In order to validate required operation of the proposed Wide-Field InfraRed Survey Telescope (WFIRST) coronagraph instrument, we have built a testbed in Jet Propulsion Laboratory (JPL), which is analogous to the baseline WFIRST coronagraph instrument architecture. Since its birth in 2016, this testbed, named as Occulting Mask Coronagraph (OMC) testbed, has demonstrated several crucial technological milestones: Broadband high contrast demonstration in both Hybrid Lyot Coronagraph (HLC) and Shape Pupil Coronagraph (SPC) modes while the Low Order Wavefront Sensing and Control (LOWFS/C) subsystem senses and corrects the dynamic flight-like wavefront disturbances. In this paper, we present up-to-date progress of HLC mode demonstration in the OMC testbed. While injecting the flight-like low photon flux starlight with expected Line of Sight (LoS) and Wavefront Error (WFE) perturbation to the OMC testbed, we demonstrate generating high contrast dark hole images. We first study the expected photon flux in actual flight environment, and estimate detection noise and estimation accuracy of the complex electric field if the wavefront sensing algorithm is used based on the pair-wise difference imaging. Then, we introduce our improved scheme to mitigate this photon-starved flight-like low flux environment. As a result, we generate a dark hole that meets the WFIRST raw contrast requirements using the 2nd magnitude star light. We establish the key ideas, describe test setups, and demonstrate test results with data analysis.

To maintain the required performance for the WFIRST Coronagraph Instrument (CGI) in a realistic space environment, a Low Order Wavefront Sensing and Control (LOWFS/C) subsystem is necessary. The WFIRST CGI LOWFS/C subsystem will use the Zernike wavefront sensor, which has a phase-shifting disk combined with the coronagraph's focal plane mask, to sense the low-order wavefront drift and line-of-sight (LoS) error using the rejected starlight. The dynamic tests on JPL's Occulting Mask Coronagraph (OMC) Testbed have demonstrated that LOWFS/C can maintain coronagraph contrast to better than 10(-8) in presence of WFIRST-like line of sight and low order wavefront disturbances in both Shaped Pupil Coronagraph (SPC) and Hybrid Lyot Coronagraph (HLC) modes. However, the previous dynamic tests have been done using a bright source with photon flux equivalent to stellar magnitude of M-V = -3.5. The LOWFS/C technology development on the OMC testbed has since then concentrated in evaluating and improving the LOWFS/C performance under the realistic photon flux that is equivalent to WFIRST Coronagraph target stars. Our recent testbed tests have demonstrated that the LOWFS/C can work cohesively with the stellar light suppression wavefront control, which brings broad band coronagraph contrast from similar to 1x10(-6) to 6x10(-9), while LOWF/C is simultaneously suppressing the WFIRST like LoS and low order wavefront drift disturbances on a source that photon flux is equivalent to a M-V = 2 star. This lab demonstration mimics the CGI initial dark hole establish process on a bright reference star. We have also demonstrated on the testbed that LOWFS/C can maintain the coronagraph contrast by suppressing the WFIRST like line-of-sight disturbances on a fainter M-V = 5 star. This mimics scenario of CGI science target observations. In this paper we will present the recent dynamic testbed performance results of LOWFS/C LoS loops and low order wavefront error correction loop on the flight like photon flux.

Hybrid Lyot Coronagraph (HLC) is one of the two operating modes of the Wide-Field InfraRed Survey Telescope (WFIRST) coronagraph instrument. Since being selected by National Aeronautics and Space Administration (NASA) in December 2013, the coronagraph technology is being matured to Technology Readiness Level (TRL) 6 by 2018. To demonstrate starlight suppression in presence of expecting on-orbit input wavefront disturbances, we have built a dynamic testbed in Jet Propulsion Laboratory (JPL) in 2016. This testbed, named as Occulting Mask Coronagraph (OMC) testbed, is designed analogous to the WFIRST flight instrument architecture: It has both HLC and Shape Pupil Coronagraph (SPC) architectures, and also has the Low Order Wavefront Sensing and Control (LOWFS/C) subsystem to sense and correct the dynamic wavefront disturbances. We present upto-date progress of HLC mode demonstration in the OMC testbed. SPC results will be reported separately. We inject the flight-like Line of Sight (LoS) and Wavefront Error (WFE) perturbation to the OMC testbed and demonstrate wavefront control using two deformable mirrors while the LOWFS/C is correcting those perturbation in our vacuum testbed. As a result, we obtain repeatable convergence below 5 x 10(-9) mean contrast with 10% broadband light centered at 550 nm in the 360 degrees dark hole with working angle between 3 lambda/D and 9 lambda/D. We present the key hardware and software used in the testbed, the performance results and their comparison to model expectations.

