Subject: Re: What should be in the EXPOSURE map ?

Folks,

In real life I am not so sure about getting help from the Bible.
However, when it comes to FITS files I am quite religious in trying to 
live up
to (and get inspiration from) the HEASARC guidelines for fits standards.
http://heasarc.nasa.gov/docs/heasarc/ofwg/ofwg_recomm.html

As far as I read the 11th commandment, it says something like
"Thou shalt not have EXPOSURE in mm2 ...."
Please see:
http://heasarc.nasa.gov/docs/heasarc/ofwg/docs/ofwg_recomm/r11.html

Søren

Niels Lund wrote:
> Hello Stephane
>
> Jerome has raised the question "What is in the EXPOSURE map?"
> He noticed that the unit for this map is 'seconds', but that
> the peak value in the map does not correspond to the 
> 'EXPOSURE' seconds. I now checked the code a found that in
> fact I write for each pixel the number of square mm illuminated 
> from this sky position multiplied by some normalization factor.
> (The code is badly written at this point, first the map is
> defined as the product of the exposure time and the illuminated
> area (which I think is what is ultimately needed), and then
> the map is redefined a few lines later as just the illuminated
> area!)
>
> I now wonder if this current way to express the map is something
> you, Stephane, have requested to conform with other input to 
> 'Mosaic_Spec'?
> If this is the case we should not change the content but only
> the units to 'mm2'. Does Mosaic_Spec take the exposure time from
> the header information and multiply each pixel with this value?
>
> JEROME NOTE: In the new version of j_ima_iros now under development 
> the exposure map will include the effects of electronic efficiency.
> This will mean that the exposure map may vary (will vary!) from 
> one scw to the next and you must use the current exposure map in 
> your mosaic program like Stephane is doing, and not use the fixed 
> maps as you have been doing up to now!
>
> niels
>
>
>   

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