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NASA NTRS2015

MISR Calibration Issues in High-Contrast Scenes, and Empirical Corrections

We diagnose the potential causes for the Multi-angle Imaging SpectroRadiometer's (MISR) persistent high aerosol optical depth (AOD) bias at low AOD with the aid of coincident MODerate-resolution Imaging Spectroradiometer (MODIS) imagery from NASA's Terra satellite. Internal reflections within the MISR instrument are responsible for a large portion of the high AOD bias in high-contrast scenes, which are especially common as broken-cloud situations over ocean. Discrepancies between MODIS and MISR nadir-viewing near-infrared (NIR) images are used to optimize nine parameters, along with a background reflectance modulation term (that was modeled separately), to represent the observed features. Independent, surface-based AOD measurements from the AErosol RObotic NETwork (AERONET) and the Marine Aerosol Network (MAN) are compared with MISR Research Algorithm (RA) AOD retrievals for 1118 coincidences to validate the corrections when applied to the nadir and off-nadir cameras. Additionally, the calibration coefficients for the red and NIR channels used for MISR over-water aerosol retrievals were reassessed with the RA to be consistent on a camera-by-camera basis. With these corrections, plus the baseline RA corrections applied (except enhanced cloud screening), the median AOD bias in the mid-visible (green) band decreases from 0.010 to 0.002, the RMSE decreases by approx. 10%, and the slope and correlation of the MISR vs. sun photometer Ångström Exponent improves. For AOD558 nm < 0.10 and with additional cloud screening, the median bias for the RA-retrieved AOD in the green band decreases from 0.011 to 0.003, compared to ~ 0.023 for the Standard Algorithm (SA). RMSE decreases by ~ 20% compared to the baseline (uncorrected) RA and by 17-53% compared to the SA. After all corrections and cloud screening are implemented, for AOD558 nm < 0.10, which includes about half the validation data, 68% absolute AOD errors for the RA have dropped to < 0.02 (approx. 0.018).

