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At least 415 records · Page 23

Using GPS Reflections for Satellite Remote Sensing

GPS signals that have reflected off of the ocean's surface have shown potential for use in oceanographic and atmospheric studies. The research described here investigates the possible deployment of a GPS reflection receiver onboard a remote sensing satellite in low Earth orbit (LEO). The coverage and resolution characteristics of this receiver are calculated and estimated. This mission analysis examines using reflected GPS signals for several remote sensing missions. These include measurement of the total electron content in the ionosphere, sea surface height, and ocean wind speed and direction. Also discussed is the potential test deployment of such a GPS receiver on the space shuttle. Constellations of satellites are proposed to provide adequate spatial and temporal resolution for the aforementioned remote sensing missions. These results provide a starting point for research into the feasibility of augmenting or replacing existing remote sensing satellites with spaceborne GPS reflection-detecting receivers.

Mickler, David↗

Video Based Sensor for Tracking 3-Dimensional Targets

Video-Based Sensor for Tracking 3-Dimensional Targets The National Aeronautics and Space Administration's (NASAs) Marshall Space Flight Center (MSFC) has been developing and testing video-based sensors for automated spacecraft guidance for several years, and the next generation of video sensor will have tracking rates up to 100 Hz and will be able to track multiple reflectors and targets. The Video Guidance Sensor (VGS) developed over the past several years has performed well in testing and met the objective of being used as the terminal guidance sensor for an automated rendezvous and capture system. The first VGS was successfully tested in closed-loop 3-degree-of-freedom (3- DOF) tests in 1989 and then in 6-DOF open-loop tests in 1992 and closed-loop tests in 1993-4. Development and testing continued, and in 1995 approval was given to test the VGS in an experiment on the Space Shuttle. The VGS flew in 1997 and in 1998, performing well for both flights. During the development and testing before, during, and after the flight experiments, numerous areas for improvement were found. The VGS was developed with a sensor head and an electronics box, connected by cables. The VGS was used in conjunction with a target that had wavelength-filtered retro-reflectors in a specific pattern, The sensor head contained the laser diodes, video camera, and heaters and coolers. The electronics box contained a frame grabber, image processor, the electronics to control the components in the sensor head, the communications electronics, and the power supply. The system works by sequentially firing two different wavelengths of laser diodes at the target and processing the two images. Since the target only reflects one wavelength, it shows up well in one image and not at all in the other. Because the target's dimensions are known, the relative positions and attitudes of the target and the sensor can be computed from the spots reflected from the target. The system was designed to work from I meter out to I 10 meters. The VGS was mounted on the Space Shuttle while its target was mounted on the Spartan free-flyer carried on the same Shuttle flight. The VGS tracked the Spartan at ranges up to 170m, and the VGS range data very closely matched the range data from the Hand-Held Laser- Rangefinder used by the astronauts on board the Shuttle. While the VGS was designed primarily as a terminal guidance sensor for an automated spacecraft, it could be applied to other uses. It could be used as an alignment aid for an operator of a remote system (giving position and attitude feedback data, as well as a camera view of the target), as a feedback system for a robotic arm, or for automated vehicle guidance. The next generation VGS, with its higher tracking rates, smaller size, and lower power could be used in more places than the original VGS, and by using LED's instead of laser diodes, the system would be eye-safe at any range. Other possible uses include tracking 3-dimensional objects with retro-reflectors mounted at various locations or motion analysis by placing several retro-reflectors on the moving object and tracking them at high speeds. There are few sensors capable of performing tasks similar to those the VGS can perform, and the next generation VGS will be even more capable than the original. Some of this work is previously presented in the papers.

