Mars Express Bistatic Radar Experiment Operations Plan and Report 08 April 2012 Summary ======= DSN Antenna: 43 Orbit: 10542 Orbit Start Time: 2012-04-10T08:44:42 HGA Pointing: Specular Start Olympus Mons End -------- ---------- -------- Specular Condition (ERT): 10:30 10:41 11:01 Target Latitude (deg N): 22.01 18.33 10.13 Longitude (deg E): 232.35 229.21 233.90 Rp (km): 3394. 3394. 3394. Incidence/Reflection Angle (deg): 51.72 52.97 55.82 Slant Range (km): 9200. 8660. 7502. Slew Angle (deg): 76.56 74.07 68.37 Doppler (carrier, fd; Hz): -12707. -12604. -11822. Doppler (echo, fr; Hz): 19243. 21689. 26045. Doppler Difference (fdd; Hz): -31950. -34292 -37867. Earth-Mars Distance (m): 1.194E+11 1.194E+11 1.194E+11 Experiment Set Up ================= This experiment was conducted using the Canberra DSS 43. Danny Kahan and Gene Goltz were in the Radio Science Support Area (RSSA) at JPL. Dick Simpson monitored by telephone from Stanford. Performance Problems and Notes ============================== At 09:40 Kahan reported that the S-RCP and S-LCP channels looked very similar; the station reported a similar observation five minutes later. After some adjustments by DSS 43 personnel, the S-LCP channel looked better (09:51). There may have been an incorrect operator directive at the end of the pre-cal, which connected the S-LCP RSR to the S-RCP LNA. The station requested permission to switch to planetary pointing predicts at about 09:56 and reported the action completed at 09:59. Kahan reported a 20 dB drop in X-RCP during the change, but most of it was recovered by 09:59. X-Band echoes were seen from the beginning with LCP slightly stronger than RCP; S-Band echoes were seen intermittently. X-RCP FGAIN was changed from 65 to 70 dB to prevent clipping during the first spacecraft calibration (09:51-10:09). There was no explicit change during the second spacecraft calibration (11:25-11:36), but Kahan said he would make the correction if it appeared necessary. He said nothing, so the assumption is that FGAIN remained at 65 except during the first spacecraft calibration. 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 65-70 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 2012/101 RSR1A RSR1B RSR2A RSR2B -------- ----- --------- ----- ----- ----- ----- ------------------------ 07:25 fgain 60 60 60 65 Set FGAIN attenuation (dB) PreCalc 08:00 1 -9.3 -7.9 -13.0 -9.9 ADC voltage levels (dB) 08:03 att auto -9.8 -9.8 -9.9 -10.1 Auto reset attenuation 17.0 13.5 11.5 9.5 Attenuator setting (dB) 08:05 2 -9.7 -0.1 -9.8 -0.1 X-Band to ambient load 08:06 3 -1.4 -0.1 -9.9 -0.1 S-LCP to ambient load 08:08 4 -1.4 -0.1 -0.4 -0.0 S-RCP to ambient load 08:10 att auto -10.0 -9.7 -9.9 -10.0 Reset attenuators 26.5 25.5 23.0 22.0 Attenuator settings (dB) Ambient load phys temps: S1=19.50C S2=20.88C X1=20.56C Local weather T=9.9C H=52.6 percent sky=clear 08:12 rec 3 e Begin 25 kHz recording 08:15 5 -10.1 -9.6 -9.8 -10.1 All to ambient load 08:20 6 -9.9 -9.7 -9.8 -9.8 XR ND ON 08:25 7 -10.0 -22.0 -9.8 -18.9 X-Band to sky 08:30 8 -9.9 -22.0 -9.8 -22.6 XR ND OFF 08:35 9 -9.8 -19.6 -9.9 -22.5 XL ND ON Confirm 12.5K ND 08:40 10 -9.9 -9.5 -9.8 -10.0 X-Band to ambient load Ambient load phys temps: S1=18.94C S2=20.56C X1=20.12C 08:45 11 -9.9 -9.7 -9.8 -10.1 XL ND OFF 08:50 12 -9.9 -22.1 -9.7 -22.5 X-Band to sky 08:55 13 -10.0 -22.1 -9.6 -22.6 SR ND ON 09:00 14 -9.9 -21.7 -19.6 -22.6 SR to sky 09:05 15 -9.9 -21.7 -21.2 -22.6 SR ND OFF Confirm 12.5K ND 09:10 16 -9.6 -21.8 -21.3 -22.5 SL ND ON 09:15 17 -18.0 -21.8 -21.3 -22.5 SL to sky 09:20 18 -26.3 -21.8 -21.3 -22.6 SL ND OFF Confirm 