[Sis-csi] Handovers (was: RE: CCSDS Cislunar Telecon)

[Kearney, Mike]

No contest that if all MCC requirements and concepts are known at the
outset of the program, we wouldn't need any flexibility.  That never
happens, though.  This time the issue was backup MCC.  The next time it
may be a new requirement to shift operations to control centers around
the globe with daylight hours to reduce night shift costs.  I know that
latter one looks ludicrous to some, but before last year, the thought
that a hurricane might shut down MCC-H looked ludicrous to some, too.
So what they're grabbing for is not solving a specific problem, but more
general flexibility for unanticipated requirements. Having said that,
fully half the camp is still squarely in the "only build to known
requirements" camp, and if that camp wins, flexibility can go out the
window as a criterion.   

 

On what's trivial...  The decision at connecting at link or network
layers is hard-wired in years in advance.  The "operational state" data
for Hurricane Rita turned out to be shipping some database parameters
from Houston to MSFC, and we immediately enabled remote operations
infrastructure that allowed telemetry display on hotel room laptops in
the Texas hill country for evacuated MCC flight controllers.  No
significant issues for transfer of operational state.  But we could only
do that for the downlink, not the uplink, because of the way the uplink
was hard-wired to originate only from MCC-H.  So control of the US
segment stayed in Moscow (via the Russian uplink), not with NASA.  So if
we're talking apples to apples here (not sure of that) then no, the
long-lead decision on ground station wiring is not trivial compared to
transferring the operational state.  It was the wiring that
unfortunately drove the ops concept, rather than vice-versa.  Hence the
interest in making the "wiring" reconfigurable with routing protocols
farther upstream.   

 

I agree that there are some issues as important as protocols
(implementation, operational culture, cost and risk), and they bear
investigation.  But the way those issues swing decisions is usually more
subjective and less predictable, depending on who's in management at the
time.  Once again:  I'm telling the devil's advocate story, for those
that may not have heard this background.   I don't consider the answer
cut-and-dried.  

 

   -=- Mike

 

Mike Kearney

NASA MSFC EO-01

256-544-2029

________________________________

From: sis-csi-bounces at mailman.ccsds.org
[mailto:sis-csi-bounces at mailman.ccsds.org] On Behalf Of Adrian J. Hooke
Sent: Thursday, September 07, 2006 12:05 PM
To: Cislunar Space Internetworking
Subject: [Sis-csi] Handovers (was: RE: CCSDS Cislunar Telecon)

 

At 07:37 AM 9/7/2006, Kearney, Mike wrote:



On the topic of all traffic passing the MOC (MCC or whatever)...  After
the ISS experience, there is a stronger desire in the manned operations
community to allow multiple facilities to connect through the ground
station to the spacecraft.  There were major constraints on operations
capabilities (especially during Hurricane Rita) that would have been
alleviated if WSGT could have been reconfigured easily to connect to a
US-based backup MCC.  


Mike: if there had been a program requirement in place to be able to
rapidly switch to a backup control center, then wouldn't this handover
capability have been implemented and tested in the ISS operational
systems? Presumably, there wasn't such a requirement and so neither WSGT
nor MCC Houston were designed to support it. The lack of the capability
probably had nothing to do with protocols - as you note, the AOS
architecture that has been in place since 1990 was designed to easily
support such a transfer - and everything to do with programmatics and
implementation choices.




I know that there are traditional ways to do that (AOS VCs) without
placing a router/IP gateway at the ground station.  But there is a
perception in some corridors that going IP based from the ground station
out gives a needed capability to deal with contingencies, and allows
low-cost reconfigurations when ops concepts change. 


Isn't whether or not such a handover is done by connecting at the Link
or Network layer an absolutely trivial and insignificant level of detail
and complexity compared with the staggering amount of vehicle
operational state that has to be handed-off between the primary and
backup control centers? 

This topic seems like a red herring. Protocol geeks should be very wary
about fostering "perceptions" that this or that protocol can solve the
world's problems. There are much larger issues at play here, and they
all have to do with implementation, operational culture, cost and risk.

///adrian


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