<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style><![endif]--><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
p
{mso-style-priority:99;
mso-margin-top-alt:auto;
margin-right:0in;
mso-margin-bottom-alt:auto;
margin-left:0in;
font-size:12.0pt;
font-family:"Times New Roman",serif;}
span.EmailStyle18
{mso-style-type:personal;
font-family:"Calibri",sans-serif;
color:windowtext;}
span.EmailStyle19
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1028" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-US" link="#0563C1" vlink="#954F72">
<div class="WordSection1">
<p class="MsoNormal"><span style="color:#1F497D">CSSM Colleagues,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">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).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Best regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">-Erik<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>From:</b> Barkley, Erik J (3970) <br>
<b>Sent:</b> Monday, May 09, 2016 2:00 PM<br>
<b>To:</b> CCSDS Service Mgmt WG <smwg@mailman.ccsds.org><br>
<b>Subject:</b> Response for AI 2016-0408-22 (Sun Alignment Angle) <o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">CSSM Colleagues,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">At the Cleveland meetings, I took an action item to "Propose definition for sun alignment angle for planning book”.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">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.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">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.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">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".<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">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 ?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best regards,<o:p></o:p></p>
<p class="MsoNormal">-Erik <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><!--[if gte vml 1]><v:shapetype id="_x0000_t75" coordsize="21600,21600" o:spt="75" o:preferrelative="t" path="m@4@5l@4@11@9@11@9@5xe" filled="f" stroked="f">
<v:stroke joinstyle="miter" />
<v:formulas>
<v:f eqn="if lineDrawn pixelLineWidth 0" />
<v:f eqn="sum @0 1 0" />
<v:f eqn="sum 0 0 @1" />
<v:f eqn="prod @2 1 2" />
<v:f eqn="prod @3 21600 pixelWidth" />
<v:f eqn="prod @3 21600 pixelHeight" />
<v:f eqn="sum @0 0 1" />
<v:f eqn="prod @6 1 2" />
<v:f eqn="prod @7 21600 pixelWidth" />
<v:f eqn="sum @8 21600 0" />
<v:f eqn="prod @7 21600 pixelHeight" />
<v:f eqn="sum @10 21600 0" />
</v:formulas>
<v:path o:extrusionok="f" gradientshapeok="t" o:connecttype="rect" />
<o:lock v:ext="edit" aspectratio="t" />
</v:shapetype><v:shape id="Group_x0020_25" o:spid="_x0000_s1026" type="#_x0000_t75" style='position:absolute;margin-left:15.85pt;margin-top:11.7pt;width:121.55pt;height:123.05pt;z-index:251659264;visibility:visible;mso-width-percent:0;mso-height-percent:0;mso-wrap-distance-left:9pt;mso-wrap-distance-top:0;mso-wrap-distance-right:9pt;mso-wrap-distance-bottom:0;mso-position-horizontal:absolute;mso-position-horizontal-relative:text;mso-position-vertical:absolute;mso-position-vertical-relative:text;mso-width-percent:0;mso-height-percent:0;mso-width-relative:margin;mso-height-relative:margin'>
<v:imagedata src="cid:image001.png@01D1B04A.F5C82C60" o:title="" cropright="-27f" />
<o:lock v:ext="edit" aspectratio="f" />
</v:shape><![endif]--><![if !vml]><span style="mso-ignore:vglayout">
<table cellpadding="0" cellspacing="0" align="left">
<tbody>
<tr>
<td width="21" height="16"></td>
</tr>
<tr>
<td></td>
<td><img width="162" height="164" src="cid:image002.png@01D1B04A.F5C82C60" v:shapes="Group_x0020_25"></td>
</tr>
</tbody>
</table>
</span><![endif]><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<br style="mso-ignore:vglayout" clear="ALL">
<p class="MsoNormal"><!--[if gte vml 1]><v:shape id="Group_x0020_21" o:spid="_x0000_s1027" type="#_x0000_t75" style='position:absolute;margin-left:2.8pt;margin-top:31.8pt;width:107.55pt;height:102pt;z-index:251661312;visibility:visible;mso-width-percent:0;mso-height-percent:0;mso-wrap-distance-left:9pt;mso-wrap-distance-top:0;mso-wrap-distance-right:9pt;mso-wrap-distance-bottom:0;mso-position-horizontal:absolute;mso-position-horizontal-relative:text;mso-position-vertical:absolute;mso-position-vertical-relative:text;mso-width-percent:0;mso-height-percent:0;mso-width-relative:margin;mso-height-relative:margin'>
<v:imagedata src="cid:image003.png@01D1B04A.F5C82C60" o:title="" cropright="-153f" />
<o:lock v:ext="edit" aspectratio="f" />
</v:shape><![endif]--><![if !vml]><span style="mso-ignore:vglayout;position:absolute;z-index:251661312;margin-left:4px;margin-top:42px;width:143px;height:136px"><img width="143" height="136" src="cid:image005.png@01D1B04A.F5C82C60" v:shapes="Group_x0020_21"></span><![endif]>Option
A: Preferred – Aperture/Topo-centric reference<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Option B: Geo-centric reference<o:p></o:p></p>
</div>
</body>
</html>