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<DIV><SPAN class=752161916-10102005><FONT face=Arial color=#0000ff size=2>I'd
suggest we keep it in. One possible source for justification is the
discussion in this document (search for SEL2):</FONT></SPAN></DIV>
<DIV><SPAN class=752161916-10102005><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=752161916-10102005><FONT face=Arial color=#0000ff size=2><A
href="http://planetary.org/aimformars/study-report.pdf">http://planetary.org/aimformars/study-report.pdf</A></FONT></SPAN></DIV>
<DIV><SPAN class=752161916-10102005><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=752161916-10102005><FONT face=Arial color=#0000ff size=2>While
it appears some of this report has been overcome by events, it may be
enough justification for at least keeping the option open.</FONT></SPAN></DIV>
<DIV><SPAN class=752161916-10102005><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=752161916-10102005><FONT face=Arial color=#0000ff
size=2>Chris</FONT></SPAN></DIV>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV></DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><FONT
face=Tahoma size=2>-----Original Message-----<BR><B>From:</B>
sis-csi-bounces@mailman.ccsds.org [mailto:sis-csi-bounces@mailman.ccsds.org]
<B>On Behalf Of </B>Kearney, Mike<BR><B>Sent:</B> Monday, October 10, 2005
12:13 PM<BR><B>To:</B> Jason A. Soloff;
sis-csi@mailman.ccsds.org<BR><B>Subject:</B> RE: [Sis-csi] Limit of Cislunar
domain<BR><BR></FONT></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Aha! That makes
sense. So earth-moon L2 is clearly part of lunar mission infrastructure.
</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">I’m a little
concerned that if we include sun-earth L2, it begs the question about why
we’re doing that for cislunar missions (or maybe it is better to say for lunar
programs). Unless there is some indicator that there is some use for
lunar missions with relays out that far. But it’s hard to see why
sun-earth L-points would be part of a lunar infrastructure.
</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">We can always say, as
Keith said, that “10 seconds is a nice boundary”. Lunar infrastructure
that we know about is at ~3.5 seconds, so for “margin” for unanticipated
elements, we picked the next round number up, namely 10 sec. I favor
that, because if we list the sun-earth L2 points as a consideration for
cislunar, someone will challenge us to say what lunar mission stuff is out
there. Or maybe not. Actually, it’s probably not a big deal either
way. </SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Keith (Scott), I
think you need to decide first, whether we use the table (per my input in Sec
2), and second, if we do, whether we mention sun-earth L2 as justification for
the 10-second round-up. </SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<DIV>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"> -=-
Mike</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Mike
Kearney</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">NASA MSFC
EO-01</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">256-544-2029</SPAN></FONT></P></DIV>
<DIV>
<DIV class=MsoNormal style="TEXT-ALIGN: center" align=center><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">
<HR tabIndex=-1 align=center width="100%" SIZE=2>
</SPAN></FONT></DIV>
<P class=MsoNormal><B><FONT face=Tahoma size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">From:</SPAN></FONT></B><FONT
face=Tahoma size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma"> Jason
A. Soloff [mailto:jason.a.soloff@nasa.gov] <BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Sunday, October 09, 2005 10:57
PM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> Kearney, Mike;
sis-csi@mailman.ccsds.org<BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> RE: [Sis-csi] Limit of Cislunar
domain</SPAN></FONT></P></DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=blue size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: blue; FONT-FAMILY: Arial">Mike
-</SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=blue size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: blue; FONT-FAMILY: Arial">The thinking at
Earth-Moon L2 is to use a halo orbit that keeps Earth in view at the same time
it provides coverage to the lunar far-side. There are a number of these
orbits studied within Exploration as well as in the SCAWG. No decision
has been made whether or not to use the L2 halo orbit, but its a nice option
to have in your pocket...</SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=blue size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: blue; FONT-FAMILY: Arial">-
Jason</SPAN></FONT></P>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P></DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">____________________________________________</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">"It's kind of fun to do the
impossible." - Walt Disney</SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Jason A. Soloff</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Chief Engineer</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Exploration Communication &
Navigation Systems</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Constellation
