Sept 1, 2022
Bought 4 seat licenses for MODTRAN6.
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It wants Ozone content as gm/cm^2 and we have it in Dobson units. Wikipedia says 1 DU is 2.69×1020 molecules per meter squared.
Molecular weight of O_3^16 is 47.992 gm/mole. One mole is 6.023E23 molecules. One square meter is 1E4 cm^2. So:
1 DU = 2.69E20 molecules/m^2 * (1m^2/1e4 cm^2) * ( 47.992 gm/mole) * (1 mole/6.023E23 molecules) = 2.1434e-06 gm/cm^2
so to get O3 in gm/cm^2 do (DU*2.1434e-06)
250 DU = 5.3586e-04 gm/cm^2
PWV is in mm, collapsing entire column density into some depth of liquid. MODTRAN6 wants gm/cm^2 of H2O. Density of water is 1 gm/cc, so 1 cm of water is 1 gm/cc.
So for this the conversion is 10 mm PWV → 1 gm/cc. Typical Pachon PWV is a few mm. Let's use a default 5mm PWV which corresponds to 0.5 gm/cm^2.
Set up point-to-point geometry from LSST elevation to 80 km, straight up.
Data go to ~/MODTRAN6
rename .tp7 output files with X.XX***.dat where X.XX is airmass to 3 sig figures
Matlab code ReadModtran6.m will then read in and act on these files. Need at least 4 of them.
The ***.psc output file is really simple; nm, T in two columns.
Default Atmosphere at zenith
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Images from March 16 2023 seq num 477 has a star with nice stellar atmosphere features. HD 73495 = Eta Pyxidis HR 3420. HD 73495. HIP 42334 is an A0V star.
Spectrum from RubinTV is
Copied images from 20230316 to local disk on laptop. Need to include bias frames as well as images of interest. Note that dispersion depends critically on disperser-to-CCD spacing so we should solve for it each time.
Note apparent m=0 stellar contamination at blue end of band3. We need to either subtract those out or median-filter with rotations.
Balmer lines are at
486.135
434.047
410.173
397.007
388.906
383.540
Downloaded seqnums
477
745-755 bias frames
Ran InjestAndAnalyze.m to create bias frames and full frame debiased images.
Ran Specexam2.m on frame AT_O_20230316_000477.full.debias.fits. m=0 star centroid is row 300.4 and col 1737.1
zoom on spectrum at absorption lines
March 21, 2023
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do geographical search on latitude -30:14:40.68 longitude -70:44:57.90; = -30.245, -70.75
Well, that didn't work so well. Try this:
https://www.esrl.noaa.gov/gmd/grad/neubrew/SatO3DataTimeSeries.jsp
That works! Can get plots as well as CSV data files:
For our site:
Ozone data file for Rubin site: Ozone2023.csv
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angle-corrected quadband throughput: Quadband.dat
Ozone for Oct 10 2023 is 300 283.7 Dobson units, interpolated to our site location.
Try to get barometric pressure right. Used https://weatherspark.com/h/d/25822/2023/10/10/Historical-Weather-on-Tuesday-October-10-2023-in-La-Serena-Chile#Figures-Pressure for barometric pressure at La Serena airport.
On Oct 10 2023 at 10 pm local the pressure at airport was 30.06 inches of mercury which is 1018 mbar. On Nov 23 2023 at 10 pm local it was the same value (precision is 0.01 inches). And at the summit we had 744.35 at that same time.
So a good pressure value to use for Oct 10 2023 is 0.74435 mbar.
Let's explore sensitivity to MODTRAN parameter choices.
Over the course of a year, barometric pressure at La Serena airport ranged from 29.8 in to 30.3 in of mercury. That's less than +- 1% variation.
PWV varies (very conservatively) from 0- 10 mm
Ozone varies from (see plot above) 250 to 300 Dobson units
Stellar colors go from -1 to 1.
So introduce perturbations that amount to mean-to-peak excursions, i.e. half the peak-to-peak value. This will show peak extinction excursions about the mean.
Let's explore sensitivity to MODTRAN parameter choices.
MATLAB program takes Star temperature, PWV, barometric pressure, and Ozone as inputs.
Pressure first:
T in 1000K. Dobson. PWV (mm). P(mbar) m1-m4. E1. E2. E3. E4. E14. E24. E34
10.5000 298.0000 5.0000 0.7327 0.0036 0.3892 0.1887 0.1194 0.1030 0.2862 0.0857 0.0164
10.5000 298.0000 5.0000 0.7400 0.0068 0.3930 0.1906 0.1205 0.1037 0.2894 0.0869 0.0168
10.5000 298.0000 10.0000 0.7400 0.0067 0.3930 0.1906 0.1205 0.1038 0.2892 0.0868 0.0167
10.5000 275.0000 5.0000 0.7400 0.0096 0.3930 0.1905 0.1195 0.1008 0.2922 0.0896 0.0187
10.5000 250.0000 10.0000 0.7400 0.0125 0.3930 0.1904 0.1185 0.0980 0.2950 0.0924 0.0206
6.0000 250.0000 10.0000 0.7400 1.0046 0.3872 0.1875 0.1184 0.0976 0.2896 0.0900 0.0208
E1 is extinction in band 1 in mag per airmass, bluest band. E14=E1-E4, etc.
We see color-extinction changes of
Final selection for Oct 10 2023:
which gives:
10.5000 283.7000 5.0000 0.7443 0.0105 0.3953 0.1916 0.1205 0.1023 0.2930 0.0893 0.0182
5.0000 283.7000 5.0000 0.7443 1.4842 0.3868 0.1875 0.1203 0.1018 0.2850 0.0857 0.0185
15.0000 283.7000 5.0000 0.7443 -0.3492 0.3975 0.1927 0.1206 0.1024 0.2951 0.0902 0.0181
8.0000 283.7000 5.0000 0.7443 0.4131 0.3929 0.1905 0.1205 0.1022 0.2908 0.0883 0.0183
Except OOPS we are using c34 as the definition of color, to reduce airmass sensitivity, recreate table with c34 in final column:
5.0000 283.7000 5.0000 0.7443 1.4842 0.3868 0.1875 0.1203 0.1018 0.2850 0.0857 0.0185 1.0369
10.5000 283.7000 5.0000 0.7443 0.0105 0.3953 0.1916 0.1205 0.1023 0.2930 0.0893 0.0182 0.6828
15.0000 283.7000 5.0000 0.7443 -0.3492 0.3975 0.1927 0.1206 0.1024 0.2951 0.0902 0.0181 0.5998
Fitting to C34 color (typcially around 0.5) gives
E14= 0.3090 -0.0231*C34
E24= 0.0964 -0.0103*C34
E34= 0.0176 +0.0009*C34
and for an A star we get E14=0.2930, E24=0.0893, E34=0.0182.