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desihub / specsim

Quick simulations of spectrograph response
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Implement flexible sky model #2

Open dkirkby opened 9 years ago

dkirkby commented 9 years ago

We currently have fixed sky surface brightness lookup tables for "dark", "grey" and "bright" conditions. This feature request is to synthesize a more realistic sky based on the observing conditions, taking into account the relative positions of the observing field, the moon, the sun, the galaxy, etc.

moustakas commented 9 years ago

Another useful dimension would be all of the above (but especially grey & bright conditions) with cirrus. This is something the BGS Working Group has discussed, with the interested parties being Connie Rockosi and Jim Annis. Jim in particular sent around some broadband sky measurements as a function of moon phase and transparency (I think....) which might be useful. Besides BGS, this added realism would also be very relevant for the (bright-time) Milky Way survey group.

dkirkby commented 9 years ago

I guess cirrus contributes to the extinction and emission (via scattering) and imprints some degree-scale structure over the FOV? That sounds complicated, but its good to have it on the list if we are planning to observe in cirrus conditions.

dkirkby commented 9 years ago

@moustakas Is Jim Annis' cirrus sky info online somewhere?

moustakas commented 9 years ago

I don't believe so; I will reach out to him.

crockosi commented 9 years ago

There is an implementation of the Krisciunas & Schaefer (1991) lunar model in the idl version of quicksim. The output is a solar spectrum scaled to give the surface brightness moon value predicted by the model. I've verified that the code reproduces the K&S 1991 data more than 30 degrees from the moon. The code is in desimodel/pro/lunarmodel.pro

dkirkby commented 8 years ago

Here is a public link to the IDL code and the K&S paper is here.

sbailey commented 8 years ago

To make it an explicit part of the ticket: this flexible sky model should include the airmass dependency of the airglow, even when the moon is down. We should get this in before using specsim for the full survey data challenge.