwasaki et al. Mariner 9 and Viking also made north polar observations. Cantor et al. used Hubble Space Telescope observations between 1990 and 1997 to determine several north polar recessions and Lambert albedos of the cap. Mars Global Surveyor went into orbit around Mars in September 1997. The wide-angle cameras on the Mars Orbiter Camera (MOC) acquire images of the entire planet every day at a resolution of approx. 7.5 km/pixel in both red (575 nm - 625 nm) and blue (400 nm - 450 nm) bandpasses (WAR and WAB). Some polar cap observations were acquired during the aerobraking (AB) and science phasing (SPO) of MGS before systematic mapping began in March, 1999 at Ls = 110 .

Benson, J. L.↗
NASA NTRS2001

Response of Silicon-Based Linear Energy Transfer Spectrometers: Implication for Radiation Risk Assessment in Space Flights

There is considerable interest in developing silicon-based telescopes because of their compactness and low power requirements. Three such telescopes have been flown on board the Space Shuttle to measure the linear energy transfer spectra of trapped, galactic cosmic ray, and solar energetic particles. Dosimeters based on single silicon detectors have also been flown on the Mir orbital station. A comparison of the absorbed dose and radiation quality factors calculated from these telescopes with that estimated from measurements made with a tissue equivalent proportional counter show differences which need to be fully understood if these telescopes are to be used for astronaut radiation risk assessments. Instrument performance is complicated by a variety of factors. A Monte Carlo-based technique was developed to model the behavior of both single element detectors in a proton beam, and the performance of a two-element, wide-angle telescope, in the trapped belt proton field inside the Space Shuttle. The technique is based on: (1) radiation transport intranuclear-evaporation model that takes into account the charge and angular distribution of target fragments, (2) Landau-Vavilov distribution of energy deposition allowing for electron escape, (3) true detector geometry of the telescope, (4) coincidence and discriminator settings, (5) spacecraft shielding geometry, and (6) the external space radiation environment, including albedo protons. The value of such detailed modeling and its implications in astronaut risk assessment is addressed. c2001 Elsevier Science B.V. All rights reserved.

manned↗
NASA NTRS2004

An Operator Method for Field Moments from the Extended Parabolic Wave Equation and Analytical Solutions of the First and Second Moments for Atmospheric Electromagnetic Wave Propagation

The extended wide-angle parabolic wave equation applied to electromagnetic wave propagation in random media is considered. A general operator equation is derived which gives the statistical moments of an electric field of a propagating wave. This expression is used to obtain the first and second order moments of the wave field and solutions are found that transcend those which incorporate the full paraxial approximation at the outset. Although these equations can be applied to any propagation scenario that satisfies the conditions of application of the extended parabolic wave equation, the example of propagation through atmospheric turbulence is used. It is shown that in the case of atmospheric wave propagation and under the Markov approximation (i.e., the delta-correlation of the fluctuations in the direction of propagation), the usual parabolic equation in the paraxial approximation is accurate even at millimeter wavelengths. The comprehensive operator solution also allows one to obtain expressions for the longitudinal (generalized) second order moment. This is also considered and the solution for the atmospheric case is obtained and discussed. The methodology developed here can be applied to any qualifying situation involving random propagation through turbid or plasma environments that can be represented by a spectral density of permittivity fluctuations.

Manning, Robert M.↗
NASA NTRS2004

Laser Range and Bearing Finder for Autonomous Missions

NASA has recently re-confirmed their interest in autonomous systems as an enabling technology for future missions. In order for autonomous missions to be possible, highly-capable relative sensor systems are needed to determine an object's distance, direction, and orientation. This is true whether the mission is autonomous in-space assembly, rendezvous and docking, or rover surface navigation. Advanced Optical Systems, Inc. has developed a wide-angle laser range and bearing finder (RBF) for autonomous space missions. The laser RBF has a number of features that make it well-suited for autonomous missions. It has an operating range of 10 m to 5 km, with a 5 deg field of view. Its wide field of view removes the need for scanning systems such as gimbals, eliminating moving parts and making the sensor simpler and space qualification easier. Its range accuracy is 1% or better. It is designed to operate either as a stand-alone sensor or in tandem with a sensor that returns range, bearing, and orientation at close ranges, such as NASA's Advanced Video Guidance Sensor. We have assembled the initial prototype and are currently testing it. We will discuss the laser RBF's design and specifications. Keywords: laser range and bearing finder, autonomous rendezvous and docking, space sensors, on-orbit sensors, advanced video guidance sensor

