Susan Valett

The Slope Imaging Multi-polarization Photon-counting Lidar: Development and performance results

The Slope Imaging Multi-polarization Photon-counting Lidar is an airborne instrument developed to demonstrate laser altimetry measurement methods that will enable more efficient observations of topography and surface properties from space. The instrument was developed through the NASA Earth Science Technology Office Instrument Incubator Program with a focus on cryosphere remote sensing. The SIMPL transmitter is an 11 KHz, 1064 nm, plane-polarized micropulse laser transmitter that is frequency doubled to 532 nm and split into four push-broom beams. The receiver employs single-photon, polarimetric ranging at 532 and 1064 nm using Single Photon Counting Modules in order to achieve simultaneous sampling of surface elevation, slope, roughness and depolarizing scattering properties, the latter used to differentiate surface types. Data acquired over ice-covered Lake Erie in February, 2009 are documenting SIMPLs measurement performance and capabilities, demonstrating differentiation of open water and several ice cover types. ICESat-2 will employ several of the technologies advanced by SIMPL, including micropulse, single photon ranging in a multi-beam, push-broom configuration operating at 532 nm.

Spaceborne laser instruments for high-resolution mapping

We discuss past, present and future spaceborne laser instruments for high-resolution mapping of Earth and planetary surfaces. Previous spaceborne-laser-altimeters projected and imaged a single laser spot for surface-height measurements. In contrast, the recent Lunar Orbiter Laser Altimeter (LOLA) instrument on the Lunar Reconnaissance Orbiter (LRO) uses a non-scanning multi-beam system for surface topography mapping. The multi-beam instrument facilitates surface slope measurement and reduces the time-to-completion for global high-resolution topographic mapping. We discuss our first-year progress on a three-year swath-mapping laser-altimetry Instrument Incubator Program (IIP) funded by the NASA Earth Science Technology Office (ESTO). Our IIP is a technology development program supporting the LIdar Surface Topography (LIST) space-flight mission that is a third-tier mission as recommended by the National Research Council (NRC) for NASAs Earth Science programs.

Polarimetric, two-color, photon-counting laser altimeter measurements of forest canopy structure

Laser altimeter measurements of forest stands with distinct structures and compositions have been acquired at 532 nm (green) and 1064 nm (near-infrared) wavelengths and parallel and perpendicular polarization states using the Slope Imaging Multi-polarization Photon Counting Lidar (SIMPL). The micropulse, single photon ranging measurement approach employed by SIMPL provides canopy structure measurements with high vertical and spatial resolution. Using a height distribution analysis method adapted from conventional, 1064 nm, full-waveform lidar remote sensing, the sensitivity of two parameters commonly used for above-ground biomass estimation are compared as a function of wavelength. The results for the height of median energy (HOME) and canopy cover are for the most part very similar, indicating biomass estimations using lidars operating at green and near-infrared wavelengths will yield comparable estimates. The expected detection of increasing depolarization with depth into the canopies due to volume multiplescattering was not observed, possibly due to the small laser footprint and the small detector field of view used in the SIMPL instrument. The results of this work provide pathfinder information for NASAs ICESat-2 mission that will employ a 532 nm, micropulse, photon counting laser altimeter.

Airborne polarimetric, two-color laser altimeter measurements of lake ice cover: A pathfinder for NASA's ICESat-2 spaceflight mission

The ICESat-2 mission will continue NASAs spaceflight laser altimeter measurements of ice sheets, sea ice and vegetation using a new measurement approach: micropulse, single photon ranging at 532 nm. Differential penetration of green laser energy into snow, ice and water could introduce errors in sea ice freeboard determination used for estimation of ice thickness. Laser pulse scattering from these surface types, and resulting range biasing due to pulse broadening, is assessed using SIMPL airborne data acquired over ice-covered Lake Erie. SIMPL acquires Polarimetrie lidar measurements at 1064 and 532 nm using the micropulse, single photon ranging measurement approach.

Digital Beamforming Synthetic Aperture Radar (DBSAR) polarimetric operation during the Eco3D flight campaign

The Digital Beamforming Synthetic Aperture Radar instrument demonstrated its first polarimetric polarization operation during the Eco-3D flight campaign, on board the NASA P3 aircraft in the summer/fall 2011. The measurements acquired during the campaign are currently being used to demonstrate DBSARs science utility by providing critical information on vegetation structure needed to estimate vegetation biomass in order to advance our understanding of the carbon cycle.

Sixteen channel, non-scanning airborne lidar surface topography (list) simulator

We report on progress in developing a new multi-beam non-scanning, swath mapping laser altimeter measurement approach for future spaceflight missions using a high repetition rate, short-pulse laser transmitter. The instrument contains multi pixel photon counting detectors, high bandwidth, sixteen-channel 8-bit digitizer and a high-throughput data system.

A 16-beam non-scanning swath mapping laser altimeter instrument

We have developed and successfully flown a 16-beam, non-scanning laser altimeter instrument with a swath width of 80 m and spatial resolution of 5 m. The Airborne Lidar Surface Topography Simulator (ALISTS) instrument was developed to demonstrate key technologies and a measurement approach achieving the efficiency required for the Lidar Surface Topography (LIST) mission. The approach employs a 10 kHz, near-infrared, microchip laser transmitter, beam splitting optics and waveform capture using a photon-sensitive, linear-mode detector array. In this paper we will present the instrument development effort and access the performance achieved during our two airborne campaigns.

Development effort of the airborne lidar simulator for the lidar surface topography (LIST) mission

In this paper we will discuss our development effort of an airborne instrument as a pathfinder for the LIdar Surface Technology (LIST) mission. This paper will discuss the system approach, enabling technologies, instrument concept, final assembly and the preparation for flight with this new multi-beam non-scanning, swath mapping laser altimeter system.

Development of the airborne lidar surface topography simulator

In 2008 we began a three-year NASA Earth Science Technology Office (ESTO) funded Instrument Incubator Program (IIP) focused on technology development for the Lidar Surface Topography (LIST) mission. The LIST mission is one of the Earth Science Decadal Survey missions recommended to NASA by the National Research Council (NRC). Our IIP objective is to demonstrate the measurement approach and key technologies needed for a highly efficient swath mapping lidar to meet the goals of the LIST mission. To demonstrate the concept we are developing the Airborne LIST Simulator (A-LISTS) instrument. In this paper we summarize the A-LISTS instrument characteristics and the approaches we are using to advance lidar capabilities and reduce risks for LIST.