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NASA NTRS2000

Holographic Optical Data Storage

Although the basic idea may be traced back to the earlier X-ray diffraction studies of Sir W. L. Bragg, the holographic method as we know it was invented by D. Gabor in 1948 as a two-step lensless imaging technique to enhance the resolution of electron microscopy, for which he received the 1971 Nobel Prize in physics. The distinctive feature of holography is the recording of the object phase variations that carry the depth information, which is lost in conventional photography where only the intensity (= squared amplitude) distribution of an object is captured. Since all photosensitive media necessarily respond to the intensity incident upon them, an ingenious way had to be found to convert object phase into intensity variations, and Gabor achieved this by introducing a coherent reference wave along with the object wave during exposure. Gabor's in-line recording scheme, however, required the object in question to be largely transmissive, and could provide only marginal image quality due to unwanted terms simultaneously reconstructed along with the desired wavefront. Further handicapped by the lack of a strong coherent light source, optical holography thus seemed fated to remain just another scientific curiosity, until the field was revolutionized in the early 1960s by some major breakthroughs: the proposition and demonstration of the laser principle, the introduction of off-axis holography, and the invention of volume holography. Consequently, the remainder of that decade saw an exponential growth in research on theory, practice, and applications of holography. Today, holography not only boasts a wide variety of scientific and technical applications (e.g., holographic interferometry for strain, vibration, and flow analysis, microscopy and high-resolution imagery, imaging through distorting media, optical interconnects, holographic optical elements, optical neural networks, three-dimensional displays, data storage, etc.), but has become a prominent am advertising, and security medium as well. The evolution of holographic optical memories has followed a path not altogether different from holography itself, with several cycles of alternating interest over the past four decades. P. J. van Heerden is widely credited for being the first to elucidate the principles behind holographic data storage in a 1963 paper, predicting bit storage densities on the order of 1/lambda(sup 3) with source wavelength lambda - a fantastic capacity of nearly 1 TB/cu cm for visible light! The science and engineering of such a storage paradigm was heavily pursued thereafter, resulting in many novel hologram multiplexing techniques for dense data storage, as well as important advances in holographic recording materials. Ultimately, however, the lack of such enabling technologies as compact laser sources and high performance optical data I/O devices dampened the hopes for the development of a commercial product. After a period of relative dormancy, successful applications of holography in other arenas sparked a renewed interest in holographic data storage in the late 1980s and the early 1990s. Currently, with most of the critical optoelectronic device technologies in place and the quest for an ideal holographic recording medium intensified, holography is once again considered as one of several future data storage paradigms that may answer our constantly growing need for higher-capacity and faster-access memories.

Timucin, Dogan A.↗

NASA NTRS2016

Veggie: Space Vegetables for the International Space Station and Beyond

The Veggie vegetable production system was launched to the International Space Station (ISS) in 2014. Veggie was designed by ORBITEC to be a compact, low mass, low power vegetable production system for astronaut crews. Veggie consists of a light cap containing red, blue, and green LEDs, an extensible transparent bellows, and a baseplate with a root mat reservoir. Seeds are planted in plant pillows, small growing bags that interface with the reservoir. The Veggie technology validation test, VEG-01, was initiated with the first test crop of 'Outredgeous' red romaine lettuce. Prior to flight, lettuce seeds were sanitized and planted in a substrate of arcillite (baked ceramic) mixed with controlled release fertilizer. Upon initiation, astronauts open the packaged plant pillows, install them in the Veggie hardware, and prime the system with water. Operations include plant thinning, watering, and photography. Plants were grown on the ISS for 33 days, harvested, and returned frozen to Earth for analysis. Ground controls were conducted at Kennedy Space Center in controlled environment chambers reproducing ISS conditions of temperature, relative humidity, and CO2. Returned plant samples were analyzed for microbial food safety and chemistry including elements, antioxidants, anthocyanins and phenolics. In addition the entire plant microbiome was sequenced, and returned plant pillows were analyzed via x-ray tomography. Food safety analyses allowed us to gain approvals for future consumption of lettuce by the flight surgeons and the payload safety office. A second crop of lettuce was grown in 2015, and the crew consumed half the produce, with the remainder frozen for later analysis. This growth test was followed by testing of a new crop in Veggie, zinnias. Zinnias were grown to test a longer duration flowering crop in preparation for tests of tomatoes and other fruiting crops in the future. Zinnias were harvested in February. Samples from the second harvest of lettuce and the zinnia harvest are frozen on the ISS and will return with the next cargo return flight. Some challenges occurred in all tests, especially in the area of watering, with plants receiving insufficient or excess water leading to stressed growth. Zinnia plants were also challenged with fungal growth. Initial tests with Veggie have given us great insight into future crop production scenarios as we work to develop regular supplemental salad crop production on ISS and larger food production systems for our journey to Mars. Funding for this research comes from NASA's Space Biology Program.

