[Spice_discussion] Re: Subsolar independent of observer

michael.aye at space.unibe.ch michael.aye at space.unibe.ch
Sun Apr 22 16:32:09 PDT 2012

I found one solution that kinda works with using subslr function:

If I set the parameter 'abcorr' of the subslr function to 'NONE' I can use any other standard solar system body as observer and will get the same answer for the subsolar point coordinates.
This method works apart from one drawback: I have to NOT choose the target body as observer, which means I can not hardcode just 'EARTH' in that lookup for the rare case I actually want the subsolar point on the Earth, but instead I need to keep a list of bodies and check if target and obs are  the same and if yes, take the next one in the list as observer.

Maybe there's a more elegant solution?

Best regards,

On 23 Apr 2012, at 01:20, Aye, Klaus-Michael (SPACE) wrote:

> Dear all,
> I was wondering if there is not a way to determine the subsolar coordinates on a body independent of an observer?
> If I understand things correctly, it is not ambiguous to ask at a given time 'et' which coordinate of a body is sub-solar?
> The reason why I need this, is that I would like to stay away from observer kernels and light-time corrections as long as possible and only concentrate on local illumination scenarios at given times. Basically, 'I' am on the body's surface and I want to know now and 'here', where is the sub-solar point?
> Best regards,
> Michael

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