Mars Express Bistatic Radar Experiment Operations Plan and Report 24 July 2005 Summary ======= DSN Antenna: 14 Pass: 784 Orbit: 1956 Orbit Start Time: HGA Pointing: Inertial Specular Condition: 2005-07-24T11:11:14 (ERT) Target: Latitude 49.44N Longitude: 155.91E (15 deg E of Mie, slightly N) Radius: 3381.523 km Incidence/Reflection Angle: 69.65 deg Slant Range: 1916 km Slew Angle: 40.69 deg Doppler (carrier, fd): -97365 Hz Doppler (echo, fr): -93877 Doppler Difference (fdd): -3488 Earth-Mars Distance: 1.303E11 m Experiment Set Up ================= This experiment was conducted using Goldstone's DSS 14. The support team at JPL included Gene Goltz, Danny Kahan, Sami Asmar, Dwight Holmes, and Dick Simpson. In the NOPE area was Jesse Velasco. MEX MOC gave the pre-pass briefing using an obsolete SOE, which required that DSS 14 uplink commands and receive telemetry. When the discrepancy was pointed out, MEX MOC admitted that there had been two SOE's. There was no one at ESOC during the first two hours of the set up who could resolve the problem, so we went ahead with our nominal BSR preparations with the concurrence of the NOPE. Eventually, MEX MOC agreed that DSS 14 had no uplink or telemetry support requirements. Jose Valencia had warned about some reconfigurations at the station, prompting concern that we might have problems acquiring data from all four channels; these proved unfounded. No receiver frequency offset (FRO) was used for this experiment. Predictions indicated that the X-band specular echo would be about 4 kHz above the carrier at the specular time and moving toward higher frequencies. Since the carrier is normally about 3 kHz below the passband center in 1-way mode, the echo would appear at the centER. In fact, the echo was visible all the way across the passband; but the choice not to use a FRO appears to have been a good one. Performance Problems ==================== Operators reported that the Briefing Message command US14 CNF MOD 102 A, which extends the dichroic reflector, was rejected; the "CNF" must be omitted. The operator practice of "time stacking" commands may have led to an incorrect configuration during the pre-cal which resulted in the X-LCP noise diode's being left on. The noise diode controller may have been reconfigured to X-RCP before the "disable" instruction had been executed on the X-LCP diode. Jesse Velasco is investigating how this happened. The error was discovered in real time and the affected steps were repeated so that the necessary calibration data were obtained. Subsequent executions of similar sequences did not lead to a reoccurrence. [Note added later: The X-LCP noise diode problem was later traced to a typo in the briefing message which incorrectly connected the X-LCP RSR to an X-RCP front end. These measurements were not used in the final calibration.] RSR recording was suspended after completion of the pre-cal. It was resumed when the spacecraft S-band carrier was turned on; these data may be useful in characterizing the "stability" of S-band during warm-up. Gene Goltz mistakenly reset the RSR attenuators when he restarted the recording; these were manually returned to near their original values over several minutes of adjustment, but the RCP data after 09:50 will have slightly different linearity characteristics than those collected before 08:32. The S-LCP channel seemed less stable than the other three in the sense that ADC amplitudes jumped around when constant levels were expected and it was harder to detect changes in noise diode status. Disk space on RSR2 ran out just before the surface echo appeared (about 11:03). Danny Kahan believes the RSR should swap automatically to a backup disk, but that did not happen in our case. We cleared some space on the original disk, but recording did not resume. Finally, we restarted the RSR (which reset the RSR attenuators) and recording was then normal. But the echo had passed; there are no usable echoes from either the S-LCP or the X-RCP channels. We had checked the disk space during setup and concluded that we had twice the space that would be needed; it is not clear