Howard, R. T.↗

A solar flare X-ray polarimeter for the Space Shuttle

An instrument has recently been built and tested which is designed to measure the polarization of the hard (5-30 keV) X-ray emission from solar flares, and thereby to investigate the energy release mechanism and constrain flare models. In particular, these measurements will help to determine whether hard X-ray bursts are produced by nonthermal or by thermal electrons. The polarimeter makes use of the angular dependence of Thomson scattering from targets of metallic lithium. It has an energy resolution of a few keV, a time resolution of 5 s, and sufficient sensitivity to measure polarization levels (3 sigma) of a few percent in about 10 s for a moderate strength solar flare. The instrumental polarization has been directly measured and found to be within the design goal of approximately 1%. This polarimeter is scheduled to be flown as part of the OSS-1 pallet on an early Space Shuttle mission.

Lemen, J. R.↗

Materials and processes for space shuttle's engines

It is pointed out that over 50 different alloys are used in construction of the space shuttle main engines (SSME). Primary construction of the SSME is by welding or brazing of wrought and cast components. Welding processes involve both gas tungsten-arc welds and electron-beam welds. Electroforming has been developed as a process to fabricate and bond structural members for the SSME. Important aspects in the selection of materials and processes are related to weight saving considerations and the high-pressure hydrogen environment. Special problems and their solution in the case of various engine components are discussed, giving attention to the oxidizer preburner, the high pressure oxidizer turbopump, and the heat exchanger.

J. R. Lewis↗

Development of the VOLT-A shuttle experiment

The NASA Lewis Research Center (LeRC) is investigating potential problems associated with the operation of high voltage solar cell arrays in the space plasma environment. At high voltages, interactions between the solar array and the space plasma could result in unacceptable levels of electrical discharge (arcing) and/or parasitic losses (current drains from the array to the plasma). The objective of the Voltage Operating Limit Tests (VOLT-A) Shuttle bay experiment is to characterize space plasma/solar cell panel interactions in low earth orbit. VOLT-A consists of an experiment plate subassembly which contains four solar panels, an electronics subassembly and a Langmuir probe subassembly mounted on an MPESS carrier. During a given 8.25 hour data taking period (5-1/2 continuous orbits), the solar panels, which represent state-of-the-art solar cell technologies, will be sequentially subjected to bias voltages in steps ranging from minus 626 V to plus 313 V. Appropriate measurements will be made at each voltage to characterize arcing and parasitic losses. Corresponding measurements of the plasma environment (plasma density, electron temperature and neutral density) will also be made. Data will be recorded on an on-board tape recorder for subsequent data reduction and analysis.

Bifano, W. J.↗

Development of the VOLT-A Shuttle experiment

The NASA Lewis Research Center (LeRC) is investigating potential problems associated with the operation of high voltage solar cell arrays in the space plasma environment. At high voltages, interactions between the solar array and the space plasma could result in unacceptable levels of electrical discharge (arcing) and/or parasitic losses (current drains from the array to the plasma). The objective of the Voltage Operating Limit Tests (VOLT-A) Shuttle bay experiment is to characterize space plasma/solar cell panel interactions in low earth orbit. VOLT-A consists of an experiment plate subassembly which contains four solar panels, an electronics subassembly and a Langmuir probe subassembly mounted on an MPESS carrier. During a given 8.25 hour data taking period (5-1/2 continuous orbits), the solar panels, which represent state-of-the-art solar cell technologies, will be sequentially subjected to bias voltages in steps ranging from minus 626 V to plus 313 V. Appropriate measurements will be made at each voltage to characterize arcing and parasitic losses. Corresponding measurements of the plasma environment (plasma density, electron temperature and neutral density) will also be made. Data will be recorded on an on-board tape recorder for subsequent data reduction and analysis.

Bifano, William J.↗

Long-term corrosion evaluation of stainless steels in Space Shuttle iodinated resin and water

