The HabEx mission concept is intended to directly image planetary systems around nearby stars, and to perform a wide range of general astrophysics and solar system observations. The baseline HabEx design would use both a coronagraph and a starshade for exoplanet discovery and characterization. We describe a lower-cost alternative HabEx mission design, which would only use a starshade for exoplanet science. The starshade would provide excellent exoplanet science performance, but for a smaller number of detected exoplanets of all types, including exoEarth candidates, and a smaller fraction of exoplanets with measured orbits. The full suite of HabEx general astrophysics and solar-system science would be supported.
The Passive A-Band Wind Sounder (PAWS) was funded through NASA's Instrument
Incubator Program (IIP) to determine the feasibility of measuring tropospheric wind speed profiles
from Doppler shifts in absorption O2 A-band. It is being pursued as a low-cost and low-risk alternative
capable of providing better wind data than is currently available. The instrument concept is adapted
from the Wind Imaging Interferometer (WINDII) sensor on the Upper Atmosphere Research Satellite.
The operational concept for PAWS is to view an atmospheric limb over an altitude range from the
surface to 20 km with a Doppler interferometer in a sun-synchronous low-earth orbit. Two orthogonal
views of the same sampling volume will be used to resolve horizontal winds from measured line-of-sight
A breadboard instrument was developed to demonstrate the measurement approach and to
optimize the design parameters for the subsequent engineering unit and future flight sensor. The
breadboard instrument consists of a telescope, collimator, filter assembly, and Michelson
interferometer. The instrument design is guided by a retrieval model, which helps to optimize key
parameters, spectral filter and optical path difference in particular.
We present a microscope imaging optics system that is suitable for simultaneously detecting two species of electrically trapped atomic ions for quantum information processing. The proposed 10x objective features all-spherical surfaces in a catadioptric modification of the Schwarzschild two-mirror configuration and is achromatic at 313 and 280 nm, the two wavelengths of the laser-induced fluorescence from 9Be+ and 24Mg+. To correct for aberrations from the fused-silica vacuum window, we use a zero-power doublet made of a positive calcium fluoride and a negative fused-silica meniscus to form an air-gapped Steinheil doublet facing the object. As a result, diffraction limited images are obtained for both wavelengths at a numerical aperture (NA) of 0.5 and a field of view (FOV) of 0.1 mm in diameter. The long working distance (> focal length) of this objective allows imaging of the ions through the vacuum window.
We present a method for measuring an optical system’s effective focal length with a single mode fiber array and a wedge prism. Light emitted by the input fiber near the focal plane is collimated, reflected back in two angularly separated beams, and detected by the output fibers in the auto-collimation configuration. Measurement precision of a micron can be achieved due to the precision of fiber spacing and the position sensitivity of single-mode coupling. Absolute accuracy depends on factors such as optical design configuration, metrology, aberrations, and environmental control, and can be better than 10 micron. By varying input wavelength and field angle, this technique can be utilized to precisely characterize chromatic dispersion and distortion of the optics. Furthermore, because the technique only requires compact opto-mechanical accessories and electronic apparatus, it can be readily carried out on large optical systems in the field.
The Reflection Grating Spectrometer of the Constellation-X mission has
two strong candidate configurations. The first configuration, the
in-plane grating (IPG), is a set of reflection gratings similar to
those flown on XMM-Newton and has grooves perpendicular to the
direction of incident light. In the second configuration, the
off-plane grating (OPG), the grooves are closer to being parallel to
the incident light, and diffract along a cone. It has advantages of
higher packing density, and higher reflectivity. Confinement of these
gratings to sub-apertures of the optic allow high spectral
resolution. We have developed a raytrace model and analysis technique
for the off-plane grating configuration. Initial estimates indicate
that first order resolving powers in excess of 1000 (defined with
half-energy width) are achievable for sufficiently long wavelengths
(λ ≥ 12Å), provided separate accommodation is made
for gratings in the subaperture region farther from the zeroth order