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

Tue Aug 16 11:46:52 EDT 2022

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

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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