Food Safety↗

NASA NTRS1972

Apollo 15 orbital science summary.

In this paper, summary results of the Apollo 15 orbital science payload are given, and some quick-look results of Apollo 16 are discussed. Geochemical instruments, consisting of gamma-ray, X-ray, and alpha particle spectrometers, have provided a chemical map of the lunar surface flown over by Apollo 15. The Laser Altimeter and frontside gravity data have shown some unexpected results with regard to the lunar shape, and provided new basis for understanding lunar mascons. A magnetometer, aboard the small subsatellite, has located magnetic anomalies principally on the lunar farside, and has shown that the small lunar magnetic field is smoother on the frontside than on the back. The mass spectrometer, in orbit aboard the Command and Service Modules, has measured unexpectedly large populations of molecules at orbital altitude (110 km), mostly due to spacecraft contamination. Two major camera systems have provided the first systematic metric quality photography and concurrent high resolution stereo coverage of the lunar surface.

Esenwein, G. F.↗

NASA NTRS1969

Apollo 6, Anomaly Report No. 6: Abnormal Structural Performance During Launch Phase

Approximately 2 minutes 13 seconds after lift-off of the Apollo 6 mission, abrupt changes of strain, vibration, and acceleration measurements were indicated in the S-IVB, instrument unit, adapter, lunar module, and command and service modules; photographs showed objects coming from the area of the adapter. The adapter, however, continued to sustain the required loads with no impairment of the mission. The investigation was first focused upon the understanding of the coupled vibration modes and characteristics of the launch vehicle and spacecraft.' Extensive test programs were conducted. It was eventually concluded that the adapter failure was not caused by vibration. Extensive study of the airborne photography and other evidence indicated that a large area of the adapter had lost inner facesheet from the honeycomb sandwich panels. Loads and stresses resulting from vibration were determined to be insufficient to initiate such a failure. The investigation was then directed toward determining the range of pressures that could have been trapped in the Apollo 6 adapter sandwich panels, and toward determining the tolerance of the panels to withstand pressure with various degrees of flaws such as adhesive voids and facesheet dents. The degradation effects of moisture and heat exposure on the adhesive strength were also studied and tested. These tests and analyses led to the conclusion that pressure internal to the sandwich panels could have caused the failure, if a large flaw existed. The pressure buildup would have been caused by aerodynamic heating effects on air and moisture trapped in the panel. The probable cause of the failure was found in the original ultrasonic inspection scan record of the affected adapter panel. In the center of the region where the adapter failed, horizontally along the station 709 panel splice, the record contained two thick anomalous lines extending several feet. Without an X-ray record of this region, the significance of this particular scan record cannot be fully understood. However, since all other evidence had indicated that the adhesive had to be weakened in a rather large area to initiate the failure, the investigation was focused intently upon the station 709 splices of other adapters. Sufficient information was developed to verify that deficient assembly techniques have consistently resulted in abnormalities in the structure at this station. These abnormalities were identified in adapters 12, 13, 14, 15, and 16. Before the splice abnormalities were pinpointed, corrective action was taken to reduce pressure "buildup in the honeycomb panels and to reduce heat degrading effects on the adhesive. This was done by drilling vent holes in the inner facesheet and covering the outer facesheet with cork. The adapters having identified abnormalities in the station 709 splice are being repaired, and the contractor is investigating ways of avoiding these -abnormalities in panels yet to be bonded.

