Overview: Real-time notes by Dick Simpson for Magellan bistatic radar passes on 5 June 1994. Eight quasi-specular tracks were observed total -- six from DSS 63 and four from DSS 14 (two overlapped). Signals were recorded alternately at S and X band, with both circular polarizations being recorded simultaneously. The track extended from near the equator to beyond Maxwell Montes; it was essentially the same for all eight orbits. Two errors in the tuning predicts for the open loop receivers complicated operations and will reduce the amount of data of scientific value. First, the original file of modified predicts proved to be too large and could not be loaded into the open loop receiving equipment. The file was edited, but not until after the first orbit, which was run using a "test" file generated at the station and manual offsets. The second problem was that the modified predicts were computed with an apparent sign error; once this was discovered, manual offsets were used to make real- time adjustments. Given that the orbits were largely redundant, the damage is minimal, but the impact on the search for ANY echo at X-band will be more severe. No X-band echo was seen at any time in the real-time displays. A sensitivity reduction of unknown origin at DSS 14 probably means that little or no useful data was acquired there. The S- band direct signal was 10 dB lower than at DSS 63, and the X-band direct signal was down by 50 dB; no echoes were seen in real-time displays at either frequency. DSS 15 was run in parallel and collected telemetry without showing signs of problems. The symptoms are consistent with a small offset in the 70-m antenna pointing (a large fraction of the S-band beamwidth), but there were no conclusions at the end of DSS 14 operations. The primary objectives of the experiment should have been accomplished at S-band with the DSS 63 data; the impact on the X- band search cannot be judged until more careful study of the actual versus predicted tuning profiles has been completed. I think it is accurate to state, however, that our operations confirmed that X-band bistatic echoes are at least rare and weak compared with echoes at S-band. S-band echoes, on the other hand, are common but show considerable variation in strength and shape, reflecting the highly diverse scattering properties of the Venusian surface. Whether echoes were obtained from Maxwell Montes is not known at this time because of the uncertainties in timing. But S- band echoes were observed during that general time period. To the extent possible radio occultations, which followed the quasi-specular track immediately, were also captured on tape. Processing of these data will be complicated by the fact that spacecraft engineering data (telemetry) was turned on part way into the occultation. The occultation time shown below typically was 60 seconds earlier than any observable effect. Items in UPPER CASE are from the pre-experiment timeline; unless noted otherwise, we believe they were executed as planned. Items in lower case are the notes made in real time. Participants: Sal Abbate (DSS 14) Tony Horton Jim Isaac Percy Montoya Dick Simpson Peter (last name unknown; handles DSN predicts) dozens of others at JPL, DSS 14, and DSS 63 NB: Frequency offsets (FROs), POCA equivalent S-band sky frequencies, attenuator settings, and RMS levels noted at various times have been placed in tables at the end of each set of orbit notes. RMS sample values should be viewed with some skepticism, as DC bias values are apparently included. For example, RMS values on the S-band channels at DSS 14 never dropped below 327. ================================================================= 11:35 BEGIN PRE-CAL USE CONFIGURATION FOR 2-CHANNEL DSP RECORDING. CARRY OUT THE SPECIAL AMBIENT LOAD CALIBRATION (STEPS 1-9 IN THE MESSAGE TO THE STATION) FOR EACH CHANNEL. 