MEX (SC 41) NEVT BSR Test DSS 43 - Pass 35 6 July 2003 Summary: This pass was scheduled primarily to check end-to-end function of DSN 70-m systems to be used for Mars Express bistatic radar; but it also included X-band uplink, X/X and X/S ranging, and various downlink modulation states. With the exception of some difficulties in obtaining Y-factors during the pre-cal (and resulting delays), my real-time assessment of the test is positive. RSR Configuration: RSR's were configured for 16-bit samples and 25 kHz (complex) sampling rates; 100 kHz subchannels were also set up in case they were needed for searching and monitoring, but this capability was never required. Disk space available before the tests was 54.2% (RSR1) and 58.8% (RSR2); during the test it appeared that disk space was being used at the rate of about 3% per hour of recording. Pre-Cal: For pre-cal measurements (cold sky, noise diode, and ambient load), the following Fgain settings looked good (in retrospect) at DSS 43. Slightly different values were actually used for the test. UWV RSR Fgain ----- --- ----- X-RCP 1A 60 S-RCP 1B 63 X-LCP 2A 60 S-LCP 2B 63 The Y-factor problems were reportedly in cabling; DSS 43 operations personnel toward the end of the test indicated that the Y-factor procedure had been successfully completed. If so, this fact was not communicated to us. In any case, the difficulties resulted in about a 10 minute delay in going to point. Toward the end of the pre-cal we proposed that the station cycle through the RSR sequence per the briefing message. About 14 minutes of data were recorded. Details are listed below in the Timeline section. Times are approximate, because the noise diodes have to be switched on and off manually, and the RSR's were started and stopped manually. Ambient load temperatures were reported later (15:46); these were presumably the temperatures at the pre-cal time, but we did not confirm. Ambient Load Temperature ------------ ----------- S-band #1 19.69C S-band #2 19.88C X-band #1 20.81C Tracking: The spacecraft came up with X-band downlink ON via the high-gain antenna, COH ON (but no uplink). X-band telemetry ON (modulation index 1.25 and symbol rate 209715.2 sps), and (uplink) command rate set to 2000 bps. The DSN generated predicts but only for X-band; Aseel compared them to RSSG X-band predicts and found they were very close (<100 Hz). She had both X- and S-band predicts, but only for one-way operations. The following looked like good settings for tracking (Fgain is in dB): Predicts 2-Way (TLM ON) 1-Way (TLM OFF) Source -------------- --------------- UWV RSR Fgain Offset Fgain Offset ----- --- -------- ----- ------ ----- ------ X-RCP 1A DSN 1-W 90 +7500 110 0 S-RCP 1B RS 1-W 90 0 90 0 X-LCP 2A DSN 1-W 70 +7500 70 0 S-RCP 2B RS 1-W 60 0 60 0 Timeline: 13:40 Begin pre-cal (30 minute delay from time in SOE in order to obtain four closed loop receivers - rather than the two originally scheduled) 13:50 Pre-Pass Briefing by MEX MOPS; several questions by DSS 43 14:15 RSR configuration for pre-cal SNT measurements UWV RSR Fgain ----- --- ----- X-RCP 1A 60 S-RCP 1B 60 (this turned out to be too little) X-LCP 2A 60 S-LCP 2B 70 (this turned out to be too much) 14:18 RSR recording ON 14:21 Noise diodes ON 14:23 Add X-band ambient load (noise diodes remain ON) 14:24 Add S-band ambient loads (noise diodes remain on) (some clipping on S-LCP) 14:26 All noise diodes OFF 14:28 End of procedure 14:32 End RSR recording 14:49 Moving to point 14:57 X U/L transmitter ON 15:22 S-band ranging in lock 15:45 Re-configured RSR's and started recording simultaneously UWV RSR Predicts Fgain Offset Plot Set ----- --- -------- ----- ------ -------- X-RCP 1A DSN 1-W 90 +7500 A S-RCP 1B RS 1-W 90 0 A X-LCP 2A DSN 1-W 70 +7500 B S-LCP 2B RS 1-W 60 0 B The offsets placed the carrier near the center of each spectrum. 