PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 2005-05-31 NOTE = " C32_TRIG_58.TXT describes the RPWS instrument configuration for the High Frequency Receiver (HFR), the Medium Frequency Receiver (MFR), the Low Frequency Receiver (LFR), the Waveform Receiver (WFR), the Wideband Receiver (WBR), the Langmuir Probe (LP), the Sounder, and the onboard Dust detection algorithm when using Trigger 58." END_OBJECT = TEXT END Trigger 58 Description Sequence: C22, C23, C24, C25, C26, C27 Trigger 58 (High Rate Cyclic Mode) This mode is designed to step through various RPWS high resolution observations over periods of order 1 hour or longer. Eight different high resolution modes are sampled for periods of 3 to 9 minutes with one complete cycle taking 1 hour. The cyclic repeats until it is stopped by the issuance of a new trigger command, typically Trigger 80. The targeted average data rate (averaged over 1 hour) is 40 kbps, but the true, compressed data rate realized is closer to 30.5 kbps although this is somewhat data dependent. Figure 1 provides an overview of the Trigger 58 cyclic. As can be seen, WBR modes are alternated with WFR modes. This is primarily to ensure that high rate modes (WBR) are separated by periods of significantly lower data rate periods (WFR) to minimize non-linear effects in SSR managment. The peak data rates for the WBR modes are of order 115 kbps while those of the WFR modes are of order 6 kbps. Specifically, this cyclic collects WBR data in 25-kHz bands centered on 8.025 MHz, 1.025 MHz, and 125 kHz, in the 75-kHz and 10.5-kHz baseband modes interspersed with periods of 2.5-kHz and 26-Hz WFR modes. The user is referred to individual descriptions of these underlying triggers (as listed in Figure 1) for details on each of these. Trigger 5A Overview __ ________ __ ________ __ ________ _____ _____ __ ________ | | | | | | | | | | | |32| 3E |34| 40 |36| 3E | 38 | 3C |3A| 40 | |__|________|__|________|__|________|_____|_____|__|________| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 0 1 2 3 4 5 6 0 0 0 0 0 0 0 Time (minutes) Step Receiver Frequency Duration ---------- -------- ------------------ --------- Trigger 32 HF-WBR 8.025 MHz 3 minutes Trigger 34 HF-WBR 1.025 MHz 3 minutes Trigger 36 HF-WBR 0.125 MHz 3 minutes Trigger 38 WBR 0 - 75 KHz 6 minutes Trigger 3A WBR 0 - 10.5 KHz 3 minutes Trigger 3C HFR Max. Spectral Res. 6 minutes Trigger 3E WFR 0 - 2.5 KHz 9 minutes Trigger 40 WFR 0 - 25 Hz 9 minutes Low Rate Measurements During the Trigger 58 Cyclic Underlying Trigger 58, the RPWS continues to collect spectral survey data over the entire RPWS frequency range (1 Hz - 16.1 MHz) as continuously as possible, provided the limitations of the RPWS hardware and software limits. The survey data are collected as follows: 1. Low Frequency Receiver: This covers the frequency range from 1 to 25 Hz using a 2- channel mode of the WFR, specifically using Ex (dipole) and Bx sensors. One waveform series of 512 samples are collected every 32 seconds simultaneously for each of these two sensors. The waveform is spectrum analyzed on board and a 28-channel(?) quasi-logarithmic spectrum is constructed by binning adjacent Fourier components. The initial AGC gain is set to20 dB for Ex and 30 dB for Bx and is updated after every waveform series (?). The AGC set point is 17, 85 (what does this mean?). These data are collected during the Trigger 3A, 3C, and 3E elements of the cyclic, (10.5-kHz WBR, high resolution HFR, and 2.5-kHz WFR). The raw data required to construct these channels are collected in Trigger 40, but are routed directly to the ground and can be filled in for this mode in ground processing, if required. The data cannot be collected in triggers 32, 34, 36, or 38 (the HF-WBR or 75-kHz WBR modes) because of hardware limitations. Beginning in C26, a periodic LFR (every 32 seconds) was included in the trigger 38 setup; the downside of this decision is that every 32 seconds, the WBR data is not acquired while the 5.12 seconds of LFR data is captured. 2. Medium Frequency Receiver: The spectral data for the frequency range from 25 Hz to 12 kHz are collected by the MFR continuously throughout Trigger 58 using the Ew and Bz sensors. A spectrum from the Ew sensor is collected during one 32-second period and the Bz spectrum is collected during the following 32-second period. Previous to C23, the MFR sensor was allowed to remain as it was previous to Trigger 58; however, starting with C23 the MFR sensor was set to use EW, in order to reduce interference between the WBR and the MFR. 3. High Frequency Receiver: When the HFR is not required to do otherwise, it is set to the so-called composite mode survey mode during Trigger 58. This is the case for Triggers 38, 3A, 3E, and 40. 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 2 n 80 1 30 50 325k-1.8MHz H2 1E 1 n 20 1 72 200 1.8M-16MHz Bands ABC require 3.16 sec to complete, H1 requires 2.524 sec, and H2 requires 1.461 sec for a total of 7.25 sec per sweep. For the HF-WBR modes the HFR is required to be in freeze mode at the frequency being analyzed by the HF-WBR. During these times, the HFR is in millisecond mode, collecting AGC values once per millisecond for use with the HF-WBR data. The AGC values are collected in sets of 2048 samples taken over 2.12 seconds. There is a __ second gap between each AGC value set. The HF-WBR modes are interrupted once per minute to collect one HFR sweep in the composite mode survey described above. Finally, the HFR is run in its highest spectral resolution mode during Trigger 3C: Correlations Channels Integ. Size Frequency Band Ant. Auto- Cross- per Band df Period Rep Steps kHz Start - Stop ---- ---- ----- ------ -------- -- ------ --- ----- ---- ------------ ABC 2E y y 32 n 1000 1 3.6-319 kHz H1 2E y 8 n 80 1 157 25 125k-4MHz H2 1E 8 n 80 1 243 50 4M-16.1MHz Bands ABC require 3.12 sec to complete, H1 requires 14.3 sec, and H2 requires 21.75 sec for a total of 39.25 sec per sweep. During C26 it was discovered that if the Sounder was running prior to a Trigger 58, then it continued running during the Trigger 58 period. This oversight was corrected for C27, and the Sounder was idled as part of the Trigger 58 setup.