https://hdl.handle.net/1721.1/108798 2026-04-05T14:13:43Z https://hdl.handle.net/1721.1/114748 Design of the Deformable Mirror Demonstration CubeSat (DeMi) Douglas, Ewan; Allan, Gregory; Barnes, Derek; Figura, Joseph S.; Haughwout, Christian A.; Gubner, Jennifer N.; Knoedler, Alex A.; LeClair, Sarah; Murphy, Thomas J; Nikolaos, Skouloudis; Merk, John; Opperman, Roedolph A.; Cahoy, Kerri L. The Deformable Mirror Demonstration Mission (DeMi) was recently selected by DARPA to demonstrate in-space operation of a wavefront sensor and Microelectromechanical system (MEMS) deformable mirror (DM) payload on a 6U CubeSat. Space telescopes designed to make high-contrast observations using internal coronagraphs for direct characterization of exoplanets require the use of high-actuator density deformable mirrors. These DMs can correct image plane aberrations and speckles caused by imperfections, thermal distortions, and diffraction in the telescope and optics that would otherwise corrupt the wavefront and allow leaking starlight to contaminate coronagraphic images. DeMi is provide on-orbit demonstration and performance characterization of a MEMS deformable mirror and closed loop wavefront sensing. The DeMi payload has two operational modes, one mode that images an internal light source and another mode which uses an external aperture to images stars. Both the internal and external modes include image plane and pupil plane wavefront sensing. The objectives of the internal measurement of the 140-actuator MEMS DM actuator displacement are characterization of the mirror performance and demonstration of closed-loop correction of aberrations in the optical path. Using the external aperture to observe stars of magnitude 2 or brighter, assuming 3-axis stability with less than 0.1 degree of attitude knowledge and jitter below 10 arcsec RMSE, per observation, DeMi will also demonstrate closed loop wavefront control on an astrophysical target. We present an updated payload design, results from simulations and laboratory optical prototyping, as well as present our design for accommodating high-voltage multichannel drive electronics for the DM on a CubeSat. 2017-09-01T00:00:00Z https://hdl.handle.net/1721.1/114746 Laser Beacon Tracking for High-Accuracy Attitude Determination Nguyen, Tam; Cahoy, Kerri CubeSat pointing capabilities have greatly improved in the past few years, paving the way for more sophisticated science and technology demonstration missions. Advances in attitude determination have led to the development of several CubeSat-sized attitude sensors capable of achieving fine attitude knowledge,most of which utilize natural light sources as references, such as in the case of star trackers and sun sensors. However, inertial-based attitude sensors often limit ground tracking capability of the satellite due to high ephemeris uncertainty of most CubeSats. Laser beacon tracking directly measures of the satellite’s attitude relative to a ground station or target, eliminating attitude errors induced in the coordinate frame conversion process. In addition, the use of a narrow-band artificial light source allows filtering techniques to be implemented, reducing the probability of false positives. In this paper, we present the development of a low-cost CubeSat-sized laser beacon camera along with detailed simulation development and results to demonstrate the attitude sensing performance of the module. The end-to-end simulation includes a laser link radiometry model, hardware model, atmospheric scintillation model, and sky radiance model at the beacon wavelength. Simulation results show that the laser beacon camera is capable of achieving an attitude accuracy of less than 0.1 mrad with a fade probability of less than 1% during daytime under most sky conditions for a satellite above 20-deg elevation in low-Earth orbit. 2015-08-01T00:00:00Z https://hdl.handle.net/1721.1/110952 Atmospheric characterization of cold exoplanets with a 1.5-m space coronagraph Maire, A. -L.; Galicher, R.; Boccaletti, A.; Baudoz, P.; Schneider, J.; Cahoy, K.; Stam, D.; Traub, W. Several small space coronagraphs have been proposed to characterize cold exoplanets in reflected light. Studies have mainly focused on technical feasibility because of the huge star/planet flux ratio to achieve in the close-in stellar environment (108-1010 at 0.2'). However, the main interest of such instruments, the analysis of planet properties, has remained highly unexplored so far. We performed numerical simulations to assess the ability of a small space coronagraph to retrieve spectra of mature Jupiters, Neptunes and super-Earths under realistic assumptions. We describe our assumptions: exoplanetary atmosphere models, instrument numerical simulation and observing conditions. Then, we define a criterion and use it to determine the required exposure times to measure several planet parameters from their spectra (separation, metallicity, cloud and surface coverages) for