The coronagraph instrument on the Wide-Field Infrared Survey Telescope-Astrophysics-Focused Telescope Asset (WFIRST-AFTA) mission study has two coronagraphic architectures, shaped pupil and hybrid Lyot, which may be interchanged for use in different observing scenarios. Each architecture relies on newly developed mask components to function in the presence of the AFTA aperture, and so both must be matured to a high technology readiness level in advance of the mission. A series of milestones were set to track the development of the technologies required for the instrument; we report on completion of WFIRST-AFTA coronagraph milestone 2—a narrowband 10−8 contrast test with static aberrations for the shaped pupil—and the plans for the upcoming broadband coronagraph milestone 5.
One of the two primary architectures being tested for the WFIRST-AFTA coronagraph instrument is the shaped pupil coronagraph, which uses a binary aperture in a pupil plane to create localized regions of high contrast in a subsequent focal plane. The aperture shapes are determined by optimization, and can be designed to work in the presence of secondary obscurations and spiders - an important consideration for coronagraphy with WFIRST-AFTA. We present the current performance of the shaped pupil testbed, including the results of AFTA Milestone 2, in which ≈ 6 × 10-9 contrast was achieved in three independent runs starting from a neutral setting.
NASA’s WFIRST-AFTA mission concept includes the first high-contrast stellar coronagraph in space. This coronagraph will be capable of directly imaging and spectrally characterizing giant exoplanets similar to Neptune and Jupiter, and possibly even super-Earths, around nearby stars. In this paper we present the plan for maturing coronagraph technology to TRL5 in 2014-2016, and the results achieved in the first 6 months of the technology development work. The specific areas that are discussed include coronagraph testbed demonstrations in static and simulated dynamic environment, design and fabrication of occulting masks and apodizers used for starlight suppression, low-order wavefront sensing and control subsystem, deformable mirrors, ultra-low-noise spectrograph detector, and data post-processing.
The Advanced Wavefront Sensing and Control Testbed (AWCT) is built as a versatile facility for developing and
demonstrating, in hardware, the future technologies of wavefront sensing and control algorithms for active optical
systems. The testbed includes a source projector for a broadband point-source and a suite of extended scene targets, a
dispersed fringe sensor, a Shack-Hartmann camera, and an imaging camera capable of phase retrieval wavefront
sensing. The testbed also provides two easily accessible conjugated pupil planes which can accommodate active optical
devices such as fast steering mirror, deformable mirror, and segmented mirrors. In this paper, we describe the testbed
optical design, testbed configurations and capabilities, as well as the initial results from the testbed hardware
integrations and tests.
Infrared interferometric nulling is a promising technology for exoplanet detection. Nulling
research for the Terrestrial Planet Finder Interferometer has explored several interferometer architectures at
the Jet Propulsion Laboratory (JPL). The most recent efforts have focused on an architecture which
employs a geometric field flip to achieve the necessary π phase delay in the interferometer. The periscope
design currently in use allows for a completely achromatic phase flip. Deep interferometric nulling
requires optical path stability, precision optical alignment, intensity balancing, and dispersion correction.
This paper will discuss recent efforts to implement a precision optical alignment, stabilize the
interferometer environment, implement optical path metrology, control intensity balance, and compensate
for dispersion introduced by beamsplitter mismatch.
The design and performance of a multifunction continuous wave dual-frequency lidar system is presented. The system
is based on the use of the nonlinear dynamics of an optically injected semiconductor laser. Under proper operating
conditions, the laser emits a dual-frequency beam with a broadly tunable microwave separation. The two optical lines
are coherently locked to each other using an external microwave synthesizer, resulting in a stable microwave beat
frequency. The lidar system is capable of simultaneous velocity and range measurement of remote targets. The velocity
is measured from the Doppler shift of the microwave beat frequency. The stability of the microwave beat frequency
enables accurate measurement of low velocities. In addition, the stable locking enables long-range measurements
because of the long microwave coherence length. Ranging is accomplished by extracting the time-of-flight information
carried on the residual microwave phase noise. We demonstrate preliminary measurements of velocities as low as 26
&mgr;m/s and range measurements of 7.95 km with 2 % accuracy.
To accomplish micro-arcsecond astrometric measurement, stellar interferometers such as SIM require the measurement of internal optical path length delay with an accuracy of ~10 picometers level. A novel common-path laser heterodyne interferometer suitable for this application was proposed and demonstrated at JPL. In this paper, we present some of the experimental results from a laboratory demonstration unit and design considerations for SIM's internal metrology beam launcher.