MISR↗
NASA NTRS2016

Virtual Microscope Views of the Apollo 11 and 12 Lunar Samples

The Apollo virtual microscope is a means of viewing, over the Internet, polished thin sections of every rock in the Apollo lunar sample collections via software, duplicating many of the functions of a petrological microscope, is described. Images from the Apollo 11 and 12 missions may be viewed at: www.virtualmicroscope.org/content/apollo. Introduction: During the six NASA missions to the Moon from 1969-72 a total of 382 kilograms of rocks and soils, often referred to as "the legacy of Apollo", were collected and returned to Earth. A unique collection of polished thin sections (PTSs) was made from over 400 rocks by the Lunar Sample Curatorial Facility at the Johnson Spacecraft Center (JSC), Houston. These materials have been available for loan to approved PIs but of course they can't be simultaneously investigated by several researchers unless they are co-located or the sample is passed back and forward between them by mail/hand carrying which is inefficient and very risky for irreplaceable material. When The Open University (OU), the world's largest Distance Learning Higher Education Establishment found itself facing a comparable problem (how to supply thousands of undergraduate students with an interactive petrological microscope and a personal set of thin sections), it decided to develop a software tool called the Virtual Microscope (VM). As a result it is now able to make the unique and precious collection of Apollo specimens universally available as a resource for concurrent study by anybody in the world's Earth and Planetary Sciences community. Herein, we describe the first steps of a collaborative project between OU and the Johnson Space Center (JSC) Curatorial Facility to record a PTS for every lunar rock, beginning with those collected by the Apollo 11 and 12 missions. Method: Production of a virtual microscope dedicated to a particular theme divides into four main parts - photography, image processing, building and assembly of virtual microscope components, and publication on a website. Two large research quality microscopes are used to collect all the images required for a virtual microscope. The first is part of an integrated package that utilizes Leica PowerMosaic software and a motorised XYZ stage to generate large area mosaics. It includes a fast acquisition camera and depending on the PTS size normally is used to produce seamless mosaic images consisting of 100-500 individual photographs. If the sample is suitable, three mosaics of each sample are recorded - plane polarised light, between crossed polars and reflected light. In order for the VM to be a true petrological microscope it is necessary to recreate the features of a rotating stage and perform observations using filters to produce polarised light. Thus the petrological VM includes the capability of seeing changes in optical properties (pleochroism and birefringence) during rotation allowing mineral identification. The second microscope in the system provides the functions of the rotating stage. To this microscope we have added a robotically controlled motor to acquire seventy-two images (5 degree intervals) in plane polarised light and between crossed polars. To process the images acquired from the two microscopes involves a combination of proprietary software (Photoshop) and our own in-house code. The final stage involves assembling all the components in an HTML5 environment. Pathfinder investigations: We have undertaken a number of pilot studies to demonstrate the efficacy of the petrological microscope with lunar samples. The first was to make available on-line images collected from the Educational Package of Apollo samples provided by NASA to the UK STFC (Science and Technical Facilities Council) for loan as educational material e.g. for schools. The real PTSs of the samples are now no longer sent out to schools removing the risks associated with transport, accidental breakage and eliminating the possibility of loss. The availability of lunar sample VM-related material was further extended to include twenty-eight specimens from all of the Apollo missions. Some of these samples were made more generally available through an ibook entitled "Moon Rocks: an introduction to the Geology of the Moon," free from the Apple Bookstore. Research possibilities: Although the Virtual Microscope was originally conceived as a teaching aid and was later recognised as a means of public outreach and engagement, we now realize that it also has enormous potential as a high level research tool. Following discussions with the JSC Curators we have received Curation and Analysis Planning Team for Extraterrestrial Materials (CAPTEM) permission to embark on a programme of digitizing the entire lunar sample PTS collection for all three of the above purposes. By the time of the 47th Lunar and Planetary Science Conference (LPSC) we will have completed 81 rocks collected during the Apollo 11 and 12 missions and the data, with cross-links to the Lunar Sample Compendium will go live on the Web at the 47th LPSC. The VM images of the Apollo 11 (41 VM images) and 12 (40 VM images) missions can be viewed at: http:/www.virtualmicroscope.org/content/apollo. The lunar sample VM will enable large numbers of skilled/unskilled microscopists (professional and amateur researchers, educators and students, enthusiasts and the simply curious non-scientists) to share the information from a single sample. It will mean that all the PTSs already cut, even historical ones, could be available for new joint investigations or private study. The scientific return from the collection will increase exponentially as a result of further debate and discussion. Simultaneously the VM will remove the need for making unnecessary multiple samplings, avoid consignment of delicate/breakable specimens (all of which are priceless) to insecure mail/courier services and reduce direct labour and indirect costs, travel budgets and unproductive travelling time necessary for co-location of collaborating researchers. For the future we have already recognized further potential for virtual technology. There is nothing that a petrologist likes more than to see the original rock as a hand specimen. It is entirely possible to recreate virtual hand specimens with 3-D hard and software, already developed for viewing fossils, located within the Curatorial Facility, http://curator.jsc.nasa.gov/lunar/lsc/index.cfm.