16:03 COH OFF; S-band carrier shifted to about -1500 Hz in spectra, X-band to about -9000 Hz 16:05 Removed frequency offsets; all carriers then at about - 1500 Hz in their respective spectra (plot sets C and D) 16:15 Noise diodes ON 16:20 Noise diodes OFF 16:27 Accidently stopped S-LCP recording (16:27:56 - 16:28:07) 17:04 X-band telemetry OFF (X-RCP saturates) 17:06 X-band Fgain reset to 110 (plot set E and F) Spurs at <-50 dBc appear around carrier at spacings of about 525 Hz 17:10 Noise diodes ON 17:15 Noise diodes OFF 18:05 X U/L transmitter OFF 18:20 Noise diodes ON (late) The following Px/N0 readings were read from the displays to see whether any effects of the noise diodes could be detected in real time. Only S-LCP shows any signs of detection (are pre 18:25 levels lower than post 18:25 readings?); in fact, the X-RCP levels suggest a NEGATIVE correlation with noise diode state. Px/N0 From Displays (dB) ----------------------------- UTC X-RCP S-RCP X-LCP S-LCP RSR1A RSR1B RSR2A RSR2B -------- ----- ----- ----- ----- 18:22:00 83.33 72.27 59.67 47.37 18:22:30 83.56 72.32 60.64 47.45 18:23:00 83.25 72.20 58.91 47.39 18:23:30 83.43 72.28 61.16 47.55 18:24:00 83.46 72.42 59.83 47.56 18:24:30 83.34 72.44 57.62 47.50 18:25:00 83.20 72.40 58.45 47.14 18:25 Noise diodes OFF 18:25:30 83.25 72.44 58.95 48.06 18:26:00 83.23 72.42 58.97 48.18 18:26:30 83.30 72.33 58.68 48.25 18:27:00 83.14 72.48 60.50 48.22 18:27:30 83.30 72.40 58.57 48.24 18:33 Plot set G and H 19:00 Noise diodes ON 19:05 Noise diodes OFF 19:07 X-band telemetry ON (spurs at 60 Hz spacing replaced by dense "grass" in spectrum as much as 20 dB above original noise level) (plot sets I and J) 20:07 X-band U/L transmitter ON, sweep ON After a couple minutes, the X-band carrier stabilizes at about -5000 Hz, S-band at about -3000 Hz. Items Needed and/or Deliverables 1. Revised briefing message(s) for remaining NEVT DSN passes 2. LMC logs for this pass 3. RSR data from this pass (delivered to Stanford on DVD-R?) 4. MON-0158 data from all 4 closed loop receivers 5. TNF data 6. ODF, Media Calibration, and Meteorology data Conclusions Test went generally very well. Support was excellent, especially from DSS 43 personnel. Y-factor procedure may need some work (depends on whether the 'cabling problem is understood and resolved) The RSR cycle during pre-cal could be reduced to three steps (cold sky, noise diodes, and ambient load). If RSR data look good, the Y-factor procedure may not be needed. But the physical temperature of the ambient loads is still needed to use the RSR cycle results; and those may only be available from the Y-factor equipment. Uplink X-band transmitter operation appeared to have no effect on downlink data. X-band telemetry modulation lowers the carrier level (expected) and raises the noise level by as much as 20 dB. It is difficult (impossible?) to detect noise diode operation from the real-time displays The AUX OSC and two-way carrier positions were always within 10 kHz of each other, expect during extremes of the sweep. This makes transition between two-way and one-way operation very easy (when using the 25 kHz sampling rate). DSN and RSSG predicts appear to be functionally equivalent (when using the 25 kHz sampling rate). Participants at JPL: Sami Asmar (RSSG) Aseel Anabtawi (RSSG) Dick Simpson (Stanford) Dick Simpson 6 July 2003