[Smwg] RE: Response for AI 2016-0408-22 (Sun Alignment Angle)

[Barkley, Erik J (3970)]

CSSM Colleagues,

To close out this action, based on the input received at the last telecon, attached please find the final presentation.    Note also that I propose that the Sun Alignment Angle be renamed to the Sun Separation Angle (SSA).

Best regards,

-Erik


From: Barkley, Erik J (3970)
Sent: Monday, May 09, 2016 2:00 PM
To: CCSDS Service Mgmt WG <smwg at mailman.ccsds.org>
Subject: Response for AI 2016-0408-22 (Sun Alignment Angle)

CSSM Colleagues,

At the Cleveland meetings, I took an action item to "Propose definition for sun alignment angle for planning book".

>From my perspective, the point of such a measurement is to indicate conjunction (in an angular sense, not radial) of a spacecraft that will potentially be tracked such that solar scintillation can be accounted for.    Too much solar scintillation and the tracking antenna and or the spacecraft can essentially be "blind" such that there really is no point in trying to communicate/track the spacecraft at that time.

I believe there are two options that can be considered. The first option and the one I prefer is with a topo-centric (or aperture) reference meaning the angle subtended from the sun to the spacecraft relative to the tracking antenna. Another option is a geocentric reference which I think is less accurate. I think this becomes more important when tracking is near to the horizon as the topo-centric reference will likely have the biggest difference relative to geocentric measurement at that time. The two pictures below illustrate the different scenarios for Earth-based tracking stations. For tracking station in space I think we in fact have no choice but to make this relative to the aperture.

Given the above, the proposed definition is something along the lines of "the predicted angular separation between the sun and the spacecraft at the indicated time, in reference to the tracking aperture".

As understand it, the important thing is not so much the alignment, but rather the separation, so perhaps this could be indicated as the Aperture-Sun-Separation Angle, but that may have an unfortunate abbreviation as in the <Bleep> angle.  So perhaps this could be the Sun-Separation Angle ?

Best regards,
-Erik


        [cid:image002.png at 01D1B04A.F5C82C60]













[cid:image005.png at 01D1B04A.F5C82C60]Option A: Preferred - Aperture/Topo-centric reference










Option B: Geo-centric reference
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.ccsds.org/pipermail/smwg/attachments/20160517/ff0acc30/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 4876 bytes
Desc: image001.png
URL: <http://mailman.ccsds.org/pipermail/smwg/attachments/20160517/ff0acc30/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.png
Type: image/png
Size: 6099 bytes
Desc: image002.png
URL: <http://mailman.ccsds.org/pipermail/smwg/attachments/20160517/ff0acc30/attachment-0001.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image003.png
Type: image/png
Size: 5881 bytes
Desc: image003.png
URL: <http://mailman.ccsds.org/pipermail/smwg/attachments/20160517/ff0acc30/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image005.png
Type: image/png
Size: 11112 bytes
Desc: image005.png
URL: <http://mailman.ccsds.org/pipermail/smwg/attachments/20160517/ff0acc30/attachment-0003.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: AI_Response-SunAlignmentAngle-090516-Rev-A.pptx
Type: application/vnd.openxmlformats-officedocument.presentationml.presentation
Size: 36732 bytes
Desc: AI_Response-SunAlignmentAngle-090516-Rev-A.pptx
URL: <http://mailman.ccsds.org/pipermail/smwg/attachments/20160517/ff0acc30/attachment.pptx>