The effects of stainless steel exposure to iodinated water is a concern in developing the Integrated Water System (IWS) for Space Station Freedom. The IWS has a life requirement of 30 years, but the effects of general and localized corrosion over such a long period have not been determined for the candidate materials. In 1978, Umpqua Research Center immersed stainless steel 316L, 321, and 347 specimens in a solution of deionized water and the Space Shuttle microbial check valve resin. In April 1990, the solution was chemically analyzed to determine the level of corrosion formed, and the surface of each specimen was examined with scanning electron microscopy and metallography to determine the extent of general and pitting corrosion. This examination showed that the attack on the stainless steels was negligible and never penetrated past the first grain boundary layer. Of the three alloys, 316L performed the best; however, all three materials proved to be compatible with an aqueous iodine environment. In addition to the specimens exposed to aqueous iodine, a stainless steel specimen (unspecified alloy) was exposed to moist microbial check valve resin and air for a comparable period. This environment allowed contact of the metal to the resin as well as to the iodine vapor. Since the particular stainless steel alloy was not known, energy dispersive spectroscopy was used to determine that this alloy was stainless steel 301. The intergranular corrosion found on the specimen was limited to the first grain boundary layer.

Krohn, Douglas D.↗

A high temperature superconductivity communications flight experiment

The proposed high temperature superconductivity (HTSC) millimeter-wave communications flight experiment from the payload bay of the Space Shuttle Orbiter to the Advanced Communications Technology Satellite (ACTS) in geosynchronous orbit is described. The experiment will use a Ka-band HTSC phased array antenna and front-end electronics to receive a downlink communications signal from the ACTS. The discussion covers the system configuration, a description of the ground equipment, the spacecraft receiver, link performance, thermal loading, and the superconducting antenna array.

Ngo, P.↗

The DSI small satellite launcher

A new launcher has been developed by DSI, that is compatible with the GAS canisters. It has the proven capability to deploy a satellite from an orbiting Shuttle that is 18 inches in diameter, 31 inches long, and weighing 190 pounds. These DSI Launchers were used aboard the Discovery (STS-39) in May 1991 as part of the Infrared Background Signature Survey (IBSS) to deploy three small satellites known as Chemical Release Observation (CRO) satellites A, B, and C. Because the satellites contained hazardous liquids (MMH, UDMH, and MON-10) and were launched from GAS Cylinders without motorized doors, the launchers were required to pass NASA Shuttle Payload safety and verification requirements. Some of the more interesting components of the design were the V-band retention and separation mechanism, the separation springs, and the launcher electronics which provided a properly inhibited release sequence operated through the Small Payload Accommodations Switch Panel (SPASP) on board the Orbiter. The original plan for this launcher was to use a motorized door. The launcher electronics, therefore has the capability to be modified to accommodate the door, if desired.

Nichols, S.↗

Development of the brine shrimp Artemia is accelerated during spaceflight

Developmentally arrested brine shrimp cysts have been reactivated during orbital spaceflight on two different Space Shuttle missions (STS-50 and STS-54), and their subsequent development has been compared with that of simultaneously reactivated ground controls. Flight and control brine shrimp do not significantly differ with respect to hatching rates or larval morphology at the scanning and transmission EM levels. A small percentage of the flight larvae had defective nauplier eye development, but the observation was not statistically significant. However, in three different experiments on two different flights, involving a total of 232 larvae that developed in space, a highly significant difference in degree of flight to control development was found. By as early as 2.25 days after reactivation of development, spaceflight brine shrimp were accelerated, by a full instar, over ground control brine shrimp. Although developing more rapidly, flight shrimp grew as long as control shrimp at each developmental instar or stage.

Flight Experiment↗

Investigating the Molecular Response in Irradiated Yeast in Support of the BioSentinel CubeSat Mission