Systems</SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">NASA / Goddard Space Flight
Center</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Code 567 / B19 /
S046</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Greenbelt, MD
20771</SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Phone:
(301)286-1368</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Blackberry:
(301)356-3708</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Fax:
(301)286-1750</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">E-Mail: <A
href="mailto:Jason.A.Soloff@nasa.gov">Jason.A.Soloff@nasa.gov</A></SPAN></FONT></P>
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style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P></DIV>
<BLOCKQUOTE
style="BORDER-RIGHT: medium none; PADDING-RIGHT: 0in; BORDER-TOP: medium none; PADDING-LEFT: 4pt; PADDING-BOTTOM: 0in; MARGIN: 5pt 0in 5pt 3.75pt; BORDER-LEFT: blue 1.5pt solid; PADDING-TOP: 0in; BORDER-BOTTOM: medium none">
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<DIV class=MsoNormal style="TEXT-ALIGN: center" align=center><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">
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</SPAN></FONT></DIV>
<P class=MsoNormal><B><FONT face=Tahoma size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">From:</SPAN></FONT></B><FONT
face=Tahoma size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma"> Keith
Hogie [mailto:Keith.Hogie@gsfc.nasa.gov] <BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Sunday, October 09, 2005 7:35
PM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> Krupiarz,
Christopher<BR><B><SPAN style="FONT-WEIGHT: bold">Cc:</SPAN></B> Kearney,
Mike; sis-csi@mailman.ccsds.org<BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> Re: [Sis-csi] Limit of
Cislunar domain</SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> I used the Sun/Earth L1/L2 values to give a
worst case boundary based on propagation delay. Technically they
are beyond the Moon's orbit but they are locations that are already being
used (e.g. SOHO, WMAP). I included them because their delay is not
real bad and you could probably still hold a voice converstation, run TCP,
or do something interactive over that sort of link. Once you get
beyond them, the next stop is pretty much Mars and those delays put you in a
whole different category. 10 seconds seemed to be a nice boundary that
also fit with locations being used. <BR><BR> I didn't worry
about the Lunar Lagrange points since they are not that far from the
Moon. It looks like they are 61,500 Km away from the Moon. I was
listing delays from an Earth centric view which probably fits with
Cislunar. I guess the question is whether we want to stick to purely
Cislunar at 2.5 seconds or if we want to stretch to Sun/Earth L1/L2 which
would cover anything out to 10 seconds. <BR><BR>Keith
Hogie<BR><BR></SPAN></FONT></P>
<DIV class=MsoNormal style="TEXT-ALIGN: center" align=center><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">
<HR tabIndex=-1 align=center width="100%" SIZE=2>
</SPAN></FONT></DIV>
<P class=MsoNormal style="MARGIN-BOTTOM: 12pt"><B><FONT face=Tahoma
size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">From:</SPAN></FONT></B><FONT
face=Tahoma size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">
sis-csi-bounces@mailman.ccsds.org [mailto:sis-csi-bounces@mailman.ccsds.org]
<B><SPAN style="FONT-WEIGHT: bold">On Behalf Of </SPAN></B>Kearney,
Mike<BR><B><SPAN style="FONT-WEIGHT: bold">Sent:</SPAN></B> Sunday, October
09, 2005 9:18 AM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B>
sis-csi@mailman.ccsds.org<BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> RE: [Sis-csi] Limit of
Cislunar domain</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">I was thinking the
implication was that if L2 is on the far side, it’s not in line-of-sight of
earth. I think that’s the reason radio telescope projects have been
talked about for L2, because the moon shields them from earth’s RF noise.
And if the comm relay at L2 is not in RF line-of-sight, then another
relay would be needed anyway. But I’m not a celestial mechanics guy,
I’m just going from diagrams I’ve seen. </SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">In any case, I
think it’s safe to say that lunar missions could have some TBD elements at
L2, hence extending our definition of Cislunar to that point.
</SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">But another source
says that L2 is 92,000 Km past the moon.</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><A
href="http://www.projectpluto.com/interest.htm">http://www.projectpluto.com/interest.htm</A></SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">The earth-moon
distance is 385,000 Km, and the round trip time delay for earth-moon is 2.5
sec, I would think that the L2 round trip time would be only 3.5 sec or
so. Not the 10 sec in your table. </SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">385+92= 477,000 Km
for earth-moon L2, not the 1,500,000 Km that you listed. I wonder if
you got the distance for earth-sun L2 instead of earth-moon L2?
</SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">I’m still confused
about who wrote this table up to begin with. Was it Chris or Keith
(Hogie)? It’s a great way to define the cislunar domain, IMHO, anyway.
</SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<DIV>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"> -=-
Mike</SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Mike
Kearney</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">NASA MSFC
EO-01</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">256-544-2029</SPAN></FONT></P></DIV>
<DIV>
<DIV class=MsoNormal style="TEXT-ALIGN: center" align=center><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">
<HR tabIndex=-1 align=center width="100%" SIZE=2>
</SPAN></FONT></DIV>
<P class=MsoNormal><B><FONT face=Tahoma size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">From:</SPAN></FONT></B><FONT
face=Tahoma size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">
Krupiarz, Christopher [mailto:Christopher.Krupiarz@jhuapl.edu] <BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Saturday, October 08, 2005 10:15
PM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> Kearney, Mike;
sis-csi@mailman.ccsds.org<BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> RE: [Sis-csi] Limit of
Cislunar domain</SPAN></FONT></P></DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<P style="MARGIN-BOTTOM: 12pt"><FONT face="Times New Roman" size=2><SPAN
style="FONT-SIZE: 10pt">Mike,<BR><BR>L2 being on the far side of the Moon is
what makes it nice as a comm relay for assets that are also on the far
side. I'm not sure about L4 and L5, but I'm with you about not being
confident in my knowledge of how these points could be used. Off-hand
if you're using relays to save power/mass on a lander, it would seem using
L4 & L5 wouldn't help much. However, L4 & L5 would give some
coverage of the far side. <BR><BR>Chris<BR><BR><BR>-----Original
Message-----<BR>From: sis-csi-bounces@mailman.ccsds.org on behalf of
Kearney, Mike<BR>Sent: Sat 10/8/2005 10:10 PM<BR>To:
sis-csi@mailman.ccsds.org<BR>Subject: RE: [Sis-csi] Limit of Cislunar
domain<BR><BR>Keith (Hogie): I was plugging your table below into
section 2...<BR><BR><BR><BR>0000.1 sec - Interaction between rovers,
landers, (e.g. local<BR>environment)<BR>0000.1 sec - Low-Earth orbit (
a few hundred kilometers one-way)<BR>0000.1 sec - Low-Lunar orbit ( a few
hundred kilometers one-way)<BR>0000.1 sec - Low-Mars orbit ( a
few hundred kilometers one-way)<BR>0000.5 sec - Earth geosync orbit
(36,000 kilometers one-way)<BR>0002.5 sec - Earth-to-Moon (384,000
kilometers one-way)<BR>0010.0 sec - Earth to L1 or L2 (1,500,000 kilometers
one-way)<BR>------------------Limit of Cislunar domain<BR>0366.0 sec - Earth
to Mars (closest = 55.000.000 kilometers one-way, 6<BR>minute,
RTT)<BR>2673.0 sec - Earth to Mars (farthest = 401,000,000 kilometers
one-way,<BR>45 minute RTT)<BR><BR><BR><BR>But I started wondering about the
usage of L1 and L2. L1 is closer to<BR>earth than the moon, so it
would really not be a factor in establishing<BR>the boundary of cislunar
missions in terms of time delay. L2 is on the<BR>far side of the moon
and wouldn't have much value for comm relays. Did<BR>you have some
other mission in mind? <BR><BR><BR><BR>In terms of comm relays, I was
wondering if L4 or L5 (preceding or<BR>following the moon in earth orbit)
have more value as comm relays. And<BR>I started wondering if anyone
what Exploration was considering as<BR>possible uses for those Lagrangian
points. I'm not confident in my<BR>understanding, and I just want
whatever text that goes into the Cislunar<BR>GB to be
credible. <BR><BR><BR><BR>Anyone have any insight into
that? <BR><BR><BR><BR>I ask the question, because a better description
of what might be done<BR>at the Lagrangian points would help the "mission
characteristics"<BR>section. <BR><BR><BR><BR> -=-
Mike<BR><BR><BR><BR>Mike Kearney<BR><BR>NASA MSFC
EO-01<BR><BR>256-544-2029<BR><BR>________________________________<BR><BR>From:
sis-csi-bounces@mailman.ccsds.org<BR>[<A
href="mailto:sis-csi-bounces@mailman.ccsds.org">mailto:sis-csi-bounces@mailman.ccsds.org</A>]
On Behalf Of Keith Hogie<BR>Sent: Thursday, September 08, 2005 12:55
AM<BR>Cc: sis-csi@mailman.ccsds.org<BR>Subject: Re: [Sis-csi] IP Header
Compression<BR><BR><BR><BR>Adrian J. Hooke wrote:<BR><BR>At 01:40 PM
9/6/2005, Keith Hogie wrote:<BR><BR><BR><BR> I agree we need to
consider issues with small packets and low rates,<BR>but how low do we need
to go. In all of the missions I have seen (non<BR>deep space), the
lowest data rates are 125 bps. This is over an order<BR>of magnitude
difference from your 10 bps. <BR><BR> For the Cislunar
environment, we need to figure out what some of our<BR>limits are. Do
we really want to burden the Cislunar design with issues<BR>that only relate
to Deep Space?<BR><BR><BR>Aren't the Lunar missions supposed to be
"training" for going to Mars?<BR>For critical emergency commanding
operations, shouldn't we be developing<BR>a robust, unified, reliable,
tested system that works wherever you go?<BR><BR><BR> For emergency
commanding I don't see any difference between Cislunar<BR>or Deep
Space. In both cases the solution is to send a string of bits<BR>that
gets decoded by hardware and do not need any protocol. The<BR>critical
hardware commands are their own frame sync, authentication, and<BR>command
all packed into a highly unique string of bits. Most
hardware<BR>decoders pick off the bits they are looking at directly from
the<BR>receiver and don't involve any flight software. This means that
there<BR>is no complex packet processing and the hardware is just looking
for<BR>particular sequence of bits. The length of this sequence is not
a<BR>function of any CCSDS or IP headers. Getting the command to
the<BR>spacecraft just requires radiating the proper string of bits.
