Bert A. Pasquale

Design for an 8-meter monolithic UV/OIR space telescope

ATLAST-8 is an 8-meter monolithic UV/optical/NIR space observatory to be placed in orbit at Sun-Earth L2 by NASAs planned Ares V cargo launch vehicle. ATLAST-8 will yield fundamental astronomical breakthroughs. A one year mission concept study has developed a detailed point design for the optical telescope assembly and spacecraft. The mission concept assumes two enabling technologies: NASAs planned Ares-V launch vehicle (scheduled for 2019) and autonomous rendezvous and docking (AR&D). The unprecedented Ares-V payload and mass capacity enables the use of a massive, monolithic, thin-meniscus primary mirror - similar to a VLT or Subaru. Furthermore, it enables simple robust design rules to mitigate cost, schedule and performance risk. AR&D enables on-orbit servicing, extending mission life and enhancing science return.

ATLAST-9.2m: a large-aperture deployable space telescope

We present results of a study of a deployable version of the Advanced Technology Large-Aperture Space Telescope (ATLAST), designed to operate in a Sun-Earth L2 orbit. The primary mirror of the segmented 9.2-meter aperture has 36 hexagonal 1.315 m (flat-to-flat) glass mirrors. The architecture and folding of the telescope is similar to JWST, allowing it to fit into the 6.5 m fairing of a modest upgrade to the Delta-IV Heavy version of the Evolved Expendable Launch Vehicle (EELV). We discuss the overall observatory design, optical design, instruments, stray light, wavefront sensing and control, pointing and thermal control, and in-space servicing options.

ATLAST-8 Mission Concept Study for 8-Meter Monolithic UV/Optical Space Telescope

ATLAST-8m is an 8-meter monolithic UV/optical/NIR space observatory which could be placed in orbit at Sun-Earth L2 by a heavily lift launch vehicle. Two development study cycles have resulted in a detailed concept including a dual foci optical design; several primary mirror launch support and secondary mirror support structural designs; spacecraft propulsion, power and pointing control design; and thermal design. ATLAST-8m is designed to yield never before achieved performance to obtain fundamental astronomical breakthroughs.

Optical design of the composite infrared spectrometer (CIRS) for the Cassini mission

The Composite Infrared Spectrometer (CIRS) is an instrument currently under development at NASA Goddard Space Flight Center for the Cassini mission to Saturn. The CIRS optical design heritage extends back to the Infrared Interferometer Spectrometer (IRIS) which flew on Voyager. CIRS is the next logical step in the exploration of the atmosphere of Saturn and Titan. It will obtain more complete sets of data with broader spectral coverage, higher spectral and spatial resolution, and greater sensitivity. The CIRS optical design consists of four subassemblies: (1) a 50.8 cm diameter Cassegrain telescope, (2) a Mid-Infrared (MIR) Michelson interferometer, (3) a Far-Infrared (FIR) polarizing interferometer, and (4) a Reference interferometer (RI).

Evaluation of Hyperspectral Snapshot Imagers onboard Nanosatellite Clusters for Multi-Angular Remote Sensing

Hyperspectral snapshot imagers are capable of producing 2D spatial images with a single exposure at selected and numerous wavelength bands instead of 1D spatial at all spectral band images like in push-broom instruments. Snapshot imagers are critical technologies for multi-angle remote sensing using distributed space missions. They help to relax the attitude control requirements of clusters of small satellites whose narrow field-of-view payloads point at the same ground spot or to increase the footprint area of small satellite constellations with wide field-of-view payloads. This paper reviews the existing spectral imagers for multi-angle remote sensing, performs a feasibility study to incorporate existing state-of-the-art snapshot imagers and proposes baseline imagers to serve as payload for the distributed nanosatellites. The overall approach includes an extensive trade study to identify the optics, spectral elements, their parameters and compare the identified choices both qualitatively and quantitatively. The proposed baseline design has an telescope aperture diameter of 7 cm, focal plane pixel size of 20 μm, 1000 pixels per side of the focal plane array sampling the scene and acousto-optic tunable filters or waveguide spatial heterodyne imagers that simulate a swath up to 90 km, image up to 86 wavebands with an SNR above 100. The tradeoff between spectral and spatial ranges sampled by the two baseline imager options has been highlighted.

