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RE: Kodiak Star Launch 80% GO



Bob, I hate to bring up topics like this but I feel I must. Your posting a
few hours ago said:

> [snip] The updated ones will show a julian date of 266.

WRONG!!!! -- the day=266 is >>NOT<< the Julian date (JD). The current Julian
Date is 2,452,174 and it represents the elapsed number of days since ~4713
BC (approximately the date that the good Rev. Usher ascribed to the
Creation).

Because this is an inconveniently large number, the term Modified Julian
Date (MJD) is given by
the equation JD-2,400,000.5 making the current MJD be 52175. The reason for
the 0.5 on the end of the constant is that JD is reckoned from Noon whilst
more common usage has the day beginning at midnite UTC (=GMT="z"). When
scientists use MJD, it is common to add the fraction of a day to this, so as
I write this message at ~00:40:00 UTC, the MJD is ~52175.03. The Calendar
date corresponding to MJD=0 was in November, 1842.

The other continuous date we often see used is the "Excel" date (which I
call XD). Excel uses elapsed days since Jan 0th, 1900 (i.e. Dec.31,1899),
making it now be XD=37157. Obviously, MJD=XD+15018.

The "266" that you incorrectly called the "Julian Date" is properly named
"Day-of-the-year" which many of us abbreviate DOY. Any attempt to call this
JD 266 immediately puts you 6700 years behind time!

Anyway -- good luck on the launch a few minutes from now.

73 de Tom, W3IWI

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