To maintain the required performance of WFIRST Coronagraph in a realistic space environment, a Low Order Wavefront Sensing and Control (LOWFS/C) subsystem is necessary. The LOWFS/C uses a Zernike wavefront sensor (ZWFS) with the phase shifting disk combined with the starlight rejecting occulting mask. For wavefront error corrections, WFIRST LOWFS/C uses a fast steering mirror (FSM) for line-of-sight (LoS) correction, a focusing mirror for focus drift correction, and one of the two deformable mirrors (DM) for other low order wavefront error (WFE) correction. As a part of technology development and demonstration for WFIRST Coronagraph, a dedicated Occulting Mask Coronagraph (OMC) testbed has been built and commissioned. With its configuration similar to the WFIRST flight coronagraph instrument the OMC testbed consists of two coronagraph modes, Shaped Pupil Coronagraph (SPC) and Hybrid Lyot Coronagraph (HLC), a low order wavefront sensor (LOWFS), and an optical telescope assembly (OTA) simulator which can generate realistic LoS drift and jitter as well as low order wavefront error that would be induced by the WFIRST telescope’s vibration and thermal changes. In this paper, we will introduce the concept of WFIRST LOWFS/C, describe the OMC testbed, and present the testbed results of LOWFS sensor performance. We will also present our recent results from the dynamic coronagraph tests in which we have demonstrated of using LOWFS/C to maintain the coronagraph contrast with the presence of WFIRST-like line-of-sight and low order wavefront disturbances.

The Shaped Pupil Coronagraph (SPC) is one of the two operating modes of the WFIRST coronagraph instrument. The SPC provides starlight suppression in a pair of wedge-shaped regions over an 18% bandpass, and is well suited for spectroscopy of known exoplanets. To demonstrate this starlight suppression in the presence of expected on orbit input wavefront disturbances, we have recently built a dynamic testbed at JPL analogous to the WFIRST flight instrument architecture, with both Hybrid Lyot Coronagraph (HLC) and SPC architectures and a Low Order Wavefront Sensing and Control (LOWFS/C) subsystem to apply, sense, and correct dynamic wavefront disturbances. We present our best up-to-date results of the SPC mode demonstration from the testbed, in both static and dynamic conditions, along with model comparisons. HLC results will be reported separately.

In February 2014, the WFIRST-AFTA mission study, Na tional Aeronautics and Space Administration (NASA) Headquarters, and the coronagraph Technical Analysi s Committee (TAC) agreed on 9 coronagraph technolog y development milestones to track the maturation WFIR ST coronagraph technology to Technology Readiness L vel (TRL) 5. Coronagraph milestone #6 was defined as: Low Order Wavefront Sensing and Control (LOWFS/C) subsystem provides pointing jitter sensing better than 0.4 mas rms per axis and meets pointing and low order wavefront drift control requirements. In this report, we describe the WFIRST Coronagraph LOWFS function, its design, modeled performance, an d experimental results that show that the LOWFS/C sub system not only can sense pointing errors better th an 0.2 mas but has also experimentally demonstrated closed loo p pointing error suppression with residuals better than 0.4 mas rms per axis for the vast majority of observatory r eaction wheel speeds. These results were originally presented to the TAC on September 29th, 2015, concurrently with the resu lts of WFIRST-AFTA CGI Milestone 5. The report is structur ed as follows. The expected WFIRST on-orbit environ me t and LOWFS/C performance objectives are described in Section 2. LOWFS/C design and performance modeling are presented in Section 3. LOWFS/C testbed hardware an d the results of testing performed to characterize LOWFS/C performance, with emphasis on pointing error sensin g and correction, are reviewed in Section 4. Sectio n 5 summarizes the coronagraph LOWFS/C status and future work.

To maintain the required WFIRST Coronagraph starlight suppression performance in a realistic space environment, a low order wavefront sensing and control (LOWFS/C) subsystem is necessary. The LOWFS/C uses the rejected stellar light from coronagraph to sense and suppress the telescope pointing drift and jitter as well as the low order wavefront errors due to changes in thermal loading on the telescope and the rest of the observatory. In this paper we will present an overview of the low order wavefront sensing and control subsystem for the WFIRST Coronagraph. We will describe LOWFS/C's Zernike wavefront sensor concept and control design, and present an overview of sensing performance analysis and modeling, predicted line-of-sight jitter suppression loop performance, as well as the low order wavefront error correction with the coronagraph's deformable mirror. We will also report the LOWFS/C testbed design and the preliminary in-air test results, which show promising performance of the Zernike wavefront sensor and FSM feedback loop.