particular cases. Finally, we attempt to define a parameter space of the potential targets. In the case of a solar-type star, we show that a small coronagraph can characterize the spectral properties of a 2-AU Jupiter up to 10 pc and the cloud and surface coverage of super-Earths in the habitable zone for a few stars within 4-5 pc. Potentially, SPICES could perform analysis of a hypothetical Earth-size planet around α Cen A and B. 2012-01-01T00:00:00Z https://hdl.handle.net/1721.1/110928 Direct imaging of exoEarths embedded in clumpy debris disks Defrere, D.; Stark, C.; Cahoy, K.; Beerer, I. The inner solar system, where the terrestrial planets formed and evolve, is populated by small grains of dust produced by collisions of asteroids and outgassing comets. At visible and infrared wavelengths, this dust cloud is in fact the most luminous component in the solar system after the Sun itself and the Earth may appear similar to a clump of zodiacal dust to an external observer. Hence, the presence of large amounts of dust in the habitable zone around nearby main-sequence stars is considered as a major hurdle toward the direct imaging of exoEarths with future dedicated space-based telescopes. In that context, we address in this paper the detectability of exoEarths embedded in structured debris disks with future space-based visible coronagraphs and mid-infrared interferometers. Using a collisional grooming algorithm, we produce models of dust clouds that simultaneously and self-consistently handle dust grain dynamics, including resonant interactions with planets, and grain-grain collisions. Considering various viewing geometries, we also derive limiting dust densities that can be tolerated around nearby main-sequence stars in order to ensure the characterization of exoEarths with future direct imaging missions. 2012-01-01T00:00:00Z https://hdl.handle.net/1721.1/110927 Combining laser frequency combs and iodine cell calibration techniques for Doppler detection of exoplanets Cahoy, K.; Fischer, D.; Spronck, J.; Demille, D. Exoplanets can be detected from a time series of stellar spectra by looking for small, periodic shifts in the absorption features that are consistent with Doppler shifts caused by the presence of an exoplanet, or multiple exoplanets, in the system. While hundreds of large exoplanets have already been discovered with the Doppler technique (also called radial velocity), our goal is to improve the measurement precision so that many Earth-like planets can be detected. The smaller mass and longer period of true Earth analogues require the ability to detect a reflex velocity of ~10 cm/s over long time periods. Currently, typical astronomical spectrographs calibrate using either Iodine absorptive cells or Thorium Argon lamps and achieve ~10 m/s precision, with the most stable spectrographs pushing down to ~2 m/s. High velocity precision is currently achieved at HARPS by controlling the thermal and pressure environment of the spectrograph. These environmental controls increase the cost of the spectrograph, and it is not feasible to simply retrofit existing spectrometers. We propose a fiber-fed high precision spectrograph design that combines the existing ~5000-6000 A Iodine calibration system with a high-precision Laser Frequency Comb (LFC) system from ~6000-7000 A that just meets the redward side of the Iodine lines. The scientific motivation for such a system includes: a 1000 A span in the red is currently achievable with LFC systems, combining the two calibration methods increases the wavelength range by a factor of two, and moving redward decreases the 'noise' from starspots. The proposed LFC system design employs a fiber laser, tunable serial Fabry-Perot cavity filters to match the resolution of the LFC system to that of standard astronomical spectrographs, and terminal ultrasonic vibration of the multimode fiber for a stable point spread function. 2010-01-01T00:00:00Z https://hdl.handle.net/1721.1/110926 CubeSat deformable mirror demonstration Cahoy, K.; Marinan, A.; Kerr, C.; Cheng, K.; Jamil, S. The goal of the CubeSat Deformable Mirror Demonstration (DeMi) is to characterize the performance of a small deformable mirror over a year in low-Earth orbit. Small form factor deformable mirrors are a key technology needed to correct optical system aberrations in high contrast, high dynamic range space telescope applications such as space-based coronagraphic direct imaging of exoplanets. They can also improve distortions and reduce bit error rates for space-based laser communication systems. While follow-on missions can take advantage of this general 3U CubeSat platform to test the on-orbit performance of several different types of deformable mirrors, this first design accommodates a 32-actuator Boston Micromachines MEMS deformable mirror. 