11:45 Operators report interruption in signal (presumably resulting from switch to Transmitter A) 11:50 DSS 63 reports radio science predicts cannot be loaded (both open loop and closed loop) 12:20 Test shows that DSP can run on self-generated open- loop predicts 12:35 DSS 63 reports that closed loop predicts which were sent a second time from JPL have loaded OK. Open loop predicts continue to fail; error message on the latter is that the file is too large. Loading program stops at 24 blocks, but error messages begin at block 20. 12:44:17 AOS (FROM EARTH OCCULTATION) 12:45 Peter has been called; he will come in to rework predict files for later orbits. 12:49 DSS 14 has successfully loaded their open loop predicts, confirming that file size may be the cause of our problems at DSS 63 (the DSS 14 file is only about 2/3 the size of the DSS 63 file). 12:50 BEGIN TRACK 12:50 DSS 63 will build predict file internally using start time 12:50, end time 21:00, start frequency 2298 MHz, and rate 0. We will give them frequency offsets to follow the echo signal. Special pre-cal will not be done ================================================================== First Orbit (Magellan Orbit #13031) S-band: DSS 63 was not able to load the original radio science predicts for the DSP. We requested that the DSP be used to generate its own predicts, a procedure that is employed in testing. We chose a constant (S-band equivalent sky) frequency of 2298 MHz, to which we would add offsets manually. The manual offsets were based on values in the adjusted tuning predicts file generated at Stanford. The echo faded in and out, but we believe we were tracking it as soon as a minute after the HGA began following the BQPC polynomial and for more than a minute after the HGA left the polynomial at the end. Echo frequencies were generally higher than we expected, but we tailored the manual offsets to follow the echo rather than rigidly adhere to the calculated tuning file. This turned out to be a good idea, when we later discovered that the adjusted tuning file had been calculated incorrectly. A spurious signal (reminiscent of the spurious signal seen last week) drifted through the spectrum, but didn't appear to cause any harm. The occultation was probably captured, but we weren't paying close attention. ------------------------------------------------------------------ 12:57:34 DSS 63 on point 13:02:52 ENGINEERING TELEMETRY OFF 13:04:52 LOS (SPACECRAFT BEGINS TURN TO VENUS) 13:09:10 DSP begins recording with nominal attenuator settings 13:12 SSI data are not coming in; complaint registered. 13:12:52 SPACECRAFT BEGINS TRACKING SURFACE TARGET 13:15 Echo visible in SSI 13:17 Echo fades in and out, apparently as it crosses different Venus surface types. 13:20 Peter has new predict set ready for later orbits. 13:26:00 Echo at 10 kHz in SSI 13:28:00 Broad echo and narrow, spurious signal visible in SSI. 13:32:14 Echo has now moved to lower frequency than spurious signal 13:35:40 SPACECRAFT ENDS TRACKING SURFACE TARGET 13:36:13 Echo remains visible 13:37:00 ADD 15 DB ATTENUATION TO CHANNELS 2,4 (SR,SL) 13:38 Direct signal (the real one) has appeared (very strong) at about 7 kHz in SSI. 13:38:40 AOS 13:38:57 ENTER OCCULTATION 13:40:40 ENGINEERING TELEMETRY ON 13:41 All signals gone 13:46:00 FOR BOTH CHANNELS 2,4 (SR,SL) SWITCH MASER TO AMBIENT LOAD FOR TWO MINUTES. REPORT TIME AND PHYSICAL TEMPERATURE OF AMBIENT LOAD TO JPL. AFTER 2 MINUTES SWITCH MASERS BACK TO COLD SKY AND END DSP RECORDING (NO LATER THAN 13:57) 13:48:15 S-band masers back to cold sky 13:48:35 DSP to idle 13:49 DSS 63 will try new predicts that Peter generated 13:54 Displays show that new predict set (NS7) has been loaded into DSP. Indications all along the line have been that this file is 22 blocks, which should still be too large. Not clear what the real limit is. Table of Frequency Offsets Time FRO (Hz) -------- -------- 13:09:40 +65000. 