SolarOrbiter PAS

Introduction

On 2022/01/13, we used a new set of PAS configuration parameters.

We tried to improve PAS counting statistics, using K=2 sub-sampling per seconds.

The PAS configuration parameters for Normal mode samplings were set to:

Full normal mode samplings

Each 100s (excepted during snapshots), PAS perform full sampling with 92 energies x 9 elevations x 11 CEMS with K=1

These samplings correspond to a TM packet with 92 x 9 x 11 = 9108 counters ⇒ 18216 bytes, before compression.
54 energies x 7 elevations x 11 CEMS with K=2

In this mode, PAS data are accumulated over K=2 sampling/s, but only transmitted once.

That generate a TM packet with a payload of 54 * 7 * 11 = 4158 int-16 counters ⇒ 8316 bytes

This packet is then compressed onboard, and sent to SSMM

In normal mode, each 300s, PAS enter in snapshot mode (9s duration):

full sampling (90 x 9 x 11)
7 x K=4 sub-samplings (36 x 5 x 11)
full sampling (90 x 9 x 11)

We got another uncontroled DPU reboot at 07:06, during a snapshot period

Problem found: uncomplete uncompressed TM data

We receive 6004 Normal mode packets on 2022/01/13, including 166 full-samplings.

After uncompressing on ground these TM packets, we could notice that:

All full sampling TM packet were complete

we received for each FS uncompressd data with 18304 bytes, where only the first 18216 are useful (due to uncompression block size factor)
1985/6004 TM packets corresponding to K=2 samplings were uncomplete

After uncompression, we received only 8192/8316 bytes (at least 124 bytes missing)

That gives a ratio of 1985 / 6004 = 33% of uncomplete TM packets

We could keep trace of these missing packets in our L1 CDF files, by setting the CDF variable COMPRESSION value to 9, rather than usual 0/1 value standing for False/True.

PAS 3D descriptors

A first plot for 00:00/08:00 show PAS data before DPU reboot.

You can look at the "COMPRESSED" panel (value 9 indicating uncomplete TM data)

documents/2022-01-13/20220113.data-descriptor.png

Zoom

PAS configuration

Here is an extract of TM that gives details on PAS configuration

APID ( 96, 6) TM (200,250) SEQ (00114,3) Size =    48  2022-01-13T00:00:13.683 : SWA_TM_PARAM_REPORT
0000 : 00 01 30 05 00 2A 00 00 00 00 00 04 00 00 5C 00
0016 : 00 00 00 00 09 00 00 01 00 00 01 00 00 00 00 00
0032 : 1A 00 00 36 00 00 01 00 00 07 00 00 02 00 00 01

Param ID                       = 3005 : StatNormParId (42 bytes)
Static.P1                      =    0
Static.P2                      =    4
Static.P3                      =   92
Static.P4                      =    0
Static.P5                      =    9
Static.P6                      =    1
Static.P7                      =    1
Static.P8                      =    0
Static.P9                      =   26
Static.P10                     =   54
Static.P11                     =    1
Static.P12                     =    7
Static.P13                     =    2
Static.P14                     =    1

Conclusion

It seems there is a problem with that 54 x 7 x 11 PAS configuration.

In 33% of cases, after uncompressing TM data, we couldn’t receive the whole expected data.

This "uncomplete data" problem was already encountered, with other configuration parameters, from 2021/06/10 to 2021/06/23.

However, the problem in this case was during snapshot (or burst) full-samplings.

It seems there is a problem with some PAS configuration parameters