Carl Weimer

CALIPSO Lidar Description and Performance Assessment

Abstract This paper provides background material for a collection of Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) algorithm papers that are to be published in the Journal of Atmospheric and Oceanic Technology. It provides a brief description of the design and performance of CALIOP, a three-channel elastic backscatter lidar on the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite. After more than 2 yr of on-orbit operation, CALIOP performance continues to be excellent in the key areas of laser energy, signal-to-noise ratio, polarization sensitivity, and overall long-term stability, and the instrument continues to produce high-quality data products. There are, however, some areas where performance has been less than ideal. These include short-term changes in the calibration coefficients at both wavelengths as the satellite passes between dark and sunlight, some radiation-induced effects on both the detectors and the laser when passing through the South Atlant...

Elevation information in tail (EIT) technique for lidar altimetry.

A technique we refer to as Elevation Information in Tail (EIT) has been developed to provide improved lidar altimetry from CALIPSO lidar data. The EIT technique is demonstrated using CALIPSO data and is applicable to other similar lidar systems with low-pass filters. The technique relies on an observed relation between the shape of the surface return signals (peak shape) and the detector photo-multiplier tube transient response (transient response tail). Application of the EIT to CALIPSO data resulted in an order of magnitude or better improvement in the CALIPSO land surface 30-meter elevation measurements. The results of EIT compared very well with the National Elevation Database (NED) high resolution elevation maps, and with the elevation measurements from the Shuttle Radar Topography Mission (SRTM).

An Overview of Ball Flash LIDAR and Related Technology Development

Ball Aerospace has been developing Flash LIDAR systems for more than 7 years, and space qualified their first system on the Sensor Test for Orion Relative-navigation Risk Mitigation (STORRM) mission in May of 2011 on STS-134. The STORRM unit demonstrated the capabilities of the flash LIDAR system for relative navigation, but other applications exist, including science applications, and landing risk mitigation on Earth and other planets. This paper provides an overview of flash LIDAR sensor systems, describes the applications and scenarios where they provide advantages over scanning systems, and provides an overview of related technology development efforts at Ball Aerospace. The current development efforts include relative navigation applications, 6-DOF relative pose determination, landing hazard detection, electronic laser beam steering, and sensor upgrades that include electronic architecture modifications.

Topographic mapping flash lidar for multiple scattering, terrain, and forest mapping

The Topographic Mapping Flash Lidar (TMFL) developed at Ball Aerospace combines a pushbroom format transmitter at 1064 nm with a flash focal plane receiver. The wide 20 degree field of view of the instrument enables broad swath coverage from a single laser pulse without the need for a scanning mechanism. These features make the TMFL design particularly well-suited for space flight. TMFL has been demonstrated during an airborne flight where data were gathered over a forest plot to measure tree waveforms. Topographic maps were assembled of river beds and geologic areas of high relief. The TMFL has also been used to observe multiple-scattering phenomena in clouds by illuminating a steam plume from the aircraft above. Signal was recorded off-axis from the illuminated laser line by as much as 1 degree. The TMFL study of multiple-scattering is valuable as it provides a unique way to significantly improve the calibration of measured backscatter for space lidars. Lidar backscatter was also measured from water surface and was shown to correlate with models of water surface roughness.

Adaptive lidar for Earth imaging from space

Laser remote sensing of the Earth from space offers many unique capabilities stemming from the unique properties of lasers. Lidars make possible three-dimensional characterizations that enable new scientific understanding of the natural processes that shape the planets oceans, surface, and atmosphere. However, the challenges to further expand on these successes remain complex. Operation of lidars from space is limited in part by the relatively low power available to the lasers, the low signal scattered back to the instrument because of the large distance to the surface, and the need for reliable and autonomous operation because of the significant investment required for satellites. The instrument complexities are compounded by the diversity in the Earth scenes as well as the variability in albedo from cloud, ice, vegetation, desert, or ocean, combined with the highly variable transmission of the laser beam through clouds, forest canopy, or ocean surface and near-surface. This paper will discuss the development of a new approach to space-based lidars that uses adaptive instrument techniques to dramatically enhance the capability of space-based lidars.

