Mars Express Bistatic Radar Experiment Operations Plan and Report 03 July 2010 Summary ======= DSN Antenna: 63 Orbit: 8323 Orbit Start Time: 2010-07-03T16:14:44 HGA Pointing: Specular Start Mid Point End -------- ---------- -------- Specular Condition (ERT): 18:39 19:16 19:49 Target Latitude (deg N): -4.98 -27.35 -48.04 Longitude (deg E): 13.86 12.00 90.12 Rp (km): 3394. 3394. 3394. Incidence/Reflection Angle (deg): 46.39 59.74 89.70 Slant Range (km): 7208. 4573. 2210. Slew Angle (deg): 87.22 60.52 0.59 Doppler (carrier, fd; Hz): -30036. -32467. -2160. Doppler (echo, fr; Hz): 24351. 23174. -1803. Doppler Difference (fdd; Hz): -54387. -55641. -357. Earth-Mars Distance (m): 2.711E+11 2.711E+11 2.711E+11 Experiment Set Up ================= This experiment was conducted using the Madrid DSS 63. John Klose and Gene Goltz were in the Radio Science Support Area (RSSA) at JPL. This report is largely based on notes provided by Goltz. Performance Problems and Notes ============================== During the X-Band pre-cal, there were three ambient load connections, rather than the normal two. This has no impact on science but suggests some confusion over the proper procedure, which may be related to the events described in the next three paragraphs. To clear some initialization ambiguities in the procedure, I asked Gene Goltz to have station personnel issue disable commands to both noise diode controllers before beginning to record pre-calibration data. In about half of the previous experiments at DSS 63 this year, the pre-cal has started with the X-RCP, S-RCP, or both diodes in the ON state; this makes extraction of the pre-cal Tsys difficult or impossible. Goltz reported no problems. The S-RCP pre-cal data show the noise diode ON-OFF sequence to be correct, but the noise diode was only operating at a 50 percent duty cycle (a problem we have noticed before, but less frequently; it is caused by not including the MFQ=ON command in the initialization. There is no evidence that the noise diode was ever turned on during the X-RCP pre-cal. The pre-cal Tsys can be calculated, but the noise diode itself can only be calculated from the post-cal data. The X-RCP noise diode appears to have operated correctly during the two MINICALS and during the post-cal. Over 18:01-18:07 there was an approximately 70 percent increase in the background noise level on X-RCP. This was during the first carrier level calibration. There is no corresponding increase on any other channel. The cause for the increase is not known. Between the experiments on 2010/170 and 2010/184, DSS 63 suffered a power outage; the maser LNA on S-RCP had to be cooled down again after the recovery. Engineers familiar with the receivers believed that the thermal cycling might result in removal of contaminants in the maser, leading to better amplitude stability - a problem that had been noted earlier, and explicitly mentioned in reports from day 170. In fact, the S-RCP levels did appear much more stable on this experiment. However, whereas the zenith Tsys was 21.2K on day 170, it was 27.5K on 184; by comparison, Tsys for S-LCP, which is normally higher, was 25.5K at zenith and averaged 25.5K during surface observations. There was a 2.5 dB dropout on S-LCP starting at 18:34, accelerating to 18:39, ten recovering quickly by 18:41. Similar drop-out have been seen in the DSS 63 S-LCP output on days 106, 135, 142, and 170. Data Acquisition ================ RSRs were configured as in Table 1. Table 1 ----------------------------------------------------- RSR Channel Mode ATT FGAIN Operator dB ------ ------- ---- ---- ----- ---------------------- RSR1A S-LCP 1-W auto 60 UNK RSR1B X-LCP 1-W auto 60 UNK RSR2A S-RCP 1-W auto 60 UNK RSR2B X-RCP 1-W auto 65 UNK RSR subchannels (SCHAN) were defined as follows: Table 2 ---------------------------------------------------------------------- Subchannel Sample Rate Comments ---------- ----------- --------------------------------------------- 1 2 ksps Occultation bandwidth (not recorded for BSR) 2 8 ksps Occultation backup (not recorded for BSR) 3 25 ksps Primary recording bandwidth 4 100 ksps Backup