The NCAR Airborne Infrared Lidar System (NAILS)

A planned airborne lidar system is presented which is intended to provide a remote sensing facility for a variety of applications. The eventual goal of the system development is a Doppler wind measurement capability for boundary layer dynamics and cloud physics applications. The first stage of development is focused initially on a direct detection lidar to measure aerosol profiles and depolarization from cloud backscatter. Because of the Doppler goal, interest in larger particles to define the top of the mixed layer, and eye safety, the first stage of the system is based on a pulsed CO2 laser. A compact, relatively simple and inexpensive system that achieves flexibility to meet the data requirements of a variety of investigators by being easily modified rather than having many different capabilities built in is the goal. Although the direct detection sensitivity is less than that for heterodyne detection, the simpler system allows the achievement of useful scientific results and operating experience towards more complex lidars while staying within budget and time constraints

Preparation of polyimides from mixtures of monomeric diamines and esters of polycarboxylic acids

Polyimides having high thermal and oxidative stability are prepared by the reaction of a mixture of monomers comprising (1) a dialkyl or tetraalkyl ester of an aromatic tetracarboxylic acid; (2) an aromatic diamine; and (3) a monoalkyl or dialkyl ester of a dicarboxylic acid where in the ratio of a:b:c is n:(n+1):2, wherein n has a value from 1 to 20. The mixture of monomers is prepared in a 30 to 70 percent by weight solution of an organic solvent, a substrate impregnated with the solution and heated at 50 to 205 C to remove said solvent and form a low molecular weight prepolymer, and thereafter heated at 275 to 350 C to cure to a high molecular weight polyimide

JWST Lessons Learned

While there is a lot of focus on how a few key parameters like aperture size and pixel count drive costs of large space telescopes, the JWST experience suggests that a lot more insight is needed to understand and control costs

Relative Navigation, Microdischarge Plasma Thruster, and Distributed Communications Experiments on the FASTRAC Mission

Enabling technologies for nanosatellite formations will be demonstrated under the Formation Autonomy Spacecraft with Thrust, Relnav, Attitude, and Crosslink (FASTRAC) program. Two °ight-ready nanosatellites will be designed, fabricated, integrated, and tested during the two year design period. Three speci¯c new and innovative technologies which will be demonstrated during the mission are Relative Navigation, Plasma Microthrusters, and Distributed Communications. A sensor set consisting of Global Positioning System (GPS) receiver, magnetometer, and MEMS Inertial Measurement Unit (IMU) will be used to determine position and coarse attitude. Using a radio crosslink, the two satellites will exchange state vector information and perform sub-meter level accuracy relative navigation. Each satellite will also contain a Microdischarge Plasma Thruster (MPT) developed at UT-Austin. This innovative device is capable of generating low-thrust, high-e±ciency propulsion at low power levels using microdischarge plasmas. The ability of the MPT to extend the life of the orbit will be determined by monitoring the orbit decay rates of the two vehicles as well as the MEMS IMU. A distributed tracking network with multiple university partners will be utilized to track the low Earth orbit satellites. Amateur radio experimenters, high schools, universities, and other interested parties will be encouraged to record telemetry from the satellites and report their data to a project web site for processing. Although the main purpose of the mission is technology demonstration, science goals will also be pursued. These include post-processing sensor measurements to determine satellite drag, as well as Earth atmospheric and magnetospheric studies

Origins Space Telescope: Baseline mission concept

The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the Universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid-and far-infrared (IR) wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of the Herschel Space Observatory, the largest telescope flown in space to date. We describe the baseline concept for Origins recommended to the 2020 US Decadal Survey in Astronomy and Astrophysics. The baseline design includes a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (Mid-Infrared Spectrometer and Camera Transit spectrometer) will measure the spectra of transiting exoplanets in the 2.8 to 20 μm wavelength range and offer unprecedented spectrophotometric precision, enabling definitive exoplanet biosignature detections. The far-IR imager polarimeter will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer will cover wavelengths from 25 to 588 μm, making wide-area and deep spectroscopic surveys with spectral resolving power R ∼ 300, and pointed observations at R ∼ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The architecture is similar to that of the Spitzer Space Telescope and requires very few deployments after launch, while the cryothermal system design leverages James Webb Space Telescope technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins\u27 natural background-limited sensitivity

The James Webb Space Telescope Mission: Optical Telescope Element Design, Development, and Performance

The James Webb Space Telescope (JWST) is a large, infrared space telescope that has recently started its science program which will enable breakthroughs in astrophysics and planetary science. Notably, JWST will provide the very first observations of the earliest luminous objects in the Universe and start a new era of exoplanet atmospheric characterization. This transformative science is enabled by a 6.6 m telescope that is passively cooled with a 5-layer sunshield. The primary mirror is comprised of 18 controllable, low areal density hexagonal segments, that were aligned and phased relative to each other in orbit using innovative image-based wavefront sensing and control algorithms. This revolutionary telescope took more than two decades to develop with a widely distributed team across engineering disciplines. We present an overview of the telescope requirements, architecture, development, superb on-orbit performance, and lessons learned. JWST successfully demonstrates a segmented aperture space telescope and establishes a path to building even larger space telescopes.Comment: accepted by PASP for JWST Overview Special Issue; 34 pages, 25 figure