[ntp:hackers] [Fwd: NTP Usage for Time Synchronization on NASA Constellation]

David L. Mills mills at udel.edu
Sat May 10 17:52:21 UTC 2008



-------- Original Message --------
Subject: 	NTP Usage for Time Synchronization on NASA Constellation
Date: 	Tue, 1 Apr 2008 13:22:21 -0500
From: 	Boydston, Alex K. (MSFC-NNM05AB50C)[DRAPER LAB] 
<Alex.K.Boydston at nasa.gov>
To: 	<mills at UDel.Edu>



Dr. Mills,
You'd probably be interested to know that your protocol is planned to be
used for Constellation as a time synchronization mechanism.

[C3I-111]  Constellation systems shall exchange time in accordance with
IETF RFC 1305, Network Time Protocol (NTP) Version 3.
Rationale:  NTP allows one system to exchange time with another system
in order to establish a common time base.  Systems may also choose to
synchronize clocks using that common time base.  Millisecond level
accuracies are attainable in low network latency environments.  This
does not preclude some Constellation systems from using other clock
synchronization mechanisms to enable clock synchronization in space
flight applications over longer distances and/or to synchronize clocks
more precisely (e.g., within 10 nsec) to meet Navigation requirements.
NTP is the open international standard for clock synchronization in the
Internet.  It has been proven through flight testing to function in
Low-Earth Orbit spaceflight applications as documented in Internet
Access to Spacecraft (http://ipinspace.gsfc.nasa.gov/
documents/Small-Sat2000Paper.doc).  NTP implementations are currently
available in most commercial real-time operating systems.  The
specification of NTP and an appropriate version number is the subject of
TDS number SIG-13-204, Time Services Study.


Do you have any inputs on this?  There is thoughts of using IEEE-1588
(PTP) or GPS synchronization.



Alex Boydston
Avionics Engineer
Draper Laboratory Task Lead for C&DH
NASA Marshall Space Flight Center
Bldg 4487/Rm B233A
256-544-8141 (office)
256-508-5181 (cellular)



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