13:11:30 +49000. 13:15 +32000. 13:17:20 +25000. 13:21:15 +15000. 13:24:35 +8000. 13:28:00 0. 13:31:00 -5000. 13:37 -12000. Attenuator Settings and RMS Levels Time Attenuators (dB) RMS Levels (mV) J1 J2 J3 J4 AD1 AD2 AD3 AD4 -------- -- -- -- -- ---- ---- ---- ---- 13:46 40 51 60 51 740 756 693 735 (amb load) Ts=26.6 13:48:15 220 500 214 498 (sky) NB: Following abbreviations are used in the table above and in similar tables below: J1 = X-RCP AD1 = RCP J2 = S-RCP AD2 = LCP J3 = X-LCP AD3 = RCP J4 = S-RCP AD4 = LCP Ts = S-band ambient load temperature (deg C) Tsr = S-RCP ambient load temperature (deg C) Tsl = S-LCP ambient load temperature (deg C) Tx = X-band ambient load temperature (deg C) Txr = X-RCP ambient load temperature (deg C) Txl = X-LCP ambient load temperature (deg C) ================================================================== Second Orbit (Magellan Orbit #13032) X-band: DSS 63 operations appeared nominal, but there are probably no good echo data. After the orbit, DSS 63 requested permission to switch the XRO-1 maser to LCP. It was at that point that we learned XRO-1 had been on X-RCP, XRO-2 had been on X-LCP, and XRO-2 was red (not working). JPL had apparently been advised of this at the beginning of the pass, but the information never reached Radio Science. The expected direct signal would have been LCP, so any direct signal we captured during this orbit would have been cross- polarized (leakage), and the only echo would have been from near nadir incidence. Although the tuning predicts loaded successfully for this orbit, we discovered on the next orbit that they had been calculated incorrectly. The errors at S-band were enough to drive the echo nearly out of the passband. During this orbit, the X- band echo position error would have been four times as large. The occultation was captured, but the data are useless because of the maser problem. ------------------------------------------------------------------ 13:57:00 BEGIN CONFIGURATION FOR X-BAND ONLY 14:17:14 AOS (FROM EARTH OCCULTATION) 14:20:52 DSS 63 receivers in lock 14:23 S-band telemetry in lock, X-band telemetry not in lock (none expected) 14:25:00 BEGIN DSP RECORDING 14:26 Direct signal at 6 kHz in SSI 14:27 Signal moves to 11800 Hz in SSI with FRO change 14:29 Signal moves to 12600 Hz in SSI with FRO change; FRO = -1500 Hz appears to be optimum for the direct signal. 14:32 Switch SSI to ODAN channel B (X-LCP) Direct signal is weaker in LCP, as expected. [We later discovered this was WRONG; LCP should have been stronger (TXA puts out LCP), but that channel was being amplified through a dead maser]. 14:34:11 SSI back to ODAN channel A (X-RCP) 14:35:49 ENGINEERING DATA OFF 14:37:49 LOS (SPACECRAFT BEGINS TURN TO VENUS) 14:39:30 Signal gone 14:40:51 DSP TUNES TO ECHO FREQUENCY (NO ACTION REQUIRED) 14:42:00 REMOVE 25 DB ATTENUATION FROM CHANNELS 1,3 (XR,XL) 14:45:49 SPACECRAFT BEGINS TRACKING SURFACE TARGET 14:47 No signal visible 14:52:42 SSI switched to ODAN channel B; no signals visible 14:57 SSI switched to ODAN channel A; no signals visible 15:08:37 SPACECRAFT ENDS TRACKING SURFACE TARGET. 15:09 No signals visible on this orbit 15:10:00 ADD 20 DB ATTENUATION TO CHANNELS 1,3 (XR,XL) 15:11:05 Direct signal appears near 18 kHz in SSI 15:11:37 AOS 15:11:54 ENTER OCCULTATION 15:11:50 SNR approximately 30 dB in SSI 15:12:39 Signal SNR approximately 5 dB, peak at about 12 kHz in SSI 15:13:07 Signal gone 15:13:37 ENGINEERING TELEMETRY ON 15:19:00 FOR BOTH CHANNELS (XR,XL) SWITCH MASER TO AMBIENT LOAD FOR TWO MINUTES. REPORT TIME AND PHYSICAL TEMPERATURE OF AMBIENT LOAD TO JPL. AFTER 2 MINUTES, SWITCH MASERS BACK TO COLD SKY AND END DSP RECORDING (NO LATER THAN 15:29). 