Mars Express Bistatic Radar Experiment Operations Plan and Report 25-26 February 2005 Summary ======= DSN Antenna: 43 Pass: 637 Orbit: 1430 Orbit Start Time: 2005-02-27T00:36:19 (SCET) HGA Pointing: Inertial Specular Condition: 2005-02-27T02:00:00 (ERT) Target: (57.33S, 38.61W, 3382 km) (see note at end) (Argyre, SE rim) Incidence/Reflection Angle: 61.64 deg Slant Range: 10373 km Slew Angle: 56.72 deg Doppler (carrier, fd): -18276 Hz Doppler (echo, fr): 9731 Hz Doppler Difference (fdd): -28007 Hz Earth-Mars Distance: 2.75685E11 m Data Acquisition ================ The experiment was supported by DSS 43 staff at the Canberra DSN complex. Also on site in Canberra were Dwight Holmes, Jose Valencia, and Tommy Thompson of JPL. The support team at JPL included Gene Goltz, Danny Kahan, Art Freiley, and Dick Simpson; Essam Marouf (Cassini Radio Science Team) was present as an observer. The experiment began with pre-calibration activities starting on 26 February at 21:45; the pre-cal was completed 45 minutes ahead of schedule. The bistatic surface observations were collected in the interval 01:45-02:15. There were conflicting schedules regarding DSS 43 support for MEX after bistatic radar; the post-calibration was completed and the RSR's stopped recording at 03:43 on 27 February. Valencia, working with Holmes and the DSS 43 staff, had refined the calibration procedure tested on 21-22 February. He distributed the new procedure at the beginning of the pre-cal period. It included an explicit confirmation of channel assignment through staged connection of ambient loads at the beginning of the pre-cal and improvements to the DTT control of noise diodes. There were no anomalies during the calibration or experiment periods, for which we can credit Valencia and the DSS 43 staff. RSRs were configured as follows. Table 1 -------------------------------------- RSR Channel Mode ATT FGAIN Operator dB ----- ------- ---- ---- ----- -------- RSR1A S-LCP 1-W auto 60 Kahan RSR1B X-LCP 1-W auto 60 Kahan RSR2A S-RCP 1-W auto 60 Goltz RSR2B X-RCP 1-W auto 60 Goltz Subchannels were defined as follows: Table 2 --------------------------------------------------------------------- Subchannel Sample Rate Comments ---------- ----------- --------------------------------------------- 1 1 ksps Used for seeking weak carrier signals 2 8 ksps 3 25 ksps Primary recording bandwidth 4 100 ksps Backup recording (able to capture both X-band residual carrier and surface echo) Predicts were provided by NSS and were for one-way operation. Table 3 lists ADC RMS levels read from RSR displays during the experiment. Times in hh:mm are in UTC from the RSSG wall clock, which appeared to be about 2 minutes fast; times in hh:mm:ss are from RSR displays. For more accurate times, see the next section of this report on Amplitude Calibration. Acronyms/abbreviations are explained below Table 3; "steps" are explained in more detail in the accompanying "procedures" document. Table 3 ----------------------------------------------------------------------------- - TIME (ERT) RSR1A RSR1B RSR2A RSR2B COMMENTS 2005-02-26 S-LCP X-LCP S-RCP X-RCP