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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Thanks for the detailed notes. I’ll try to add some comments / answers below<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal">Felix<o:p></o:p></p>
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<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> SIS-DTN <sis-dtn-bounces@mailman.ccsds.org>
<b>On Behalf Of </b>sburleig.sb--- via SIS-DTN<br>
<b>Sent:</b> 13 February 2023 19:19<br>
<b>To:</b> 'Sanchez Net, Marc (US 332H)' <marc.sanchez.net@jpl.nasa.gov>; sis-dtn@mailman.ccsds.org<br>
<b>Subject:</b> Re: [Sis-dtn] Notes from the NASA DTN F2F Meeting<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US">Marc, thanks for sending this on.  A couple of thoughts in-line below.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US">Scott<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> SIS-DTN <<a href="mailto:sis-dtn-bounces@mailman.ccsds.org">sis-dtn-bounces@mailman.ccsds.org</a>>
<b>On Behalf Of </b>Sanchez Net, Marc (US 332H) via SIS-DTN<br>
<b>Sent:</b> Monday, February 13, 2023 9:10 AM<br>
<b>To:</b> <a href="mailto:sis-dtn@mailman.ccsds.org">sis-dtn@mailman.ccsds.org</a><br>
<b>Subject:</b> [Sis-dtn] Notes from the NASA DTN F2F Meeting<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US">Hi All,<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US">Here are the notes/questions for the SIS-DTN WG that I recorded at the NASA DTN face-to-face meeting.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoListParagraph" style="margin-left:72.0pt;text-indent:-18.0pt;mso-list:l1 level1 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-family:Symbol"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">        
</span></span></span><![endif]><span lang="EN-US">BPv7<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:108.0pt;text-indent:-18.0pt;mso-list:l1 level2 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-family:"Courier New""><span style="mso-list:Ignore">o<span style="font:7.0pt "Times New Roman"">  
</span></span></span><![endif]><span lang="EN-US">Leigh Torgerson pointed out that in the assumptions of the proposed RTP book there is the following statement: “<i>arbitrary bundle sizes—the multicast mechanism must not impose arbitrary limits that are less
 than the maximum bundle size on the size of bundles.”</i>. The question then becomes whether having a bundle size (10 MB) in the spec restricts other specifications in any way.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:108.0pt;text-indent:-18.0pt;mso-list:l1 level2 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-family:"Courier New""><span style="mso-list:Ignore">o<span style="font:7.0pt "Times New Roman"">  
</span></span></span><![endif]><span lang="EN-US">Should we add a requirement (maybe a “should” rather than a “shall”) for CLAs to notify BP when transmission with that CLA is possible? This would provide minimal indication of whether transmission via a CLA
 is possible.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:72.0pt;text-indent:-18.0pt;mso-list:l0 level1 lfo2">
<![if !supportLists]><span lang="EN-US" style="font-family:Wingdings"><span style="mso-list:Ignore">Ø<span style="font:7.0pt "Times New Roman""> 
</span></span></span><![endif]><span lang="EN-US">Would this be a requirement that implementations would have to satisfy in order to be considered BPv7 compliant?  Isn’t it strictly an implementation consideration?  How would it contribute to interoperability?<br>
<b><span style="color:#70AD47">FF: What would be the exact semantics of ‘transmission is possible’? It may depend on the implementation and the specific CLA. It could mean, I am ready to take it into an internal queue, I actually have already established a
 connection (for connection-oriented CLA), I take it and sent it but there is no guarantee, …<br>
Although it seems useful, it might be difficult to define it in a generic way and certainly implementations may have their own strategies (eg., we have a ready to send flag but also activation and connection states and can report when a bundle left the full
 stack). So, I would currently treat it as an implementation matter.</span></b><o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:108.0pt;text-indent:-18.0pt;mso-list:l1 level2 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-family:"Courier New""><span style="mso-list:Ignore">o<span style="font:7.0pt "Times New Roman"">  
</span></span></span><![endif]><span lang="EN-US">Compressed Bundle Reporting:<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:144.0pt;text-indent:-18.0pt;mso-list:l1 level3 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-family:Wingdings"><span style="mso-list:Ignore">§<span style="font:7.0pt "Times New Roman""> 
