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13th International Laser Ranging
Workshop
"Toward Millimeter Accuracy"
Submitted
Abstracts
Detectors and Optical Chain Components (G. Kirchner and L. Grunwaldt)
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| New Detection Package at Graz | Georg Kirchner |
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Austrian Academy of Sciences Franz Koidl At present, SLR Graz is using a simple, straightforward detection package: After the main receiving telescope, the 14 mm beam passes a 0.3 nm interference filter, and is focused on the C-SPAD surface. While this setup is simple, stable and reliable, the 0.3 nm filter usually only allows a maximum of 30% to 40% transmission; it is also difficult to operate it in MultiColor schemes. To improve the total transmission of the optical receiver channel, we are building now a new detection package, which uses dispersion for wavelength filtering as well as for wavelength separation for MultiColor Operation. Because the effective filter bandwidth will be less than 0.15 nm, and the overall transmission of the receiver package should be more than 70% due to omitting any interference filter, the calculated improvement in signal to noise ratio should be a factor of 4. In addition, the dispersion scheme allows for efficient wavelength separation, again with minimized optical losses. Oral paper; received August 9, 2002 |
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| The advantages of Avalanche Photodiode (APD) arrays in laser ranging applications | Jana Strasburg |
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University of Washington T. Murphy, C. Stubbs, E. Adelberger The Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) is a new lunar ranging campaign aimed at achieving millimeter precision. At the heart of APOLLO is an integrated array of avalanche photodiodes developed at MIT's Lincoln Laboratories. These devices are capable of detecting the arrival of a single photon with high temporal precision (< 50 ps), at detection efficiencies as high as 50%. The integrated array format allows one to create a range profile with each laser shot by detecting multiple return photons, thereby eliminating the strong-signal biasing encountered with a single detector. The array format also preserves spatial information, facilitating target acquisition and tracking. We are currently using a 4 x 4 array, but the timing system can easily be multiplexed to handle arrays of 10 x 10 elements or larger. Lincoln Labs is presently testing 32 x 32 devices. Oral paper; received August 20, 2002 |
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| Characterization of a Microchannel Plate Photomultiplier Tube with a High Sensitivity GaAs Photocathode | Paul H ink |
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1000 New Holland Avenue Charles Tomasetti, Joesph Wright, John Martin Presented by: John Martin The characteristics of an 18mm photomultiplier tube (PMT) having a high sensitivity GaAs photocathode have been studied. This PMT, the BURLE 85104, uses a dual microchannel plate (MCP) electron multiplier. We report measurements that include standard DC response, single electron sensitivity and resolution, time response, pulse and count rate linearity, and dark counts as a function of temperature. Data is also presented for a gated version of the PMT that has a high-speed anode. The properties of these MCP-PMTs make them well suited for applications such as LIDAR, fluorescence microscopy and chemiluminescence. Oral paper; received August 21, 2002 |
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| Time walk compensation of a SPAD with linear photo detection | Etienne Samain |
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OCA The photo detection with a photo diode in the Geiger mode appears promising because of the time stability, the sensitivity, and the simplicity of the device. The transit time between the pulse arrival and the moment when the signal reaches a given detection threshold depends on the photon number in the light pulse. A precise knowledge of this photon number permits to eliminate this time walk if a correction table is known. A device using an auxiliary linear light sensor to measure this photon number coupled with a photo-diode in the Geiger mode for the timing purpose is presented here. This device is designed for both the space and ground segment of the T2L2 (Time Transfer by Laser Link) experiment and could be used in the frame of the satellite laser ranging activities. Oral paper; received August 23, 2002 |
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| SPAD Detector Package for Space Born Applications | Ivan Prochazka |
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Czech Technical University in Prague The SPAD detector package for the space born applications is under development for several space missions (T2L2 experiments, transponder, altimeter). The detector is based on the SPAD chips with and active area with 25 um diameter and a newly designed active quenching and gating circuit. The ultra short circuit dead time permits to operate the SPAD in both gated and ungated modes with dark count rates below 10 kHz and timing resolution better than 100 psec. The first results will be presented. Oral paper; received August 28, 2002 |
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| Testing of MCP PMTS: Use of Fiber Optic Coupled Gbps Laser Drivers to Create Ersatz Laser Return Pulses | Thomas Cuff |
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Honeywell-TSI Richard Chabot From an operational point of view, it is important to be able to test the MCP (Micro Channel Plate) PMT (PhotoMultiplier Tube) front end of LIDAR transceivers used in SLR (Satellite Laser Ranging) work. In the day-to-day operation of SLR systems, one needs to have an independent method of ascertaining that the receiver half of the LIDAR transceiver is functioning properly. In addition, the sensitivity and stability of the MCP PMT front end of the LIDAR transceiver also needs to be periodically checked against a standardized source to prevent long and short term errors from insinuating themselves into the production data stream. The creation of ersatz laser return pulses is also useful when developing new LIDAR systems such as NASA’s micro-laser altimeter and SLR2k robotic observatory. This paper describes a number of ways of constructing a laser return pulse generator from COTS (Commercial Off The Shelf) parts. In particular, we detail the use of currently available single chip laser drivers – normally employed in fiber optic LAN (Local Area Network) and WAN (Wide Area Network) telecommunication systems – as the “heart”; of the generator. Fiber optics is used to “plumb”; the ersatz laser return pulses together with the optical noise baseline to the output connector of the generator. The use of fiber optics allows one to conveniently fold the optic path within the generator without utilizing mirrors or prisms needed in a free space design and so results in a flatter volume for the generator and obviates the need for enclosing the generator in a light tight box. Since the specifying and ordering of single chip laser drivers and fiber optic components involve considerable amounts of jargon this aspect will also be covered. Oral paper; received September 06, 2002 |
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Last Updated:
September 6, 2002