RMS RMS RMS RMS ---------- ----- ----- ----- ----- ----------------------------------------- - 22:30 28 28 29 28 Step 1: All RSRs to sky; ATT set by AUTO 22:35 28 89 29 89 Step 2: X to AMB 22:36 84 89 28 89 Step 3: SL(LNA2) to AMB 22:38 84 88 87 89 Step 4: SR(LNA1) to AMB 22:39 Step 5d: Reset all RSR ATT using AUTO 22:40 29 29 29 30 Step 5e: All RSRs recording 22:45 Step 5c: Ambient load temperatures: S1=21.94C S2=22.69C X1=20.75C 22:46 DSS 43 wx: overcast, 17C, 67% humidity 22:47 Step 6: XR ND on 22:48 29 29 29 31 22:51 Step 7: XR, XL to sky 22:52 30 7 29 12 22:57 29 7 29 7 Step 8: XR ND off 23:01 29 10 29 7 Step 9: XL ND on 23:07 29 30 29 30 Step 10: XR, XL to AMB 23:12 Step 10c: Ambient load temperatures: S1=22:06C S2=22.81C X1=20.62C 23:12 29 29 30 30 Step 11: XL ND off 23:16 29 7 30 7 Step 12: XR, XL to sky; SR ND on 23:18 Simpson requests 10 min w/SL ND on 23:21 DSS 43 makes "B" connection to RSR's so they can monitor (but not control) the open loop channels 23:27 29 7 9 7 Step 13: SR to sky 23:32 29 7 7 7 Step 14: SR ND off 23:37 30 7 8 7 Step 15: SL ND on DSS 43 offers to stay here 10 min; accept 23:47 9 7 7 7 Step 16: SL to sky 23:49 Step 17b: Ambient load temperatures: S1=22.12C S2=22.88C X1=20.56C 23:52 8 7 7 7 Step 17: All RSRs to sky, all NDs off 23:53 DSS 43 explains that it needs control of SR LNA at beginning of track; otherwise no configuration changes 23:59 End of pre-cal; RSRs continue to record 2005-02-27 ---------- 00:10 8 8 8 XR subchannel 4 carrier at -28 kHz with Pc/No=60 dB/Hz; XL at 30 dB/Hz 00:31 8 7 8 7 00:37:28 XR FGAIN reset to 70 00:38:15 XL FGAIN reset to 70 00:40:28 XL FGAIN returned to 60 00:40:29 XR FGAIN returned to 60 00:52:20 X TLM off; S-band carrier appears SR Pc/No=45 dB, SL Pc/No=12 dB XR Pc/No=67 dB, XL Pc/No=42 dB, XR histogram approximately 50% full scale 01:00 XR, XL FRO set to +25400 Hz; carrier moves to -28 kHz (subchannel 4) SR, SL FRO set to +2750 Hz; carrier moves to -4 kHz 01:02 All FROs reset to 0 01:14 DSS 43 confirms CONSCAN off 01:23 8 7 8 7 XR carrier dropping 01:24 XR Pc/No=61, XL Pc/No=38, SR Pc/No=44 01:25 Mini-cal Step 1: XR ND on 01:27 8 7 8 12 01:30 8 7 9 7 Mini-cal Step 2: SR ND on 01:33 8 10 8 7 Mini-cal Step 3: XL ND on 01:36 10 7 8 7 Mini-cal Step 4: SL ND on 01:39 8 7 8 7 Mini-cal Step 5: all NDs off (end) 01:41:10 XL FRO set to +25400 Hz; no carrier seen 01:41:13 SL FRO set to +2750 Hz; no carrier seen 01:41:15 XR FRO set to +25400 Hz; no carrier seen 01:41:17 SR FRO set to +2750 Hz; no carrier seen 01:45:00 Start XR, XL subchannel; 4 RSR recording 01:49 Visually confirmed FRO=0 from each display 01:55 Possible X echo; near f=0, width = 1 kHz 01:58 Faint XL echo near -200 Hz 02:00:27 Fairly convincing XR echo centered on f=0 02:02:40 Possible SR carrier and echo at f=+/-4 kHz 02:05 No consistent echoes 02:15 8 7 8 7 Stop XR, XL subchannel 4 recording 02:16 8 7 8 12 Mini-cal Step 1: XR ND on 02:19 8 7 9 7 Mini-cal Step 2: SR ND on 02:23 8 10 8 8 Mini-cal Step 3: XL ND on 02:26 10 7 8 7 Mini-cal Step 4: SL ND on 02:29 8 7 8 8 Mini-cal Step 5: all NDs off 02:30 All FROs set to 0 XR Pc/No=30 at f=-2900 Hz SR