</span></span></span><![endif]><span lang="EN-US">How that CBR handle bundle fragmentation?<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:72.0pt;text-indent:-18.0pt;mso-list:l0 level1 lfo2">
<![if !supportLists]><span lang="EN-US" style="font-family:Wingdings"><span style="mso-list:Ignore">Ø<span style="font:7.0pt "Times New Roman""> 
</span></span></span><![endif]><span lang="EN-US">I would think that fragmentary bundles are simply bundles; they should be reported to the nodes that created them, that is, the nodes that generated the fragments.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:72.0pt"><b><span lang="EN-US" style="color:#70AD47">FF: 1. We should avoid fragmentation as much as possible! For CREB I would specify that the block has to be replicated in *one* fragment and set the block processing
 control flags to not replicate in each fragment. Thus, reporting can only happen once the complete bundle is re-assembled. Independent CREB can be inserted into the fragments themselves but these are completely independent from the CREBs in the unfragmented
 bundle (everything else seem to get very ugly and comples).<o:p></o:p></span></b></p>
<p class="MsoListParagraph" style="margin-left:144.0pt;text-indent:-18.0pt;mso-list:l1 level3 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-family:Wingdings"><span style="mso-list:Ignore">§<span style="font:7.0pt "Times New Roman""> 
</span></span></span><![endif]><span lang="EN-US">Why do we need CBR to define a new extension block with the FSN and flow sequence? PACE is using the service numbers in the transmit EID as the FSN, so they are able to uniquely identify flows and bundles within
 the flow without having an extension block.<br>
<b><span style="color:#70AD47">FF: Maybe Flow ID is not a good term but we need something like this for flexibility. The Flow ID can be used to enable efficient reporting in specific network set-ups. E.g., if you would just use the service number and you would
 have two destinations with different node numbers but same service number and would send alternating to both of them, the reports would not compress well (or you would need to add node numbers); you could have similar situations in case you would sent to different
 next hops at the same time and want to have reception reporting from those. Service numbers are more an E2E thing.</span></b><o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:144.0pt;text-indent:-18.0pt;mso-list:l1 level3 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-family:Wingdings"><span style="mso-list:Ignore">§<span style="font:7.0pt "Times New Roman""> 
</span></span></span><![endif]><span lang="EN-US">Should we have a dedicated reporting mechanism for bundle expiration?<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:144.0pt"><span lang="EN-US" style="color:#70AD47">FF: We have bundle deletion; this covers it (+ maybe next answer).<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:144.0pt;text-indent:-18.0pt;mso-list:l1 level3 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-family:Wingdings"><span style="mso-list:Ignore">§<span style="font:7.0pt "Times New Roman""> 
</span></span></span><![endif]><span lang="EN-US">Can we make bundle reporting extensible so that missions have the ability to have their reporting reasons?<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:144.0pt"><b><span lang="EN-US" style="color:#70AD47">FF: I guess we could simply add an optional text string to each report array. However, I would not standardize the content and it would be mission (or Agency specific).
 I would hope that we could get some interoperable failure reporting via Network Management.<o:p></o:p></span></b></p>
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</span></span></span><![endif]><b><span lang="EN-US" style="color:#70AD47">LTPv2 (FF:
<a id="OWAAM740D41DDDAE84D149B7E185CEC010CC5" href="mailto:jpmayer@gmv.com"><span style="font-family:"Calibri",sans-serif;color:#70AD47;text-decoration:none">@Jeremy Pierce Mayer</span></a>: Please correct me if I am wrong).</span></b><b><span lang="EN-US"><o:p></o:p></span></b></p>
<p class="MsoListParagraph" style="margin-left:108.0pt;text-indent:-18.0pt;mso-list:l1 level2 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-family:"Courier New""><span style="mso-list:Ignore">o<span style="font:7.0pt "Times New Roman"">  
</span></span></span><![endif]><span lang="EN-US">Will LTPv2 have a way to signal to the receiver the size of the LTP block? This would facilitate memory allocation at the receiver.<br>
<b><span style="color:#70AD47">FF: Yes, block size included in all segment.</span></b><o:p></o:p></span></p>
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</span></span></span><![endif]><span lang="EN-US">Will LTPv2 have a “hook” to get notified when the underlying link is down. This can be used to pause timers, etc.<br>
