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This report details our development fo a computer controlled spotlight with four actuated degrees-of-freedom for pan, tilt, linear movement and beam focusing. We review the mechanical structure, kinematic model, calibration data, and control algorithm.
Lighting designs for architectural (aesthetic) purposes, vision and safety, and plant growth have many features in common but several crucial ones that are not. The human eye is very sensitive to the color (wavelength) of light, whereas plants are less so. There are morphological reactions, particularly to the red and blue portions of the light spectrum but, in general, plants appear to accept and use light for photosynthesis everywhere over the PAR region of the spectrum. In contrast, the human eye interprets light intensity on a logarithmic scale, making people insensitive to significant differences of light intensity. As a rough rule, light intensity must change by 30 to 50% for the human eye to recognize the difference. Plants respond much more linearly to light energy, at least at intensities below photosynthetic saturation. Thus, intensity differences not noticeable to the human eye can have significant effects on total plant growth and yield, and crop timing. These factors make luminaire selection and lighting system design particularly important when designing supplemental lighting systems for plant growth. Supplemental lighting for plant growth on the scale of commercial greenhouses is a relatively expensive undertaking. Light intensities are often much higher than required for task (vision) lighting, which increases both installation and operating costs. However, and especially in the northern regions of the United States (and Canada, Europe, etc.), supplemental lighting during winter may be necessary to produce certain crops (e.g., tomatoes) and very useful to achieve full plant growth potential and crop timing with most other greenhouse crops. Operating costs over the life of a luminaire typically will exceed the initial investment, making lighting efficacy a major consideration. This report reviews tests completed to evaluate the efficiencies of various commercially-available High-Pressure Sodium luminaires, and then describes the results of using a commercial lighting design computer program, Lumen-Micro, to explore how to place luminaires within greenhouses and plant growth chambers to achieve light (PAR) uniformity and relatively high lighting efficacies. Several suggestions are presented which could encourage systematic design of plant lighting systems.
A meeting on the potential contributions of plant science to the goals of Controlled Ecological Life Support System (CELSS) research produced discussions that helped to focus on a variety of topics. In the area of volatiles and soluble organics, microbial activity, disease, and productivity, participants emphasized the need to know more about the consequences of closure for the growth of plants. Under nutrient delivery systems, the problems focus on the need to maintain a stable, optimum nutrient system. Lighting systems discussions emphasized unique methods of direct lighting and development of improved irradiation sources. Flight experiment opportunities were outlined by one speaker. Documentation of the Plant Growth Module was discussed. The last day's discussion focused on the organization of the research group to be involved in the development and use of a two to three cubic meter sealed chamber and ancillary equipment.
A Global Positioning System Synchronized Active Light Autonomous Docking System (GPSSALADS) for automatically docking a chase vehicle with a target vehicle comprises at least one active light emitting target which is operatively attached to the target vehicle. The target includes a three-dimensional array of concomitantly flashing lights which flash at a controlled common frequency. The GPSSALADS further comprises a visual tracking sensor operatively attached to the chase vehicle for detecting and tracking the target vehicle. Its performance is synchronized with the flash frequency of the lights by a synchronization means which is comprised of first and second internal clocks operatively connected to the active light target and visual tracking sensor, respectively, for providing timing control signals thereto, respectively. The synchronization means further includes first and second Global Positioning System receivers operatively connected to the first and second internal clocks, respectively, for repeatedly providing simultaneous synchronization pulses to the internal clocks, respectively. In addition, the GPSSALADS includes a docking process controller means which is operatively attached to the chase vehicle and is responsive to the visual tracking sensor for producing commands for the guidance and propulsion system of the chase vehicle.
A Global Positioning System Synchronized Active Light Autonomous Docking System (GPSSALADS) for automatically docking a chase vehicle with a target vehicle comprising at least one active light emitting target which is operatively attached to the target vehicle. The target includes a three-dimensional array of concomitantly flashing lights which flash at a controlled common frequency. The GPSSALADS further comprises a visual tracking sensor operatively attached to the chase vehicle for detecting and tracking the target vehicle. Its performance is synchronized with the flash frequency of the lights by a synchronization means which is comprised of first and second internal clocks operatively connected to the active light target and visual tracking sensor, respectively, for providing timing control signals thereto, respectively. The synchronization means further includes first and second Global Positioning System receivers operatively connected to the first and second internal clocks, respectively, for repeatedly providing simultaneous synchronization pulses to the internal clocks, respectively. In addition, the GPSSALADS includes a docking process controller means which is operatively attached to the chase vehicle and is responsive to the visual tracking sensor for producing commands for the guidance and propulsion system of the chase vehicle.
