How Do I Rate This?
The blue stars show the average user rating for this item. To add your own rating, move your cursor over the stars to highlight them in gold, and click to show your rating. One star highlighted is the lowest rating, all five is the highest. Once you have rated an item, your rating is added to the average.
Large Aperture Systems
Apertures play a key role in remote sensing techniques as well as ensuring the accuracy and sensitivity of telescope mirrors and radar scanning. Researchers at JPL are leading several efforts to advance lightweight structures, adaptive optics, and wavefront sensing. By using high precision modeling and analysis, researchers have developed several technologies for use on current and future missions.
Astronomy apertures are telescopes that are optimized for a particular set of science goals with needs ranging from optical to centimeter-wave frequencies. Earth-science apertures involve both imaging telescopes in the visible to IP and radiometers and radar systems from millimeter –wave to radio frequencies.
At NASA’s Jet Propulsion Laboratory (JPL), there is a wide range of technologies used in large aperture systems. They involve not only optical components but also the techniques in high precision modeling and analysis techniques.
The capabilities of remote sensing instruments depend critically on the size and quality of the aperture that collects and redistributes radiation, the first step in extracting information from observations made in space exploration.
Wavelengths of Interest for Large Aperture Systems
Depiction of wavelengths of use to large aperture systems
Ultraviolet (UV)
Ultraviolet (UV) light emitted by the Sun is typically absorbed into the Earth’s atmosphere before it hits the surface. Ranging from 1 nanometer (nm) to about 400 nm, most electronic transmission energies match this wavelength.
Visible Light
This is the range in which the sun and stars similar to it emit most of their radiation. Visible light electronic transition energies usually match with ultraviolet (UV) light. However, visible light (and near-infrared light) is not typically absorbed and emitted by electronic transitions in individual atoms and molecules, which is why atmospheres appear transparent.
Infrared
Infrared (IR) radiation is electromagnetic radiation whose wavelength is longer than that of visible light, but shorter than that of terahertz radiation and microwaves. Infrared radiation has wavelengths between about 750 nm and .1 mm, spanning three orders of magnitude.
Sub-MM Wave (or Far- Infrared)
The submillimeter wavelength refers to astronomical observations carried out in the region of the electromagnetic spectrum with wavelengths from approximately 0.1 to 1.0 millimeter.
The submillimeter waveband is one of the last parts of the electromagnetic spectrum to be investigated. This is due to the technical challenge of making sensitive detectors, and to the effects of the Earth's atmosphere. Atmospheric molecules, primarily water vapor, both absorb (dim) the signal from astronomical sources and emit their own radiation that acts to mask the astronomical signals.
Microwave
The microwave refers to astronomical observations carried out in the region of about 1 mm to a few centimeters in wavelength.
Radio Wave Region (RF)
The Radio Frequency (RF) wavelength refers to the study of celestial objects by measurement and analysis of the electromagnetic radiation they emit in a longer wavelength--ranging from 1 mm to 30 m (0.04 in. to 100 ft).
Lightweight telescope for space science and communications
In June 2007, the Precision Environment Test Enclosure (PETE) lab completed construction and acceptance testing at the Jet Propulsion Laboratory (JPL). This facility provides a unique integrated environment for deploying, characterizing and modeling large precision deployed structures. These structures will be an enabling technology for future NASA missions across the spectrum—from those in the visible to infrared, sub-millimeter, or microwave apertures too large to fit unfolded in a launch shroud. Dimensional stability is the overriding structural design driver for these large deployable apertures. The stability is driven by constraints derived from the system’s mass and structural stability and to thermal and dynamical loads. As the aperture size increases, and the systems mass density is correspondingly decreased, the ability to test the performance of these apertures in a 1-g environment requires both a unique facility and special testing methodologies. The PETE is an enclosure with 10m Å~ 5m Å~ 3m (L Å~ W Å~ H) usable volume that is controlled under ambient temperature to a thermal stability of <0.01 C°/Hr, acoustic control of <35 dBA. It has been installed within a Class 100,000 clean room and utilizes a variety of instrumentation equipment for precision measurements of structures within the room or for the room itself. (Reference IEEEAC paper #1268, Version 1, Updated 2007:12:13)
Precision deployment is an enabling technology for future NASA large aperture missions. Possible concept missions include optical, infrared, sub-millimeter, or microwave apertures too large to fit unfolded in a launch shroud. Dimensional stability is the overriding structural design driver for these large deployable apertures. The stability is driven by constraints derived from the system's mass and structural stability and to thermal and dynamical loads. As the aperture size increases, and the systems mass density is correspondingly decreased, the ability to test the performance of these apertures in a 1-g environment requires both a unique facility and special testing methodologies. (Reference: IEEEAC paper #1360, Version 2, Updated January 9, 2007)
Integrated Low Temperature Thermal Control
Fundamental to the precision aperture deployable facility is a precision environment test enclosure that will allow controlled experiments to validate new technologies. The enclosure operates in a controlled but ambient temperature and pressure environment. The driving requirements for the enclosure came from the range of concept missions and associated aperture needs. The most extreme requirements are driven by optical structures where the visible wavelengths dictate the amount of structural deformation allowed and hence vibration and thermal environment control. But also at longer wavelengths, into the millimeter and sub-millimeter wavelengths, control of the environment becomes important to meet error budgets at the aperture, and when using membrane systems even in the microwave, a controlled environment is advantageous. The enclosure has a usable volume of 10m by 5m by 3m (L W H). It has been installed within a Class 100,000 clean room at the Jet Propulsion Laboratory and maintains this rating within the enclosure with the air handling equipment operational. A set of hard points on the ceiling and walls was designed to hold the range of envisioned structures and apertures. A set of compressed air drops, power, and Internet and phone ports was supplied. Feed-through holes to the external room are available for external test equipment, computers and data collection systems. A set of doors for moving the test articles and a viewing window is in place.