recording Table 3 lists ADC amplitude levels read from RSR displays during the experiment. Times are in UTC and should be considered approximate. "Steps" are as defined in the briefing message. RSR ATT settings are in units proportional to dB. Acronyms and abbreviations are explained after Table 3. Table 3 ----------------------------------------------------------------------------- Activity Time Step # S-LCP X-LCP S-RCP X-RCP Notes / Comments 2010/184 RSR1A RSR1B RSR2A RSR2B -------- ----- --------- ----- ----- ----- ----- ------------------------ Set-Up 15:35 FGAIN 60 60 60 65 FGAIN settings (dB) Pre-Cal 16:13 1 -7.4 -15.8 -5.8 -9.4 16:14 att auto -9.8 -9.7 -10.1 -10.2 ADC amplitudes (dB) 17.0 17.5 21.0 26.5 Set attenuators (dB) 16:18 2 -9.7 -0.3 -10.2 -0.2 16:20 3 -0.6 -0.3 -10.1 -0.3 16:22 "4,5" -0.6 -0.3 -0.9 -0.2 Amb load phys temps S1=20.56 S2=24.75 X1=16.38 16:23 att auto -9.6 -10.2 -9.9 -3.5 Local weather: T=26.4C H=39.4 percent sky=clear 28.0 29.5 31.5 31.5 Set attenuators (dB) 16:25 rec 3 e Begin 25 kHz recording 16:27 6 -9.6 -10.2 -10.0 -3.4 16:39 7 -9.5 -10.2 -10.1 -3.3 Repeat Step 2 at 16:35 16:45 8 -9.6 -21.7 -10.1 -15.1 16:50 9 -9.6 -21.7 -10.1 -15.1 16:57 10 -9.6 -19.8 -10.1 -15.2 Confirm 12.5K ND 17:02 "11,12" -9.6 -10.0 -10.1 -3.4 Amb load phys temps: S1=20.88 S2=25.19 X1=16.44 17:07 13 -9.6 -10.3 -10.0 -3.4 17:12 14 -9.6 -21.8 -10.0 -15.3 17:17 15 -9.7 -21.7 -10.0 -15.3 17:22 16 -9.6 -21.8 -19.7 -15.2 17:27 17 -9.6 -21.6 -21.0 -15.2 Confirm 12.5K ND 17:32 18 -9.5 -21.7 -20.9 -15.2 17:37 19 -19.1 -21.7 -20.9 -15.2 17:42 20 -20.8 -21.8 -21.1 -15.3 Amb load phys temps: S1=20.88 S2=25.38 X1=16.31 17:47 21/end -21.1 -21.7 -21.0 -15.0 BOT 17:50 -20.7 -21.6 -21.0 -15.0 Collect TLM to 18:01 18:16 -20.8 -21.4 -21.1 -13.8 Switch to Mars pointing predicts 18:18 sfro 3/SX +8K +51K +8K +51K Tuning offset (Hz) sfro 34/X +28K +28K Tuning offset (Hz) MINICAL1 18:20 1 -20.8 -21.5 -21.2 -12.0 Confirm 12.5K ND 18:23 2 -20.7 -21.4 -19.1 -13.8 18:26 3 -20.8 -19.6 -21.1 -13.7 18:29 4 -19.0 -21.5 -21.0 -13.8 18:32 5 -20.8 -21.4 -21.0 -13.7 18:35 end -20.9 -21.2 -21.0 -13.7 BSR 18:39 rec 4 e -22.2 -21.4 -21.0 -13.7 Begin 100 kHz recording 19:24 sfro 3/X +42K +42K Tuning offset (Hz) 19:33 sfro 3/X +32K +32K Tuning offset (Hz) 19:36 sfro 3/X +21K +21K Tuning offset (Hz) 19:40 sfro 3/X +11K +11K Tuning offset (Hz) 19:44 sfro 3/SX 0 0 0 0 Tuning offset (Hz) OCC ING 19:50 END BSR 19:51 rec 4 d -20.4 -21.1 -20.6 -13.6 End 100 kHz recording MINICAL2 19:51 1 -20.3 -21.1 -20.6 -11.8 Confirm 12.5K ND 19:54 2 -20.3 -21.1 -18.7 -13.4 19:56 3 -20.4 -19.4 -20.7 -13.5 19:58 4 -18.7 -21.3 -20.6 -13.5 20:00 5 -20.3 -21.1 -20.6 -13.6 20:02 end -20.4 -21.1 -20.6 -13.5 OCC EGR 20:04 EOT 20:10 stow -20.3 -21.0 -20.0 -13.9 Post-Cal 20:23 1 -9.7 -10.2 -9.9 -3.4 Amb load phys temps: S1=19.75 S2=24.44 X1=15.81" 20:30 2 -9.7 -10.2 -9.9 -3.2 20:33 3 -9.6 -10.3 -9.8 -3.4 20:36 4 -9.7 -10.0 -9.9 -3.4 20:39 5 -9.5 -10.3 -9.9 -3.4 20:42 6 -19.2 -21.8 -20.8 -15.1 20:45 7 -20.7 -19.9 -20.8 -15.2 20:48 8 -20.7 -21.9 -18.9 -15.2 20:51 9 -20.8 -21.8 -20.8 -12.8 20:54 10 -20.6 -21.8 -20.8 -15.1 Amb load phys temps: S1=19.44 S2=24.12 X1=15.62 Local weather: T=22.7C H=51.7 percent sky=partly cloudy EOA 20:57 11/end -20.6 -21.8 -20.8 -15.1 End 25 kHz recording AMB = ambient load BOT = Beginning of Track BW = bandwidth CNR = Carrier to noise ratio CONSCAN = conical scan tracking CW = continuous wave (carrier only) EOA = End of activity EOT = End of Track FRO = frequency offset HGA = high-gain antenna LOS = loss of signal ND = noise diode No = noise power NOP = Network Operations Plan occn = occukltation Pc = carrier power rcvr = receiver S1 = ambient load for S-RCP S2 = ambient load for S-LCP s/c = spacecraft SL = S-LCP SNR = Signal to noise ratio SR = S-RCP TLM = telemetry X1 = Ambient load for both X-band channels XL = X-LCP XR = X-RCP Post Analysis Summary X-Band Power: X-Band data were processed to power spectra with 60 second averaging (sums of 1464 individually calculated 1024-point spectra). The 69 minutes of 25 kHz data were divided into 12 time intervals -- five with split echoes (caused by