The Probe of Inflation and Cosmic Origins (PICO) is a probe-class mission concept currently under study by NASA. PICO will probe the physics of the Big Bang and the energy scale of inflation, constrain the sum of neutrino masses, measure the growth of structures in the universe, and constrain its reionization history by making full sky maps of the cosmic microwave background with sensitivity 80 times higher than the Planck space mission. With bands at 21-799 GHz and arcmin resolution at the highest frequencies, PICO will make polarization maps of Galactic synchrotron and dust emission to observe the role of magnetic fields in Milky Way's evolution and star formation. We discuss PICO's optical system, focal plane, and give current best case noise estimates. The optical design is a two-reflector optimized open-Dragone design with a cold aperture stop. It gives a diffraction limited field of view (DLFOV) with throughput of 910 cm2sr at 21 GHz. The large 82 square degree DLFOV hosts 12,996 transition edge sensor bolometers distributed in 21 frequency bands and maintained at 0.1 K. We use focal plane technologies that are currently implemented on operating CMB instruments including three-color multi-chroic pixels and multiplexed readouts. To our knowledge, this is the first use of an open-Dragone design for mm-wave astrophysical observations, and the only monolithic CMB instrument to have such a broad frequency coverage. With current best case estimate polarization depth of 0.65 µKCMB-arcmin over the entire sky, PICO is the most sensitive CMB instrument designed to date.
As it has for the past few years, numerical modeling is being used to predict the on-orbit, high-contrast imaging performance of the WFIRST coronagraph, which was recently defined to be a technology demonstrator with science capabilities. A consequence has been a realignment of modeling priorities and revised applications of modeling uncertainty factors and margins, which apply to multiple factors such as pointing and wavefront jitter, thermally-induced deformations, polarization, and aberration sensitivities. At the same time, the models have increased in fidelity as additional parameters have been added, such as time-dependent pupil shear and mid-spatial-frequency deformations of the primary and secondary mirrors, detector effects, and reaction-wheel-speed-dependent pointing and wavefront jitter.
SPHEREx, a mission in NASA’s Medium Explorer (MIDEX) program recently selected for Phase-A implementation, is an all-sky survey satellite that will produce a near-infrared spectrum for every 6 arcsecond pixel on the sky. SPHEREx has a simple, high-heritage design with large optical throughput to maximize spectral mapping speed. While the legacy data products will provide a rich archive of spectra for the entire astronomical community to mine, the instrument is optimized for three specific scientific goals: to probe inflation through the imprint primordial non-Gaussianity left on today’s large-scale cosmological structure; to survey the Galactic plane for water and other biogenic ices through absorption line studies; and to constrain the history of galaxy formation through power spectra of background fluctuations as measured in deep regions near the ecliptic poles. The aluminum telescope consists of a heavily baffled, wide-field off-axis reflective triplet design. The focal plane is imaged simultaneously by two mosaics of H2RG detector arrays separated by a dichroic beamsplitter. SPHEREx assembles spectra through the use of mass and volume efficient linear variable filters (LVFs) included in the focal plane assemblies, eliminating the need for any dispersive or moving elements. Instead, spectra are constructed through a series of small steps in the spacecraft attitude across the sky, modulating the location of an object within the FOV and varying the observation wavelength in each exposure. The spectra will cover the wavelength range between 0.75 and 5.0 µm at spectral resolutions ranging between R=35 and R=130. The entire telescope is cooled passively by a series of three V-groove radiators below 80K. An additional stage of radiative cooling is included to reduce the long wavelength focal plane temperature below 60K, controlling the dark current. As a whole, SPHEREx requires no new technologies and carries large technical and resource margins on every aspect of the design.
The FINESSE spectrometer design (0.45 to 5 μm at a resolution of greater than 80 at f/12) is placed in context by reviewing history of unit magnification relays and spectrometers. Related imaging spectrometers are also described.
End-to-end numerical optical modeling of the WFIRST coronagraph incorporating wavefront sensing and control is used to determine the performance of the coronagraph with realistic errors, including pointing jitter and polarization. We present the performance estimates of the current flight designs as predicted by modeling. We also describe the release of a new version of the PROPER optical propagation library, our primary modeling tool, which is now available for Python and Matlab in addition to IDL.
The WFIRST Coronagraph Instrument will perform direct imaging of exoplanets via coronagraphy of the host star. It uses both the Hybrid Lyot and Shaped Pupil Coronagraphs to meet the mission requirements. The Phase A optical design fits within the allocated instrument enclosure and accommodates both coronagraphic techniques. It also meets the challenging wavefront error requirements. We present the optical performance including throughput of the imaging and IFS channels, as well as the wavefront errors at the first pupil and the imaging channel. We also present polarization effects from optical coatings and analysis of their impacts on the performance of the Hybrid Lyot coronagraph. We report the results of stray light analysis of our Occulting Mask Coronagraph testbed.