Granade, Stephen R.↗
NASA NTRS2004

SIM PlanetQuest: Science with the Space Interferometry Mission

SIM - the Space Interferometry Mission - will perform precision optical astrometry on objects as faint as R magnitude 20. It will be the first space-based astrometric interferometer, operating in the optical band with a 10-m baseline. The Project is managed by the Jet Propulsion Laboratory, California Institute of Technology, in close collaboration with two industry partners, Lockheed Martin Missiles and Space, and TRW Inc., Space and Electronics Group. Launch of SIM is currently planned for 2009. In its wide-angle astrometric mode, SIM will yield 4 microarcsecond absolute position and parallax measurements. Astrometric planet searches will be done in a narrow-angle mode, with an accuracy of 4 microarcseconds or better in a single measurement. As a pointed rather than a survey instrument, SIM will maintain.its astrometric accuracy down to the faintest, magnitudes, opening up the opportunity for astrometry of active galactic nuclei to better than 10 pas. SIM will define a new astrometric reference frame, using a grid of approximately 1500 stars with positions accurate to 4 microarcseconds. The SIM Science Team comprises the Principal Investigators of ten Key Projects, and five Mission Scientists contributing their expertise to specific areas of the mission. Their science programs cover a wide range of topics in Galactic and extragalactic astronomy. They include: searches for low-mass planets - including analogs to our own solar system - tlie formation and dynamics of our Galaxy, calibration of the cosmic distance scale, and fundamental stellar astrophysics. All of the science observing on SIM is competitively awarded; the Science Team programs total about 40% of the total available, and the remainder will be assigned via future NASA competitions. This report is a compilation of science summaries by members of the Science Team, and it illustrates the wealth of scientific problems that microarcsecond-precision astrometry can contribute to. More information on SIM, including copies of this report, may be obtained from the project web site, at http://sim. jpl.nasa.gov.

Unwin, Stephen↗
NASA NTRS1999

K-Band Phased Array Developed for Low- Earth-Orbit Satellite Communications

Future rapid deployment of low- and medium-Earth-orbit satellite constellations that will offer various narrow- to wide-band wireless communications services will require phased-array antennas that feature wide-angle and superagile electronic steering of one or more antenna beams. Antennas, which employ monolithic microwave integrated circuits (MMIC), are perfectly suited for this application. Under a cooperative agreement, an MMIC-based, K-band phased-array antenna is being developed with 50/50 cost sharing by the NASA Lewis Research Center and Raytheon Systems Company. The transmitting array, which will operate at 19 gigahertz (GHz), is a state-of-the-art design that features dual, independent, electronically steerable beam operation ( 42 ), a stand-alone thermal management, and a high-density tile architecture. This array can transmit 622 megabits per second (Mbps) in each beam from Earth orbit to small Earth terminals. The weight of the total array package is expected to be less than 8 lb. The tile integration technology (flip chip MMIC tile) chosen for this project represents a major advancement in phased-array engineering and holds much promise for reducing manufacturing costs.

