MC Time

MC Time Accuracy

From: Takao Nakagawa <nakagawa@astro.isas.jaxa.jp>
To: irts-e
Cc: nakagawa
Subject: IRTS MC time
Date: Fri, 26 May 95 22:20:12 +0900

Dear Colleagues,

This mail concerns the accuracy of the SFU/MC-time.

The accuracy of the MC timing clock is about 10^-6, so it will make
a 1 s error within 10 days.

The MC TIME clock was adjusted to 0 at the following timing.

        MC = 0                  95-03-18 09:42:04

The MC TIME clock was a little bit slower than the true time, and it
was about 3s behind the true time on April 11. Hence the SFU system
people made the +3s correction at the following timing:

        Delta MC = +3s          95-04-11 16:48:24

Just after the correction, the difference between the MC time and the
true time was much less than 1s (we don't know how small it was).

But after a while, the MC time was again behind the ture time, and it
was about 5s behind the true time on May 10 (After the copletion of
the IRTS observation). Hence the SFU system people made the +5s
correction at the following timing:

        Delta MC = +5s          95-05-10 05:56:28

Just after the correction, the difference between the MC time and the
true time was much less than 1s (we don't know how small it was).

All of the timing of the commands and data transmission is controlled
by the MC time. Hence we have to pay attention to the above effect to
make detailed data reduction. The SFU people say that simple linear
interpolations between the above timings are sufficient for most of
the data reduction.

If you have any questions, please contact me.


Best Regards,

Takao Nakagawa

MC Time Delay

                        June 9, 95
                        T. Nakagawa

Time                    Delay (s)

95/03/18 09:42:04       0.000
95/03/20 08:41:39       0.192
95/03/22 09:54:54       0.480
95/03/24 06:59:58       0.672
95/03/26 06:01:38       0.912
95/03/28 05:01:55       1.288
95/03/30 04:05:03       1.336
95/04/02 02:37:35       1.768
95/04/04 03:20:56       1.960
95/04/06 05:52:26       2.192
95/04/08 08:11:48       2.432
95/04/10 08:52:21       2.672
(95/04/11 16:48:22  +3.0s correction)
95/04/12 14:36:05       0.288
95/04/14 13:37:47       0.528
95/04/16 12:38:46       0.768
95/04/18 15:08:47       0.960
95/04/20 15:39:23       1.192
95/04/22 13:01:31       1.384
95/04/26 11:11:18       1.864
95/04/28 10:05:53       2.192

The on-board MC time is behind the true time as listed above.
                        ^^^^^^
Last modified: Nov 27, 1997