The objective of the Diffuse X-ray emission from the Local Galaxy (DXL) sounding rocket experiment is to distinguish the soft X-ray emission due to the Local Hot Bubble (LHB) from that produced via Solar Wind charge exchange (SWCX). Enhanced interplanetary helium density in the helium focusing cone provides a spatial variation to the SWCX that can be identified by scanning through the focusing cone using an X-ray instrument with a large grasp. DXL consists of two large proportional counters refurbished from the Aerobee payload used during the Wisconsin All Sky Survey. The counters utilize P-10 fill gas and are covered by a thin Formvar window (with Cyasorb UV-24 additive) supported on a nickel mesh. DXL's large grasp is 10 cm2 sr for both the 1/4 and 3/4 keV bands. DXL was successfully launched from White Sands Missile Range, New Mexico on December 12, 2012 using a Terrier Mk70 Black Brant IX sounding rocket.
The Sheath Transport Observer for the Redistribution of Mass (STORM) instrument is a prototype soft
X-ray camera also successfully own on the DXL sounding rocket. STORM uses newly developed slumped micropore (`lobster eye') optics to focus X-rays onto a position sensitive, chevron configuration, microchannel plate detector. The slumped micropore optics have a 75 cm curvature radius and a polyimide/aluminum filter bonded to its surface. STORM's large field-of-view makes it ideal for imaging SWCX with exospheric hydrogen for future missions. STORM represents the first flight of lobster-eye optics in space.
Lasers can be engineered and specifically designed for particular remote sensing applications. Laser material
selection criteria in this venture are reliability, efficiency, and operation at a specific wavelength. Traditionally, atmospheric
researchers adapted existing lasers to remote sensing applications. However, research programs at NASA Langley Research
Center has fundamentally altered the way by which laser materials are selected using quantum mechanical modeling. A
program of development to predict new laser materials, as well as new methods utilizing existing laser materials, specifically
designed to improve lidar or DIAL performance is discussed. This article will cover specifics of the development program
A novel ultraviolet laser is demonstrated using a dual wavelength Nd:YAG oscillator, sum frequency and second harmonic process. Synchronous pulses at 1.052 and 1.319 micrometers are amplified, mixed and subsequently doubled, producing pulses at 0.293 micrometers. An attractive feature of this laser design is that it is line tunable. With a properly designed resonator, a potential of 44 possible ultraviolet laser transitions can be operated, resulting in a line tunable UV laser in the wavelength range 0.263 to 0.339 micrometers.
A novel method of making a line tunable, visible and near ultraviolet, laser source is proposed and
demonstrated. It requires only a single laser and 2 nonlinear crystals. It can produce outputs with
wavelengths that cover much of the spectrum from 0.26 to 0.67 &mgr;m.
Pulsed lasers are useful for remote sensing of wind and greenhouse gases to better understand the atmosphere and its impact on weather patterns and the environment. It is not always practical to develop and optimize new laser systems empirically due to the time and expense associated with such endeavors. A practical option is to use a laser model to predict various performance parameters and compare these with the needs required for a particular remote sensing application. This approach can be very useful in determining the efficacy of potential laser systems, saving both time and money before proceeding with the actual construction of a laser device. As a pedagogical example, the modeling of diode pumped Tm:Ho:YLF and Tm:Ho:LuLF lasers are examined. Tm:Ho lasers operating around 2.0 μm have been used for wind measurements such as clear air turbulence and wake vortices. The model predictions for the laser systems examined here are compared to the actual laser performance, validating the usefulness of the modeling approach. While Tm:Ho fluoride lasers are used as a pedagogical example, the model is applicable to any lanthanide series pulsed laser system. This provides a useful tool for investigating potential laser systems that meet the requirements desired for a variety of remote sensing applications.