Anzic, Godfrey↗
NASA NTRS2000

Observational Model for Precision Astrometry with the Space Interferometry Mission

The Space Interferometry Mission (SIM) is a space-based 10-m baseline Michelson optical interferometer operating in the visible waveband that is designed to achieve astrometric accuracy in the single digits of the microarcsecond domain. Over a narrow field of view SIM is expected to achieve a mission accuracy of 1 microarcsecond. In this mode SIM will search for planetary companions to nearby stars by detecting the astrometric "wobble" relative to a nearby reference star. In its wide-angle mode, SIM will provide 4 microarcsecond precision absolute position measurements of stars, with parallaxes to comparable accuracy, at the end of its 5-year mission. The expected proper motion accuracy is around 3 microarcsecond/year, corresponding to a transverse velocity of 10 m/ s at a distance of 1 kpc. The basic astrometric observable of the SIM instrument is the pathlength delay. This measurement is made by a combination of internal metrology measurements that determine the distance the starlight travels through the two arms of the interferometer, and a measurement of the white light stellar fringe to find the point of equal pathlength. Because this operation requires a non-negligible integration time, the interferometer baseline vector is not stationary over this time period, as its absolute length and orientation are time varying. This paper addresses how the time varying baseline can be "regularized" so that it may act as a single baseline vector for multiple stars, as required for the solution of the astrometric equations.

TILE OBSERVATIONS↗
NASA NTRS2002

SIM: An end-to-end simulation of the Space Interferometer Mission

We present the basic elements and first results of an end-to-end simulation package whose purpose is to test the validity of the Space Interferometer Mission design. The fundamental simulation time step is one millisecond, with substructure at 118 ms, and the total duration of the simulation is five years. The end product of a given wide-angle astrometry run is an estimated grid star catalog over the entire sky with an accuracy of about 4 micro-arcseconds.

SIM Space Interferometer Mission Space telescopes ↗
NASA NTRS1998

Design Aspects of the Microstrip Reflectarray

The microstrip reflectarray has been identified as one of the enabling technologies to achieve low mass, conformal mounting, wide-angle beam scanning, etc. for NASA's future speceborne high-gain antennas.

microstrip reflectarray bandwidth mutual coupling↗
NASA NTRS2002

SIM grid verification program RFP

The objective of this program is to verify the astrometric stability of a catalog of stars to be used as the reference grid for SIM's wide-angle astrometric science.

SIM grid RFP↗
NASA NTRS2004

Dual-Frequency Airborne Scanning Rain Radar Antenna System

A compact, dual-frequency, dual-polarization, wide-angle-scanning antenna system has been developed as part of an airborne instrument for measuring rainfall. This system is an upgraded version of a prior single-frequency airborne rain radar antenna system and was designed to satisfy stringent requirements. One particularly stringent combination of requirements is to generate two dual-polarization (horizontal and vertical polarizations) beams at both frequencies (13.405 and 35.605 GHz) in such a way that the beams radiated from the antenna point in the same direction, have 3-dB angular widths that match within 25 percent, and have low sidelobe levels over a wide scan angle at each polarization-and-frequency combination. In addition, the system is required to exhibit low voltage standing-wave ratios at both frequencies. The system (see figure) includes a flat elliptical scanning reflector and a stationary offset paraboloidal reflector illuminated by a common-aperture feed system that comprises a corrugated horn with four input ports one port for each of the four frequency-and-polarization combinations. The feed horn is designed to simultaneously (1) under-illuminate the reflectors 35.605 GHz and (2) illuminate the reflectors with a 15-dB edge taper at 13.405 GHz. The scanning mirror is rotated in azimuth to scan the antenna beam over an angular range of 20 in the cross-track direction for wide swath coverage, and in elevation to compensate for the motion of the aircraft. The design of common-aperture feed horn makes it possible to obtain the required absolute gain and low side-lobe levels in wide-angle beam scanning. The combination of the common-aperture feed horn with the small (0.3) focal-length-to-diameter ratio of the paraboloidal reflector makes it possible for the overall system to be compact enough that it can be mounted on a DC-8 airplane.

