Laser production for NASA's Global Ecosystem Dynamics Investigation (GEDI) lidar

Stysley, Paul R.; Coyle, D. Barry; Clarke, Greg B.; Frese, Erich; Blalock, Gordon; Morey, Peter A.; Kay, Richard B.; Poulios, Demetrios; Hersh, Michael J.

doi:10.1117/12.2239889

Cited by 9 publications

(6 citation statements)

References 4 publications

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“…NASA's Global Ecosystem Dynamics Investigation (GEDI) spaceborne lidar mission, which was successfully launched on the 5th December 2018, will make near global measurements of the Earth's land surface within the orbital bounds of the International Space Station (51.6 • S to 51.6 • N; Dubayah et al, 2014;Stysley et al, 2016). A number of data products will be derived from the measurements, including ground elevation, canopy height, foliage profiles, and above-ground biomass density (AGBD).…”

Section: Introductionmentioning

confidence: 99%

The GEDI Simulator: A Large‐Footprint Waveform Lidar Simulator for Calibration and Validation of Spaceborne Missions

Hancock

Armston

Hofton

et al. 2019

Earth and Space Science

194

149

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NASA's Global Ecosystem Dynamics Investigation (GEDI) is a spaceborne lidar mission which will produce near global (51.6°S to 51.6°N) maps of forest structure and above‐ground biomass density during its 2‐year mission. GEDI uses a waveform simulator for calibration of algorithms and assessing mission accuracy. This paper implements a waveform simulator, using the method proposed in Blair and Hofton (1999; https://doi.org/10.1029/1999GL010484), and builds upon that work by adding instrument noise and by validating simulated waveforms across a range of forest types, airborne laser scanning (ALS) instruments, and survey configurations. The simulator was validated by comparing waveform metrics derived from simulated waveforms against those derived from observed large‐footprint, full‐waveform lidar data from NASA's airborne Land, Vegetation, and Ice Sensor (LVIS). The simulator was found to produce waveform metrics with a mean bias of less than 0.22 m and a root‐mean‐square error of less than 5.7 m, as long as the ALS data had sufficient pulse density. The minimum pulse density required depended upon the instrument. Measurement errors due to instrument noise predicted by the simulator were within 1.5 m of those from observed waveforms and 70–85% of variance in measurement error was explained. Changing the ALS survey configuration had no significant impact on simulated metrics, suggesting that the ALS pulse density is a sufficient metric of simulator accuracy across the range of conditions and instruments tested. These results give confidence in the use of the simulator for the pre‐launch calibration and performance assessment of the GEDI mission.

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Section: Introductionmentioning

confidence: 99%

The GEDI Simulator: A Large‐Footprint Waveform Lidar Simulator for Calibration and Validation of Spaceborne Missions

Hancock

Armston

Hofton

et al. 2019

Earth and Space Science

194

149

View full text Add to dashboard Cite

show abstract

“…Our method requires having pre-and post-fire LiDAR data, which is a constraint given the limited spatial and temporal coverage of airborne LiDAR sensors. The method is potentially applicable to the recently launched Global Ecosystem Dynamics Investigation (GEDI) sensor onboard the International Space Station (Dubayah et al 2014;Stysley et al 2016). The sampling scheme should be taken into account, as it will not provide co-registered footprints.…”

Section: Discussionmentioning

confidence: 99%

Evaluating the potential of LiDAR data for fire damage assessment: A radiative transfer model approach

Garcı́a

North

Viana-Soto

et al. 2020

Remote Sensing of Environment

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“…This is not of too much concern to us because we will be operating the LDAs well below the operational values of our test. 6 We were able to operate our test sample of LDAs for > 3.5 Billion shots at GEDI laser parameters while seeing minimal changes to their required performance. The 3.5 Billion shots value was more than expected to be completed during GEDI's 2-year scheduled mission lifetime.…”

Section: Laser Diode Array (Lda) Testing Methods and Performancementioning

confidence: 99%

Component-level selection and qualification for the Global Ecosystem Dynamics Investigation (GEDI) laser altimeter transmitter

Frese

Chiragh²,

Switzer³

et al. 2018

Laser Radar Technology and Applications XXIII

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Flight quality solid-state lasers require a unique and extensive set of testing and qualification processes, both at the system and component levels to insure the laser's promised performance. As important as the overall laser transmitter design is, the quality and performance of individual subassemblies, optics, and electro-optics dictate the final laser unit's quality. The Global Ecosystem Dynamics Investigation (GEDI) laser transmitters employ all the usual components typical for a diode-pumped, solid-state laser, yet must each go through their own individual process of specification, modeling, performance demonstration, inspection, and destructive testing. These qualification processes and results for the laser crystals, laser diode arrays, electro-optics, and optics, will be reviewed as well as the relevant critical issues encountered, prior to their installation in the GEDI flight laser units.https://ntrs.nasa.gov/search.jsp?R=20180002473 2020-08-05T18:42:28+00:00Zyear mission will be installed aboard the International Space Station and measure the 3D volume and structure of the Earth's biomass using laser altimetry and digitized waveform recovery techniques. 1 The GEDI laser transmitters, of which three will be on board, need to generate and send > 5 Billion laser pulses at > 10 mJ to the Earth, with sub-16 ns pulse widths, running at 242 pulses/sec, with high precision pointing knowledge and low jitter. Since the lasers will be operational for most part only over land masses, the total shot count is roughly 1/3 the total value of a 242 Hz system running continuously, or ~ 2.5 Billion shots/year/laser. The GEDI laser is an oscillator-only design, relatively large for a TEM00 transmitter, in lieu of a more typical master oscillator power amplifier (MOPA) design used for pulse energies >10 mJ. The Oscillator-only design demanded ~1/3 fewer optics than an equivalent MOPA design. This reduced optics count allowed us to focus more attention on critical component testing and selection for every part. In particular, we focussed much attention on the Nd:YAG laser slabs, the laser diode arrays (LDA), and the KD*P electro-optic Q-Switches (QS). We performed extensive testing on all of these components with customized testing hardware developed in-house. Our High Output Maximum Efficiency Resonator (HOMER) laser design provided the TRL-6 (technology readiness level) or "flight qualified" requirement needed for the GEDI project, with proven long life, high efficiency, and good stability. 2,3

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Laser production for NASA's Global Ecosystem Dynamics Investigation (GEDI) lidar

Cited by 9 publications

References 4 publications

The GEDI Simulator: A Large‐Footprint Waveform Lidar Simulator for Calibration and Validation of Spaceborne Missions

The GEDI Simulator: A Large‐Footprint Waveform Lidar Simulator for Calibration and Validation of Spaceborne Missions

Evaluating the potential of LiDAR data for fire damage assessment: A radiative transfer model approach

Component-level selection and qualification for the Global Ecosystem Dynamics Investigation (GEDI) laser altimeter transmitter

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