Michael A. Krainak

Frequency stabilization of distributed-feedback laser diodes at 1572 nm for lidar measurements of atmospheric carbon dioxide

We demonstrate a wavelength-locked laser source that rapidly steps through six wavelengths distributed across a 1572.335 nm carbon dioxide (CO(2)) absorption line to allow precise measurements of atmospheric CO(2) absorption. A distributed-feedback laser diode (DFB-LD) was frequency-locked to the CO(2) line center by using a frequency modulation technique, limiting its peak-to-peak frequency drift to 0.3 MHz at 0.8 s averaging time over 72 hours. Four online DFB-LDs were then offset locked to this laser using phase-locked loops, retaining virtually the same absolute frequency stability. These online and two offline DFB-LDs were subsequently amplitude switched and combined. This produced a precise wavelength-stepped laser pulse train, to be amplified for CO(2) measurements.

Preliminary measurements with an automated compact differential absorption lidar for the profiling of water vapor

The design and preliminary tests of an automated differential absorption lidar (DIAL) that profiles water vapor in the lower troposphere are presented. The instrument, named CODI (for compact DIAL), has been developed to be eye safe, low cost, weatherproof, and portable. The lidar design and its unattended operation are described. Nighttime intercomparisons with in situ sensors and a radiosonde are shown. Desired improvements to the lidar, including a more powerful laser, are also discussed.

Performance of planar-waveguide external cavity laser for precision measurements

A 1542-nm planar-waveguide external cavity laser (PW-ECL) is shown to have a sufficiently low level of noise to be suitable for precision measurement applications. Its frequency noise and intensity noise was comparable or better than the non-planar ring oscillator (NPRO) and fiber laser between 0.1 mHz to 100 kHz. Controllability of the PW-ECL was demonstrated by stabilizing its frequency to acetylene ((13)C(2)H(2)) at 10(-13) level of Allan deviation. The PW-ECL also has the advantage of the compactness of a standard butterfly package, low cost, and a simple design consisting of a semiconductor gain media coupled to a planar-waveguide Bragg reflector.

Free Space Laser Communication Experiments from Earth to the Lunar Reconnaissance Orbiter in Lunar Orbit

Laser communication and ranging experiments were successfully conducted from the satellite laser ranging (SLR) station at NASA Goddard Space Flight Center (GSFC) to the Lunar Reconnaissance Orbiter (LRO) in lunar orbit. The experiments used 4096-ary pulse position modulation (PPM) for the laser pulses during one-way LRO Laser Ranging (LR) operations. Reed-Solomon forward error correction codes were used to correct the PPM symbol errors due to atmosphere turbulence and pointing jitter. The signal fading was measured and the results were compared to the model.

Space-qualified silicon avalanche-photodiode single-photon-counting modules

Abstract A space-qualified silicon avalanche-photodiode (APD) based single-photon-counting-module (SPCM) was developed for the Geoscience Laser Altimeter System (GLAS) on board NASAs Ice, Cloud, and Land Elevation Satellite (ICESat). Numerous improvements were made over the commercially available SPCMs in both performance and reliability. The measured optoelectronic parameters include, 65% photon detection efficiency at the 532nm wavelength, 15–17 mega-counts per second (Mcps) maximum count rate and less than 200s−1 dark counts before exposure to space radiation.

Afterpulsing Effects in Free-Running InGaAsP Single-Photon Avalanche Diodes

We demonstrate large-area (80 mum diameter) InP-based single-photon avalanche diodes for Geiger-mode operation at 1.06 mum with dark count rates of ~1000 Hz at high detection efficiencies of 30% at 237 K, as well as simulations of dark count rate and detection efficiency that provide good agreement with measured data. Experimental results obtained using free-running operation illustrate the strong impact of afterpulsing effects for short (~200 ns) hold-off times. We present an analysis of these free-running results that quantifies the contribution of afterpulsing to the total count rate.

Laser Sounder for Active Remote Sensing Measurements of CO 2 Concentrations

We report on progress of our CO2 laser sounder laboratory breadboard system the goal of which is to measure the integrated column abundance of CO2 to better than 1 ppm from low Earth orbit globally, measuring at all latitudes and seasons through day and night. The challenge for an orbiting CO2 instrument is to achieve high precision not high sensitivity. We have made simple yet significant improvements to our active, optical-sensing laser-sounder instrument and real-time data processing that now enables absolute absorption measurements to better than plusmn 0.05% for over 10 hours before re-calibration (equivalent to a 1 ppm precision from orbit). Data from an eight day, 0.8 Km open path comparison test with a LICOR shows excellent agreement.

A dual format communication modem development for the Laser Communications Relay Demonstration (LCRD) program

The LCRD will demonstrate optical communications relay services between a geosynchronous satellite and Earth over an extended period, and thereby gain the knowledge and experience base that will enable NASA to design, procure, and operate cost-effective future optical communications systems and relay networks. LCRD is the next step in NASA eventually providing an optical communications service on the Next Generation Tracking and Data Relay Satellites (TDRS). LCRD will demonstrate some optical communications technologies, concepts of operations, and advanced networking technologies applicable to Deep Space missions. In this paper we describe the integrated dual format (PPM/DPSK) modem testbed development and performance.

A laser sounder for measuring atmospheric trace gases from space

Mounting concern regarding global warming and the increasing carbon dioxide (CO2) concentration has stimulated interest in the feasibility of measuring CO2 mixing ratios from space. Precise satellite observations with adequate spatial and temporal resolution would substantially increase our knowledge of the atmospheric CO2distribution and allow improved modeling of the CO2 cycle. Current estimates indicate that a measurement precision of better than 1 part per million (1 ppm) will be needed in order to improve estimates of carbon uptake by land and ocean reservoirs. A 1-ppm CO2 measurement corresponds to approximately 1 in 380 or 0.26% long-term measurement precision. This requirement imposes stringent long-term precision (stability) requirements on the instrument In this paper we discuss methods and techniques to achieve the 1-ppm precision for a space-borne lidar.

Narrowband, tunable, frequency-doubled, erbium-doped fiber-amplifed transmitter

We report on the development of a fiber-based laser transmitter designed for active remote sensing spectroscopy. The transmitter uses a master oscillator power amplifier (MOPA) configuration with a distributed feedback diode-laser master oscillator and an erbium-doped fiber amplifier. The output from the MOPA is frequency-doubled with a periodically poled potassium titanium oxide phosphate crystal. With 35 W of single-frequency peak optical pump power, 8 W of frequency-doubled peak power was achieved. The utility of this single-frequency, wavelength tunable, power scalable laser was then demonstrated in a spectroscopic measurement of diatomic oxygen A band.