Gibson, E. K.↗
NASA NTRSDate not supplied

VTXO: the Virtual Telescope for X-ray Observations

The Virtual Telescope for X-ray Observations (VTXO) will use lightweight Phase Frensel Lenses (PFLs) in a virtual X-ray telescope with 1 km focal length and with nearly 50 milli-arcsecond angular resolution. Laboratory characterization of PFLs have demonstrated near diffraction-limited angular resolution in the X-ray band, but they require long focal lengths to achieve this quality of imaging. VTXO is formed by using precision formation flying of two SmallSats: a smaller, 6U OpticsSat that houses the PFLs and navigation beacons while a larger, ESPA-class DetectorSat contains an X-ray camera, a charged-particle radiation monitor, a precision star tracker, and the propulsion for the formation flying. The baseline flight dynamics uses a highly-elliptical supersynchronous geostationary transfer orbit to allow the inertial formation to form and hold around the 90,000 km apogee for 10 hours of the 32.5-hour orbit with nearly a year mission lifetime. The guidance, navigation, and control (GN&C) for the formation flying uses standard CubeSat avionics packages, a precision star tracker, imaging beacons on the Optics Sat, and a radio ranging system that also serves as an inter-satellite communication link. VTXO’s fine angular resolution enables measuring the environments nearly an order of magnitude closer to the central engines of bright compact X-ray sources compared to the current state of the art. This X-ray imaging capability allows for the study of the effects of dust scattering nearer to the central objects such as Cyg X-3 and GX 5-1, for the search for jet structure nearer to the compact object in X-ray novae such as Cyg X-1and GRS 1915+105, and for the search for structure in the termination shock of in the Crab pulsar wind nebula. The In this paper, the VTXO science performance, SmallSat and instrument designs,and mission description is be described. The VTXO development was supported as one of the selected 2018 NASA Astrophysics SmallSat Study (AS3) missions.

John Krizmanic↗
NASA NTRS1993

Three high duty cycle, space-qualified mechanisms

The Michelson Doppler Imager (MDI) is a scientific instrument aboard the Solar and Heliospheric Observatory (SOHO) spacecraft. In 1995, the spacecraft will be put into a halo orbit about the L1 Lagrangian point (equal Sun and Earth gravity). The MDI looks at the sun continuously and takes a picture with a large format CCD camera every 3 seconds. The design goal of the mission is 6 years, so over 60 million pictures will be taken. The sun, being a high intensity source, provides a signal with a single pixel noise level of 0.2 percent. Many images are combined to measure the oscillatory motion of the sun so very high performance is required of the mechanisms in order that they not add noise to the data. The MDI instrument is made up of two parts, the electronics package and the optics package. This paper describes the design and testing of three mechanisms on the MDI which are required to operate large numbers of times.

Akin, David↗
NASA NTRS2004

Flow visualization and characterization of evaporating liquid drops

An optical system, consisting of drop-reflection image, reflection-refracted shadowgraphy and top-view photography, is used to measure the spreading and instant dynamic contact angle of a volatile-liquid drop on a non-transparent substrate. The drop-reflection image and the shadowgraphy is shown by projecting the images of a collimated laser beam partially reflected by the drop and partially passing through the drop onto a screen while the top view photograph is separately viewed by use of a camera video recorder and monitor. For a transparent liquid on a reflective solid surface, thermocapillary convection in the drop, induced by evaporation, can be viewed nonintrusively, and the drop real-time profile data are synchronously recorded by video recording systems. Experimental results obtained from this technique clearly reveal that evaporation and thermocapillary convection greatly affect the spreading process and the characteristics of dynamic contact angle of the drop.