where the estimation error occurred. Most of the data on the RSR disks belongs to Cassini. Data Acquisition ================ The set up period began at 06:05. DSS 14 announced that it was ready to begin the pre-calibrations about 15 minutes later; but we waited 30 minutes, hoping for resolution of the SOE question by MEX MOC. The pre-calibration was mostly nominal. ADC levels suggested that the X-LCP noise diode had not been turned off at Step-11; so we repeated Steps-8, 11, 9, 11, and 13 after Step-18. These confirmed the diagnosis, gave us the needed 5 minutes of data with the diode turned off, and restored the noise diode controller to its desired configuration prior to BOT. DSS 14 was tracking the spacecraft before 09:00. DSS 14 reported that the X- band receiver was in lock shortly after. The S-band unmodulated carrier was turned on about 09:54; S-band predicts had to be delivered in real time, delaying lock on that band. X-band modulation was turned off about 10:11, and the slew toward Mars inertial pointing began at 10:46. Because the specular condition occurred early in the BSR window, we conducted MiniCal #1 simultaneously with Slew #1. RSR2 ran out of disk space about three minutes after completion of the MiniCal. There were good echoes visible on all four channels between 11:09 and 11:15; X-RCP peaked at 35 dB SNR at 11:11 and had a width of about 2500 Hz - the value predicted for beam-limited scattering. RSR2 was recording again at 11:16 in S-LCP and 11:17 (X-LCP). Since there was no post-experiment BCAL, we started MiniCal #2 at 11:20, completed it at 11:35, and then moved directly to the Post-Cal, which was completed at 12:12. The station was released at 12:15, 65 minutes early. RSRs were configured as in Table 1: Table 1 --------------------------------------------- RSR Channel Mode ATT FGAIN Operator dB ----- ------- ---- ---- ----- --------------- RSR2A S-LCP 1-W auto 60 Kahan RSR2B X-LCP 1-W auto 60 Kahan RSR3A X-RCP 1-W auto 65 Goltz RSR3B S-RCP 1-W auto 60 Goltz RSR subchannels (SCHAN) were defined as follows: Table 2 --------------------------------------------------------------------- Subchannel Sample Rate Comments ---------- ----------- --------------------------------------------- 1 1 ksps 2 8 ksps 3 25 ksps Primary recording bandwidth 4 100 ksps Backup recording Table 3 lists ADC amplitude levels read from RSR displays during the experiment. Where available, signal-to-noise ratios, frequency offsets, and other measurements are also listed. Times are in UTC read from a wall clock and may not reflect actual times when configurations changed. "Steps" are as defined in the briefing message. Acronyms and abbreviations are explained after Table 3. Table 3 ------------------------------------------------------------------------------ TIME (ERT) RSR2A RSR2B RSR3A RSR3B COMMENTS 2005-07-06 S-LCP X-LCP X-RCP S-RCP ADC ADC ADC ADC (dB) (dB) (dB) (dB) ---------- ------ ------ ------ ------ --------------------------------------- End-to-End Configuration Check 06:36 -9.8 -10.2 -9.9 -10.3 All channels to sky; all ATTEN auto set 06:38 -10.9 -0.4 -0.2 -10.2 Step 2: X-band to AMB 06:40 -1.5 -0.4 -0.2 -10.2 Step 3: S-LCP to AMB 06:42 -1.5 -0.6 -0.1 -0.5 Step 4: S-RCP to AMB 06:43 Begin DSS 14 shift change Pre-Calibration 06:45 Reset all ATTEN using auto feature 06:50 Shift change completed; AMB physical temperatures and weather conditions: S1 = 19.06C S2 = 25.12C X1 = 16.88C T = 29.0C H = 30.2 percent Sky = partly cloudy 06:55 -10.0 -9.9 -10.1 -9.6 Begin RSR SCHAN=3 (25 kHz) recording 07:00 -10.0 -9.8 -10.1 -9.6 Step 5: Config ND controllers 07:05 -10.0 -9.7 -9.9 -9.6 Step 6: XR ND on; confirm 12.5K setting 07:10 -10.0 -21.6 -19.9 -9.7 Step 7: X-band to sky 07:15 -10.0 -21.5 -22.1 -9.6 Step 8: XR ND off; confirm 12.5K 07:20 -10.0 -19.4 -22.0 -9.6 Step 9: XL ND on; confirm 12.5K 07:25 -9.9 -10.5 -10.0 -9.6 Step 10: X-band to AMB; AMB physical temperatures as follows: S1 = 19.06C S2 = 24.94C X1 = 16.88C 07:30 -9.9 -10.4 -9.9 -9.6 Step 11: XL ND off 07:35 -10.0 -19.4 -22.0 -9.6 Step 12: X-bands to sky; DSS 14 confirms that XL ND is off despite high