Pc/No=17 at f=-1300 Hz 02:32:12 XR Pc/No=33, SR Pc/No=25 02:37:32 8 7 8 8 HGA returned to Earth point XR Pc/No=66.9, XL Pc/No=41.9 SR Pc/No=44.4, SL Pc/No=19.8 02:45 DSS 43 agrees to begin post-cal at 03:00 02:58 XR Pc/No=66.9, XL Pc/No=41.8 SR Pc/No=44.3, SL Pc/No=17.2 02:58:01 LOS on all channels 03:11 Going to zenith, after some confusion with MEX ops over end of track 03:16 30 29 30 30 Post-cal Step 1: Ambient load temperatures S1=21.44C S2=22.62C X1=18.18C 03:17 30 29 30 31 Post-cal Step 2: XR ND on 03:20 30 29 30 29 Post-cal Step 3: SR ND on 03:22 DSS 43 confirms SR ND on 03:23 29 30 30 29 Post-cal Step 4: XL ND on 03:25 30 30 29 29 03:26 30 29 29 30 Post-cal Step 5: SL ND on 03:31 9 7 8 7 Post-cal Step 6: all RSRs to sky, SL ND on 03:32 8 10 8 7 Post-cal Step 7: XL ND on 03:35 8 7 9 7 Post-cal Step 8: SR ND on 03:38 8 7 7 12 Post-cal Step 9: XR ND on 03:41 8 7 7 7 Post-cal step 10: all NDs off Ambient load temperatures: S1=21.38C S2=22.38C X1=18.22C 03:43:00 8 7 8 7 Stop RSR recordings AMB = ambient load CONSCAN = conical scan tracking FRO = frequency offset HGA = high-gain antenna LOS = loss of signal NB = 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 Amplitude Calibration ===================== Data from the Pre-Calibration and Post-Calibration were used to determine the operating system temperature (Top) for each receiver channel at zenith. The value of each noise diode was obtained by calibration against Top and the ambient load temperature Tamb, either directly or indirectly. During the bistatic experiment, the (time varying) system temperature in each channel was obtained by comparison of the background radiothermal noise with the energy injected by the now-calibrated noise diode. "Intervals" in Table 4 refer to the center times associated with 10 second average power spectra. The data were processed in three segments. Interval 1 was the center time (22:41:04) of the first spectrum in the pre-calibration segment. Interval 475 was the time (01:15:04) of the first spectrum in the second segment -- a mini-calibration, the bistatic radar experiment itself, and a second mini-calibration. Interval 913 was the time (03:10:04) of the first spectrum in the post-calibration segment. Not all intervals are shown in Table 4; transition times and times when the system state was ambiguous were omitted. Table 4XR ------------------------------------------- Center Times Intervals Configuration ----------------- --------- ------------- Pre-Calibration (zenith) ------------------------ 22:41:04-22:45:34 1- 28 AMB X1=20.75 at 22:45 22:45:54-22:49:54 30- 54 AMB+ND 22:50:24-22:54:54 57- 84 SKY+ND 22:55:14-23:04:54 86- 144 SKY 23:05:14-23:14:54 146- 204 AMB X1=20.62 at 23:12 23:15:23-23:29:54 207- 294 SKY 23:30:04-23:44:54 295- 384 SKY (power drifting up slightly) 23:45:04-23:59:54 385- 474 SKY X1=20.56 at 23:49 Bistatic Radar (tracking) ------------------------- 01:15:04-01:22:54 475- 522 SKY + carrier 01:23:04-01:24:54 524- 534 SKY + sidelobes (slew) 01:25:04-01:27:54 536- 552 SKY+ND 01:28:14-01:30:54 554- 570 SKY 01:31:04-01:44:53 571- 654 SKY 01:45:04-02:11:54 655- 816 