Trigger B2 Description
Sequence: C40, ...
Trigger B2 ( Titan & Icy Satellite Closest Approach with 10-KHz WBR)
This mode assumes a background survey mode, such as 8A or A0, is running,
although the HFR settings are set for the "Inner Magnetosphere Night-Time"
mode, with fast time constants, as in Triggers A0 or 8E. The duty cycle of
the Langmuir Probe and the WFR are increased, and 10-KHz WBR is added.
First of all, Trigger B2 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.
In addition to stopping the LFDR data acquisition, the data compression
algorithm for the WFR is changed to "packed" mode, so that this faster
data rate can be accomplished. The Langmuir Probe sweep rate is increased
to once every 24 seconds. While a faster rate would be desirable, this would
cause interference in the WFR data, also being acquired every 24 seconds.
Between each LP sweep, a 256-point density mode measurement is made at 20 Hz.
The 10-KHz WBR is added, using the EX antenna, but the sample size is limited
to 1536 compressed bytes in order to accomplish a particular bitrate. These
compressed bytes generally resulted in almost 3000 samples during a test
in C40. The target bit rate is 100 kbps. Measured bitrate was only about
90 kbps during the C40 test.
| Receiver |
Frequency Range |
Sensors |
Time between Snapshots |
| MFR |
25 - 12 KHz |
EZ, 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 |
8 or 16 seconds |
| LP |
N/A |
Langmuir Probe |
24 seconds |
| WBR |
0 - 10 KHz |
EX |
0.125 second |
The HFR is in a modified "Composite Survey" mode, which 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 either 8
or 16 seconds to reduce the bit rate.
No Sounder measurements are made in this mode. No onboard dust detection is done either.