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A mobile optical remote sensing system for environmental monitoring is described. The system, housed in a full-size truck with a laboratory floor surface of 6.0 X 2.3 M 2 , is mainly intended for differential absorption lidar (DIAL) applications but can also be used for laser-induced fluorescence monitoring and for absorption measurements using classical light sources. The system has a 40-cm diam receiving telescope and a fully steerable flat mirror in a transmitting/receiving dome. A Nd:YAG-pumped dye laser with auxiliary nonlinear frequency conversion is the preferred transmitter in DIAL measurements. Measurement examples for atmospheric SO 2 and NO 2 monitoring with automatic concentration map drawings are given and further uses are discussed.

For the conventional needle probe, the standard mode (line source in an infinite medium) is achieved simply by inserting the probe into unconsolidated material or into a hole drilled in harder material.A half space mode is achieved by embedding the needle probe in an epoxy material of low thermal conductivity (<0.2 Wm 1 K x ) and grinding the material away until the needle is flush with a flat surface. The sample to be measured is placed on the half space surface, and the conductivity is measured in the usual way. Either configuration is capable of yielding values of thermal conductivity of consolidated rocks comparable in accuracy to values obtained with the steadystate, divided-bar technique most commonly used for these rocks. The linesource techniques are of particular advantage for materials that prove difficult to machine into the cylindrical disk specimens required for the steady-state apparatus. The half space probe is of additional value for rocks that are too friable to machine, but too hard to allow the drilling of the long, small diameter (38 x 1 mm) holes required for the standard application of the needle probe.

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