Chao, David F.↗
NASA NTRSDate not supplied

An Updated Model for the Effect of Atmospheric Absorption on Sounding Rockets

A very high-resolution R > 20,000 Far Ultraviolet full-disk, solar spectrograph will be launched in the Spring of 2023. This paper describes the in-flight wavelength calibration techniques and the fortuitous retrieval of Earth’s thermospheric information during the flight. Building and calibration of the Full-sun Ultraviolet Rocket Spectrograph (FURST) is currently underway. The purpose of this instrument is to obtain the highest resolution and most complete Far Ultra-Violet (FUV) spectra of the full disk Sun. This so-called "Sun-as-a-star" spectra will allow direct comparisons between our Sun and other stars measured by the Hubble Space Telescope(HST) and the upcoming James Webb Space Telescope (JWST). The Solar Physics groups at NASA Marshall Space Flight Center (MSFC) and Montana State University (MSU) have been developing the tools and procedures necessary to achieve the high spectral resolution goal. These include, among other things, improved tracking of error propagation, in-situ monitoring of the camera gain with a radioactive Fe-55 source, and the development of a simulated spectral calibration map under a noisy diagnostic-lamp signal. This mapping introduces a clocked CCD in order to obtain sub-pixel spectral resolution and overcome the Nyquist limit by about a factor of 2. Aside from the main purpose of FURST, we have been investigating the effect of absorption in the upper atmosphere at sounding-rocket altitudes (about 100-300 km). We present here an improved model of the optical depth caused by the thermospheric Oxygen cross-section and H and O self-absorption. This data-based model uses concentric spherical shells to account for the curvature of the Earth’s atmosphere and refraction. Using these calculations, we present the anticipated effect on the signal received by FURST, how that signal changes over the course of the flight-path These absorption peaks would provide wavelength fiducials at line-center that might add to in-flight calibration of the instrument. Many studies have found ways to correct for these so-called "Telluric" lines. However, it may be that these lines can in fact be a useful tool to further improve our calibration, rather than simply a nuisance to be corrected for! Finally, we discuss the inversion problem: how we could take actual flight data and back-out the atmospheric data (such as density and temperature) from any such sounding rocket flight that shows evidence of atmospheric absorption.

Nicolas Donders↗
NASA NTRS1983

A multiwavelength study of the short-period cataclysmic variable V442 Ophiuchi

The results of a program of observations of the cataclysmic variable V442 Oph from UV to IR wavelengths are reported. The observations comprise IUE SWP and LWR-camera spectra from October, 1981; UBVr and R photometry at Manastash Ridge Observatory from August, 1980; UBV photometry and IR measurements at Kitt Peak from July, 1981; and Coudespectroscopy at Mt. Wilson from June, 1980, and at Mt Lemmon from July, 1982. Tables of data, plots of H-alpha and He-II radial velocity, sample spectra, light curves, and a log-log diagram of F(lambda) vs lambda are given. Flux-ratio analysis of the IR data indicates a disk with very little optically thin material anad an outer-edge temperature of about 7920 K. The calculated period (3.37 h) and mass-accretion rate (1 x 10 to the -8th solar mass/yr) are compared to those of similar objects, and V442 Oph is found to be similar in this respect to systems like H2252-035. Its lack of a rotational period and the weakness of the optical and UV line emissions, however, are more like the old nova V603 Aql.

Shafter, A. W.↗
NASA NTRS1988

Astronomy and astrophysics with the Advanced X-ray Astrophysics Facility

The optics and instruments of the Advanced X-ray Astrophysics Facility (AXAF) are described. The instrument capabilities are reviewed so that potential users of AXAF may plan supporting research in the years prior to launch. The AXAF is to be built around a large-area high-resolution grazing-incidence X-ray telescope, with a complement of imaging and spectroscopic instruments which can be maintained and/or replaced in orbit. An important feature of the AXAF is the aspect system. It utilizes solid state star cameras and fiducial lights to permit both image reconstruction (on the ground) with minimal blurring due to spacecraft and internal motions, and placement of the X-ray image on the sky to an accuracy of 1 arcsec.

Weisskopf, Martin C.↗
NASA NTRS2014

A Spitzer Space Telescope Survey of Extreme Asymptotic Giant Branch Stars in M32

We investigate the population of cool, evolved stars in the Local Group dwarf elliptical galaxy M32, using Infrared Array Camera observations from the Spitzer Space Telescope. We construct deep mid-infrared colour-magnitude diagrams for the resolved stellar populations within 3.5 arcminutes of M32's centre, and identify those stars that exhibit infrared excess. Our data is dominated by a population of luminous, dustproducing stars on the asymptotic giant branch (AGB) and extend to approximately 3 magnitudes below the AGB tip. We detect for the first time a sizeable population of 'extreme' AGB stars, highly enshrouded by circumstellar dust and likely completely obscured at optical wavelengths. The total dust-injection rate from the extreme AGB candidates is measured to be 7.5 x 10 (sup −7) solar masses per year, corresponding to a gas mass-loss rate of 1.5 x 10 (sup −4) solar masses per year. These extreme stars may be indicative of an extended star-formation epoch between 0.2 and 5 billion years ago.