receiver tuning offset changes, FRO) and seven during which the echo drifted within the passband at fixed FRO. One of the split echo intervals also included an average spectrum in which the echo had drifted off the lower edge of the passband. The directly propagating carrier did not appear in the 25 kHz passband until the last four spectra; except for these four spectra, the carrier tracking window was used to find the frequency bin with maximum echo power. Carrier suppression was used to process spectrum 66 since the returning carrier was between the two components of the surface echo. Int Times Spectra Noise Bins Echo Echo Bins Notes Peak --- ----------------- ------- --------------- ------- ---------------- ------ A 18:39-19:18 01-39 104:405,769:916 410:760 410:760 B 19:18-19:24 40-45 104:200,620:916 205:615 410:615->205:430 BC 19:24-19:25 46 104:200,769:916 205:765 205:760 [1] C 19:25-19:32 47-53 705:916 104:700 450:700->104:370 [2] CD 19:32-19:34 54-55 615:916 104:610 104:610 [3,4] D 19:34-19:36 56-57 104:150,520:916 155:515 155:515 DE 19:36-19:37 58 104:150,775:916 155:770 155:770 [1] E 19:37-19:40 59-61 104:150,775:916 155:770 380:770->155:520 EF 19:40-19:41 62 104:150,825:916 155:820 155:820 [1] F 19:41-19:44 63-65 104:200,730:916 205:725 400:725->205:515 Int Times Spectra Noise Bins Carrier Echo Bins Notes Peak --- ----------------- ------- --------------- ------- ---------------- ------ FG 19:44-19:45 66 104:150,850:916 365:369 155:845 [1,5] G 19:45-19:48 67-69 104:360,769:916 365:369 500:765->375:600 [6] Notes: [1] Split echo resulting from change in X-Band receiver tuning offset [2] Echo may be spilling over lower edge of passband at end [3] Spectrum 54: echo spilling over lower edge [4] Spectrum 55: split echo, most of which is in-band at new frequency [5] Processed with carrier suppression ON [6] Ingress occultation at approximately 19:49:30 S-Band Power: S-Band data were processed in the same way. The echo signals were weak so two different integrations were used (60 s and 360 s -- first four rows and fifth row, respectively, in the table below). The directly propagating carrier was in frequency bin 123 for most of the experiment; after the FRO at 19:44 it was in bin 451. Int Times Spectra Noise Bins Carrier Echo Bins Notes Peak --- ----------------- ------- --------------- ------- ---------------- ------ A 18:39-19:23 01-44 129:615,823:916 121:125 700:820->620:820 B 19:23-19:44 45-65 129:190,745:916 121:125 615:820->185:365 BC 19:44-19:45 66 129:190,620:916 449:453 195:615 C 19:45-19:48 67-69 104:445,580:916 449:453 490:575->460:515 All 18:38-19:45 01-11 124:200,843:916 [1] 205:840 [1] Notes: [1] Carrier peak was tracked in bins 121:125 through spectrum 10, then in bins 449:453 in spectrum 11. Carrier suppression was used throughout, though it only made a difference in spectrum 11, when the carrier appeared between the two split echo components. S-RCP Tsys was higher than expected, but mre stable than during other recent experiments. S-LCP was anomalous during this experiment. There was a 2.5 dB drop in RSR output just as the surface observations began. The drop began at about 18:35, accelerated to its maximum value just after 18:39, then recovered quickly to its previous level (18:41). The gain correction in file A184183D.GNC was modeled as 2640.200 0.3324 0. 0. 66888.000 66996.000 !SLCP 25 kHz correction 2676.100 0.7889 0. 0. 66996.000 67068.000 !SLCP 25 kHz correction 2732.900 4.6574 0. 0. 67068.000 67115.000 !SLCP 25 kHz correction 2951.800 13.9692 0. 0. 67115.000 67154.000 !SLCP 25 kHz correction 3496.600 -14.6286 0. 0. 67154.000 67203.000 !SLCP 25 kHz correction 2779.800 -2.6044 0. 0. 67203.000 67248.000 !SLCP 25 kHz correction 2662.600 -0.6222 0. 0. 67248.000 67284.000 !SLCP 25 kHz correction 2640.200 0. 0. 0. 67284.000 72000.000 !SLCP 25 kHz correction Later diagnostic work indicated that a cable following the HEMT had broken. It was replaced and tests indicated performance had returned to normal. Dick Simpson Original: 2010-06-29 Added Post-Analysis Summary: 2010-07-27 Corrected Table 3: 2011-03-17 Removed PDS unfriendly characters: 2011-05-31