Mars Express Bistatic Radar Experiment Operations Plan and Report 07 February 2012 Summary ======= DSN Antenna: 14 Orbit: 10325 Orbit Start Time: 2012-02-07T02:57:55 HGA Pointing: Specular Start Ascend EQX End -------- ---------- -------- Specular Condition (ERT): 05:45 06:34 07:14 Target Latitude (deg N): -40.14 -0.19 69.56 Longitude (deg E): 128.78 213.69 130.61 Rp (km): 3394. 3394. 3394. Incidence/Reflection Angle (deg): 70.74 64.47 47.31 Slant Range (km): 5553. 697. 3808. Slew Angle (deg): 38.53 51.07 85.37 Doppler (carrier, fd; Hz): 25743. 42993. -10035. Doppler (echo, fr; Hz): 40634. 36661. -48836. Doppler Difference (fdd; Hz): -14891. 6331. 38801. Earth-Mars Distance (m): 1.129E+11 1.129E+11 1.129E+11 Experiment Set Up ================= This experiment was conducted using the Goldstone DSS 14. Danny Kahan and Gene Goltz were in the Radio Science Support Area (RSSA) at JPL. Jesse Velasco was in the JPL NOPE area. Dick Simpson monitored by telephone from Stanford. Performance Problems and Notes ============================== Kahan noted that there is no longer an S-Band maser at DSS 14; both LNAs are HEMT devices. Simpson requested performance data on the HEMTs, which Kahan will track down. Echoes were visible in all four channels as soon as the experiment began. There was brief, but strong, S-Band interference at 06:17-06:18. 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 2012/038 RSR2A RSR2B RSR3A RSR3B -------- ----- --------- ----- ----- ----- ----- ------------------------ Set-Up 01:50 FGAIN 60 60 60 65 FGAIN settings (dB) Pre-Cal 03:07 1 -16.9 -9.6 -11.8 -10.2 All rcvrs to SKY 03:08 att auto -10.1 -10.3 -10.2 -10.1 ADC amplitude 5.0 12.5 9.5 11.5 Attenuator settings (dB) 03:10 2 -10.2 -0.3 -10.3 -0.1 XR and XL to AMB 03:11 3 -2.7 -0.2 -10.2 -0.0 SL to AMB 03:13 4 -2.7 -0.3 -1.8 -0.1 SR to AMB 03:15 att auto -9.7 -10.0 -10.0 -10.0 Reset attenuators 12.5 24.5 18.5 24.0 Attenuator settings (dB) Ambient load temps: S1=17.88C S2=20.31C X1=16.62C Local weather: T=9.8C H=21.2 percent sky=partly cloudy 03:18 rec 3 e Begin 25 kHz recording 03:20 5 -9.7 -10.0 -9.9 -10.0 Configure noise diodes 03:25 6 -9.7 -10.1 -10.1 -9.8 XR=AMB+ND 03:30 7 -9.7 -22.1 -9.9 -20.3 XR=SKY+ND; XL=SKY 03:35 8 -9.6 -22.3 -10.0 -22.6 XR=SKY 03:40 9 -9.7 -20.5 -9.8 -22.6 XL+SKY+ND Confirmed 12.5K ND 03:45 10 -9.8 -9.9 -9.9 -9.9 XR=AMB; XL=AMB+ND Ambient load temps: S1=17.75C S2=20.12C X1=16.38C 03:50 11 -9.7 -10.0 -9.8 -9.9 XL=AMB 03:55 12 -9.7 -22.2 -9.8 -22.6 XR=SKY; XL=SKY 04:00 13 -9.7 -22.1 -9.7 -22.5 SR=AMB+ND 04:05 14 -9.7 -22.1 -18.0 -22.6 SR=SKY+ND 04:10 15 -9.6 -22.1 -19.2 -22.5 SR=SKY Confirmed 12.5K ND 04:15 16 -9.5 -22.2 -19.2 -22.4 SL=AMB+ND 04:20 17 -16.6 -22.2 -19.0 -22.4 SL=SKY+ND 04:25 18 -17.6 -22.3 -19.2 -22.5 SL=SKY Confirmed 12.5 K ND Ambient load temps: S1=17.62C S2=20.00C X1=16.12C 04:30 end -17.7 -22.2 -19.2 -22.5 Stop 25 kHz recording BOT 05:00 -17.3 -20.1 -18.4 -16.5 X-Band AOS 05:07 S-Band AOS 05:22 rec 3 e -17.3 -20.5 -18.7 -17.0 TLM off 05:23 Resume 25 kHz recording 05:28 DSS 14 switch to Mars pointing predicts 05:29 sfro 3 0 +10k 0 +10k 25 kHz RSR offsets, Hz sfro 4 0 -18k 0 -18k 100 kHz offsets, Hz MiniCal1 05:30 1 -16.5 -20.8 -18.7 -16.1 XR=SKY+ND Confirmed 12.5K ND 05:33 2 -14.8 -20.7 -17.6 -16.8 XR=SKY; SR=SKY+ND 05:36 3 -14.2 -19.5 -18.8 -17.3 SR=SKY; XL=SKY+ND 05:39 4 -12.9 -20.7 -18.6 -17.4 XL=SKY; SL=SKY+ND 05:42 5 -13.8 -20.9 -18.7 -17.4 SL=SKY 05:45 end -13.8 -20.9 -18.7 -17.5 BSR 05:45 rec 4 e Begin 100 kHz recording 06:15 sfro 3 +2k +2k RSR tuning offset (Hz) 06:29 sfro 3 -5k -5k RSR tuning offset (Hz) 06:30 sfro 3 -4k -4k RSR tuning offset (Hz) 06:34 sfro 3 -13k -13k RSR tuning offset (Hz) 06:36 sfro 3 -7k -7k RSR tuning offset (Hz) 06:37 sfro 3 -21k -21k RSR tuning offset (Hz) 06:39 sfro 3 -27k -27k RSR tuning offset (Hz) 06:40 sfro 3 -10k -10k RSR tuning offset (Hz) 06:41 sfro 3 -33k -33k RSR tuning offset (Hz) 06:43 sfro 3 -39k -39k RSR tuning offset (Hz) 06:44 sfro 3 -13k -13k RSR tuning offset (Hz) 06:47 sfro 3 -48k -48k RSR tuning offset (Hz) 06:51 sfro 3 -15k -15k RSR tuning