ICESat laser altimeter measurement time validation system

• Published in: Measurement science & technology Vol. 14; no. 11; pp. 1978 - 1985
• Main Authors: Magruder, L A, Suleman, M A, Schutz, B E
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.11.2003; Institute of Physics
• Subjects: Applied sciences; Biological and medical applications; Exact sciences and technology; Fundamental areas of phenomenology (including applications); General equipment and techniques; Global environmental pollution; Instruments for environmental pollution measurements; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Metrological applications; Optics; Physics; Pollution; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Services and terminals of telecommunications; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Telemetry. Remote supervision. Telewarning. Remote control; Telemetry: remote control, remote sensing; radar; Laser ranging; Timing circuits; Ice sheet; Altimeters; Sensors; Calibration; Timing; Experimental study; Ice caps
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/14/11/016

NASA launched its Ice, Cloud and Land Elevation Satellite (ICESat) in January 2003. The primary goal of this laser altimeter mission is to provide determination of volumetric changes in the ice sheets, specifically in Antarctica and Greenland. The instrument performance requirements are driven by the scientific goal of determining a change in elevation on the centimetre level over the course of a year's time. One important aspect of the altimeter data is the time of measurement, or bounce time, associated with each laser shot, as it is an important factor that assists in revealing the temporal changes in the surface (land/ice/sea) characteristics. In order to provide verification that the laser bounce time is accurately being determined, a ground-based detector system has been developed. The ground-based system methodology time-tags the arrival of the transmitted photons on the surface of the Earth with an accuracy of 0.1 ms. The timing software and hardware that will be used in the ground-based system has been developed and extensively tested. One particular test utilized an airborne laser equipped to produce a similar signal to that of ICESat. The overflight of the detectors by the aircraft was successful in that the signals were detected by the electro-optical devices and appropriately time-tagged with the timing hardware/software. There are many calibration and validation activities planned with the intention to help resolve the validity of the ICESat data, but pre-launch analysis suggests the ground-based system will provide the most accurate recovery of timing bias.