Space↗
NASA NTRS1981

The Space Telescope

The Space Telescope, still under construction, is discussed in light of the constraints imposed on ground-based telescopes. The history of the Space Telescope is traced from its conceptual origin to its actual construction, and design considerations used to determine the Space Telescope construction are described. The optical system of the telescope will have an aperture of 2.4 m, a focal ratio of 24, and a front of primary to focus of 1.5 m. The fine guidance system will use astigmatic images at the edge of the field of view to provide the guidance signal for maintaining stability to 0.007 arcseconds. The guidestars are required for 85% of random fields located at the galactic poles, and the system sensitivity must meet performance specifications for stars brighter than 13.5 magnitude. The scientific instruments - the wide field camera, the faint object camera, the faint object spectrograph, the high resolution spectrograph, the high speed photometer, and the fine guidance sensors - are discussed in detail. Finally, the operations system, including schedule contraints and the Science Institute, is presented.

Odell, C. R.↗
NASA NTRS1994

GHRS Spectroscopy of individual stars in R136a

The installation of the Corrective Optics Space Telescope Axial Replacement (COSTAR) Instrument on the Hubble Space Telescope (HST) makes it possible to observe stars in very crowded regions with high spatial and spectral purity. To demonstrate this capability, we have used the Goddard High Resolution Spectrograph (GHRS) to obtain spectra of two stars in the dense center of the 30 Doradus ionizing cluster: R136a5, and its nearest neighbor, R136a2, only 0.17 sec away. R136a5 is shown to ben an O3f/WN star, while R136a2 is a WN4-w star. From both Wide Field/Planetary Camera (WFPC) photometry and GHRS, spectroscopy we estimate the following properties of R136a5: T(sub eff) = 42,500 K, R = 16.4 solar radius, L(sub bol) = 8 x 10(exp 5) solar luminosity, and M approx. equals 50 solar mass -- all indicating that, despite its spectral type, R136a5, as indicated by the strength of He II lambda 1640 emission. The observed mass-loss rate, dot-M = 1.8 x 10(exp -5) solar mass/yr, is an order of magnitude higher than is assumed by current stellar evolutionary models. We argue that this high rate of mass loss will alter drastically the evolutionary path of R136a5. If so, evolutionary models for massive stars require substantial revision.

Heap, Sara R.↗
NASA NTRS2004

Coastal Research Imaging Spectrometer

The Coastal Research Imaging Spectrometer (CRIS) is an airborne remote sensing system designed specifically for research on the physical, chemical, and biological characteristics of coastal waters. The CRIS includes a visible-light hyperspectral imaging subsystem for measuring the color of water, which contains information on the biota, sediment, and nutrient contents of the water. The CRIS also includes an infrared imaging subsystem, which provides information on the temperature of the water. The combination of measurements enables investigation of biological effects of both natural and artificial flows of water from land into the ocean, including diffuse and point-source flows that may contain biological and/or chemical pollutants. Temperature is an important element of such measurements because temperature contrasts can often be used to distinguish among flows from different sources: for example, a sewage outflow could manifest itself in spectral images as a local high-temperature anomaly. Both the visible and infrared subsystems scan in pushbroom mode: that is, an aircraft carrying the system moves along a ground track, the system is aimed downward, and image data are acquired in across-track linear arrays of pixels. Both subsystems operate at a frame rate of 30 Hz. The infrared and visible-light optics are adjusted so that both subsystems are aimed at the same moving swath, which has across-track angular width of 15 . Data from the infrared and visible imaging subsystems are stored in the same file along with aircraft- position data acquired by a Global Positioning System receiver. The combination of the three sets of data is used to construct infrared and hyperspectral maps of scanned areas (see figure). The visible subsystem is based on a grating spectrograph and a rapid-readout charge-coupled-device camera. Images of the swatch are acquired in 256 spectral bands at wavelengths from 400 to 800 nm. The infrared subsystem, which is sensitive in a single wavelength band of 8 to 10 m, is based on a focal-plane array of HgCdTe photodetectors that are cooled to an operating temperature of 77 K by use of a closed-Stirling-cycle mechanical cooler. The nonuniformities of the HgCdTe photodetector array are small enough that the raw pixel data from the infrared subsystem can be used to recognize temperature differences on the order of 1 C. By use of a built-in blackbody calibration source that can be switched into the field of view, one can obtain bias and gain offset terms for individual pixels, making it possible to offset the effects of nonuniformities sufficiently to enable the measurement of temperature differences as small as 0.1 C.