Vision Navigation Sensor (VNS) with Adaptive Electronically Steerable Flash LIDAR (ESFL)

Ball Aerospace has been developing Flash LIDAR systems for more than 7 years, and space qualified their first system on the Sensor Test for Orion Relative-navigation Risk Mitigation (STORRM) mission in May of 2011 on STS-134. The STORRM unit demonstrated the capabilities of the flash LIDAR system for relative navigation, but other applications exist, including science applications, and landing risk mitigation on Earth and other planets. One key technology for making the flash LIDAR a more broadly applicable sensor is the addition of electronically steerable laser projection optics to provide flexibility in operations and to optimize the use of the limited number of photons available. This principle is important in any application where mass and power are limited commodities. The addition of Electronically Steerable Flash LIDAR (ESFL) capability to the VNS enables the system to offer the functionality of both scanning and flash LIDARs simultaneously, without any mechanisms. This paper provides an overview of the Vision Navigation Sensor (VNS) flash LIDAR and the work towards a common navigation sensor that meets NASA’s common specification through the addition of ESFL. Potential mass and volume reductions are also covered to balance the mass and volume required by ESFL. Finally, an overview of a control scheme to maximize the utility of ESFL for earth science applications is presented.

Fully transparent photon sieve

Regular photon sieve (PS) may only have up to ~25% transmission of light. The low transmission limits its applications in many fields such as satellite remote sensing when the reflected light incident on the PS is relatively weak. Binary PS was developed to overcome the low transmission problem of PS. However, binary PS which involves using different optical materials/thicknesses in different zones of the PS at a nanometer or micron scale, is not easy to manufacture. Therefore, in this study, we developed a fully transparent PS concept. We can use laser photolithography to simply make holes on a sheet of fully transparent material. With specifically designed optical thickness and PS-patterned pinholes, the transparent sheet can effectively focus light to its focal point. This concept is validated both by the finite-difference time domain (FDTD) modeling and by laboratory prototypes in this study.

The Optical Autocovariance Wind Lidar. Part I: OAWL Instrument Development and Demonstration

AbstractWe present the motivation, instrument concept, hardware descriptions, and initial validation testing for a Doppler wind lidar (DWL) system that uses optical autocovariance (OA) in a field-w...

Optical Autocovariance Wind Lidar (OAWL): aircraft test-flight history and current plans

To address mission risk and cost limitations the US has faced in putting a much needed Doppler wind lidar into space, Ball Aerospace and Technologies Corp, with support from NASA’s Earth Science Technology Office (ESTO), has developed the Optical Autocovariance Wind Lidar (OAWL), designed to measure winds from aerosol backscatter at the 355 nm or 532 nm wavelengths. Preliminary proof of concept hardware efforts started at Ball back in 2004. From 2008 to 2012, under an ESTO-funded Instrument Incubator Program, Ball incorporated the Optical Autocovariance (OA) interferometer receiver into a prototype breadboard lidar system by adding a laser, telescope, and COTS-based data system for operation at the 355 nm wavelength. In 2011, the prototype system underwent ground-based validation testing, and three months later, after hardware and software modifications to ensure autonomous operation and aircraft safety, it was flown on the NASA WB-57 aircraft. The history of the 2011 test flights are reviewed, including efforts to get the system qualified for aircraft flights, modifications made during the flight test period, and the final flight data results. We also present lessons learned and plans for the new, robust, two-wavelength, aircraft system with flight demonstrations planned for Spring 2016.

Frequency stabilized lasers for space applications

metrology, spectroscopy, atomic clocks and geodesy. This technology will be a key enabler to several proposed NASA science missions. Although lasers such as Q-switched Nd-YAG are now commonly used in space, other types of lasers - especially those with narrow linewidth - are still few in number and more development is required to advance their technology readiness. In this paper we discuss a reconfigurable laser frequency stabilization testbed, and end-to-end modeling to support system development. Two important features enabling testbed flexibility are that the controller, signal processing and interfaces are hosted on a field programmable gate array (FPGA) which has spacequalified equivalent parts, and secondly, fiber optic relay of the beam paths. Given the nonlinear behavior of lasers, FPGA implementation is a key system reliability aspect allowing on-orbit retuning of the control system and initial frequency acquisition. The testbed features a dual sensor system, one based upon a high finesse resonator cavity which provides relative stability through Pound-Drever-Hall (PDH) modulation and secondly an absolute frequency reference by dither locking to an acetylene gas cell (GC). To provide for differences between ground and space implementation, we have developed an end-to-end Simulink/ Matlab®-based control system model of the testbed components including the important noise sources. This model is in the process of being correlated to the testbed data which then can be used for trade studies, and estimation of space-based performance and sensitivities. A 1530 nm wavelength semiconductor laser is used for this initial work.