Light reflection produced by the satellite power system and the possible effects of that light on the human eye, plants, and animals were studied. For the human eye, two cases of reflected light, might cause eye damage if viewed for too long. These cases are: (1) if, while in low Earth orbit, the orbital transfer vehicle is misaligned to reflect the Sun to Earth there exists a maximum safe fixation time for the naked eye of 42.4 secs; (2) reflection from the aluminum paint on the back of the orbital transfer vehicle, while in or near low Earth orbit, can be safely viewed by the naked eye for 129 sec. For plants and animals the intensity and timing of light are not a major problem. Ways for reducing and/or eliminating the irradiances are proposed.
A lighting system has been developed to provide structured illumination allowing photogrammetry to be performed during and after landing on extraterrestrial bodies. The system, known as Directed Illumination of Sunlight Collimated and Observed Beneath a Lunar Lander (DISCOBaLL), provides patterned lighting suitable for two- and multiple-camera photogrammetry, allowing several different measurements to be obtained including pre-landing terrain shape, visualization and localization of the ejecta sheet during landing, and post-landing terrain shape enabling quantitative measurement of plume-induced cratering. The paper explains the methodology of designing the DISCOBaLL, describes multiple prototypes, and shows the performance of these prototypes using actual solar radiation in a laboratory setting.
A lighting system has been developed to provide structured illumination allowing photogrammetry to be performed during and after landing on extraterrestrial bodies. The system, known as Directed Illumination of Sunlight Collimated and Observed Beneath a Lunar Lander (DISCOBaLL), provides patterned lighting suitable for two- and multiple-camera photogrammetry, allowing several different measurements to be obtained including pre-landing terrain shape, visualization and localization of the ejecta sheet during landing, and post-landing terrain shape enabling quantitative measurement of plume-induced cratering. The paper explains the methodology of designing the DISCOBaLL, describes multiple prototypes, and shows the performance of these prototypes using actual solar radiation in a laboratory setting.
The advance in solid state light emitting technologies and optics for lighting and visual communication necessitates the evaluation of how NASA envisions spacecraft lighting architectures and how NASA uses industry standards for the design and evaluation of lighting systems. Current NASA lighting standards and requirements for existing architectures focus on the separate ability of a lighting system to throw light against a surface or the ability of a display system to provide the appropriate visual contrast. This project investigated large luminous surface lamps as an alternative or supplement to overhead lighting. The efficiency of the technology was evaluated for uniformity and power consumption.
The design of a greenhouse that will be a component of a long-term habitat on Mars is presented. The greenhouse will be the primary food source for people stationed on Mars. The food will be grown in three identical underground modules, pressurized at 1 atm to allow a shirt-sleeve environment within the greenhouse. The underground location will support the structure, moderate the large environmental variations on the surface, and protect the crops from cosmic radiation. The design effort is concentrated on the outer structure and the lighting system for the greenhouse. The structure is inflatable and made of a Kevlar 49/Epoxy composite and a pipe-arched system that is corrugated to increase stiffness. This composite is pliable in an uncured state, which allows it to be efficiently packaged for transport. The lighting system consists of several flat-plate fiber optic solar collectors with dual-axis tracking systems that will continually track the sun. This design is modeled after the Himawari collector, which was designed by Dr. Kei Mori and is currently in use in Japan. The light will pass through Fresnel lenses that filter out undesirable wavelengths and send the light into the greenhouses by way of fiber optic cables. When the light arrives at the greenhouse, it is dispersed to the plants via a waveguide and diffuser system.
Front-end stray light baffles for optical imaging systems are used to limit the amount of out-of-field light that reaches the entrance pupil of the optical system. From star tracker baffles to the outer barrel of the Hubble Space Telescope, it is vital to design the locations and apertures of baffle vanes so that the inner walls of the baffle are not simultaneously visible to both stray light sources and the optical entrance pupil. Various designs have been presented for arbitrary cylindrical baffle tubes and explicitly specified conical tubes, but no working generalized algorithm has been presented where the baffle tube can take an arbitrary conical form. Haghshenas and Johari presented what should be a working recursive algorithm, but the published equations have two errors that result in incorrect output. Corrections to their equations are presented here. Additionally, tolerancing in the field of baffle design has typically been accomplished by slightly increasing the field-of-view of the baffle system to avoid clipping the optical field due to mechanical tolerance errors. A new way of incorporating fabrication, alignment, and environmental tolerancing is presented that is more consistent with typical mechanical engineering practice. Furthermore, it is included in the recursive equations with some demonstration of their impact.