Source record↗

DOE OSTI2022

Design of a high-resolution Rayleigh-Taylor experiment with the Crystal Backlighter Imager on the National Ignition Facility

The Rayleigh-Taylor (RT) instability affects a vast range of High Energy Density (HED) length scales, spanning from supernova explosions (10 13 m) to inertial confinement fusion (10 -6 m). In inertial confinement fusion, the RT instability is known to induce mixing or turbulent transition, which in turn cools the hot spot and hinders ignition. The fine-scale features of the RT instability, which are difficult to image in HED physics, may help determine if the system is mixing or is transitioning to turbulence. Earlier diagnostics lacked the spatial and temporal resolution necessary to diagnose the dynamics that occur along the RT structure. A recently developed diagnostic, the Crystal Backlighter Imager (CBI), [1,2] can now produce an x-ray radiograph capable of resolving the fine-scale features expected in these RT unstable systems. This paper describes an experimental design that adapts a well-characterized National Ignition Facility (NIF) platform to accommodate the CBI diagnostic. Simulations and synthetic radiographs highlight the resolution capabilities of the CBI in comparison to previous diagnostics. Furthermore, the improved resolution of the system can provide new observations to study the RT instability's involvement in mixing and the transition to turbulence in the HED regime.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1973

Skylab experiments. Volume 1: Physical science, solar astronomy

The basic subject of this volume is the solar astronomy program conducted on Skylab. In addition to descriptions of the individual experiments and the principles involved in their performance, a brief description is included of the sun and the energy characteristics associated with each zone. Wherever possible, related classroom activities have been identified and discussed in some detail. It will be apparent that the relationships rest not only in the field of solar astronomy, but also in the following subjects: (1) physics - optics, electromagnetic spectrum, atomic structure, etc.; (2) chemistry - emission spectra, kinetic theory, X-ray absorption, etc.; (3) biology - radiation and dependence on the sun; (4) electronics - cathode ray tubes, detectors, photomultipliers, etc.; (5) photography; (6) astronomy; and (7) industrial arts.

Source record↗

NASA NTRS1977

The Luna and Zond programs

These series have included flyby, lunar-orbiting, and soft-landing missions. A variety of experiments were carried out by these spacecraft including studies of magnetism, X-ray and gamma ray emissions, gravitational anomalies, and chemical composition. Soil samples, near- and farside photography (both color and black and white), and earth-cloud photography were also acquired.

Source record↗

NASA NTRS1978

Definition and detailed characterization of lunar surface units using remote observations

Remote sensing techniques are reviewed in terms of their application to the study of the lunar surface. These techniques include: reflectance spectroscopy (UV and IR), X-ray and gamma-ray analysis, alpha-particle spectroscopy, thermal emission, polarimetry, photography, and visual observation. Each technique is indexed with respect to its usefulness in either describing the appearance and location of a feature, classifying the feature in terms of a broader category, or supplying additional quantitative data. Special attention is given to the mare deposits of the Imbrium basin.

Head, J. W.↗

NASA NTRS2017

Surveys of Returned ISS Hardware for MMMOD Impacts

Since February 2001, the Hypervelocity Impact Technology (HVIT) group at the Johnson Space Center (JSC) in Houston has performed 35 post-flight inspections on space exposed hardware returned from the International Space Station (ISS). Data on 1,188 observations of micrometeoroid and orbital debris (MMOD) damage have been collected from these inspections. Survey documentation typically includes impact feature location and size measurements as well as microscopic photography (25-200x). Sampling of impacts sites for projectile residue was performed for the largest features. Results of energy dispersive X-ray spectroscopic analysis to discern impactor source are included in the database when available. This paper will focus on two inspections, the Pressurized Mating Adapter 2 (PMA-2) cover returned in 2015 after 1.6 years exposure with 26 observed impact features, and two Airlock shield panels returned in 2010 after 8.75 years exposure with 58 MMOD impacts. Feature sizes from the observed data are compared to predictions using the Bumper 3 risk assessment code.

Hyde, J. L.↗