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The Very Large Array has been used in C configuration to map an area similar or equal to 0.3 deg(2) at 1.4 GHz with 5 sigma sensitivities of 0.305, 0.325, 0.380, and 0.450 mJy beam(-1)over four equal subareas.
The Very Large Array (VLA) was used to map compact radio sources in NGC 660, a starburst galaxy, which is also a strong infrared emitter.
We report 8510-MHz (3,5-cm) radar observations of the Earth crossing asteroid (ECA) 6489 Golevka (1991 JX) obtained between June 3 and June 15, 1995, at Goldstone, the Very Large Array and the Evpatoria (Ukraine) and Kashima (Japan) radio antennas.
Using the Very Large Array, we have carried out new, sensitive radio continuum observations at 6 and 3.6 cm of the HH 1-2 region. The comparison between the 6 cm maps made from data taken in 1986.2 and 1992.9 indicates that VLA 1, the exciting source of the HH 1-2 flow, has suffered a morphological change that is attributed to the motion of a symmetric pair of knots along the axis of the radio jet.
We present radio observations of the gravitational lens PKS1830-211 at 8.4 and 15 GHz acquired using the Very Large Array.
An acoustic and aerodynamic study was made of a 26%-scale unpowered Boeing 777 aircraft semispan model in the NASA Ames 40- by 80-Foot Wind Tunnel for the purpose of identifying and attenuating airframe noise sources. Simulated approach and landing configurations were evaluated at Mach numbers between 0.12 and 0.24. Cruise configurations were evaluated at Mach numbers between 0.24 and 0.33. The research team used two Ames phased-microphone arrays, a large fixed array and a small traversing array, mounted under the wing to locate and compare various noise sources in the wing high-lift system and landing gear. Numerous model modifications and noise alleviation devices were evaluated. Simultaneous with acoustic measurements, aerodynamic forces were recorded to document aircraft conditions and any performance changes caused by the geometric modifications. Numerous airframe noise sources were identified that might be important factors in the approach and landing noise of the full-scale aircraft. Several noise-control devices were applied to each noise source. The devices were chosen to manipulate and control, if possible, the flow around the various tips and through the various gaps of the high-lift system so as to minimize the noise generation. Fences, fairings, tip extensions, cove fillers, vortex generators, hole coverings, and boundary-layer trips were tested. In many cases, the noise-control devices eliminated noise from some sources at specific frequencies. When scaled to full-scale third-octave bands, typical noise reductions ranged from 1 to 10 dB without significant aerodynamic performance loss.
ABSL Space Products is the world leading supplier of Lithium-ion batteries for space applications and has pioneered the use of small capacity COTS cells within large arrays. This small-cell approach has provided many benefits to space application designers through increased flexibility and reliability over more traditional battery designs. The ABSL 18650HC cell has been used in most ABSL space battery applications to date and has a recommended End Of Charge Voltage (EOCV) of 4.2V per cell. For all space applications using the ABSL 18650HC so far, this EOCV has been used at all stages of battery life from ground checkout to in orbit operations. ABSL and NASA have identified that, by using a lower EOCV for the same equivalent Depth Of Discharge (DOD), battery capacity fade could be reduced. The intention of this paper is to compare battery performance for systems with fixed and variable EOCV. In particular, the effect of employing the blanket value of 4.2V per cell versus utilizing a lower EOCV at Beginning Of Life (BOL) before gradually increasing it (as the effects of capacity fade drive the End Of Discharge Voltage closer to the acceptable system level minimum) is analyzed. Data is compared from ABSL in-house and NASA GRC tests that have been run under fixed and variable EOCV conditions. Differences in capacity fade are discussed and projections are made as to potential life extension capability by utilizing a variable EOCV strategy.
A method is provided for detecting cracks and other imperfections in a solar cell, which includes scanning a narrow light beam back and forth across the cell in a raster pattern, while monitoring the electrical output of the cell to find locations where the electrical output varies significantly. The electrical output can be monitored on a television type screen containing a raster pattern with each point on the screen corresponding to a point on the solar cell surface, and with the brightness of each point on the screen corresponding to the electrical output from the cell which was produced when the light beam was at the corresponding point on the cell. The technique can be utilized to scan a large array of interconnected solar cells, to determine which ones are defective.