Remote sensing requires efficient lasers that are tunable over a short wavelength range around a particular atmospheric absorption feature of interest. High efficiency usually implies lanthanide series lasers. Although lanthanide series lasers have sufficient tuning capability, they must operate at preselected atmospheric absorption features. Often, there is no commonly available laser that operates at the requisite wavelength. This type of problem can be addressed using compositional tuning to create a laser at a preselected wavelength where none existed before. Quantum mechanics is an invaluable tool to predict the effects of compositional tuning. Quantum mechanical predictions are confirmed with spectroscopic measurements. Laser performance data for a laser that operates at 0.9441 μm, a preselected water vapor absorption feature, are featured.
We measured the tunability of a Nd:YAG, 946-nm microchip laser as the function of the laser crystal length and the reflectivity of the output mirror. A decrease in the tunable range is observed with the decrease in the reflectivity of the output mirror and the crystal length. The center oscillation wavelength is estimated to be ~946.1 nm. The oscillation wavelength varies between ~945.8 and ~946.4 nm for our experiments.
Two-micron lasers can be used in a variety of remote sensing and medical applications. In recent years, such lasers have been used for remote sensing of wind and CO2 to expand our understanding of the global weather system. The detection of clear air turbulence and wake vortex from aircraft has been proven to enhance air travel safety. In this paper, we present the design and performance of a high-energy diode pumped solid-state 2-micron laser transmitter. There has been a large body of work on 2 μm laser crystals using Tm and Ho ions doped in YLF and YAG hosts, but the use of LuLiF4 as a host is relatively recent. Studies comparing Ho:LuLiF4 and Ho:YLF show that both crystals have similar emission cross-sections for both 2.05 μm and 2.06 μm transitions. Tm:Ho:LuLiF4 has proven to produce 15%-20% more energy than Tm:Ho:YLF. This is primarily attributed to the variation of the thermal population distribution in the Ho: 5I7 and 5I8 energy levels. The laser crystal used for this experiment is grown in the crystalline a-axis. The resonator is a bow tie ring configuration with 3-m length. One of the mirrors in the resonator has a 3.5m curvature, which sets up a 1.8 mm TEMoo mode radius. The output mirror reflectivity is 72% and it is the dominant source of the resonator loss. An acousto-optic Q-Switch with Brewster angle switches the Q of the oscillator and defines the polarization of the laser output. This laser has a potential to produce a multi joule energy and replace the traditionally used Ho: Tm: YLF crystal.
Lasers operating around 2.0 jm have several remote sensing applications including wind velocity, water vapor and green house gasses. An attractive approach to 2.0 m lasers has a Tm:glass fiber laser pumping a Ho:YAG laser, thereby avoiding problems that are associated with the Ho:Tm up conversion process. Toward this end, both Tm:silica and Tm:ZBLAN fiber lasers are evaluated as well as a Tm laser pumped Ho:YAG. Performance of these devices is
We report on a diode pumped Tm: YLF laser generating 1.9 micrometers output. Recently, research is being pursued to produce laser wavelength around 2 micrometers by separating the Ho and Tm ions in different laser hosts. Compared to co-doped laser hosts; a higher efficiency performance can be achieved by directly pumping the Holmium with a 1.9 micrometers Tm laser due to the elimination of energy sharing between Tm and Ho as well as deleterious upconversion effects in co-doped systems. A 300-mJ Tm:YLF laser at room temperature has been demonstrated. The laser design and laser performance is described. To our knowledge, this is the highest energy ever reported for this laser material.
An H2O vapor remote sensing instrument which could operate in the 0.94 micrometer region would have several highly desirable characteristics. Among the characteristics are access to absorption lines with approximately the correct strength and the availability of good detection systems. A good candidate for the laser for such a system is a Nd:garnet laser operating on one of the 4F3/2 to 4I9/2 transitions. To make such a system a reality, NASA Langley has investigated compositional tuning to develop a laser at precisely the correct wavelength and methods of improving the efficiency. Both efforts have achieved success. A flashlamp pumped Nd:YAG laser operating at room temperature on the 0.946 micrometer transition has achieved a threshold of 12 J and a slope efficiency of 0.009.