ALBERT

Description: The Jet Propulsion Laboratory is developing a new imaging interferometer that has double the efficiency of conventional interferometers and only a fraction of the mass and volume. The project is being funded as part of the Defense Advanced Research Projects Agency (DARPA) Photonic Wavelength And Spatial Signal Processing program (PWASSSP).

Description: This paper discusses the development and design of an experimental test cell for ground-based testing to provide requirements for the Spaceflight Holography Investigation in a Virtual Apparatus (SHIVA) experiment. Ground-based testing of a hardware breadboard set-up is being conducted at Marshall Space Flight Center in Huntsville, Alabama. SHIVA objectives are to test and validate new solutions of the general equation of motion of a particle in a fluid, including particle-particle interaction, wall effects, motion at higher Reynolds Number, and a motion and dissolution of a crystal moving in a fluid. These objectives will be achieved by recording a large number of holograms of particle motion in the International Space Station (ISS) glove box under controlled conditions, extracting the precise three- dimensional position of all the particles as a function of time, and examining the effects of all parameters on the motion of the particles. This paper will describe the mechanistic approach to enabling the SHIVA experiment to be performed in a ISS glove box in microgravity. Because the particles are very small, surface tension becomes a major consideration in designing the mechanical method to meet the experiments objectives in microgravity, To keep a particle or particles in the center of the test cell long enough to perform and record the experiment and to preclude contribution to particle motion, requires avoiding any initial velocity in particle placement. A Particle Injection Mechanism (PIM) designed for microgravity has been devised and tested to enable SHIVA imaging. Also, a test cell capture mechanism, to secure the test cell during vibration on a specially designed shaker table for the SHIVA experiment will be described. Concepts for flight design are also presented.

Description: The High resolution Airborne Wideband Camera (HAWC) and the Submillimeter High Angular Resolution Camera II (SHARC 11) will use almost identical versions of an ion-implanted silicon bolometer array developed at the National Aeronautics and Space Administration's Goddard Space Flight Center (GSFC). The GSFC "Pop-Up" Detectors (PUD's) use a unique folding technique to enable a 12 x 32-element close-packed array of bolometers with a filling factor greater than 95 percent. A kinematic Kevlar(Registered Trademark) suspension system isolates the 200 mK bolometers from the helium bath temperature, and GSFC - developed silicon bridge chips make electrical connection to the bolometers, while maintaining thermal isolation. The JFET preamps operate at 120 K. Providing good thermal heat sinking for these, and keeping their conduction and radiation from reaching the nearby bolometers, is one of the principal design challenges encountered. Another interesting challenge is the preparation of the silicon bolometers. They are manufactured in 32-element, planar rows using Micro Electro Mechanical Systems (MEMS) semiconductor etching techniques, and then cut and folded onto a ceramic bar. Optical alignment using specialized jigs ensures their uniformity and correct placement. The rows are then stacked to create the 12 x 32-element array. Engineering results from the first light run of SHARC II at the CalTech Submillimeter Observatory (CSO) are presented.

Description: We have designed, built, and flight-tested a new star camera for daytime guiding of pointed balloon-borne experiments at altitudes around 40 km. The camera and lens are commercially available, off-the-shelf components, but require a custom-built baffle to reduce stray light, especially near the sunlit limb of the balloon. This new camera, which operates in the 600- to 1000-nm region of the spectrum, successfully provides daytime aspect information of approx. 10 arcsec resolution for two distinct star fields near the galactic plane. The detected scattered-light backgrounds show good agreement with the Air Force MODTRAN models used to design the camera, but the daytime stellar magnitude limit was lower than expected due to longitudinal chromatic aberration in the lens. Replacing the commercial lens with a custom-built lens should allow the system to track stars in any arbitrary area of the sky during the daytime.