The National Aeronautics and Space Administration (NASA) Exploration Systems Enterprise is planning a series of human and robotic missions to the Earth's moon and to Mars. These missions will require communication and navigation services. This paper1 sets forth presumed requirements for such services and concepts for lunar and Mars telecommunications network architectures to satisfy the presumed requirements. The paper suggests that an inexpensive ground network would suffice for missions to the near-side of the moon. A constellation of three Lunar Telecommunications Orbiters connected to an inexpensive ground network could provide continuous redundant links to a polar lunar base and its vicinity. For human and robotic missions to Mars, a pair of areostationary satellites could provide continuous redundant links between Earth and a mid-latitude Mars base in conjunction with the Deep Space Network augmented by large arrays of 12-m antennas on Earth.
The James Webb Space Telescope, scheduled to replace the Hubble in 2013, must simultaneously observe hundreds of faint galaxies. This requirement has led to the development of a programmable transmission mask which can be adapted to admit light with arbitrary pattern of galaxies into its spectrograph. This programmable mask will contain a large array of micro-electromechanical (MEMs) devices called MicroShutters. These microscopic shutters physically open and close like the shutter on a camera, except each shutter is microscopic in size and an array 365 by 171 is used to select the objects under spectroscopic observation at a given time, and to block the unwanted background light from other areas. NASA developed and is currently refining the exceptionally difficult process of manufacturing these shutters. This paper describes how the authors used LabVIEW FPGA and a reconfigurable I/O board to control the shutters in a test chamber and how the flexibility of the system allows us to continue to modify the control algorithms as NASA optimizes the performance of the MicroShutter arrays.
For optimum performance, a ground antenna system must maximize the ratio of received signal to the receiving system noise power, defined as the ratio of antenna gain to system-noise temperature (G/T). The total system noise temperature is the linear combination of the receiver noise temperature (including the feed system losses) and the antenna noise contribution. Hence, for very low noise cryogenic receiver systems, antenna noise-temperature properties are very significant contributors to G/T.It is well known that, for dual reflector systems designed for maximum gain, the gain performance of the antenna system is the same for both Cassegrain and Gregorian configurations. For a12-meter antenna designed to be part of the large array based Deep Space Network, a Cassegrain configuration designed for maximum G/T at X-band was 0.7 dB higher than the equivalent Gregorian configuration. This study demonstrates that, for maximum GIT, the dual shaped Cassegrain design is always better than the Gregorian.
On May 5, 2006 a four-second duration, low-energy, approximately 10(exp 59) erg, Gamma-Ray Burst (GRB) was observed, spatially associated with a z=0.0894 galaxy. Here, we report the discovery of the GRB optical afterglow and observations of its environment using gemini-south, Hubble Space Telescope (HST), Chandra, Swift and the Very Large Array. The optical afterglow of this GRB is spatially associated with a prominent star forming region in the Sc-type galaxy 2dFGRS S173Z112. Its proximity to a star forming region suggests that the progenitor delay time, from birth to explosion, is smaller than about 10 Myr. Our HST deep imaging rules out the presence of a supernova brighter than an absolute magnitude of about -11 (or -126 in case of 'maximal' extinction) at about two weeks after the burst, and limits the ejected mass of radioactive Nickel 56 to be less than about 2x10(exp -4) solar mass (assuming no extinction). Although it was suggested that GRB 060505 may belong to a new class of long-duration GRBs with no supernova, we argue that the simplest interpretation is that the physical mechanism for this burst is the same as for short-duration GRBs.
LMSAL and NIST are developing position-sensitive x-ray strip detectors based on Transition Edge Sensor (TES) microcalorimeters optimized for solar physics. By combining high spectral (E/ delta E approximately equals 1600) and temporal (single photon delta t approximately equals 10 micro s) resolutions with imaging capabilities, these devices will be able to study high-temperature (>l0 MK) x-ray lines as never before. Diagnostics from these lines should provide significant new insight into the physics of both microflares and the early stages of flares. Previously, the large size of traditional TESs, along with the heat loads associated with wiring large arrays, presented obstacles to using these cryogenic detectors for solar missions. Implementing strip detector technology at small scales, however, addresses both issues: here, a line of substantially smaller effective pixels requires only two TESs, decreasing both the total array size and the wiring requirements for the same spatial resolution. Early results show energy resolutions of delta E(sub fwhm) approximately equals 30 eV and spatial resolutions of approximately 10-15 micron, suggesting the strip-detector concept is viable.