2012-01-01T00:00:00Z https://hdl.handle.net/1721.1/110899 First results on a new PIAA coronagraph testbed at NASA Ames Belikov, R.; Pluzhnik, E.; Connelley, M. S.; Witteborn, F. C.; Lynch, D. H.; Cahoy, K. L.; Guyon, O.; Greene, T. P.; McKelvey, M. E. Direct imaging of extrasolar planets, and Earth-like planets in particular, is an exciting but difficult problem requiring a telescope imaging system with 1010 contrast at separations of 100 mas and less. Furthermore, the current NASA science budget may only allow for a small 1-2 m space telescope for this task, which puts strong demands on the performance of the imaging instrument. Fortunately, an efficient coronagraph called the Phase Induced Amplitude Apodization (PIAA) coronagraph has been maturing and may enable Earth-like planet imaging for such small telescopes. In this paper, we report on the latest results from a new testbed at NASA Ames focused on testing the PIAA coronagraph. This laboratory facility was built in 2008 and is designed to be flexible, operated in a highly stabilized air environment, and to complement existing efforts at NASA JPL. For our wavefront control we are focusing on using small Micro-Electro- Mechanical-System deformable mirrors (MEMS DMs), which promises to reduce the size of the beam and overall instrument, a consideration that becomes very important for small telescopes. At time of this writing, we are operating a refractive PIAA system and have achieved contrasts of about 1.2×10-7 in a dark zone from 2.0 to 4.8 λ/D (with 6.6×10-8 in selected regions). In this paper, we present these results, describe our methods, present an analysis of current limiting factors, and solutions to overcome them. 2009-01-01T00:00:00Z https://hdl.handle.net/1721.1/110730 Nonlinear Optics for Frequency-Doubling in Nanosatellite Laser Communication Clark, James; Cahoy, Kerri Free-space optical communication attracts interest due to its promise of higher data rates for similar size, weight, and power costs compared with radio systems. However, while satellite-to-ground optical communication has been tested from low Earth orbit and the Moon, intersatellite optical links are still an area of active research and development. Second-harmonic generation (SHG, or “frequency doubling”) with nonlinear optics may improve the link margins of laser systems that serve as crosslinks as well as downlinks. For example, the output of a 1550 nm laser could be doubled to 775 nm on command, allowing the satellite to use whichever wavelength is advantageous (e.g. improved detector and propagation properties), without spending the mass budget for an entire second laser system. Link-budget analysis suggests that a nanosatellite crosslink can gain 3-4 dB of link margin with a frequency-doubler. This improvement is largely driven by the reduction in beamwidth that comes with the higher frequency. It is not substantially greater than the improvement that comes with using the same narrower beamwidth at 1550 nm. However, SHG would allow a diffraction-limited system to use different beamwidths for beacon acquisition and communication without any moving parts. 2016-08-10T00:00:00Z https://hdl.handle.net/1721.1/109159 End-to-end simulation of high-contrast imaging systems: methods and results for the PICTURE mission family Douglas, Ewan S.; Hewawasam, Kuravi; Mendillo, Christopher B.; Cahoy, Kerri L; Cook, Timothy A.; Finn, Susanna C. Finn; Howe, Glenn A.; Kuchner, Marc, J.; Lewis, Nikole K.; Marinan, Anne D.; Mawet, Dimitri; Chakrabarti, Supriya We describe a set of numerical approaches to modeling the performance of spaceflight high-contrast imaging payloads. Mission design for high-contrast imaging requires numerical wavefront error propagation to ensure accurate component specifications. For constructed instruments, wavelength and angle-dependent throughput and contrast models allow detailed simulations of science observations, allowing mission planners to select the most productive science targets. The PICTURE family of missions seek to quantify the optical brightness of scattered light from extrasolar debris disks via several high-contrast imaging techniques: sounding rocket (the Planet Imaging Concept Testbed Using a Rocket Experiment) and balloon flights of a visible nulling coronagraph, as well as a balloon flight of a vector vortex coronagraph (the Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph, PICTURE-C). The rocket mission employs an on-axis 0.5m Gregorian telescope, while the balloon flights will share an unobstructed off-axis 0.6m Gregorian. This work details the flexible approach to polychromatic, end-to-end physical optics simulations used for both the balloon vector vortex coronagraph and rocket visible nulling coronagraph missions. We show the preliminary PICTURE-C telescope and vector vortex coronagraph design will achieve 10−8 contrast without post-processing as limited by realistic optics, but not considering polarization or low-order errors. Simulated science observations of the predicted warm ring around Epsilon Eridani illustrate the performance of both missions. 2015-09-01T00:00:00Z