We are developing a stable and precise spectrograph for the Large Binocular Telescope (LBT) named “iLocater.” The instrument comprises three principal components: a cross-dispersed echelle spectrograph that operates in the YJ-bands (0.97-1.30 μm), a fiber-injection acquisition camera system, and a wavelength calibration unit. iLocater will deliver high spectral resolution (R~150,000-240,000) measurements that permit novel studies of stellar and substellar objects in the solar neighborhood including extrasolar planets. Unlike previous planet-finding instruments, which are seeing-limited, iLocater operates at the diffraction limit and uses single mode fibers to eliminate the effects of modal noise entirely. By receiving starlight from two 8.4m diameter telescopes that each use “extreme” adaptive optics (AO), iLocater shows promise to overcome the limitations that prevent existing instruments from generating sub-meter-per-second radial velocity (RV) precision. Although optimized for the characterization of low-mass planets using the Doppler technique, iLocater will also advance areas of research that involve crowded fields, line-blanketing, and weak absorption lines.
We describe the optical design of a spaceborne f/1.3 catadioptric telescope with a 9 degree field and 77 cm aperture that is being proposed to study objects in the Kuiper belt, Sedna Region, and Oort cloud.
We describe a method approaching direct optimization of the rms wavefront error of a lens including tolerances. By
including the effect of tolerances in the error function, the designer can choose to improve the as-built performance with
a fixed set of tolerances and/or reduce the cost of production lenses with looser tolerances. The method relies on the
speed of differential tolerance analysis and has recently become practical due to the combination of continuing increases
in computer hardware speed and multiple core processing We illustrate the method’s use on a Cooke triplet, a double
Gauss, and two plastic mobile phone camera lenses.
We provide an overview of the design drivers for mobile camera phone cameras, with particular attention paid to
aspheric order. The designer is often tempted to use high order aspheres (e.g. 18th order). However, better as-built
performance can often be obtained at lower orders.
Head Mounted Displays (HMDs) have been utilized by the military for various applications since the 1980's. In the
1990's, this technology migrated to the consumer market. Most of these early systems suffered the major drawback
that they were "look-at" versus "see through" systems, which prevented the user from seeing their environment.
This reduced the utility of the devices and could potentially lead to safety issues.
This presentation discusses the optical design of a novel see-through High Definition display device with a 40
degree field of view.
Mid-infrared polarimetry remains an underexploited technique; where available it is limited in spectral coverage from
the ground, and conspicuously absent from the Spitzer, JWST and Herschel instrument suites. The unique characteristics
of SOFIA afford unprecedented spectral coverage and sensitivity in the mid-infrared waveband. We discuss the
preliminary optical design for a 5-40μm spectro-polarimeter for use on SOFIA, the SOFIA Mid-InfraRed Polarimeter
(SMIRPh). The design furthers the existing 5-40μm imaging and spectroscopic capabilities of SOFIA, and draws on
experience gained through the University of Florida's mid-IR imagers, spectrometer and polarimeter designs of T-ReCS
and CanariCam. We pay special attention to the challenges of obtaining polarimetric materials suitable at both these
wavelengths and cryogenic temperatures. Finally, we (briefly) present an overview of science highlights that could be
performed from a 5-40μm imaging- and spectro-polarimeter on SOFIA. Combined with the synergy between the
possible future far-IR polarimeter, Hale, this instrument would provide the SOFIA community with unique and exciting
science capabilities, leaving a unique scientific legacy.
Easily manufactured lenses can be designed using global optimization with the results sorted based on their predicted asbuilt
performance. The most easily manufactured lens depends critically on the performance goals.
The Advanced Helmet Mounted Display (AHMD), augmented reality visual system first presented at last year's Cockpit and Future Displays for Defense and Security conference, has now been evaluated in a number of military simulator applications and by L-3 Link Simulation and Training. This paper presents the preliminary results of these evaluations and describes current and future simulator and training applications for HMD technology. The AHMD blends computer-generated data (symbology, synthetic imagery, enhanced imagery) with the actual and simulated visible environment. The AHMD is designed specifically for highly mobile deployable, minimum resource demanding reconfigurable virtual training systems to satisfy the military's in-theater warrior readiness objective. A description of the innovative AHMD system and future enhancements will be discussed.
We recently completed a preliminary design of a novel illumination system. The concept of this design is to integrate the incident irradiance from a small source such that an otherwise non-uniformly iluminated target is uniformly illuminated, while maintaining high radiometric throughput. Our design incorporates a collector to efficiently gather flux from the source, two multi-element faceted arrays, and a flux relay. We explore the concept behind our design and show a preferred embodiment and its predicted peformance.
