ABSTRACT
Measurements of atmospheric turbulence along a path can be quantified by scintillometers and differential image motion monitors (DIMMs). The two instruments often measure different levels of turbulence, sometimes varying by nearly an order of magnitude. A high-fidelity numerical simulation was leveraged to assess the measurement performance of both a scintillometer and a DIMM system. When a non-ideal detector is combined with range-dependent turbulence, significant differences between the scintillometer and DIMM are observed. The difference in measurements obtained with the numerically simulated scintillometer and DIMM was consistent with those observed in side-by-side measurements with the instruments.
ABSTRACT
A laser-illuminated differential image motion monitor (DIMM) is presented that is able to measure the atmospheric coherence length r 0 along horizontal ground paths. This is accomplished by implementing a mono-static setup in which the transmitter and receiver are co-located and transmit to a retroreflective target. The impact of propagating along a folded path through the same volume of turbulent atmosphere is investigated in detail and the overall impact to angle-of-arrival measurements described. In addition, an outdoor test campaign was conducted to validate the findings by testing two commercial scintillometers and the laser DIMM side by side in both bi-static and mono-static configurations. Both analytical and experimental results show that under certain conditions, folded-path propagation can be treated identically to traditional single-path propagation.