High charge (Z) and energy (E) (HZE) nuclei comprised in the galactic cosmic rays are main contributors to space radiation risk. They induce many lesions in living matter such as non-specific oxidative damage and the double-strand breaks (DSBs), which are considered key precursors of early and late effects of radiation. There is increasing evidence that cells respond collectively rather than individually to radiation, suggesting the importance of cell signaling1. The transforming growth factor (TGF ) is a signaling peptide that is expressed in nearly all cell type and regulates a large array of cellular processes2. TGF have been shown to mediate cellular response to DNA damage3 and to induce apoptosis in non-irradiated cells cocultured with irradiated cells4. TFG molecules are secreted by cells in an inactive complex known as the latency-associated peptide (LAP). TGF is released from the LAP by a conformational change triggered by proteases, thrombospondin-1, integrins, acidic conditions and .OH radical5. TGF then binds to cells receptors and activates a cascade of events mediated by Smad proteins6, which might interfere with the repair of DNA. Meanwhile, increasingly sophisticated Brownian Dynamics (BD) algorithms have appeared recently in the literature7 and can be applied to study the interaction of molecules with receptors. These BD computer models have contributed to the elucidation of signal transduction, ligand accumulation and autocrine loops in the epidermal growth factor (EGF) and its receptor (EFGR) system8. To investigate the possible roles of TGF in an irradiated cell culture, our Monte-Carlo simulation codes of the radiation track structure9 will be used to calculate the activation of TFG triggered by .OH produced by low doses of HZE ions. The TGF molecules will then be followed by a BD algorithm in a medium representative of a cell culture to estimate the number of activated receptors.
The James Webb Space Telescope, scheduled to replace the Hubble in 2013, must simultaneously observe hundreds of faint galaxies. This requirement has led to the development of a programmable transmission mask which can be adapted to admit light from an arbitrary pattern of galaxies into its spectrograph. This programmable mask will contain a large array of micro-electromechanical (MEMs) devices called MicroShutters. These microscopic shutters physically open and close like the shutter on a camera, except each shutter is microscopic in size and an array 365 by 171 is used to select the objects under spectroscopic observation at a given time, and to block the unwanted background light from other areas. NASA developed and is currently refining the exceptionally difficult process of manufacturing these shutters. This paper describes how the authors used LabVIEW FPGA and a reconfigurable I/O board to control the shutters in a test chamber and how the flexibility of the system allows us to continue to modify the control algorithms as NASA optimizes the performance of the MicroShutter arrays.
This slide presentation shows several case studies for fault protection. The cases involve a discovery-class mission to excavate material from a comet, rendezvous with two asteroids and develop a prototype system for a next-generation Deep Space Network consisting of ndca large array of small antennas.
Of the high performance detector technologies currently being developed, Microwave Kinetic Inductance Detectors (MKIDs) have the greatest promise for scaling to very large arrays (approx.10(exp 5) detectors). Such arrays can provide high quantum efficiency, and can be designed to provide background limited performance over a wide range of incident powers, making them candidates for a wide range of instruments, ranging from suborbital imagers to spaceborne spectrometers. We are extending Microwave Kinetic Inductance Detectors (MKIDs) technology to the 40 - 400 microns spectral regions via a novel detector concept. In this approach thin film superconducting microstrip lines are used to simultaneously absorb and readout the incident signal with high inter-pixel isolation. Progress on these fabrication and test efforts will be presented.
This paper gives a detailed description of the design of the A3 Subscale Diffuser Test (SDT) Article Design. The subscale diffuser is a geometrically accurate scale model of the A3 altitude rocket facility. It was designed and built to support the SDT risk mitigation project located at the E3 facility at Stennis Space Center, MS (SSC) supporting the design and construction of the A3 facility at SSC. The subscale test article is outfitted with a large array of instrumentation to support the design verification of the A3 facility. The mechanical design of the subscale diffuser and test instrumentation are described here