Mars Express Bistatic Radar Experiment Operations Plan and Report 03 September 2009 Summary ======= DSN Antenna: 63 Pass: 2287 Orbit: 7272 Orbit Start Time: 2009-09-02T23:25:52 HGA Pointing: Specular Start Center End -------- ---------- -------- Specular Condition (ERT): 04:14 04:45 05:21 Target Latitude (deg N): -61.20 -62.02 -55.74 Longitude (deg E): 298.60 266.84 236.04 Rp (km): 3394. 3394. 3394. Incidence/Reflection Angle (deg): 67.17 72.90 77.52 Slant Range (km): 7033. 9414. 11315. Slew Angle (deg): 45.66 34.20 24.97 Doppler (carrier, fd; Hz): -54000. -42193. -29038. Doppler (echo, fr; Hz): -47809. -34323. -22365. Doppler Difference (fdd; Hz): -6191. -7870. -6672. Earth-Mars Distance (m): 2.380E+11 2.380E+11 2.380E+11 Experiment Set Up ================= This experiment was conducted using Madrid's DSS 63. Danny Kahan and Gene Goltz were in the Radio Science Support Area (RSSA) at JPL. Dick Simpson was on vacation after the MaRS/VeRa meetings in Port Townsend, WA. This report is based on notes provided by Kahan and Goltz. Performance Problems and Notes ============================== There was clipping of the X-RCP carrier during the BCAL measurements before and after the surface observations. Evidence indicates that the X-RCP attenuator was not correct after the auto reset at 23:53 in the pre-cal. X-RCP levels were 6-7 dB higher than normal during the remainder of the experiment. But clipping occurred only when the spacecraft HGA was aimed directly at Earth and modulation was turned off. The X-Band spacecraft transmitted frequency shifted upward by approximately 170 Hz at about 05:15:45. A similar shift can be seen in the surface echo frequency, and there were correspondingly smaller shifts at S-Band. Smaller shifts may have taken place earlier. The cause for these is unknown. 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 60 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 2009/245 RSR1A RSR1B RSR2A RSR2B -------- ----- --------- ----- ----- ----- ----- ------------------------ FGAIN 23:20 60 60 60 60 Pre-Cal 23:44 1 -17.9 -17.1 -9.9 -2.5 ADC amplitudes (dB) 23:45 att auto -9.8 -9.6 -9.8 -10.0 16.5 17.0 19.5 26.5 Attenuator settings (dB) 23:47 2 -10.0 -0.2 -9.8 -0.2 ADC amplitudes (dB) 23:49 3 -0.8 -0.1 -9.9 -0.2 23:51 4 -0.6 -0.1 -0.4 -0.3 23:53 att auto -9.9 -9.7 -10.0 -3.3 27.5 29.0 31.0 31.5 Attenuator settings (dB) AMB load phys temps: S1=17.75 S2=21.31 X1=14.94 Local weather: T=21.8C H=20.5 percent sky=clear 23:58 rec 3 e Begin 25 kHz recording 23:58 5 -9.9 -9.7 -10.0 -3.4 ADC amplitudes (dB) 2009/246 00:05 6 -9.9 -9.7 -9.8 -3.2 00:10 7 -9.9 -21.7 -9.9 -12.7 00:15 8 -9.9 -21.7 -9.8 -15.1 00:20 9 -9.9 -19.8 -10.0 -15.1 Confirmed 12.5K ND 00:25 10 -9.9 -9.6 -9.9 -3.4 AMB load phys temps: S1=17.62 S2=21.00 X1=14.75 00:30 11 -9.8 -9.9 -10.0 -3.3 00:35 12 -9.8 -21.8 -10.1 -15.1 00:40 13 -10.1 -21.8 -9.8 -15.1 00:45 14 -9.8 -21.9 -19.4 -15.2 00:50 15 -9.9 -21.8 -21.4 -15.2 Confirmed 12.5K ND 00:55 16 -9.7 -21.7 -21.3 -15.1 01:00 17 -19.3 -21.6 -21.3 -15.1 01:05 18 -21.2 -21.7 -21.4 -15.1 AMB load phys temps: S1=17.19 S2=20.60 X1=14.38 01:10 end -21.0 -21.7 -21.4 -15.0 Stop 25 kHz recording BOT 01:25 -19.7 -19.0 -19.3 -12.2 Collect TLM until 03:40 03:50 rec 3 e -20.7 -21.0 -20.9 -13.2 Resume 25 kHz recording 03:55 -20.7 -21.0 -20.9 -13.0 DSS 63 switch to Mars pointing predicts 03:59 sfro 3/SX +25K +25K +25K +25K Rcvr tuning offset (Hz) MiniCal1 03:59 1 -20.7 -21.0 -20.9 -11.4 Confirmed 12.5K ND 04:02 2 -20.8 -21.0 -19.0 -13.1 04:05 3 -20.7 -19.3 -20.8 -13.3 04:08 4 -18.9 -21.0 -20.9 -13.5 04:11 5 -20.8 -21.0 -20.9 -13.3 04:14 end -20.9 -21.0 -20.8 -13.4 BSR 04:14 sfro 3/SX 0 0 0 0 Begin 100 kHz recording 05:21 sfro 3/SX +25K +25K +25K +25K End 100 kHz recording MiniCal2 05:21 1 -20.9 -21.2 -21.0 -14.7 Confirmed 12.5K ND 05:24 2 -21.0 -21.2 -19.0 -14.8 05:27 3 -20.8 -19.3 -21.0 -14.4 05:30 4 -19.0 -21.2 -21.0 -14.3 05:33 5 -21.0 -21.2 -21.0 -14.3 End 05:36 -21.0 -21.2 -21.0 -14.4 DSS 14 switch to s/c pointing predicts 05:36 sfro 3/SX 0 0 0 0 Rcvr tuning offset (Hz) EOT 05:46 stow -21.0 -21.3 -21.1 -13.3 PostCal 05:50 1 -9.9 -9.6 -9.8 -3.4 AMB load phys temps: S1=15.94 S2=18.92 X1=13.81 05:55 2 -9.8 -9.7 -9.7 -3.1 05:58 3 -9.9 -9.6 -9.6 -3.3 06:01 4 -10.0 -9.4 -9.9 -3.3 06:04 5 -9.7 -9.6 -9.8 -3.2 06:07 6 -19.1 -21.4 -21.2 -14.9 06:10 7 -21.0 -19.5 -21.3 -14.9 06:13 8 -21.1 -21.6 -19.2 -15.1 06:16 9 -21.0 -21.5 -21.1 -12.5 06:19 10 -21.0 -21.5 -21.2 -15.0 AMB load phys temps: S1=15.88 S2=18.75 X1=13.38 Local weather: T=19.0C H=63.2 percent sky=clear EOA 06:22 end -21.0 -21.5 -21.1 -14.9 End 25 kHz recording AMB = ambient load BOT = Beginning of Track 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 Pc = carrier power rcvr = receiver S1 = ambient load for S-RCP S2 = ambient load for S-LCP 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 No FROs were required and the X-Band surface echo drifted slowly 6-8 kHz higher than the carrier throughout the observations. The time interval was split into two halves, to minimize the amount of noise in the echo window. Dielectric constants are mostly in the range 2.0-2.5 with smaller values in the first half of the experiment. S-Band drifted less by 3/11 and a constant window was used for calculating the echo power. There is too little power in the S-LCP echo for confident estimates of dielectric constant at 10-second averaging. The results with 60-seconds averaging are more convincing, but only over the first third of the experiment where the inferred dielectric constants are in the range 3.0-4.5. The S-Band echo may not be beam limited. In the last spectrum the S-RCP half-power width is 2 bins (48.8 Hz, or about 5 percent of the predicted beam-limited bandwidth). The measured bandwidth corresponds to an rms surface slope of 0.84 deg. The measured X-Band bandwidth is within a factor of 2 of the predicted beam-limited bandwidth at the same time; it may or may not be limited. If not, the corresponding rms surface slope is 2.4 deg. Dick Simpson Original: 2009-11-30 Updated based on processing: 2009-12-02