12.5K ND Ambient load phys temps: S1=19.06C S2=20.25C X1=20.06C end 09:25 rec 3 d -26.5 -21.5 -21.3 -22.6 End 25 kHz recording; antenna to point BOT 09:45 -19.1 -21.5 -21.3 -17.6 S/X AOS, X-TLM OFF 09:51 70 Reset XR FGAIN (dB) 09:53 rec 3 e Resume 25 kHz recording 09:59 -19.1 -21.0 -20.9 -17.7 DSS 43 to Mars antenna pointing predicts 10:09 sfro 3/XS +8k +32k +8k +32k Rcvr tuning offsets (Hz) 65 Reset XR FGAIN (dB) MiniCal1 10:10 1 -19.2 -21.2 -20.8 -15.9 XR ND ON Confirm 12.5K ND 10:13 2 -19.1 -21.2 -19.3 -17.7 XR ND OFF, SR ND ON -23.6 10:16 3 -19.0 -19.2 -21.0 -21.7 SR ND OFF, XL ND ON 10:19 4 -17.8 -21.3 -20.9 -17.8 XL ND OFF, SL ND ON 10:22 5 -19.1 -21.2 -20.9 -17.9 SL ND OFF 10:22 end -19.1 -21.1 -20.9 -17.9 All to sky BSR 10:30 rec 4 e -19.1 -21.2 -21.0 -17.7 Begin 100 kHz recording end 11:01 rec 4 d -19.1 -21.2 -21.0 -17.8 End 100 kHz recording MiniCal2 11:02 1 -19.2 -21.2 -21.0 -16.0 XR ND ON Confirm 12.5K ND 11:05 2 -19.1 -21.3 -19.2 -17.8 XR ND OFF, SR ND ON 11:08 3 -19.1 -19.3 -21.0 -17.8 SR ND OFF, XL ND ON 11:11 4 -17.9 -21.2 -20.9 -21.6 XL ND OFF, SL ND ON 11:14 5 -19.2 -21.3 -21.0 -21.6 SL ND OFF 11:17 end -19.1 -21.3 -21.0 -21.5 All to sky 11:18 sfro 3/XS 0 0 0 0 Remove all FROs DSS 43 returns to s/c pointing predicts EOT 11:36 -19.1 -21.3 -20.9 -20.2 Move antenna to zenith; do not stow PostCal 11:41 1 -10.0 -9.7 -9.7 -9.6 All to ambient loads Ambient load phys temps: S1=19.19C S2=19.44C X1=20.12C 11:48 2 -9.9 -9.6 -9.6 -9.2 XR ND ON 11:51 3 -9.8 -9.7 -9.5 -9.8 XR ND OFF, SR ND ON 11:54 4 -10.0 -9.5 -9.7 -9.7 SR ND OFF, XL ND ON 11:57 5 -9.7 -9.6 -9.6 -9.6 XL ND OFF, SL ND ON 12:00 6 -18.1 -21.7 -21.3 -22.0 All to sky 12:04 7 -19.3 -19.4 -21.3 -22.3 SL ND OFF, XL ND ON 12:08 8 -19.2 -21.7 -19.4 -22.2 XL ND OFF, SR ND ON 12:11 9 -19.2 -21.6 -21.4 -18.4 SR ND OFF, XR ND ON 12:14 10 -19.2 -21.7 -21.2 -22.3 XR ND OFF Ambient load phys temps: S1=19.19C S2=19.25C X1=20.12C Local weather: T= 4.3C H=81.8 percent sky=clear EOA 12:18 rec 3 d -19.3 -21.7 -21.3 -22.1 End 25 kHz recording 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 X-Band echoes were easily detectable in both polarizations at both 10 and 60 second averaging; the measurement procedure appears to have been good. X-RCP system temperature was only 0.3K lower than X-LCP system temperature during the track; from the pre- and post-cals, the difference was 0.5-1.5K. X-LCP may have been under-estimated by a few percent; this would make the X- Band dielectric constant slightly larger than calculated, where the values are already surprisingly large. S-Band echoes are barely detectable. With 60 second averaging, the S- LCP echo can be seen during the final 6-8 minutes and (perhaps) during the first couple minutes. The S-RCP echo is almost impossible to see except for the final 3-4 minutes. If either echo is smaller than 20 zW, it is probably not worth talking about dielectric constant; that means none of the S-Band measurements can be turned into dielectric constant, since none of the S-RCP values ever reached 20 zW. S-RCP system temperature during the track was about 2K higher than during the pre- and post-cals. S-LCP system temperature was about 5K higher during the track than during the pre- and post-cals. This seems too high. Further, S-LCP was typically 15K higher than S-RCP, implying that the microwave configuration at S-Band was not correct. It would be interesting to estimate how much of the total echo was captured in X-RCP and X-LCP: that is, what fraction of the oblique forward scattering was specular. Dick Simpson Original: 2012-04-10 Post Analysis Summary added: 2013-05-08