The<BR>length of the hardware command is just a function of how many bits
you<BR>think you need to make sure your command doesn't occur in normal
data<BR>transfers. <BR><BR> My main concern is for all the other
operational modes there is a very<BR>large disconnect between things that
will work in a Cislunar environment<BR>and a long haul link to Mars.
If you consider the following round trip<BR>times (RTT):<BR><BR>0000.1 sec -
Interaction between rovers, landers, (e.g. local<BR>environment)<BR>0000.1
sec - Low-Earth orbit ( a few hundred kilometers one-way)<BR>0000.1
sec - Low-Lunar orbit ( a few hundred kilometers one-way)<BR>0000.1 sec -
Low-Mars orbit ( a few hundred kilometers one-way)<BR>0000.5 sec
- Earth geosync orbit (36,000 kilometers one-way)<BR>0002.5 sec -
Earth-to-Moon (384,000 kilometers one-way)<BR>0010.0 sec - Earth to L1 or L2
(1,500,000 kilometers one-way)<BR>------------------Limit of Cislunar
domain<BR>0366.0 sec - Earth to Mars (closest = 55.000.000 kilometers
one-way, 6<BR>minute, RTT)<BR>2673.0 sec - Earth to Mars (farthest =
401,000,000 kilometers one-way,<BR>45 minute RTT)<BR><BR> When you
look at distances like these there is a huge break between<BR>Cislunar ones
and Mars. In the Cislunar area it is actually possible<BR>to do
interactive things like interactive audio, video, and data access.<BR>You
can consider security protocols that negotiate security details.
At<BR>L1 and L2 things get a bit uncomfortable at 10 seconds RTT but that
is<BR>still manageable. At Lunar distances you can do most anything
you do on<BR>Earth. A 2.5 second delay is a bit long for some
interactive operations<BR>but it is not really any longer than what happens
when you surf the open<BR>Internet and hit a bit of congestion. The
main point is that out to L1<BR>and L2 you can actually do interactive
operations This also applies to<BR>systems on Mars and orbiting around
Mars. <BR><BR> However, when you move to the long haul link
between Earth and Mars,<BR>the RTT jumps up to over 100 or 1,000 times that
of the Earth and Moon.<BR>With a 6 to 45 minute RTT, you can't carry on an
interactive voice or<BR>video conversation and lots of interactive data
access just doesn't<BR>work. On a Earth-to-Mars link you are forced to
shift to an operations<BR>concept of two one-way links. Operations
must shift into email-like<BR>file store-and-forward or one-way streaming of
data. <BR><BR> So I don't see any real problem with using
the same hardware<BR>commanding solution in Cislunar or Earth-to-Mars
scenarios. Some file<BR>store-and-forward and one-way streaming
operations will also work for<BR>both environments. Of course any
acknowledgments on the file-store-and<BR>forward will take lots
longer. <BR><BR> My concern is that other there are lots of
protocols and applications<BR>that will work fine in an interactive Cislunar
environment but just<BR>don't work for Earth-to-Mars. We don't want to
limit our Cislunar<BR>solutions to only those that will also work for
Earth-to-Mars. I think<BR>we need to develop our Cislunar solutions
and then see if any of them<BR>will also work in a Earth-to-Mars
scenario. <BR><BR><BR><BR>----------------------------------------------------------------------<BR>
Keith
Hogie
e-mail: Keith.Hogie@gsfc.nasa.gov<BR> Computer Sciences
Corp. office: 301-794-2999 fax:
301-794-9480<BR> 7700 Hubble Dr.<BR> Lanham-Seabrook, MD
20706 USA 301-286-3203 @
NASA/Goddard<BR>----------------------------------------------------------------------</SPAN></FONT></P></BLOCKQUOTE></DIV></BLOCKQUOTE></BODY></HTML>