The BioSentinel CubeSat mission is NASA’s first deep space bioscience mission scheduled to fly as a secondary payload onboard Artemis I. BioSentinel seeks to understand the impacts of deep space radiation on living organisms using the model organism Saccharomyces cerevisiae, or budding yeast. In recent years, the BioSentinel team has conducted ground-based investigations into the effects of ionizing radiation (IR) on budding yeast to better understand spaceflight data. One investigation focuses on the impacts of radiation on budding yeast metabolics using the redox dye alamarBlue, an indicator that will also be used onboard BioSentinel. In this investigation, we have observed metabolic changes in both wild-type and in mutant yeast cells deficient in DNA repair. The focus of our research is to support the ongoing investigation into the molecular mechanisms that explain these observed changes. To do this, we first conducted preliminary research into the metabolic processes of S. cerevisiae to identify any potential vulnerabilities to radiation. We then conducted a statistical kinetic analysis on past experimental metabolic data, in addition to an analysis of data from a multisensor metabolic rig experiment. Ultimately, we identified numerous redox-related changes with increasing doses of radiation in both wild-type and mutant cells. These findings highlight the mitochondrial Electron Transport Chain (ETC) as a potential candidate process to account for these observed changes. Specifically, we are focused on the electron carriers of the ETC, including NADH and FADH2, given their participation in numerous redox mechanisms. We propose future experiments, including NADH assays, an investigation into the glycerol-3-phosphate shuttle, and investigations into other ETC complexes.

BioSentinel↗

Halogen Redox Shuttle Explains Voltage-Induced Halide Redistribution in Mixed-Halide Perovskite Devices

Voltage-induced halide segregation greatly limits the optoelectronic applications of mixed-halide perovskite devices, but a mechanistic explanation behind this phenomenon remains unclear. In this work, we use electron microscopy and elemental mapping to directly measure the halide redistribution in mixed-halide perovskite solar cells with quasi-ion-impermeable contact layers under different bias polarities to find iodide and bromide accumulation at the cathode and anode, respectively. This is consistent with a mechanism based on preferential iodide oxidation at the anode, leading to unbalanced I$^{+}_{i}$, I$^{-}_{X}$, and Br$^{-}_{X}$ fluxes. Importantly, switching the anode from "inert" Au to "active" Ag prevents segregation because Ag oxidation precludes the oxidation of lattice iodide, which suggests employing redox-active additives as a general strategy to suppress halide segregation. Finally, these results show that halide perovskite devices operate as solid-state electrochemical cells when threshold voltages are exceeded, providing fresh insight to understand the impacts of voltage bias on halide perovskite devices.

14 SOLAR ENERGY↗

Effects of clinorotation and microgravity on sweet clover columella cells treated with cytochalasin D

The cytoskeleton of columella cells is believed to be involved in maintaining the developmental polarity of cells observed as a reproducible positioning of cellular organelles. It is also implicated in the transduction of gravitropic signals. Roots of sweet clover (Melilotus alba L.) seedlings were treated with a microfilament disrupter, cytochalasin D, on a slowly rotating horizontal clinostat (2 rpm). Electron micrographs of treated columella cells revealed several ultrastructural effects including repositioning of the nucleus and the amyloplasts and the formation of endoplasmic reticulum (ER) whorls. However, experiments performed during fast clinorotation (55 rpm) showed an accumulation (but no whorling) of a disorganized ER network at the proximal and distal pole and a random distribution of the amyloplasts. Therefore, formation of whorls depends upon the speed of clinorotation, and the overall impact of cytochalasin D suggests the necessity of microfilaments in organelle positioning. Interestingly, a similar drug treatment performed in microgravity aboard the US Space Shuttle Endeavour (STS-54, January 1993) caused a displacement of ER membranes and amyloplasts away from the distal plasma membrane. In the present study, we discuss the role of microfilaments in maintaining columella cell polarity and the utility of clinostats to simulate microgravity.

manned↗

The Manned Maneuvering Unit - 'A nice flying machine'

The need for untethered maneuvers in extravehicular space was recognized early in the NASA manned spaceflight program, leading to experiments during the Gemini flights. The Space Shuttle crews are now equipped with a Manned Maneuvering Unit (MMU) which employs 24 gaseous nitrogen thrusters to furnish six-degree-of-freedom mobility and is fitted with fully redundant electronics, electrical, and propulsion subsystems. The MMU thrusters are operated with translational and rotational hand controllers at the ends of the MMU arms.