NASA's Stratospheric Observatory for IR Astronomy (SOFIA) will enable unprecedented IR acuity at wavelengths obscured from the ground. To help open this new chapter in the exploration of the IR universe, we are developing the Airborne IR Echelle Spectrometer (AIRES) as a facility science instrument. Full funding was awarded for a four year development in October, 1997. The instrument is scheduled to come on-line with the observatory in the Fall of 2001. It will be used to investigate a broad range of phenomena that occur in the interstellar medium. AIRES will use a 1200 mm long, 76 degree blaze angle echelle to combine high resolution spectroscopy with diffraction-limited imaging in the cross-dispersion direction. Its three 2D detector arrays will prove good sensitivity over a decade in wavelength. An additional array will be used as a slit viewer for (lambda) <EQ 28 micrometers to image source morphology and to verify telescope pointing. Our scientific motivation, preliminary optical design and packaging, focal plane configuration, echelle prototyping, and cryostat layout are described.
A separated spacecraft optical interferometer mission concept proposed for NASA's New Millennium Program is described. The interferometer instrument is distributed over three small spacecraft: two spacecraft serve as collectors, directing starlight toward a third spacecraft which combines the light and performs the interferometric detection. As the primary objective is technology demonstration, the optics are modest size, with a 12-cm aperture. The interferometer baseline is variable from 100 m to 1 km, providing angular resolutions from 1 to 0.1 milliarcseconds. Laser metrology is used to measure relative motions of the three spacecraft. High-bandwidth corrections for stationkeeping errors are accomplished by feedforward to an optical delay line in the combiner spacecraft; low-bandwidth corrections are accomplished by spacecraft control with an electric propulsion or cold-gas system. Determination of rotation of the constellation as a whole uses a Kilometric Optical Gyro, which employs counter-propagating laser beams among the three spacecraft to measure rotation with high accuracy. The mission is deployed in a low-disturbance solar orbit to minimize the stationkeeping burden. As it is well beyond the coverage of the GPS constellation, deployment and coarse stationkeeping are monitored with a GPS-like system, with each spacecraft providing both transmit and receive ranging and attitude functions.
The second generation Wide-Field/Planetary Camera (WF/PC-II) for the Hubble Space Telescope (HST) was modeled to access the impact of manufacturing, alignment, and environmental tolerances on performance. This analysis showed that the lateral registration of the image of the Optical Telescope Assembly (OTA) pupil to the surface providing the spherical correction must be aligned and maintained through launch to 50 microns; WF/PC-I was an order of magnitude less sensitive. Inherited WF/PC-I hardware was subjected to new WF/PC-II environmental tests. As a result WF/PC-II was reconfigured to ensure on-orbit performance: the focus mechanism was removed to increase stability through launch and on- orbit, and four formerly fixed mirrors were actuated, to provide capability for on-orbit pupil alignment. This paper traces the evolution of the WF/PC-II error budget from its WF/PC-I beginnings to the current configuration.
The second generation Wide-Field/Planetary Camera (WF/PC-II) for the Hubble Space Telescope (HST) was modeled to access the impact of manufacturing, alignment, and environmental tolerances on performance. This analysis showed that the lateral registration of the image of the optical telescope assembly (OTA) pupil to the surface providing the spherical correction must be aligned and maintained through launch to 50 microns; WF/PC-I was an order of magnitude less sensitive. Inherited WF/PC-I hardware was subjected to new WF/PC- II environmental tests. As a result WF/PC-II was reconfigured to ensure on-orbit performance: the focus mechanism was removed to increase stability through launch and on- orbit, and four formerly fixed mirrors were actuated, to provide capability for on-orbit pupil alignment. This paper traces the evolution of the WF/PC-II error budget from its WF/PC-I beginnings to the current configuration. This information should be of general interest to designers of future HST instruments.
An experiment was performed on a front-side illuminated CCD to measure its linear diattenuation at 550 nm and 650 nm as a function of angle of incidence. The linear diattenuation of the CCD varies from 0 to 12 percent for 550 nm light from 0 to 40 deg and is less for the longer wavelength.
The objective of a number of optical instruments is to measure the intensity accurately without bias as to the incident polarization state. One method to overcome polarization bias in optical systems is the insertion of a spatial pseudodepolarizer. Both the degree of depolarization and image degradation (from the polarization aberrations of the pseudodepolarizer)
are analyzed for two depolarizer designs: (1) the Cornu pseudodepolarizer, effective for linearly polarized light, and (2) the dual Babinet compensator pseudodepolarizer, effective for all incident polarization states. The image analysis uses a matrix formalism to describe the polarization dependence of the diffraction patterns and optical transfer function.