offset (Hz) 07:11 sfro 3 -45k -45k RSR tuning offset (Hz) 07:14 rec 4 d End 100 kHz recording MiniCal2 07:15 1 -14.0 -21.6 -19.2 -16.6 XR=SKY+ND Confirm 12.5K ND 07:18 2 -14.0 -21.7 -17.9 -17.4 XR=SKY; SR=SKY+ND 07:21 3 -13.9 -20.1 -19.1 -17.5 SR=SKY; XL=SKY+ND 07:24 4 -13.0 -21.6 -19.1 -17.4 XL=SKY; SL=SKY+ND 07:27 5 -14.0 -21.7 -19.0 -17.5 SL=SKY 07:30 end DSS 14 return to S/C pointing predicts 07:31 sfro 3 0 0 0 0 All tuning offsets 0 EOT 07:44 -14.0 -22.2 -19.3 -22.4 Move antenna to zenith (do not stow) Post-Cal 07:52 1 -6.0 -10.0 -9.9 -9.9 All to AMB Ambient load temps: S1=16.75C S2=18.19C X1=15.31C 07:55 2 -6.0 -10.0 -9.9 -9.7 XR=AMB+ND 07:58 3 -6.0 -10.2 -9.7 -9.9 XR=AMB; SR=AMB+ND 08:01 4 -5.9 -9.8 -9.9 -9.9 SR=AMB; XL=AMB+ND 08:04 5 -5.8 -10.0 -9.9 -9.9 XL=AMB; SL=AMB+ND 08:07 6 -13.0 -22.1 -19.0 -22.4 All to SKY; SL=SKY+ND 08:10 7 -14.0 -20.4 -19.0 -22.3 SL=SKY; XL=SKY+ND 08:13 8 -13.9 -22.2 -17.8 -22.6 XL=SKY; SR=SKY+ND 08:16 9 -14.1 -22.1 -19.0 -20.2 SR=SKY; XR=SKY+ND 08:19 10 -14.0 -22.2 -19.0 -22.5 XR=SKY Ambient load temps: S1=16.69C S2=18.12C X1=15.19C Local weather: T=8.3C H=24.3 percent sky=cloudy EOA 08:23 end AMB = ambient load BOT = Beginning of Track BW = bandwidth C = Celsius 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 k = kilo, thousand K = Kelvin LOS = loss of signal ND = noise diode No = noise power NOP = Network Operations Plan occn = occultation Pc = carrier power rcvr = receiver S1 = ambient load for S-RCP S2 = ambient load for S-LCP s/c = spacecraft SKY = receiver looking a sky 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 There were major signal dynamics in both amplitude and Doppler during this experiment. X-Band echo power was computed by defining an echo window and letting the FRO changes keep the signal within it. This appears to have been successful except for X-Band over about 06:19-06:31 when the echoes were strongest and moving fastest and may have spilled over into the noise window(s). The error in Tsys appears to be less than 5 percent and the error in echo power is probably no more than that since most power within the echo window was echo rather than noise (error will be in scaling X-RCP and X-LCP power and not in removing the noise pedestal - and it should be comparable in both polarizations. There is a Brewster angle transition in both the S- and X-Band data, but it is a little hard to tell exactly when it occurs because the signal powers are decreasing quickly at about the same time as the dominant polarization is switching. Everything happens as the specular point crosses Stealth near periapsis (northward equator crossing is at about 147 W longitude) and the incidence angle passes through 60 degrees (at about 13 N latitude). 10 s average X-Band spectra merged with 60 s S-Band average spectra appears to be a good combination. S-Band dielectric constant may be slightly higher than the X-Band value until about 06:10. Signals are reasonably strong and stable over this time; so these should be reliable values. Until about 06:24, the S-Band dielectric constant holds at about 3, then drops linearly to 2 just before 06:30. Meanwhile, X-Band dielectric constant is increasing to almost 5 at 06:24, then shoots upward to almost 7 before dropping sharply by 06:30. All four channels have weak echoes by 06:35, rise slightly around 06:37, drop again around 06:40, and then have modest and approximately constant values for the remainder of the experiment. After about 06:30, S-Band dielectric constant approximately tracks the X-Band value, though the weak echo signals (especially S-LCP) are reminders that we should be cautious in deriving dielectric constant. Noise power density looks reasonable in all four channels. S-LCP was by far the largest. S-RCP and X-LCP were comparable, and X-RCP was lowest. The two X-Band noise power densities drop more sharply with elevation angle, as expected. Dick Simpson Original: 2012-02-08 Updated comment about S-Band interference: 2012-04-10 Added Post Analysis Summary: 2013-06-19 Minor edits to Post Analysis Summary: 2013-06-26