Bollendonk, W. W.↗

A lidar technology experiment from Space Shuttle - Lidar In-Space Technology Experiment (LITE)

Plans to conduct a technology experiment with a Shuttle-based lidar instrument are described. The design of the Lidar In-Space Technology Experiment (LITE) is presented, including performance goals for the laser transmitter, telescope, optical receiver, and associated electronics. Experimental results from space flight of the LITE instrument are used to define performance criteria and designs for future atmospheric sounding experiments planned for the Space Station, Earth Observing System platform, and for more complex scientific lidar experiments.

Poole, H. E.↗

Space Experiments with Particle Accelerators (SEPAC)

The purpose of Space Experiments with Particle Accelerators (SEPAC) on the Atmospheric Laboratory for Applications and Science (ATLAS 1) mission, is to carry out active and interactive experiments on and in the earth's ionosphere, atmosphere, and magnetosphere. The instruments to be used are an electron beam accelerator (EBA), plasma contactor, and associated instruments the purpose of which is to perform diagnostic, monitoring, and general data taking functions. Four major classes of investigations are to be performed by SEPAC. They are: beam plasma physics, beam-atmosphere interactions, the use of modulated electron beams as transmitting antennas, and the use of electron beams for remote sensing of electric and magnetic fields. The first class consists mainly of onboard plasma physics experiments to measure the effects of phenomena in the vicinity of the shuttle. The last three are concerned with remote effects and are supported by other ATLAS 1 investigations as well as by ground-based observations.

Obayashi, Tatsuzo↗

Kennedy's Biomedical Laboratory Makes Multi-Tasking Look Easy

If it is one thing that Florida has in abundance, it is sunshine and with that sunshine heat and humidity. For workers at the Kennedy Space Center that have to work outside in the heat and humidity, heat exhaustion/stroke is a real possibility. It might help people to know that Kennedy's Biomedical Laboratory has been testing some new Koolvests(Trademark) that can be worn underneath SCAPE suits. They have also been working on how to block out high noise levels; in fact, Don Doerr, chief of the Biomedical Lab, says, "The most enjoyable aspect is knowing that the Biomedical Lab and the skills of its employees have been used to support safe space flight, not only for the astronaut flight crew, but just as important for the ground processing personnel as well." The NASA Biomedical Laboratory has existed in the John F. Kennedy's Operations and Checkout Building since the Apollo Program. The primary mission of this laboratory has been the biomedical support to major, manned space programs that have included Apollo, Apollo-Soyuz, Skylab, and Shuttle. In this mission, the laboratory has been responsible in accomplishing much of the technical design, planning, provision, fabrication, and maintenance of flight and ground biomedical monitoring instrumentation. This includes the electronics in the launch flight suit and similar instrumentation systems in the spacecraft. (Note: The Lab checked out the system for STS-128 at Pad A using Firing room 4 and ground support equipment in the lab.) During Apollo, there were six engineers and ten technicians in the facility. This has evolved today to two NASA engineers and two NASA technicians, a Life Science Support contract physiologist and part-time support from an LSSC nurse and physician. Over the years, the lab has enjoyed collaboration with outside agencies and investigators. These have included on-site support to the Ames Research Center bed rest studies (seven years) and the European Space Agency studies in Toulouse, France (two years). The lab has also actively collaborated with the US Army Institute for Surgical Research, the USAF School of Aerospace Medicine, and the USN Naval Experimental Diving Unit. Because the lab often evaluates various forms of commercial-off-the-shelf life support equipment, the laboratory works closely with private companies, both domestic and foreign. The European companies seem to be more proactive and participatory with the advancement of personal protective equipment. Because these companies have viewed the space program's unique need for advanced forms of personal protective equipment, some have responded with new designs based on the prediction that these advances will soon find markets in the commercial sector. Using much of the same skills and equipment, the laboratory also addresses physiological testing of humans by supporting flight experiments and personnel involved with ground processing. While Johnson Space Center is primarily responsible for flight experiments, the Kennedy's Biomedical Lab provides the local support. However, as stated above, there are many challenges facing KSC workers that gain the attention of this lab in the measurement of the problem and the selection and testing of countermeasures. These include respiratory protection, whole body suits, hearing protection and heat stress, among many others.

Dunn, Carol Anne↗