Global Shutter Flash Lidar (GSFL) is a powerful technology for a host of 3D ranging applications. GSFL generates real-time organized point clouds without motion distortion, which makes it an attractive technology for applications involving moving targets such as remote sensing, guidance navigation and control (GNC), and space situational awareness. In contrast to scanning lidar modalities, the field of view of GSFL is fixed, requiring an external gimbal in order to extend the field of regard without degrading the LIDAR range performance. To overcome this challenge, Advanced Scientific Concepts LLC has developed a GSFL that incorporates Liquid Crystal Polarization Gratings (LCPG) to steer the field of view of the GSFL, resulting in an increased field of regard. Passive LCPGs are thin birefringent solid films that steer light to one of two deflection angles, depending on the polarization handedness of the circularly polarized input light. Electrically variable liquid crystal wave plates included in the stack enable control of polarization handedness to select the desired steering angle at each LCPG. Not only does this result in a step and stare scanner that is simple to control and does not introduce motion blur, but it is also ideal for platforms that have low SWaP requirements. Here we present the operational concepts of the non-mechanical beam steering and quantify the effects of the LCPGs on the GSFL performance.
Linear mode global shutter flash LIDAR (gsf-LIDAR) is addressing the need for 3D sensing in a wide range of space, airborne, autonomous vehicle, and marine applications. Flash LIDAR produces real time dense 3D point clouds, enriched with scene intensity information, that are not subject to motion distortion. Current and future applications require extended range performance from a low Size Weight and Power (SWaP) 3D sensor. A Linear Mode LIDAR with photon sensitivity comparable to Geiger Mode sensing is needed to meet the challenges. Geiger mode APDs sensors require high repetition rate lasers to allow multiple frame summing and the associated processing overhead creates a significant SWaP burden. Advanced Scientific Concepts LLC has developed a linear mode gsf-LIDAR camera which has significant improvements in the minimum photon detection threshold, 10X for a single frame and over 30X with the aid of frame summing, which offers long range performance with low flux photon counting capability. ASC 3D Flash LIDAR uncooled testing demonstrated sub 30 photon detection with a low repetition rate laser. This performance improvement enables low SWaP sensors for enhanced space-based LIDAR capabilities for rendezvous /docking and planetary landing hazard detection and avoidance applications.
Global shutter flash LIDAR is the sensor of choice for space-based autonomous relative navigation applications. Advanced Scientific Concepts (ASC) has recently delivered LIDAR cameras to the NASA / Lockheed- Martin OSIRSRex and the NASA / Boeing CST-100 Starliner programs. These are two of the first operational space programs to use global shutter, flash LIDAR based relative navigation systems. The OSIRIS-REx spacecraft was launched in September 2016 and is the first opportunity to understand how global shutter flash LIDAR performance and reliability is impacted by long term exposure to the deep space environment.
KEYWORDS: LIDAR, Mars, Pulsed laser operation, Sensors, Staring arrays, Receivers, Distance measurement, Monte Carlo methods, 3D acquisition, Laser energy
Future planetary and lunar landers can benefit from a hazard detection (HD) system that employs a lidar to create a highresolution
3D terrain map in the vicinity of the landing site and an onboard computer to process the lidar data and
identify the safest landing site within the surveyed area. A divert maneuver would then be executed to land in this safe
site. An HD system enables landing in regions with a relatively high hazard abundance that would otherwise be
considered unacceptably risky, but are of high interest to the scientific community. A key component of a HD system is
a lidar with the ability to generate a 3D terrain image with the required range precision in the prescribed time and fits
within the project resource constraints. In this paper, we present the results obtained during performance testing of a
prototype "GoldenEye" 3D flash lidar developed by ASC, Inc. The testing was performed at JPL with the lidar and the
targets separated by 200 m. The analysis of the lidar performance obtained for different target types and albedos, pulse
energies, and fields of view is presented and compared to key HD lidar requirements identified for the Mars 2018 lander.
Integration of active optical components typically serves five goals: enhanced performance, smaller space, lower power dissipation, higher reliability, and lower cost. We are manufacturing widely tunable laser diodes with an integrated high speed electro absorption modulator for metro and all-optical switching applications. The monolithic integration combines the functions of high power laser light generation, wavelength tuning over the entire C-band, and high speed signal modulation in a single chip. The laser section of the chip contains two sampled grating DBRs with a gain and a phase section between them. The emission wavelength is tuned by current injection into the waveguide layers of the DBR and phase sections. The laser light passes through an integrated optical amplifier before reaching the modulator section on the chip. The amplifier boosts the cw output power of
the laser and provides a convenient way of power leveling. The modulator is based on the Franz-Keldysh effect for a wide band of operation. The common waveguide through all sections minimizes optical coupling losses. The packaging of the monolithically integrated chip is much simpler compared to
a discrete or hybrid solution using a laser chip, an SOA, and an external modulator. Since only one optical fiber coupling is required, the overall packaging cost of the transmitter module is largely reduced. Error free transmission at 2.5Gbit/s over 200km of standard single mode fiber is obtained with less than 1dB of dispersion penalty.
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