Lucey, Paul G.↗
NASA NTRSDate not supplied

Invited: uPSP Launch Vehicle Demonstration Test at NASA Ames Research Center

The Unsteady Pressure-Sensitive Paint (uPSP) Development Team outof NASA Ames Research Center (ARC) has spent the past five yearsimproving the systems and processes to advance the uPSP technology for production-level wind tunnel testing. Already considered turnkey for small-scale and research applications, development in acquisition, calibration, data transfer, and data processing were needed to be useful to customers testing at NASA wind tunnels. This development focused at ARC at the Unitary Plan Wind Tunnel (UPWT) 11-by 11-ft Transonic Wind Tunnel due to the large optical access of the test section and the NASA Advanced Supercomputer(NAS), also located at ARC. A Launch Vehicle Demonstration Test (LVDT) at the UPWT represents a milestone of this initial phase of development where several new improvements were demonstrated in a production wind tunnel environment for the first time. LVDT was conducted in April 2024 and used a 4% forebody Space Launch System (SLS) Block 1B model as the test article. Both a crew and cargo configuration were tested, with varying Mach numbers, pressures, model positions, and camera magnifications. This paper summarizes the details of the test and is part of a collection with four additional papers that provide greater detail on: high-speed lifetime methodology, spectral proper orthogonal decomposition analysis, quality of high-resolution data compared to Corcos model, and data quality, calibration, and uncertainty.

SLS↗
NASA NTRS1995

Gamma Ray Burst Optical Counterpart Search Experiment (GROCSE)

GROCSE (Gamma-Ray Optical Counterpart Search Experiments) is a system of automated telescopes that search for simultaneous optical activity associated with gamma ray bursts in response to real-time burst notifications provided by the BATSE/BACODINE network. The first generation system, GROCSE 1, is sensitive down to Mv (approximately) 8.5 and requires an average of 12 seconds to obtain the first images of the gamma ray burst error box defined by the BACODINE trigger. The collaboration is now constructing a second generation system which has a 4 second slewing time and can reach Mv (approximately) 14 with a 5 second exposure. GROCSE 2 consists of 4 cameras on a single mount. Each camera views the night sky through a commercial Canon lens (f/1.8, focal length 200 mm) and utilizes a 2K x 2K Loral CCD. Light weight and low noise custom readout electronics were designed and fabricated for these CCDs. The total field of view of the 4 cameras is 17.6 x 17.6 (degree). GROCSE 2 will be operated by the end of 1995. In this paper, the authors present an overview of the GROCSE system and the results of measurements with a GROCSE 2 prototype unit.

