**3. Update of the concept of signal/noise ratio**

It transpired that the signal/background noise ratio (S/N) is ambiguous due to the accuracy of the measurement of the scattering signal by the use of the extended strobe. Indeed, when ti = const and S/N = const for the system I, this automatically means the constancy accuracy of the scattering signal (∂ = const) from strobe to strobe. For example, we set ∂ = 10% for σ ~ 0.1 km-1 for the basic equipment (system I) with S/N = 10. For the systems of type II, the signal is accumulated over time intervals the value of which is not constant, but rather varies in such a way that satisfies the condition: ti (n) = (ti (n-1) + ti)) is ti (n)> ti (n-1). The

The basis for the reception of new results is a series of works on the laser sounding of the atmosphere in stable nightime conditions. This has allowed the development of certain methods for the structural-statistical processing of an initial remote signal. The aim is to reveal the signs of the steady organisation of the frequency structure of environmental

The generalised regular structure comes from the summary of the sequence of the discrete readouts. They were received by the scanning of the investigated volume of the environment in a horizontal plane to a set of directions and with the set angular permission

During the following stage, the signal is represented in the form of a regular structure of local maxima and minima. There was a separate analysis of the 'plus' and 'minus' structures

These components behave as whole object and are registered as a uniform regular structure (type harmonious) only in the case of a steadily vertical stratified environment. When the infringement of the stability of the stratification of environmental communication between the 'plus' and 'minus' structures decreases, they become increasingly independent of one another other. The degree of such dependence can be characterised by a certain numerical

The thermodynamic stability of the environment and its stratification can be characterised numerically by a special generalised parameter on the basis of Richardson's number. With the infringement of the thermodynamic stability of the environment, this parameter adopts wavy characteristics on a vertical plane. The length of such a 'wave' with the falling of the

The integrated regular structure of vertical thermodynamic distribution is an indicator of

It is possible to speak about the communication of the optical structure horizontal stability with the vertical stability of the thermodynamic structure of the environment and its

Besides this, the infringement of the stability of the environment leads to the infringement of the stability of the revealed structure and the occurrence of obvious anomalies within the structure (Polkanov, Y. A. et al., 1991; Polkanov, Y. A. et al., 2008) whose behaviour can provide information on the direction of the reorganisation (self-organisation) of the

It transpired that the signal/background noise ratio (S/N) is ambiguous due to the accuracy of the measurement of the scattering signal by the use of the extended strobe. Indeed, when ti = const and S/N = const for the system I, this automatically means the constancy accuracy of the scattering signal (∂ = const) from strobe to strobe. For example, we set ∂ = 10% for σ ~ 0.1 km-1 for the basic equipment (system I) with S/N = 10. For the systems of type II, the signal is accumulated over time intervals the value of which is not constant, but rather varies in such a way that satisfies the condition: ti (n) = (ti (n-1) + ti)) is ti (n)> ti (n-1). The

stratification as being an indicator of such stability (Polkanov, Y. A. et al. 1989).

parameter (Polkanov, Y. A. et al., 1991; Polkanov, Y. A. et al., 2009).

inhomogeneities.

(Polkanov, Y. A. et al., 1989).

(Polkanov, Y. A. and Kudinov. V. N., 1989).

environmental stability was decreased.

such stratification of the environment.

**3. Update of the concept of signal/noise ratio** 

environment.

essential point here is the rise of the level of the recorded background illumination with the increasing duration of the strobe. The scattering signal increases from the strobe to strobe – in general – to the so-called maximum accumulated signal (Kovalev, V. A., 1973).

The background illumination level is significantly higher than the corresponding internal noise receiver (in.ns = 0.1 for ti = 0.4 ms). It exceeds the signal of system I, with a point, but is comparable with the level of the scattering of the signal of system II (τ < 3). In this case, the accuracy of the scattering signal and the background are similar, and they can be used as useful signals on an equal basis.

In fact, we have a mixture of two signals - the scattering signal and the background signal. Their value increases from strobe to strobe and the first of them (S) rises to a certain level (Wmax) whilst the second of them (b) increases linearly with time and indefinitely.

In these circumstances, the accuracy of the scattering signal increases when S/N = const (1 because a strobe the length of the time of registration is increasing.

Thus, there is a new dependence - ∂ (t) which was previously unavailable for system I . Table 1 lists the measurement error depending upon the distance ls (n) corresponding to the interval gating ts (n), if S/N = 10 = const, for σ = 0.1 km-1, nb = 50, ti = 0.4 s.


Table 1. The measurement error decreases with increasing interval gating.

Model calculations showed that the measurement accuracy of the scattering signal for system II is several times higher than the measurement accuracy for system I. This means that for the same radiation power of remote systems, greater measurement accuracy is achieved for systems of type II through special time organisation and its recording of the digitised signal (∂II ≠ const ≤ ∂I = const).

We can talk about the actual incompleteness of the concept of the signal/background ratio for the registration systems of type II when the strobe length (a single reference signal) depends upon the position of the laser pulse on a remote line sensing. Moreover, it is possible that the signal/background ratio is less than unity but that the measurement accuracy remains high. This is possible when the signal/internal noise ratio (S/in.ns) and the background/internal noise ratio (b/in.ns) is much higher than 1. An example of such situations is provided by Table 2.


Table 2. Signal/background ratio, depending upon the length of the strobe (km) and where the measurement error δ = 10% (const).

The obtained simulation results suggest that the measurement accuracy was higher than expected, if only to carry out the calculation of the signal/background ratio for systems of type II.

Looking at Remote Sensing the Timing of an

Fig. 2. Discrete-time signal xc(t) processing for System I.

with a high transparency of the atmosphere (~ 10-2 km-1).

**signal** 

Organisation's Point of View and the Anticipation of Today's Problems 223

We shall call this remote sensing system (lidar) as a base 'System I' (the old system), and a

Fig. 3. Discrete-time signal xc(t) processing for System II (T1 = T, T2 = 2T, T3 = 3T, T4 = 4T).

The calculation of the signal/background ratio and the corresponding measurement errors of the scattering signal is carried to the appropriate conditions of 'twilight' (∂1) and 'cloudy day' (∂2) when the level of background illumination increases by two orders of magnitude. The following table shows the dynamic range (DR) and signal/background ratio for the a wide range length of the path sounding (L) for each value of the extinction coefficient (σ) from the real range. The level of illumination is selected for the corresponding conditions

**4.1 The simulation results of the proposed temporal organisation of the detected** 

system with increasing intervals of registration (strob) 'System II' (the new system).