Front-end stray light baffles for optical imaging systems are used to limit the amount of out-of-field light that reaches the entrance pupil of the optical system. From star tracker baffles to the outer barrel of the Hubble Space Telescope, it is vital to design the locations and apertures of baffle vanes so that the inner walls of the baffle are not simultaneously visible to both stray light sources and the optical entrance pupil. Various designs have been presented for arbitrary cylindrical baffle tubes and explicitly specified conical tubes, but no working generalized algorithm has been presented where the baffle tube can take an arbitrary conical form. Haghshenas and Johari presented what should be a working recursive algorithm, but the published equations have two errors that result in incorrect output. Corrections to their equations are presented here. Additionally, tolerancing in the field of baffle design has typically been accomplished by slightly increasing the fieldof-view of the baffle system to avoid clipping the optical field due to mechanical tolerance errors. A new way of incorporating fabrication, alignment, and environmental tolerancing is presented that is more consistent with typical mechanical engineering practice and margin against those fabrication errors is included in the recursive equations with demonstration of their benefit.
Coherent noise elimination in coherent light imaging systems by time averaging noise concentrations through lens rotation about optical axis
Light curves produced from color observations taken during New Horizons approach to the Pluto-system by its Multi-spectral Visible Imaging Camera (MVIC, part of the Ralph instrument) are analyzed. Fifty seven observations were analyzed, they were obtained between 9th April and 3rd July 2015, at a phase angle of 14.5 degrees to 15.1 degrees, sub-observer latitude of 51.2 degrees North to 51.5 degrees North, and a sub-solar latitude of 41.2 degrees North. MVIC has four color channels; all are discussed for completeness but only two were found to produce reliable light curves: Blue (400-550 nm) and Red (540-700 nm). The other two channels, Near Infrared (780-975 nm) and Methane-Band (860-910 nm), were found to be potentially erroneous and too noisy respectively. The Blue and Red light curves show that Charon's surface is neutral in color, but slightly brighter on its Pluto-facing hemisphere. This is consistent with previous studies made with the Johnson B and V bands, which are at shorter wavelengths than that of the MVIC Blue and Red channel respectively.
Light curve for eclipsing stars with scattering envelopes applied to V444 Cygni binary system
In our day to day lives, the availability of light, with which to see our environment, is often taken for granted. The designers of land based lighting systems use sunlight and artificial light as their toolset. The availability of power, quantity of light sources, and variety of design options are often unlimited. The accessibility of most land based lighting systems makes it easy for the architect and engineer to verify and validate their design ideas. Failures with an implementation, while sometimes costly, can easily be addressed by renovation. Consider now, an architectural facility orbiting in space, 260 miles above the surface of the earth. This human rated architectural facility, the International Space Station (ISS) must maintain operations every day, including life support and appropriate human comforts without fail. The facility must also handle logistics of regular shipments of cargo, including new passengers. The ISS requires accommodations necessary for human control of machine systems. Additionally, the ISS is a research facility and supports investigations performed inside and outside its livable volume. Finally, the facility must support remote operations and observations by ground controllers. All of these architectural needs require a functional, safe, and even an aesthetic lighting environment. At Johnson Space Center, our Habitability and Human Factors team assists our diverse customers with their lighting environment challenges, via physical test and computer based analysis. Because of the complexity of ISS operational environment, our team has learned and developed processes that help ISS operate safely. Because of the dynamic exterior lighting environment, uses computational modeling to predict the lighting environment. The ISS' orbit exposes it to a sunrise every 90 minutes, causing work surfaces to quickly change from direct sunlight to earthshine to total darkness. Proper planning of vehicle approaches, robotics operations, and crewed Extra Vehicular Activities are mandatory to ensure safety to the crew and all others involved. Innovation in testing techniques is important as well. The advent of Solid State Lighting technology and the lack of stable national and international standards for its implementation pose new challenges on how to design, test and verify individual light fixtures and the environment that uses them. The ISS will soon be replacing its internal fluorescent lighting system to a solid state LED system. The Solid State Lighting Assembly will be used not only for general lighting, but also as a medical countermeasure to control the circadian rhythm of the crew. The new light source has performance criteria very specific to its spectral fingerprint, creating new challenges that were originally not as significant during the original design of the ISS. This presentation will showcase findings and toolsets our team is using to assist in the planning of tasks, and design of operational lighting environments on the International Space Station.
The inflatable structure serves as an ideal greenhouse while being feasible to transport and easy to assemble on Mars. Locating the structure underground protects it from the extreme environmental variations on the surface. The proposed lighting system provides all the necessary light for photosynthesis with little external power demand. These considerations make the proposed greenhouse design a viable means of providing an ongoing food supply for a Martian colony.