Trigger B0 Description

Sequence: S02, tested in C40
Trigger B0 (SOI trigger, planned for Saturn Orbital Insertion)

This mode is designed to autonomously step through various RPWS high resolution observations during the weeklong interval leading up to and including SOI. This period runs from 2004-175T00:00:00 until 2004-183T03:06:40 (shortly after the main engine burn), and is characterized by a "quiet" period, when no commanding from the spacecraft to instruments is allowed. Consequently this single trigger will be executed shortly before the quiet period (at precisely 2004-174T23:54:30) and will run for more than a week.

Several reference points are defined for the period: 
Interval    Start Time             Stop Time           Bit Rate    Notes
------      -----------------      -----------------   --------    -----------------------
PRESOI      2004-175T00:00:00      2004-181T19:00:00   9000        Toggle WBR once/hr
SOINBOUND   2004-181T19:00:00      2004-183T00:42:00   3300        Toggle WBR once/hr
SOIARPC     2004-183T00:42:00      2004-183T00:52:00   100000      Ring Plane 10KHz WBR
SOIINNER    2004-183T00:52:00      2004-183T01:12:00   100000      Toggle WBR continuously
SOIBURN     2004-183T01:12:00      2004-183T02:52:00   1310        No WBR
SOIINNER    2004-183T02:52:00      2004-183T03:06:40   100000      Toggle WBR continuously
For the PRESOI period, there will be continuous DSN tracking. After that, all data must be recorded (hence the lowered bitrate during the INBOUND interval). For the PRESOI and SOINBOUND periods the background mode is the "Inner Survey Night" mode, Trigger 8E. It is like the standard survey mode, except that fast integration constants are used by the HFR bands H1 and H2. Also there is no sounder throughout. Here is a description of the mode:

Modified Trigger 8E ( Night-time Inner Survey Mode )

This mode is designed to provide a Night-time Inner (i.e., < 10 Rs) Survey mode, with standard temporal resolution and spectral resolution. Both low-frequency and high-frequency WFR measurements are made, using a "toggle" mode. Dust detection is included. Langmuir Probe sweeps are performed every 640 seconds. The Sounder is disabled. LFDR measurements are made every 16 seconds, using LFDR toggle mode, which provides MFR2 replacement data. The HFR uses shorter integration constants for H1 and H2, with the goal to detect SED's.

Receiver Frequency Range Sensors Time between Snapshots
LFR 1 - 25 Hz EX, BX 32 seconds
MFDR 70 - 1700 Hz EX, BX 32 seconds
MFR 25 - 12 KHz EX, BZ 32 seconds
WFR 1 - 25 Hz EX,EW,BX,BY,BZ 320 seconds
WFR .1 - 2.5 KHz EX,EW,BX,BY,BZ 320 seconds
HFR 3.6 KHz - 16 MHz EX, EW 16 seconds
LP N/A Langmuir Probe 640 seconds



The HFR is in a modified "Composite Survey" mode, which now includes both auto- and cross-correlations for H1, and differs from standard Survey mode in that its integration constants for H1 and H2 are shorter. This mode is defined by: 
          Correlations     Channels        Integ.                Size Frequency
Band Ant. Auto-  Cross-    per Band   df   Period    Rep   Steps kHz  Start - Stop
---- ---- -----  ------    --------   --   ------    ---   ----- ---- ------------
ABC  2E   y         y        16       n    1000      1                3.6-319 kHz
H1   2E   y         y         2       n    20        1     60    25   325k-1.8MHz
H2   1E   n         n         1       n    10        1     72    200  1.8M-16MHz
Bands ABC require 3.16 sec to complete, H1 requires 1.57 sec, and H2 requires 0.65 sec for a total of 5.62 sec per sweep. However, the time between analyses is set to 16 seconds to reduce the bit rate.

PRESOI Interval

During the Pre-SOI interval, in addition to the 8E mode, a burst of WBR data is acquired once per hour, at 13 minutes after each hour. Initially 80-KHz WBR is acquired. This is a 224-second long data set, consisting of 1024 uncompressed data samples acquired every 1/8 second. This is followed immediately by a similar 224-second burst of 10-KHz WBR data. There are 163 acquisitions of this sort in this period.

SOINBOUND Interval

During the SOINBOUND interval, in addition to the 8E mode, a burst of WBR data is acquired once per hour, at 2 minutes after each hour. Initially 80-KHz WBR is acquired. This is a 69-second long data set, consisting of 1024 uncompressed data samples acquired every 1/8 second. This is followed immediately by a similar 69-second burst of 10-KHz WBR data. There are 29 acquisitions of this sort in this period. For the last hour of the SOINBOUND period, the background mode is modified to the RINGSAT mode, Trigger A8. This mode will be used for the Ring-Plane Crossing and SOI Inner periods. It is described here:

Modified Trigger A8 ( RNGSAT, Rings & Satellite Regions & Titan Intermediate)

This mode uses the night-time inner survey mode as its background setup, and on top of that overlays fast WFR data acquisition. In order to do this, the LFDR data acquisition is stopped (it can be synthesized on the ground, using the fast WFR data.) A WFR snapshot, in its nominal 5-channel and 2048-sample mode, is acquired every 24 seconds. The WFR is run in toggle mode, so these snapshots alternate between 25 Hz mode and 2.5 KHz mode. The Langmuir Probe does a sweep every 48 seconds, and between sweeps does a 1-Hz density mode measurement, acquiring 44 data samples. The Sounder has been disabled for the SOI period. In-flight measured bit rate was 5700 bps.

Receiver Frequency Range Sensors Time between Snapshots
MFR 25 - 12 KHz EX, BZ 32 seconds
WFR 1 - 25 Hz EX,EW,BX,BY,BZ 48 seconds
WFR .1 - 2.5 KHz EX,EW,BX,BY,BZ 48 seconds
HFR 3.6 KHz - 16 MHz EX, EW 16 seconds
LP N/A Langmuir Probe 48 seconds


SOIINNER Intervals, before and after the Main Engine Burn

During the innermost SOI intervals, except during the burn, the A8 mode is used as the background mode. In addition, WBR data is acquired continuously, toggling between the 10-KHz and 80KHz bands every minute. A snapshot is taken every 1/8 second, consisting of 1437 uncompressed data bytes. The reason this is done is to target a 100 kbps data rate. The reason the data is not compressed is because compressing the 80-KHz data results in interruptions in the WFR and WBR data acquisitions, since they can not both be done at the same time unless the data is left uncompressed.

SOIBURN Interval

During the SOI Burn, the inner night-time survey mode, trigger 8E, is used. No WBR data is acquired.