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Ray, Timothy J. (GSFC-583.0) wrote:
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<p class="MsoNormal"><font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;">Sounds good
Pat.</span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;">Just out of
curiosity, is there some
advantage to using the older epoch?</span></font></p>
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The 1958 epoch is the only one that is documented in the Blue Book for
CCSDS time code formats. If we want to standardize on some other
epoch, we will either need to do so informally in the interoperability
test plan (which is how I understand Pat's suggestion) or else define
it formally in the AMS spec. I think we would run into some resistance
if we strayed from what's currently in the spec for this field, since
it took quite a bit of back-and-forth with other CCSDS folks to arrive
at the current text.<br>
<br>
Scott<br>
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<p class="MsoNormal"><b><font color="black" face="Tahoma" size="2"><span
style="font-size: 10pt; font-family: Tahoma; color: windowtext; font-weight: bold;">From:</span></font></b><font
color="black" face="Tahoma" size="2"><span
style="font-size: 10pt; font-family: Tahoma; color: windowtext;">
<a class="moz-txt-link-abbreviated" href="mailto:sis-ams-bounces@mailman.ccsds.org">sis-ams-bounces@mailman.ccsds.org</a>
[<a class="moz-txt-link-freetext" href="mailto:sis-ams-bounces@mailman.ccsds.org">mailto:sis-ams-bounces@mailman.ccsds.org</a>] <b><span
style="font-weight: bold;">On
Behalf Of </span></b>Donahue, Pat<br>
<b><span style="font-weight: bold;">Sent:</span></b> Wednesday,
August 20, 2008
12:35 PM<br>
<b><span style="font-weight: bold;">To:</span></b>
<a class="moz-txt-link-abbreviated" href="mailto:sis-ams@mailman.ccsds.org">sis-ams@mailman.ccsds.org</a><br>
<b><span style="font-weight: bold;">Subject:</span></b> [Sis-ams]
Time Tag -
CCSDS Time</span></font></p>
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size="3"><span style="font-size: 12pt;"> </span></font></p>
<p class="MsoNormal"><font color="blue" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: blue;">For
interoperability sake, just like we
have agreed to an "Unsegmented" CCSDS format, I suggest that we also
agree to all use the 1958 epoch as our basis, and 4 bytes of course
time (since
you need that many bytes to properly contain the number of seconds
since Jan 1,
1958).</span></font></p>
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size="3"><span style="font-size: 12pt;"> </span></font></p>
<p class="MsoNormal"><font color="blue" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: blue;">By the way,
if you are working with the
Jan 1, 1970 epoch in Unix just add 378691200 and you will have the
number
of seconds since Jan 1, 1958. Correct me if I am wrong.</span></font></p>
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