Microelectromechanical Systems (MEMS) Deformable Mirrors (DMs) are a key technology option for adaptive optics instruments for space applications because they provide high-precision wavefront control with small form-factor, low-power devices. The Deformable Mirror Demonstration Mission (DeMi) CubeSat demonstrated a MEMS DM in space for the first time in order to raise the Technology Readiness Level (TRL) of the technology for future space applications such as high-contrast imaging of exoplanets and optical communications. The DeMi payload demonstrated a 140-actuator MEMS DM from Boston Micromachines Corporation. DM performance was measured with a Shack Hartmann wavefront sensor (SHWFS). The DeMi CubeSat began on-orbit operations in July 2020 and has since met the mission goals of measuring individual actuator displacements to a precision of 12 nm and correcting wavefront errors in space to <100 nm RMS error. The DeMi mission has raised the TRL of MEMS DM technology from a 5 to a 9. This paper summarizes the DeMi payload design and the results from over a year of on-orbit operations. Individual actuator measurements from ground and space operations show the MEMS DM actuating in space with similar performance and measurement uncertainty to ground data with no dead or under-actuating actuators detected. Wavefront control experiments show the DeMi payload correcting thermal- and vibration-induced wavefront errors in space.
A key aspect of the search for earth-like exoplanets with direct imaging, is determining if the exoplanet is in the habitable zone. For mission design of potential future direct imaging missions, such as HabEx and LUVOIR, an efficient cadence of observations is needed. Previous work has shown that three epochs, spanning more than half a period, is the minimum to determine orbital parameters to 10%. One aspect that still needs improvement is the ability to fit multiple planets with limited prior information about which planet is which. Since data from direct observations is expected to consist of multiple objects at each epoch, looking at each epoch separately is not sufficient to decide whether 1) a detected object is part of an exosolar system and 2) which planet it corresponds to. Existing multi-planet trajectory matching libraries, such as “Orbits For The Impatient” (OFTI), currently require the user to specify which data points belong to which planet. This assumes that the user has already matched true-positive detections to planets. Additionally, this planet matching between detected objects needs to be taken into account when assessing the impact of observation scheduling on the accuracy of trajectory estimation. To address this need for fitting orbits to multiple objects with limited knowledge, we propose an approach that uses a Monte Carlo study of different observation schedules and planetary systems. For each case we automatically match observations to planets and check the accuracy of the match. By considering a large number of such cases, we provide constraints on the number of observations and their spacing necessary to “deconfuse” the detections. We present preliminary planet matching success rates for several observation schedules based on simulated planetary systems and assess the accuracy of trajectory fitting combined with OFTI.
Microelectromechanical systems (MEMS) deformable mirrors (DMs) can provide high-precision wavefront control with a small form-factor, low power device. This makes them a key technology option for future space telescopes requiring adaptive optics for high-contrast imaging of exoplanets with a coronagraph instrument. The Deformable Mirror Demonstration Mission (DeMi) CubeSat payload is a miniature space telescope designed to demonstrate MEMS DM technology in space for the first time. The DeMi payload contains a 50-mm primary mirror, an internal calibration laser source, a 140-actuator MEMS DM from Boston Micromachines Corporation, an image plane wavefront sensor, and a Shack–Hartmann wavefront sensor (SHWFS). The key DeMi payload requirements are to measure individual actuator wavefront displacement contributions to a precision of 12 nm and correct both static and dynamic wavefront errors in space to less than 100-nm RMS error. The DeMi mission will raise the technology readiness level of MEMS DM technology from a five to at least a seven for future space telescope applications. We summarize the DeMi optical payload design, calibration, optical diffraction model, alignment, integration, environmental testing, and preliminary data from in-space operations. Ground testing data show that the DeMi SHWFS can measure individual actuator deflections on the MEMS DM to within 10 nm of interferometric calibration measurements and can meet the 12-nm precision mission requirement for actuator deflection voltages between 0 and 120 V. Payload data from throughout environmental testing show that the MEMS DM and DeMi payload survived environmental testing and provides a valuable baseline to compare with space data. Initial data from space operations show the MEMS DM actuating in space with a median agreement between individual actuator measurements from space and equivalent ground testing data of 12 nm.
The Deformable Mirror Demonstration Mission (DeMi) is a 6U CubeSat that will characterize the on-orbit performance of a Microelectromechanical Systems (MEMS) deformable mirror (DM) with both an image plane wavefront sensor and a Shack-Hartmann wavefront sensor (SHWFS). Coronagraphs on future space telescopes will require precise wavefront control to detect and characterize Earth-like exoplanets. High-actuator count MEMS deformable mirrors can provide wavefront control with low size, weight, and power. The DeMi payload will characterize the on-orbit performance of a 140 actuator MEMS Deformable Mirror (DM) with 5.5 μm maximum stroke, with a goal of measuring individual actuator wavefront displacement contributions to a precision of 12 nm. The payload will be able to measure low order aberrations to λ/10 accuracy and λ/50 precision, and will correct static and dynamic wavefront phase errors to less than 100 nm RMS. We present an overview of the payload design, the assembly, integration, and test process, and report on the development and validation of an optical diffraction model of the payload. Launch is planned for late 2019.
Coronagraphs on future space telescopes will require precise wavefront correction to detect Earth-like exoplanets near their host stars. High-actuator count microelectromechanical system (MEMS) deformable mirrors provide wavefront control with low size, weight, and power. The Deformable Mirror Demonstration Mission (DeMi) payload will demonstrate a 140 actuator MEMS Deformable Mirror (DM) with 5:5 μm maximum stroke. We present the flight optomechanical design, lab tests of the flight wavefront sensor and wavefront reconstructor, and simulations of closed-loop control of wavefront aberrations. We also present the compact flight DM controller, capable of driving up to 192 actuator channels at 0-250V with 14-bit resolution. Two embedded Raspberry Pi 3 compute modules are used for task management and wavefront reconstruction. The spacecraft is a 6U CubeSat (30 cm x 20 cm x 10 cm) and launch is planned for 2019.
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.
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