<b><span style="color:#70AD47">FF: Yes, similar to Rx/Tx Opportunity Windows in CFDP I would propose.</span></b><o:p></o:p></span></p>
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</span></span></span><![endif]><span lang="EN-US">Will LTPv2 have a way to aggregate report segments and report segment acknowledgements to reduce overhead?<o:p></o:p></span></p>
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</span></span></span><![endif]><span lang="EN-US">Will LTPv2 have a ping mechanism for the tx/rx engines to assess whether the link is running?<br>
<b><span style="color:#70AD47">FF: No, I think the Opportunity Window mechanism should be enough and that should be fed by ‘the environment’ (e.g if there is bitlock).</span></b><o:p></o:p></span></p>
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</span></span></span><![endif]><span lang="EN-US">Will LTPv2 have a concept of transmission deadline, which causes the tx to stop sending a block if it is not available at the destination by a certain moment? This could be used in conjunction with the bundle
 lifetime to cancel LTPv2 sessions proactively.<br>
<b><span style="color:#70AD47">FF: No, but cancel can be requested. </span></b><o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:108.0pt;text-indent:-18.0pt;mso-list:l1 level2 lfo1">
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</span></span></span><![endif]><span lang="EN-US">APL has reported the following issues related to LTP that we way want to consider in LTPv2<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:144.0pt;text-indent:-18.0pt;mso-list:l1 level3 lfo1">
<![if !supportLists]><span lang="EN-US" style="font-family:Wingdings"><span style="mso-list:Ignore">§<span style="font:7.0pt "Times New Roman""> 
</span></span></span><![endif]><span lang="EN-US">Unspecified behavior that allows a memory leak and provide a method of denial-of-service attack. See
<a href="https://eur05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnasa%2FHDTN%2Fissues%2F19&data=05%7C01%7CFelix.Flentge%40esa.int%7C508617eb5c734acb263308db0deedf7c%7C9a5cacd02bef4dd7ac5c7ebe1f54f495%7C0%7C0%7C638119091828391986%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=jCGSrsoYTmFb0wmdoW3ZupiFnvtv3NQ8WyPUWl2IfR0%3D&reserved=0">
https://github.com/nasa/HDTN/issues/19</a><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:144.0pt"><b><span lang="EN-US" style="color:#70AD47">FF:
</span></b><b><span lang="EN-US" style="color:#70AD47">Yes, we should have session timeouts.</span></b><b><span lang="EN-US"><o:p></o:p></span></b></p>
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</span></span></span><![endif]><span lang="EN-US">LTP should guarantee that a reception report is sent when all data is received, not necessarily in response to a checkpoint. See
<a href="https://eur05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnasa%2FHDTN%2Fissues%2F23&data=05%7C01%7CFelix.Flentge%40esa.int%7C508617eb5c734acb263308db0deedf7c%7C9a5cacd02bef4dd7ac5c7ebe1f54f495%7C0%7C0%7C638119091828391986%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=tIX8%2B%2B4h1JdcDDFg5%2FP7Q8WPc6gHUgqIhXOVZifGjqg%3D&reserved=0">
https://github.com/nasa/HDTN/issues/23</a> <o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:144.0pt"><b><span lang="EN-US" style="color:#70AD47">FF:
</span></b><b><span lang="EN-US" style="color:#70AD47">OK, I know we discussed session close behavior which should cover this (Jeremy to confirm).<o:p></o:p></span></b></p>
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</span></span></span><![endif]><span lang="EN-US">LTP should allow the transmit engine to delay sending data segments or reports long enough to receive out-of-order segments that would affect the retransmission behavior. See
<a href="https://eur05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnasa%2FHDTN%2Fissues%2F22&data=05%7C01%7CFelix.Flentge%40esa.int%7C508617eb5c734acb263308db0deedf7c%7C9a5cacd02bef4dd7ac5c7ebe1f54f495%7C0%7C0%7C638119091828391986%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=BVeStvbQqGJTIq7VPqCA4INB6GVh5z6K%2FlsTqBwwGUw%3D&reserved=0">
https://github.com/nasa/HDTN/issues/22</a> and <a href="https://eur05.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnasa%2FHDTN%2Fissues%2F24&data=05%7C01%7CFelix.Flentge%40esa.int%7C508617eb5c734acb263308db0deedf7c%7C9a5cacd02bef4dd7ac5c7ebe1f54f495%7C0%7C0%7C638119091828391986%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=iZD%2FsgFPBgcSIAo206ZmG6GNJxKpwGiC0y12UQsr2r4%3D&reserved=0">
https://github.com/nasa/HDTN/issues/24</a>. <o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:144.0pt"><b><span lang="EN-US" style="color:#70AD47">FF:
</span></b><b><span lang="EN-US" style="color:#70AD47">Yeah, I see similar issues with CFDP (in particular, if we use different bands). Not sure whether we should have this as part of the standard or keep it as implementation matter (like currently for CFDP).