SKY (echoes) 02:12:03-02:14:53 817- 834 SKY 02:15:13-02:17:53 836- 852 SKY+ND 02:18:13-02:20:53 854- 870 SKY 02:21:03-02:27:53 871- 912 SKY Post-Calibration (zenith) ------------------------- 03:13:54-03:15:14 936- 944 AMB 03:15:34-03:18:24 946- 963 AMB+ND X1=18.19 at 03:16 03:18:44-03:28:54 965-1026 AMB 03:29:14-03:36:24 1028-1071 SKY 03:36:44-03:39:23 1073-1089 SKY+ND 03:39:43-03:42:53 1091-1110 SKY X1=18.12 at 03:41 Table 4SR ------------------------------------------- Center Times Intervals Configuration ----------------- --------- ------------- Pre-Calibration (zenith) ------------------------ 22:41:04-23:14:53 1- 204 AMB S1=????? at 22:45 23:15:23-23:24:54 207- 264 AMB+ND 23:25:14-23:29:54 266- 294 SKY+ND 23:30:14-23:59:53 296- 474 SKY Bistatic Radar (tracking) ------------------------- 01:15:04-01:22:54 475- 522 SKY + carrier 01:23:04-01:27:54 523- 552 SKY + sidelobes (slew) 01:28:14-01:30:54 554- 570 SKY 01:31:14-01:33:54 572- 588 SKY+ND 01:34:04-01:44:53 589- 654 SKY 01:45:04-02:14:53 655- 834 SKY (echoes?) 02:15:03-02:17:53 835- 852 SKY 02:18:13-02:20:53 854- 870 SKY+ND 02:21:13-02:27:53 872- 912 SKY Post-Calibration (zenith) ------------------------- 03:12:24-03:18:34 927- 964 AMB 03:18:44-03:21:24 965- 981 AMB+ND 03:21:54-03:27:24 984-1017 AMB 03:27:44-03:33:24 1019-1053 SKY 03:33:44-03:36:24 1055-1071 SKY+ND 03:36:44-03:42:53 1073-1110 SKY Table 4XL ------------------------------------------- Center Times Intervals Configuration ----------------- --------- ------------- Pre-Calibration (zenith) ------------------------ 22:41:04-22:49:54 1- 54 AMB X1=????? at 22:45 22:50:24-22:59:54 57- 114 SKY 23:00:04-23:04:54 116- 144 SKY+ND 23:05:24-23:09:54 147- 174 AMB+ND 23:10:13-23:14:53 176- 204 AMB 23:15:23-23:29:54 207- 294 SKY 23:30:04-23:44:54 295- 384 SKY (power drifting slightly higher) 23:45:04-23:59:54 385- 474 SKY Bistatic Radar (tracking) ------------------------- 01:15:04-01:22:54 475- 522 SKY + carrier 01:23:04-01:27:54 523- 552 SKY + sidelobes (slew) 01:28:04-01:30:54 553- 570 SKY 01:31:14-01:33:54 572- 588 SKY+ND 01:34:14-01:36:54 590- 606 SKY 01:37:04-01:44:53 607- 654 SKY 01:45:04-02:14:53 655- 834 SKY (echoes) 02:15:03-02:17:53 835- 852 SKY 02:18:03-02:20:53 853- 870 SKY 02:21:03-02:23:53 872- 888 SKY+ND 02:24:13-02:27:53 890- 912 SKY Post-Calibration (zenith) ------------------------- 03:14:04-03:21:24 937- 981 AMB 03:21:44-03:24:24 983- 999 AMB+ND 03:24:34-03:28:54 1001-1026 AMB 03:29:14-03:30:24 1028-1035 SKY 03:30:44-03:33:24 1037-1053 SKY+ND 03:33:44-03:42:53 1055-1110 SKY Table 4SL ------------------------------------------- Center Times Intervals Configuration ----------------- --------- ------------- Pre-Calibration (zenith) ------------------------ 22:41:04-23:34:54 1- 324 AMB S2=????? at ????? 23:35:04-23:44:54 325- 384 AMB+ND 23:45:14-23:49:54 386- 414 SKY+ND 23:50:13-23:59:53 416- 474 SKY Bistatic Radar (tracking) ------------------------- 01:15:05-01:30:54 475- 570 SKY 01:31:04-01:33:54 571- 588 SKY 01:34:14-01:36:54 590- 606 SKY+ND 01:37:14-01:39:54 608- 624 SKY 01:40:04-01:44:53 625- 654 SKY 01:45:04-02:14:53 655- 834 SKY (echoes?) 