Precise and Efficient Formation Keeping at Earth-Sun L2 for Starshade Missions
UNKNOWN
Martin, Stefan R.↗
Engineering topics
Bottom, Michael
Publications and source records attributed to Bottom, Michael.
Precise and efficient formation keeping at Earth-Sun L2 for Starshade missions
This paper reports work aimed at maturing the technology readiness level of starshade formation sensing and control for the starshade science phase.
Martin, Stefan R.↗
Smartphone scene generator for efficient characterization of visible imaging detectors
Full characterization of imaging detectors involves subjecting them to spatially and temporally varying illumination patterns over a large dynamic range. Here we present a scene generator that fulfills many of these functions. Based on a modern smartphone, it has a number of good features, including high spatial resolution (13 um), high dynamic range (∼104), near-Poisson limited illumination stability over time periods from 100 ms to many days, and no background noise. The system does not require any moving parts and may be constructed at modest cost. We present the optical, mechanical, and software design, test data validating the performance, and application examples.
Demers, Richard T.↗
Lessons for WFIRST CGI from Ground-Based High-Contrast Systems
The Coronagraph Instrument (CGI) for NASA’s Wide Field Infrared Survey Telescope (WFIRST) will constitute a dramatic step forward for high-contrast imaging, integral field spectroscopy, and polarimetry of exoplanets and circumstellar disks, aiming to improve upon the sensitivity of current ground-based direct imaging facilities by 2–3 orders of magnitude. Furthermore, CGI will serve as a pathfinder for future exo-Earth imaging and characterization missions by demonstrating wavefront control, coronagraphy, and spectral retrieval in a new contrast regime, and by validating instrument and telescope models at unprecedented levels of precision. To achieve this jump in performance, it is critical to draw on the experience of ground-based high-contrast facilities. We discuss several areas of relevant commonalities, including: wavefront control, post-processing of integral field unit data, and calibration and observing strategies.
Xuan, Wenhao↗
WFIRST Coronagraph Detector Trap Modeling Results and Improvements
The WFIRST coronagraph is being designed to detect and characterize mature exoplanets through the starlight reflected from their surfaces and atmospheres. The light incident on the detector from these distant exoplanets is estimated to be on the order of a few photons per pixel per hour. To measure such small signals, the project has baselined the CCD201 detector made by e2v, a low-noise and high-efficiency electron-multiplying charge-coupled device (EMCCD), and has instituted a rigorous test and modeling program to characterize the device prior to flight. An important consideration is detector performance degradation over the proposed mission lifetime due to radiation exposure in space. To quantify this estimated loss in performance, the project has built a detector trap model that takes into account detailed trap interactions at the sub-pixel level, including stochastic trap capture and release, and the deferment of charge into subsequent pixels during parallel and serial clocking of the pseudo-two-phase CCD201 device. This paper describes recent detector trap model improvements and modeling results.
Holland, Andrew↗
HabEx Space Telescope Guiding Systems
The HabEx (Habitable Exoplanet Imaging Mission) study is developing concepts for a next generation space telescope operating from the ultraviolet to the infrared. HabEx is making exoplanet science the primary mission objective and adding two secondary payload instruments for general astrophysics, including ultraviolet spectroscopy. For exoplanet work, two approaches are being developed. The first is a coronagraph with two separate channels to cover a broad spectral range from 450 nm to 1000 nm in two observations. The second is a starshade to cover the band 300 nm to 1000 nm in a single observation. These instruments are complementary; the coronagraph can make rapid survey observations while the starshade can reach closer in to the star and once on target, enables more efficient spectroscopic observations. This paper describes some of the key design considerations necessary to enable coronagraph and starshade observations.
Shaklan, Stuart↗
Precise starshade stationkeeping and pointing with a Zernike wavefront sensor
Starshades, large occulters positioned tens of thousands of kilometers in front of space telescopes, o er one of the few paths to imaging and characterizing Earth-like extrasolar planets. However, for the starshade to generate a su ciently dark shadow on the telescope, the two must be coaligned to just 1 meter laterally, even at these large separations. The principal challenge to achieving this level of control is in determining the position of the starshade with respect to the space telescope. In this paper, we present numerical simulations and laboratory results demonstrating that a Zernike wavefront sensor coupled to a WFIRST-type telescope is able to deliver the stationkeeping precision required, by measuring light outside of the science wavelengths. The sensor can determine the starshade lateral position to centimeter level in seconds of open shutter time for stars brighter than eighth magnitude, with a capture range of 10 meters. We discuss the potential for fast (ms) tip/tilt pointing control at the milli-arcsecond level by illuminating the sensor with a laser mounted on the starshade. Finally, we present early laboratory results.
Shaklan, Stuart↗