Home   Tutorial Forecasts Legend Forecasts Trends Climatology Team Bibliography Credit to ALTA Contact Choose a date

# ARCHIVE - Forecast relative to the night starting on 2020/10/24 MST

Note: click on a figure to magnify the image.
Date of figures refers to the start of night in MST.

# LINC-NIRVANA

LINC-NIRVANA is the layer-oriented MCAO system of LBT in which the two DMs are conjugated at 126 m and 7.1 km above ground layer. The wind speed at which the system is therefore sensible is the integral of the wind speed of each turbulence layers developed inside the depth of field weighted by the correspondent CN2, normalized by the turbulence developed in the whole depth of field (see Eq.1). The total depth of field ΔH is defined as ΔH = 2 (d/θ) centred at the conjugated plane height, where d is the distance between two adjacent actuators projected on the pupil (or metapupil) of the telescope and θ is the FOV. In the specific case the depths of field are:

for DM1: ΔH126m = [-163,415]m = 578m
for DM2: ΔH7.1km = [5072,9127]m = 4055m

where we considered FOVDM1=6 arcmin and FOVDM2=2 arcmin.
 $V_{eq} = \left[ \frac{\int_{H_{min}}^{H_{max}} |v(h)|^{5/3} C_N^2(h) dh}{\int_{H_{min}}^{H_{max}} C_N^2(h) dh} \right]^{3/5}$ (1)

Hmin and Hmax are the extremes of the vertical slabs. Fig.1 and Fig.2 show the equivalent wind speed Veq temporal evolution integrated on the respective depth of field ΔHi between the sunset and the sunrise as indicated in Eq.1 during the night.
Astronomical dusk and dawn are shown too. On the x-axis is time in UT (bottom), in MST (top). Raw data points frequency is equal to the model time-step (typically from a fraction of second up to a few seconds depending on the model configuration used). Data points are re-sampled at a frequency of 20 minutes after a 1-hour moving average. The error bars are the sigma over the 20 minutes sampling, computed before the moving average. Veq gives us an information on how fast/slow an AO system has to run.  Fig. 1: Veq temporal evolution between the sunset and the sunrise related to the atmospheric slab sensed by DM1. Fig. 2: Veq temporal evolution between the sunset and the sunrise related to the atmospheric slab sensed by DM2.