 At least, we could put corresponding notes in the standard (it may not even be based on timeouts but also other mechanisms).</span></b><b><span lang="EN-US"><o:p></o:p></span></b></p>
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</span></span></span><![endif]><span lang="EN-US">Others wishes from the community<o:p></o:p></span></p>
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</span></span></span><![endif]><span lang="EN-US">DTN multicast<o:p></o:p></span></p>
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</span></span></span><![endif]><span lang="EN-US">Provide mechanisms for in-order delivery, lack of gaps, and lack of duplicates (similar to DTPC, but more modular, any possibly not end-to-end)<o:p></o:p></span></p>
<p class="MsoListParagraph" style="margin-left:72.0pt;text-indent:-18.0pt;mso-list:l0 level1 lfo2">
<![if !supportLists]><span lang="EN-US" style="font-family:Wingdings"><span style="mso-list:Ignore">Ø<span style="font:7.0pt "Times New Roman""> 
</span></span></span><![endif]><span lang="EN-US">Having more options on the DTPC feature menu has been an open item for many years.  DTPC is just a prototocol that ought to be stackable like any other protocol.  If the DTPC spec says that the layer above it
 can only be the end-to-end user application, then the spec should be revised.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:54.0pt"><b><span lang="EN-US" style="color:#70AD47">FF: We should also analyse what could be achieved with CBR Delivery Reports.<o:p></o:p></span></b></p>
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</span></span></span><![endif]><span lang="EN-US">Standard CCSDS format for contact plans<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:72.0pt"><b><span lang="EN-US" style="color:#70AD47">FF: Can we build on existing standards like the simple schedule format?<o:p></o:p></span></b></p>
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</span></span></span><![endif]><span lang="EN-US">DNS-like service to avoid having to manually rely on IANA/SANA registries.<o:p></o:p></span></p>
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</span></span></span><![endif]><span lang="EN-US">Stream of video/voice via DTN. KPLO used a non-standard version of BSSP and yet SIS-MIA might be working on RTP over DTN.<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:72.0pt"><b><span lang="EN-US" style="color:#70AD47">FF: I am not a fan of the ‘unreliable / reliable’ channel approach in BSSP. We are looking into doing something like this just using LTP red. Without errors, we should
 have the data as fast as with green (no need to close the session before presenting it); if there are errors, we are protected by re-transmission (and would just store and not present). Out-of-order can be detected by bundle timestamps. One disadvantage may
 be that it is tight to LTP (so, even for terrestrial use) but I would not see an issue with just using LTP/UDP. Bundle streaming over LTP should even be fine for multi-hop if we can define bundle priorities (another wish).<o:p></o:p></span></b></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US">-----------------------------------------------------------------------------------------------------------------------<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US">Marc Sanchez Net (332H)<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US" style="font-size:10.0pt;color:gray">Telecommunications Engineer</span><span lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt;background:white"><span lang="EN-US" style="font-size:10.0pt;color:gray">Jet Propulsion Laboratory<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt;background:white"><span lang="EN-US" style="font-size:10.0pt;color:gray">Cell:</span><span lang="EN-US" style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#222222"> </span><span lang="EN-US" style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black"><a href="mailto:(617)%20953-7977">(617)
 953-7977</a></span><span lang="EN-US" style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#0070C0">
</span><span lang="EN-US" style="font-size:10.0pt;color:gray">|</span><span lang="EN-US" style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#0070C0">
</span><span lang="EN-US" style="font-size:10.0pt;color:gray">Email:</span><span lang="EN-US" style="font-size:10.0pt;font-family:"Arial",sans-serif;color:#222222"> </span><span lang="EN-US" style="color:black"><a href="mailto:marc.sanchez.net@jpl.nasa.gov"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:blue">marc.sanchez.net@jpl.nasa.gov</span></a></span><span lang="EN-US" style="font-size:9.5pt;font-family:"Arial",sans-serif;color:#222222"><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US">-----------------------------------------------------------------------------------------------------------------------<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span lang="EN-US"><o:p> </o:p></span></p>
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