02:15:13-02:20:53 836- 870 SKY 02:21:03-02:23:53 871- 888 SKY 02:24:13-02:26:53 890- 906 SKY+ND 02:27:13-02:27:53 908- 912 SKY Post-Calibration (zenith) ------------------------- 03:13:24-03:24:24 933- 999 AMB 03:24:44-03:27:24 1001-1017 AMB+ND 03:27:44-03:30:24 1019-1035 SKY+ND 03:30:44-03:42:53 1037-1110 SKY Error in HGA Targeting ====================== There was an apparent error in the targeting of the bistatic radar experiment. A specular point target, originally chosen for the geometry which would apply at 2005-02-27T01:45:00 Earth received time (ERT), was shifted to 02:00:00. In the experiment request sent to ESOC, the time was updated, but the target coordinates were not changed. When the high-gain antenna (HGA) pointing maneuver was designed, the HGA was told to go to the old target at the new time. To determine the high-gain antenna (HGA) pointing error, the geometry is calculated here. Distances/vectors are in meters; angles are in degrees. Constants: Rp = 3.3897E+06 Radius of assumed spherical Mars pi = 3.1416E+00 For reference, these are J2000 (Earth mean equator and equinox) vectors as derived by the Stanford program BSRGEOM. They are valid for the geometry at 02:00:00 ERT; light time corrections have been included. Only DOS is used in this calculation. "Mars" here is the planet's center of mass. DOD = [-6.8399E+10 2.4392E+11 1.0875E+11] Mars to DSS 43 |DOD| = 2.7569E+11 DOS = [-8.2208E+06 -3.0494E+06 -8.6878E+06] Mars to spacecraft |DOS| = 1.2343E+07 DOP = [-2.7645E+06 1.5686E+06 -1.1777E+06] Mars to specular point |DOP| = 3.3897E+06 Target coordinates in Mars planetocentric fixed-body coordinates: Correct specular point target at 02:00:00: LAT1 = -55.989 deg LON1 = -35.997 deg DOP1A = [1.5339E+06 -1.1144E+06 -2.8098E+06] Mars to correct target |DOP1A| = 3.3897E+06 Incorrect target: LAT2 = -57.330 deg LON2 = -38.610 deg DOP2A = [1.4298E+06 -1.1418E+06 -2.8534E+06] Mars to wrong target |DOP2A| = 3.3897E+06 Angular separation between these vectors (seen from center of Mars): vsep(DOP1A,DOP2A) = 1.9642 deg Difference between these vectors and its magnitude. The separation is equivalent to about 2 degrees of longitude at Mars' equator. DOP2A-DOP1A = [-1.0417E+05 -2.7420E+04 -4.3589E+04] |DOP2A-DOP1A| = 1.1620E+05 Fixed Body to J2000 rotation matrix (valid for t0 = 2005-02-27T02:00:00 ERT): | -8.8413E-01 -3.3830E-01 3.2229E-01 | M = | 1.3881E-01 -8.4880E-01 -5.1017E-01 | | 4.4615E-01 -4.0600E-01 7.9740E-01 | Fixed body target vectors converted to J2000 at t0: DOP1B = M'*DOP1A = [-2.7645E+06 1.5686E+06 -1.1777E+06] |DOP1B| = 3.3897E+06 DOP2B = M'*DOP2A = [-2.6957E+06 1.6439E+06 -1.2320E+06] |DOP2B| = 3.3892E+06 where M' = transpose(M) = inverse(M) Spacecraft to Target Vectors in J2000 coordinates: DSP1B = DOP1B - DOS = [ 5.4563E+06 4.6180E+06 7.5101E+06] |DSP1B| = 1.0368E+07 DSP2B = DOP2B - DOS = [ 5.5252E+06 4.6933E+06 7.4558E+06] |DSP2B| = 1.0399E+07 Spacecraft to target unit vectors in J2000: USP1B = norm(DSP1B) = [ 0.5263 0.4454 0.7243] USP2B = norm(DSP2B) = [ 0.5313 0.4513 0.7170] Angle between the unit vectors (error in HGA pointing): vsep(USP1B,USP2B) = 0.6145 deg