PALAO/PHARO 2.2 mm image of Titan just starting to eclipse first star of a binary system. The binary separation is ~1.5 arcseconds. (Resolution with AO ~ 0.1 arcsec; without AO > 1 arcsec)
Adaptive Optics
Observation of Titan occultation using Palomar Adaptive Optics System
Adaptive optics usually refers to systems that are meant to correct for the deleterious effects of atmospheric turbulence. These systems are designed to update and correct at high frequencies (up to ~ 3 kHz). Active optics refers to corrections for various types of deformations in the system, e.g. in the primary, support structure, etc. These systems update at much slower rates and can use different correction elements. For more information about adaptive optics projects at JPL.
The telescopes of the Palomar Observatory are involved in a wide variety of astronomical research programs. Utilizing advanced adaptive optics; the studies conducted here range from the hunt for near-Earth asteroids to probing distant galaxies and quasars at the farthest reaches of the universe. The Palomar Observatory is home to many telescopes. Some of them are famous and some are not. All of them contribute to our understanding of the universe
Wavefront Sensing and Control
Wavefront sensing and control are the component-level technologies that power active and adaptive optical systems. As its name suggests, wavefront sensing provides a means of measuring and comparing the wavefront actually found within an optical system with the ideal. Wavefront sensing can also be employed as a means of fingerprinting an optical system, i.e. retrieving the system's nominal optical prescription as well as indicating the origins of observed aberrations. Wavefront control is the means by which inputs obtained from a wavefront sensing capability are transformed into changes in deformable or otherwise reconfigurable elements within an optical system, bringing the measured wavefront into closer conformance with the ideal. For more information, click here: Wavefront sensing and control are the component-level technologies that power active and adaptive optical systems. As its name suggests, wavefront sensing provides a means of measuring and comparing the wavefront actually found within an optical system with the ideal. Wavefront sensing can also be employed as a means of fingerprinting an optical system, i.e. retrieving the system's nominal optical prescription as well as indicating the origins of observed aberrations. Wavefront control is the means by which inputs obtained from a wavefront sensing capability are transformed into changes in deformable or otherwise reconfigurable elements within an optical system, bringing the measured wavefront into closer conformance with the ideal.
The James Webb Telescope (JWST) will have a unique and profound role in transforming our understanding of astrophysics and the origins of galaxies, stars, and planetary systems. In order to carry out its mission, one of the key technologies is the development of wavefront sensing and control, as well as innovative and powerful new technologies ranging from optics to detectors to thermal control systems.
Metrology
The next generation of astrophysics missions will require highly precise control of active optics on flexible structures. Laser metrology gauges provide the sensing for these control loops. Advances in metrology subsystems architectures, components and data processing are required. Interferometric detection of the stellar fringes is critical to measurements of astrophysical objects. Beam combiners measure starlight fringes. Through nulling beam combination at low temperatures, detecting and characterizing extra-solar planets will be possible. Innovations are needed in instrument design and fabrication, optical components, and detectors in the following areas:
Metrology:
High-precision metrology gauges.
Ultra-stable lasers for precision metrology.
Absolute optical metrology systems.
Three-dimensional relative metrology to 0.01-1 nanometers.
Frequency shifters for metrology gauges.
Laser frequency stabilization systems for space based lasers.
Integrated lightweight beam launchers.
Full-aperture metrology gauges.
Embedded grating technology.
High-precision optical fiducials.
Optical surface measurements at .001 to.0001 wave accuracy.
Fiber-optic systems and components for routing metrology laser signals.
Interferometric Detection:
Interferometric beam combiners at visible, infrared, and ultraviolet wavelengths.
Low-background, 10 micrometer infrared detectors.
High frame rate/ultra-low read noise CCD and infrared detector arrays.
Precision Deployable Aperture Systems (PDAs)
Operating From Millimeter Waves Through Optics
Accomplishments
Design and construction of Precision Environment Test Enclosure
Construction and testing of a Precision Deployable Testbed Article
Installation and validation of Interferometric Metrology System
Development of integrated model validation system for RF and optical structures
Integrated Modeling
IMOS
The Integrated Modeling of Optical Systems (IMOS) tool was developed at JPL that couples structural, optical, thermal and control disciplines in optical mechanical systems. This modeling tool was widely used at JPL. Integrated modeling and analysis involves the capability to assess identified performance metrics of a system by combining models, measurements, and uncertainty analysis, as well as defining interfaces among existing tools.
CIELO
A new tool is in development at JPL called CIELO. CIELO supports fully integrated structural-thermal-optical analysis using a common model (realized as a finite element mesh) based on a NASTRAN hosting environment.
RSS
Send
Bookmark
