[Isocops] EXT :Re: IBEX Goat Herder for 15 & 16 August 2022

[NIgel Angold]

Thanks, Ryan.

That sounds quite plausible.

Nigel

> Tyler, Ryan S [US] (SP) <mailto:Ryan.Tyler at ngc.com>
> August 16, 2022 at 08:46
>
> My best guess is that it was just a matter of bad timing jumping us 
> out of our spin rate “groove”.
>
> It hasn’t been a problem to date, but every time we re-set the clock 
> we see a jump in spin rate, maybe up to 4.3 rpm or something like 
> that, as the estimator tries to make sense of the jump in timing 
> between the ACS time (which updates right when we set the clock) and 
> star tracker time (which updates a minute or so later). Normally, this 
> sort of thing cleans itself up within 10 minutes or so.
>
> My hypothesis is that the estimator decided that the best explanation 
> for what it saw, due to unfortunate timing, was that the spin rate had 
> jumped significantly. And then once it got into that regime it got 
> stuck there, trying to fit all of the star tracker data into the 
> context of that spin rate regime. So instead of assuming that the next 
> star tracker reading was a fraction of a rotation away from the last 
> it assumes it’s a few rotations plus a fraction of a rotation away 
> from the last.
>
> Thus, once we got it back into the 4.17-ish rpm groove, it was able to 
> latch back on and interpret the star tracker data correctly.
>
> In some sense, I’m surprised this sort of thing hasn’t happened before 
> given the time jump. Either repeating what we did or simply restarting 
> the estimator should clear it up if it happens again.
>
> -Ryan
>
> *From:*NIgel Angold <nangold at princeton.edu>
> *Sent:* Tuesday, August 16, 2022 11:00 AM
> *To:* Perry, Timothy E [US] (SP) <Timothy.Perry at ngc.com>; Tyler, Ryan 
> S [US] (SP) <Ryan.Tyler at ngc.com>
> *Cc:* Carol Weaver <carol.weaver at unh.edu>; Ibex Mission Operations 
> <ibexops at gmail.com>; ISOC at New Hampshire <isocops at lists.sr.unh.edu>; 
> Ken Fairchild <fair-play at comcast.net>; Ken Fairchild UNH 
> <Ken.Fairchild at unh.edu>; Nigel Angold 
> <angoldconsulting at earthlink.net>; Wesley, Sheral R [US] (SP) 
> <Sheral.Wesley at ngc.com>; Wynn, Reese [US] (SP) <Reese.Wynn at ngc.com>
> *Subject:* EXT :Re: IBEX Goat Herder for 15 & 16 August 2022
>
> Any idea what might have caused the spin rate to jump to 30.2 rpm? New 
> razor?
>
> Thanks,
> Nigel
>
> NIgel Angold <mailto:nangold at princeton.edu>
> August 16, 2022 at 07:59
> Any idea what might have caused the spin rate to jump to 30.2 rpm?New 
> razor?
>
> Thanks,
> Nigel
>
> Perry, Timothy E [US] (SP) <mailto:Timothy.Perry at ngc.com>
> August 15, 2022 at 21:20
>
> All,
>
> We completed the series of 3 USAK01 contacts for testing changes to 
> improve our tracking data. During the USAK01 contact 15Aug22 @18:00 I 
> set the spacecraft clock and the star tracker spin rate jumped to 30.2 
> rpm. This value stayed there for the duration of the pass. On the 
> following USAK01 pass @20:30 we changed the Kalman filter input to 
> ground command and set the values to zero and disabled the star 
> tracker input. Using just the static Z rate the spin rate started to 
> come down but it never settled out. On the final pass of the night 
> USAK01 08/16/22 at 02:30 we enabled the star tracker spin rate and 
> disabled the static z rate and the value stabilized at the 4.177 spin 
> rate and residuals were low. We changed the Kalman filter input back 
> to STA_PCT_VAL and the ACE looked nominal. We watched it for the 
> duration of the pass and it stayed solid.
>
> Tasks Accomplished:
>
> SSR Dump -> Dump New
>
> Set Spacecraft Clock
>
> Reset FDC Totals
>
> Reset 18 Day timer
>
> CAR # 1258 Orbit 579 ATS uplink
>
> IBEX_2022_237_o0579a_v001 98 commands
>
> CAR 1257 Redump Orbit 576 SSR Data – Dumped 17136 blocks of 26390 blocks
>
> Will dump the rest on the next orbit
>
> Star tracker issue troubleshooting
>
> Results from the Inertial Maneuver:
>
> Q1 -0.48704600 ActNor.EstInrToBdy[0]
>
> Q2 0.36519700 ActNor.EstInrToBdy[1]
>
> Q3 0.79329000 ActNor.EstInrToBdy[2]
>
> Q4 0.01037000 ActNor.EstInrToBdy[3]
>
> GPS sec 1344617486 ActNor.EstTime
>
> UTC time *08/15/2022 16:51:12 *output
>
> MPS Diff *0.800 *deg
>
> MPS Cmd Vector X -0.769676000
>
> MPS Cmd Vector Y 0.589292000
>
> MPS Cmd Vector Z 0.245629000
>
> CSS Angle TLM 0.454134
>
> CSS Sun-Pointing Angle 0.908268
>
> 11 Aug 22 @02:00:00
>
> CSS Angle TLM 0.775817
>
> CSS Sun-Pointing Angle 1.551634
>
> 15 Aug 22 @16:30:00
>
> *Pre-Burn *
>
> Thruster 1 3888 11 Aug 22 @02:00:00
>
> Thruster 2 3792
>
> Thruster 3 4416
>
> Thruster 4 4512
>
> *Post-Burn *
>
> Thruster 1 4176 15 Aug 22 @16:30:00
>
> Thruster 2 4080
>
> Thruster 3 4720
>
> Thruster 4 4816
>
> *Number of Pulses *
>
> Thruster 1 288
>
> Thruster 2 288
>
> Thruster 3 304
>
> Thruster 4 304
>
> *Thruster Pairs *
>
> Thruster 1 & 2 576
>
> Thruster 3 & 4 608
>
>

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