Description: Coronagraphs for extra-solar planet detection remove diffracted stellar light through the combination of a coronagraphic mask and a Lyot stop. When the entrance pupil contains a nearly perfect wave fiont, most of the stellar light is absorbed at the mask. Light scattered around the spot due to mid- and high-spatial frequency phase errors in the pupil appears at the Lyot plane as speckles whose amplitudes are proportional to the local wave front phase residuals. The speckles scale with optical wavelength but are not radially smeared. The Eclipse deformable mirror (DM) can be used to modify the Lyot amplitude distribution, providing a simple means of estimating the residual phase content and controlling the wave front. To reduce the detrimental noise carried by uncontrollable high-spatial frequency wave front components, theLyot plane signal is filtered at the science plane to pass only the controllable spatial frequencies that contribute to the dark hole. The Lyot stop is then reimaged onto a detector. We demonstrate through simulations that this approach signiscantly improves the signal-to-noise ratio of the planet measurement.

Description: We characterize the spectroscopic line spread functions of the spectroscopic CCD modes for high contrast objects. Our long range goal is to develop tools that accurately extract spectroscopic information of faint, point or extended sources in the vicinity of bright, point sources at separations approaching the realizable angular limits of HST with STIS. Diffracted and scattered light due to the HST optics, and scattered light effects within the STIS are addressed. Filter fringing, CCD fringing, window reflections, and scattering within the detector and other effects are noted. We have obtained spectra of several reference stars, used for flux calibration or for coronagraphic standards, that have spectral distributions ranging from very red to very blue. Spectra of each star were recorded with the star in the aperture and with the star blocked by either the F1 or F2 fiducial. Plots of the detected starlight along the spatial axis of the aperture are provided for four stars. With the star in the aperture, the line spread function is quite noticeable. Placing the star behind one of the fiducials cuts the scattered light and the diffracted light, is detectable even out to 1OOOOA. When the star is placed behind either fiducial, the scattered and diffracted light components, at three arcseconds displacement from the star, are below lop6 the peak of the star at wavelengths below 6000A; at the same angular distance, scattered light does contaminate the background longward of 6000A up to a level of 10(exp -5).

Description: TopHat is a balloon-borne instrument designed to operate on the top of a balloon. From this location, the experiment could efficiently observe using a clean beam with extremely low sidelobes. The experiment was designed to scan a large portion of the sky directly above it and to map the anisotropy of the Cosmic Microwave Background (CMBR) and thermal emission from galactic dust. The instrument used a one meter class telescope with a five band single pixel radiometer spanning the frequency range from 150-600 GHz. The radiometer used bolometric detectors operating at approx. 250 mK. Here, we will report on the flight of the TopHat experiment over Antarctica in January, 2001 and describe the scientific goals, the operation, and in-flight performance.

Description: There are major variations in energy flux within and across the region of a large city. These variations have impacts in disparate areas, such as human health, environmental monitoring and mitigation, and energy consumption. Knowledge of the variations also has utility to urban and regional planners, and climate modelers. The authors have developed a system which permits robust measurement of both the magnitude of the energy flux variation and the absolute value of energy flux over regions of the size of large cites. The technique uses properly acquired and processed multispectral imagery with bands in the visible, near-IR and thermal portions of the electromagnetic spectrum. With proper knowledge of the atmosphere and geometries of acquisition it is possible to compute the energy budget for individual pixels. The reality of this technique is demonstrated using data acquired over Salt Lake City, Utah. The deficiencies in the results emphasize the critical nature of various design and engineering features usually ignored in airborne and satellite imaging systems.

Description: This paper describes a lifetime PSP system that has recently been developed using pulsed light-emitting diode (LED) lamps and a new interline transfer CCD camera technology. This system alleviates noise sources associated with lifetime PSP systems that use either flash-lamp or laser excitation sources and intensified CCD cameras for detection. Calibration curves have been acquired for a variety of PSP formulations using this system, and a validation test was recently completed in the Subsonic Aerodynamic Research Laboratory (SARL) at Wright-Patterson Air Force Base (WPAFB). In this test, global surface pressure distributions were recovered using both a standard intensity-based method and the new lifetime system. Results from the lifetime system agree both qualitatively and quantitatively with those measured using the intensity-based method. Finally, an advanced lifetime imaging technique capable of measuring temperature and pressure simultaneously is introduced and initial results are presented.