Hussein, Ziad A.↗
NASA NTRS2004

SIM spectral characteristics and accuracy analysis

The Space Interferometry Mission (SIM) will perform global astrometry (full sky), local wide-angle (15 degree) and narrow-angle (1 degree) observations to search extra-solar planets, and can calibrate stellar and galactic evolution theories. The astrometric accuracy of the SIM mission depends on spectral characteristics of the optics, detectors and targets. This paper will discuss the photometric throughput of the SIM instrument, and analyze effects of wavefront errors, optical mismatches and control biases as a function of wavelength. The color dependence models of the instrument optics including mirrors, lenses, field-stop and beam-splitter are presented. The performances of different detectors with a variety of coatings are compared. A model of the SIM fringe spectrometer is created. For early and late types of stars, brightness dependency errors are analyzed for different combinations of optics and detectors. Visibility loss due to imperfect optics is investigated in detail. Based on the models of instrument and estimated visibilities, the astrometric accuracies for various kinds of stars are evaluated. It is important to emphasize that not only light sources, mirrors, lenses, field stop and detectors are all wavelength dependent, but also fringe visibility loss, wavefront error, optics control error, etc. are all a function of wavelengths. For the first time the estimate of SIM performance is based on spectral analysis of all factors above, rather than monochromatic approximations of detected fringes, or simply adopted constants. This paper summarizes the astrometric accuracies for a wide range of stars and various combinations of optical design and detector configurations. It has been verified that SIM has astrometric accuracy of about 4 μas for targets with different spectra.

Shao, Michael↗
NASA NTRS2003

The development of inflatable array antennas

The deployable array antenna using an inflatable or thin-membrane structure has been identified as one of the enabling technologies to achieve low-mass, high packaging efficiency, low cost, and reliable deployment for future NASNJPL spacebome high-gain and large aperture antennas. Array antennas, when compared to parabolic reflectors, although suffering from limited bandwidth performance, offer wide-angle beam scanning capability and a more reliable flat “natural” aperture. To demonstrate the feasibility and capability of this low-mass array technology, three antenna concepts using inflatable and thin-membrane structures were initiated in 1997 at JPL and several breadboard units have been successfully developed. These three concepts are (1) the inflatable phased array, (2) the inflatable reflectarray, and (3) frame-supported thin membrane array antenna. All three concepts utilize the printed microstrip antenna technology. Although all three concepts will be briefly presented, this paper will discuss in more detail of the recent development of the second concept. The first concept of inflatable phased arrays that have been constructed are 3 to 5-meter size L-band dual-polarized synthetic aperture radar (SAR) arrays for Earth remote sensing application. They all consist of a rectangular configuration with inflatable cylindrical tubes that support and tension a multi-layer thin-membrane radiating aperture with microstrip patches and microstrip power divider lines. For the second concept, an inflatable reflectarray was developed for future deep-space telecom applications. It is a 3m Ka-band inflatable reflectarray (1.8 kg/m2). This reflectarray uses inflated torus tubes to support and tension a flat-membrane reflectarray surface. The reflectarray surface emulates a curved parabolic reflecting surface. However, because of its flat surface being a “natural surface”, it is much easier to achieve and more reliable to maintain the required surface tolerance than that of a curved parabola during long space flight. For the third concept, an L-band dual polarized SAR array with a 5m x 3m aperture and 2.5 kg/m2 of mass has recently been demonstrated. It consists of seven foldable panels each having a rectangular frame that supports a two-layer thinmembrane microstrip subarray aperture. Each frame is made of light-weight graphite composite material. The chief advantage of this deployable “frame” concept is that each frame is able to rigidly support an appropriate number of T/R modules and phase shifters to achieve the desired power distribution and beam scanning. Several technology challenges, such as the development of rigidizable inflatable tubes, a controlled deployment mechanism, thin-membrane thermal effects, a low-mass inflation system, membrane mounted T/R modules, means to counter surface tolerance issues, etc. are being investigated and will be discussed in the presentation. With foreseeable success in the development of these challenging areas, the inflatable/thin-membrane array antennas could be mature enough in a few years for actual space flight.

Lou, Michael↗