Park, H. S.↗
NASA NTRS2022

The NEID Port Adapter at WIYN: On-Sky Fast Guiding Performance

NEID (NN-explore Exoplanet Investigations with Doppler spectroscopy) is an optical, fiber-fed spectrometer installed on the WIYN 3.5m Telescope. The radial velocity precision that NEID is expected to reach requires the stellar jitter (i.e., the slight irregular movement of the stellar image induced by atmospheric turbulence, wind-shake, etc.) to be controlled within 0.05 arc-seconds 90% of the time in nominal observing conditions (i.e., 0.8-arcsecond seeing and mild winds). To achieve that, the NEID Port Adapter incorporates a fast, first-order wavefront correction system, which implements an Electron-Multiplying CCD camera and a tip/tilt piezo stage to capture and stabilize the stellar image. Here, we use on-sky data to demonstrate the performance of this system under various observing conditions.

Dan Li↗
NASA NTRS1994

Hubble Space Telescope faint object camera instrument handbook (Post-COSTAR), version 5.0

The faint object camera (FOC) is a long-focal-ratio, photon-counting device capable of taking high-resolution two-dimensional images of the sky up to 14 by 14 arc seconds squared in size with pixel dimensions as small as 0.014 by 0.014 arc seconds squared in the 1150 to 6500 A wavelength range. Its performance approaches that of an ideal imaging system at low light levels. The FOC is the only instrument on board the Hubble Space Telescope (HST) to fully use the spatial resolution capabilities of the optical telescope assembly (OTA) and is one of the European Space Agency's contributions to the HST program.

Nota, A.↗
NASA NTRS2000

Recent Enhancements of the Phased Array Mirror Extendible Large Aperture (PAMELA) Telescope Testbed at MSFC

Recent incremental upgrades to the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed have enabled the demonstration of phasing (with a monochromatic source) of clusters of primary mirror segments down to the diffraction limit. PAMELA upgrades include an improved Shack-Hartmann wavefront sensor, passive viscoelastic damping treatments for the voice-coil actuators, mechanical improvement of mirror surface figures, and optical bench baffling. This report summarizes the recent PAMELA upgrades, discusses the lessons learned, and presents a status of this unique testbed for wavefront sensing and control. The Marshall Space Flight Center acquired the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope in 1993 after Kaman Aerospace was unable to complete integration and testing under the limited SDIO and DARPA funding. The PAMELA is a 36-segment, half-meter aperture, adaptive telescope which utilizes a Shack-Hartmann wavefront sensor, inductive coil edge sensors, voice coil actuators, imaging CCD cameras and interferometry for figure alignment, wavefront sensing and control. MSFC originally obtained the PAMELA to supplement its research in the interactions of control systems with flexible structures. In August 1994, complete tip, tilt and piston control was successfully demonstrated using the Shack-Hartmann wavefront sensor and the inductive edge sensors.

Rakoczy, John↗
NASA NTRS2001

Recent Enhancements of the Phased Array Mirror Extendible Large Aperture (PAMELA) Telescope Testbed at MSFC

Recent incremental upgrades to the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed have enabled the demonstration of phasing (with a monochromatic source) of clusters of primary mirror segments down to the diffraction limit. PAMELA upgrades include in improved Shack-Hartmann wavefront sensor, passive viscoelastic damping treatments for the voice-coil actuators, mechanical improvement of mirror surface figures, and optical bench baffling. This report summarizes the recent PAMELA upgrades, discusses the lessons learned, and presents a status of this unique testbed for wavefront sensing and control. The Marshall Space Flight Center acquired the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope in 1993 after Kaman Aerospace was unable to complete integration and testing under the limited SDIO and DARPA funding. The PAMELA is a 36-segment, half-meter aperture, adaptive telescope which utilizes a Shack-Hartmann wavefront sensor, inductive coil edge sensors, voice coil actuators, imaging CCD cameras and interferometry for figure alignment, wavefront sensing and control. MSFC originally obtained the PAMELA to supplement its research in the interactions of control systems with flexible structures. In August 1994, complete tip, tilt and piston control was successfully demonstrated using the Shack-Hartmann wavefront sensor and the inductive edge sensors.

Rakoczy, John↗