Page Comparison

Sept 1, 2022

Bought 4 seat licenses for MODTRAN6. 

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http://cds-espri.ipsl.fr/tapas/project?methodName=home_en 

RUNNING MODTRAN6

Feb 20, 2023

Go to 

/usr/local/bin/MODTRAN6.0/bin/macos

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Clicking on Edit function brings up a range of panels

Unit conversions

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

Used MODTRAN6 to generate transmission data for Rubin elevation up to 100 km. Used 5mm PWV and 250 Dobson units. Used ReadModtran6.m MATLAB code to convert from cm^-1 to nm and extract total transmission, ozone, and water. 
Stable Transmission is Transmission/(water*Ozone), and is basically the Rayleigh scattering portion in blue. 
The quadnotch filter avoids the O2 lines, doesn't go that far into the red. 

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Expected range of PWV is given by  The GPS water vapor monitor and thermal astronomy at Gemini South (note this is an estimate from Paranal). So 5mm is a sensible default value. 

Targets

Calspec standards that are both bright and rather AB-flat.
From https://www.eso.org/sci/observing/tools/standards/spectra/stanlis.html 

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Here's a list of bright A0 stars from Simbad in the right dec band: 

Polar A0 stars: 

Exposure times

HD 185975 is V=8.1
In 30 sec integration it gets hologram peak of 2500, sum of 60K ADU at peak, in typical seeing. A mag 6 star is 7X brighter so we'd get peak of 17K ADU, not saturated. So 30 sec seems good for V=6-8.

March 5 2023- synthetic photometry

Downloaded MuCol CalSpec data files from STSCI. https://archive.stsci.edu/hlsps/reference-atlases/cdbs/current_calspec/ 
data files are mucol_mod_004.fits and mucol_stis_006.fits:
mucol_stis_006.fits
mucol_mod_004.fits

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Here is a plot of (lambda/8000)*F_lambda, which is photon spectrum for this source: 

LATISS throughput estimates, ab initio

data files are in  laptop directory /Users/cstubbs/data/AuxTel/throughput

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Color-airmass terms:

For a color difference of Mu Col -flat =  delta(B1-B2) = (22.4303 - 21.9940) - (20.5042 - 20.4675) = 0.4363 - 0.0367 = +0.3996, we get an extinction difference of 3.5 mmag/airmass. 
For a color difference of Mu Col -flat = delta(B3-B4) =   (21.9831-21.5152) - (23.1427-22.3052) = 0.4679 - 0.8375 = -0.3696 we get an extinction difference of 0.7 mmag/airmass
                                                   

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Compare to photon-flat source:

Quick-look comparison with observations from March 2, 2023

SEE BELOW FOR ERROR FOUND AND CORRECTED IN BAND 4

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A toy example of determining excess extinction. 
March 13 2023

Determined effective band center for observations of Mu Col by computing, band per band, lambda_eff=sum(lambda*detected photon spectrom on ground)/sum(photon specrum on ground) for atmosphere at 1.4 airmasses and Mu Col photon spectrum and estimated throughput. 
Resulting band centers are

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define lambdanorm=lambda/500. 

March 19 2023, wavelength solution for quadnotch + 300 l/mm disperser. 

 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

Image Modified

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

Image Modified

March 21, 2023

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403, 404, 405, 436, 437, 438, 444, 445, 446, 477, 478, 479, 485,
            486, 487, 512, 513, 514, 536, 537, 538, 560, 561, 562, 595, 596,
            597, 695, 696, 697

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November 23, 2023 - revisions for quadband paper 1. 

We've done an analysis of observations from Oct 10, 2023 on Aux Tel with masked quadband filter. There is about a 1% discrepancy between photometry and MODTRAN predictions. 

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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 

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So the conversation factor is  2.2379e+03. The Sentinel5 ozone value for Oct 10 2023 is therefore 0.1248*  2.2379e+03 = 279.3 Dobson units. NASA said 284. 

Res

The conversion factor is 2.2379e+03 to go from Sentinal 5 units to Dobson units. 

For Oct 10 2023 the Sentinel 5 value was 0.1248 (better precision obtained by downloading CSV file) which corresponds to 279.3 Dobson units. This is to be compared to NASA OMI value of 283.7. 

November 26, 2023

Trying to understand how MODTRAN makes excess extinction prediction. An excellent paper is Patat et al about extinction above Paranal. They also see, even after accounting for aerosols, and excess extinction predicted by LBLRTM (line by line radiative transfer model). 
Their Figure 4: 
Image Added

If observed - model is negative, then model extinction is > observed. Difference between 570 nm and 380 nm is 0.75 percent. We see about 1% 
So this is indeed possibly a real discrepancy, and our measurement might not be the culprit. 

How about aerosols? Take our band centers as 373,  445, 508, 575. Patat aerosol estimate from 2011 would imply (see figure below) 

Image Added

Image Added