ADC value 07:40 -10.0 -19.3 -22.0 -9.4 Step 13: SR ND on 07:45 -9.9 -19.3 -21.9 -18.8 Step 14: SR to sky 07:50 -10.0 -19.3 -22.0 -21.2 Step 15: SR N D off; confirm 12.5K 07:55 -9.9 -19.2 -21.9 -21.2 Step 16: SL ND on 08:00 -17.9 -19.1 -21.8 -21.2 Step 17: SL to sky 08:05 -18.8 -19.3 -22.0 -21.2 Step 18: SL ND off; AMB physical temperatures as follows: S1 = 19.19C S2 = 24.75C X1 = 16.88C 08:10 -19.7 -19.2 -21.8 -21.2 Repeat Step 8: config DC01 ND controller 08:15 -20.8 -21.7 -21.9 -21.2 Repeat Step 11: XL ND off 08:20 -20.3 -19.3 -21.8 -21.4 Repeat Step 9: XL ND on 08:25 -18.7 -21.3 -21.8 -21.3 Repeat Step 11: XL ND off 08:30 -19.1 -21.3 -21.9 -21.3 Repeat Step 13 DC01: configure for XR 08:32 Stop RSR recordings BOT and non-BSR Activities 08:55 DSS 14 tracking 09:05 DSS 55 drops uplink 09:20 Begin 1-way reception 09:32 -19.9 -20.3 -9.7 -10.2 ADC amplitudes (Goltz had apparently reset the ATTEN values at this point) 34 63 Pt/No (dB/Hz) -2912 -2914 Carrier offset in SSI (Hz) 09:33 DSS 14 reports rain Bistatic Radar Activities 09:50 -20.2 -20.5 -10,3 -10.3 Start RSR SCHAN=3 recordings 09:57 Manually set XR ATTEN=24.0 09:58 -19.3 -20.9 -20.9 -21.3 Manually set SR ATTEN=14.0 25 34 64 51 Pt/No (dB/Hz) -1314 -2917 -2911 -1339 Carrier offset in SSI (Hz) 10:37 -17.8 -21.0 -20.7 -21.4 ADC amplitudes 25 42 72 52 Pt/No (dB/Hz) -1356 -2973 -2970 -1354 Carrier offset in SSI (Hz) 10:44 -19.1 -21.0 -20.8 -21.4 Mini-Calibration #1 10:45 -19.4 -21.2 -19.0 -21.5 Step 1: XR ND on 10:46 Begin Slew #1 10:48 -19.2 -21.0 -21.5 -19.2 Step 2: XR ND off; SR ND on 26 33 37 28 PT/No (dB/Hz) -1339 -2908 -2901 -1336 Carrier offset in SSI (Hz) 10:51 -17.9 -19.2 -21.5 -21.5 Step 3: SR ND off; XL ND on 10:52 -19.3 SL unstable (reason UNK) 10:54 -18.2 -21.1 -21.4 -21.6 Step 4: XL ND off; SL ND on 10:57 -20.0 -21.1 -21.6 -21.5 Step 5: SL ND off; Surface Echo Period 10:57 Begin RSR SCHAN=4 recordings 11:03 RSR2 out of disk space 11:06 Stop RSR2 SCHAN=4 recording 11:07 -21.3 20 Pt/No (dB/Hz) -2870 Carrier offset in SSI (Hz) 11:09 -21.0 -21.3 -21.6 Big echo (2500 Hz wide) 20 27 31 23 Echo Pt/No (dB/Hz) -1253 -2500 -4154 -1252 Echo position in SSI (Hz) 11:11 -21.1 -21.3 -21.5 ADC amplitude 21 30 35 27 Echo Pt/No (dB/Hz) -549 755 895 -307 Echo position in SSI (Hz) 11:15 Weak XR echo nears high edge of 25 kHz window 11:16 RSR2B recording with default ATTEN 11:17 RSR2A recording with default ATTEN Mini-Calibration #2 11:20 -10.4 -9.8 -19.4 -21.6 Step 1: XR ND on 11:23 -21.4 -19.3 Step 2: XR ND off, SR ND on Stop RSR3 (X-band) SCHAN=4 recording Manually reset ATTEN=19.5 on RSR2 (both) 11:25 -17.1 -19.7 -21.5 11:26 -17.5 -17.7 -21.5 -21.5 Step 3: SR ND off, XL ND on 11:29 -16.1 -19.7 -21.6 -21.6 Step 4: XL ND off, SL ND on 11:32 -19.6 -21.5 -21.7 Step 5: SL ND off Post-Calibration 11:37 Goltz directs DSS 14 to begin post-cal 11:41 -7.9 -8.2 -9.9 -9.9 Step 1: All to AMB; antenna at zenith. AMB physical temperatures as follows: S1 = 18.81C S2 = 24.17C X1 = 16.94C 11:45 -8.0 -8.3 -9.7 -9.9 Step 2: XR ND on 11:48 -8.0 -8.4 -9.8 -9.7 Step 3: XR ND off; SR ND on 11:51 -7.9 -8.1 -9.8 -9.9 Step 4: SR ND off, XL ND on 11:54 -7.8 -8.2 Step 5: XL ND off, SL ND on 11:57 -16.2 -20.1 -22.1 -21.6 Step 6: All to sky 12:00 -16.8 -18.0 -22.0 -21.6 Step 7: SL ND off, XL ND on 12:03 -17.2 -20.1 -22.0 -19.2 Step 8: XL ND off, SR ND on 12:06 -16.1 -20.1 -19.8 -21.8 Step 9: SR ND off, XR ND on 12:09 -17.6 -20.2 -22.1 -21.6 Step 10: XR ND off; AMB physical temperatures and weather as follows: S1 = 18.75C S2 = 23.94C X1 = 16.88C T = 28.3C H = 34.5 percent Sky = rain stopped; partly cloudy 12:15 Stop RSR SCHAN=3 recordings AMB = ambient load BOT = Beginning of Track CONSCAN = conical scan tracking CW = continuous wave (carrier only) EOT = End of Track FRO = frequency offset HGA = high-gain antenna LOS = loss of signal ND = noise diode No = noise power Pc = carrier power S1 = ambient load for S-RCP S2 = ambient load for S-LCP SL = S-LCP SR = S-RCP TLM = telemetry X1 = Ambient load for both X-band channels XL = X-LCP XR = X-RCP 2005-07-25: original (RAS) 2006-06-26: Updated Summary, added note re XL noise diode; minor edits (RAS)