Optical Design of WFIRST-AFTA Wide-Field Instrument

The WFIRST-AFTA Wide-Field Infrared Survey Telescope TMA optical design provides 0.28-sq°FOV Wide Field Channel at 0.11” pixel scale, operating at wavelengths between 0.76-2.0μm, including a spectrograph mode (1.35-1.95μm.) An Integral Field Channel provides a discrete 3”x3.15” field at 0.15” sampling.

Wide field instrument preliminary design for the Wide Field InfraRed Survey Telescope

We present the Wide Field Infra-Red Survey Telescope (WFIRST) wide field instrument concept based on the reuse of a 2.4m telescope recently made available to NASA. Two instrument channels are described, a wide field channel (~0.8x0.4degrees, 300Mpix, imaging and spectroscopy over 0.76-2.0um), and an integral field unit (3x3 arcsec, 1Mpix, R{2pixel} ~100 over 0.6-2.0um). For this mission concept, the telescope, instruments, and spacecraft are in a geosynchronous orbit and are designed for serviceability. This instrument can accomplish not only the baseline exoplanet microlensing, dark energy, and infrared surveys for WFIRST, but can perform at higher angular resolution and with deeper observations. This enables significant opportunities for more capable general observer programs. The emphasis on achieving very good imaging stability is maintained from the previous work.

Comparative Concepts for ATLAST Optical Designs

The ATALST (Advanced Technology for Large Aperture Space Telescopes) effort has presented several design incarnations. Here we will compare the design and performance of the 9.2m segmented, the 8m monolithic on-axis and 8m x 6m off-axis concepts.

Optical Alignment and Test of the James Webb Space Telescope Integrated Science Instrument Module

The James Webb Space Telescope (JWST) is a 6.6 m diameter, segmented, deployable telescope for cryogenic IR space astronomy (~40 K). The JWST observatory architecture includes the optical telescope element (OTE) and the integrated science instrument module (ISIM) element that contains four science instruments (SI) including a guider. The SIs and Guider are mounted to a composite metering structure with outer dimensions of 2.1 times 2.2 times 1.9 m. The SI and guider units are integrated to the ISIM structure and optically tested at NASA/Goddard Space Flight Center as an instrument suite using an OTE SIMulator (OSIM). OSIM is a high-fidelity, cryogenic JWST telescope simulator that features a 1.5 m diameter powered mirror. The SIs are aligned to the structures coordinate system under ambient, clean room conditions using laser tracker and theodolite metrology. Temperature-induced mechanical SI alignment and structural changes are measured using a photogrammetric measurement system at ambient and cryogenic temperatures. OSIM is aligned to the ISIM mechanical coordinate system at the cryogenic operating temperature via internal mechanisms and feedback from alignment sensors in six degrees of freedom. SI performance, including focus, pupil shear and wavefront error, is evaluated at the operating temperature using OSIM. We describe the ambient and cryogenic optical alignment, test and verification plan for the ISIM element.

DESTINY : The Dark Energy Space Telescope

We have proposed the development of a low-cost space telescope, Destiny, as a concept for the NASA/DOE Joint Dark Energy Mission. Destiny is a 1.65m space telescope, featuring a near-infrared (0.85-1.7m) survey camera/spectrometer with a large flat-field Field Of View (FOV). Destiny will probe the properties of dark energy by obtaining a Hubble diagram based on Type Ia supernovae (SN) and a large-scale mass power spectrum derived from weak lensing distortions of field galaxies as a function of redshift.