15:19:40 Ambient load temperature 26.8 15:21:20 DSP to idle 15:22:00 DSS 63 requests permission to switch the XRO-1 maser to X-LCP. They have been running with XRO-1 on X-RCP and XRO-2 on X-LCP; but XRO-2 is red. Since the stronger signal is on LCP, they argue that it would make sense to have the better maser on LCP also. We had not heard about the XRO-2 problem before; we ponder the implications. There is no backup to the masers at 63. 15:45 We agree with the recommendation to switch the good maser to X-LCP. Table of Frequency Offsets Time FRO (Hz) -------- -------- 14:27 -1300. 14:29 -1500. POCA Equivalent S-Band Sky Frequencies Time Frequency (Hz) -------- -------------- 15:04:02 2297985423. Attenuator Settings and RMS Levels Time Attenuators (dB) RMS Levels (mV) J1 J2 J3 J4 AD1 AD2 AD3 AD4 -------- -- -- -- -- ---- ---- ---- ---- 14:29 63 51 63 51 162 40 164 38 14:35:20 167 40 168 40 14:38:25 156 40 157 39 14:39:30 156 39 156 39 14:42 40 51 40 51 1052 115 1061 110 15:10 60 51 60 51 171 39 173 39 15:11:50 251 40 246 39 15:19:40 332 40 331 39 (Tx=26.8) ================================================================== Third Orbit (Magellan Orbit #13033) S-band: Execution was nominal except that the S-band echo drifted to higher frequencies than expected. We entered manual offsets and recovered most of it, but it was typically 10 kHz higher in frequency than it should have been during the central part of the observing period. The occultation was captured. ------------------------------------------------------------------ 15:29:00 BEGIN CONFIGURATION FOR S-BAND ONLY 15:50:12 AOS (FROM EARTH OCCULTATION) 15:52 Signal present with 25 dB SNR in SSI No frequency offset entered at start-up. 15:55:16 SSI shows signal at 25 dB SNR with peak at 12200 Hz. 15:58:00 BEGIN DSP RECORDING 16:08:20 SSI SNR remains at 25 dB, peak remains at 12300 Hz. 16:08:46 ENGINEERING DATA OFF 16:09:00 SSI SNR at 33 dB, peak at 12300 Hz. 16:10:46 LOS (SPACECRAFT BEGINS TURN TO SURFACE TARGET) 16:11:22 Signal fading 16:15:51 DSP TUNES TO ECHO FREQUENCY (NO ACTION REQUIRED) 16:16:00 REMOVE 15 DB ATTENUATION FROM CHANNELS 2,4 (SR,SL) 16:18:46 SPACECRAFT BEGINS TRACKING SURFACE TARGET 16:19:45 Very broad echo possible at about 15 kHz in SSI; it comes and goes over the next 5 minutes or so, but is never very prominent. 16:25 Spur moving in from left side of SSI (resembles spurious signal seen in SSI data last time) 16:27 No echo visible for several minutes; wonder whether it drifted off high side of SSI. 16:27:51 Echo appears immediately at about 15 kHz in SSI after FRO change 16:30:41 Echo and spur both at 11700 Hz in SSI after another FRO change 16:32:45 Echo at 11 kHz in SSI; spur at 16 kHz 16:38 No echo seen for past 1 minute 16:39 Intermittent echoes for past 1 minute 16:40:36 Narrow echo visible at 12500 Hz in SSI 16:41:34 SPACECRAFT ENDS TRACKING SURFACE TARGET 16:42:36 Direct signal weak at 8 kHz in SSI; echo at 11 kHz 16:43:00 ADD 15 DB ATTENUATION TO CHANNELS 2,4 (SR,SL) 16:44 Direct signal SNR approximately 33 dB, peak at 7 kHz in SSI 16:44:34 AOS 16:44:51 Direct signal at 13500 Hz in SSI 16:44:52 ENTER OCCULTATION 16:45:28 Begin occultation; signal decreases as follows: 16:45:28 23 dB SNR 16:45:35 30 dB 16:45:42 23 dB 16:45:49 14 dB 16:46:04 4 dB 16:46:11 3 dB 16:46:25 2 dB 16:46:40 0 dB (gone) 16:46:34 ENGNEERING DATA ON 16:52:00 FOR BOTH CHANNELS 2,4 (SR,SL) SWITCH MASER TO AMBIENT LOAD FOR TWO MINUTES. REPORT TIME AND PHYSICAL TEMPERATURE OF AMBIENT LOAD TO JPL. AFTER 2 MINUTES SWITCH MASERS BACK TO COLD SKY AND END DSP RECORDING (NO LATER THAN 17:02) 16:54:13 DSP to idle Table of Frequency Offsets Time FRO (Hz) -------- -------- 15:55:16 -1500. 16:27:51 +5000. 16:30:41 +10000. 16:39:00 +5000. 16:44:51 -2000. POCA Equivalent S-Band Sky Frequencies Time Frequency (Hz) -------- -------------- 16:11:46 2298062936. 16:16:56 (correct?) 2298049558. 16:16:36 (correct?) 2298047035. Attenuator Settings and RMS Levels Time Attenuators (dB) RMS Levels (mV) J1 J2 J3 J4 AD1 AD2 AD3 AD4 -------- -- -- -- -- ---- ---- ---- ---- 15:55:16 60 51 60 51 302 543 300 540 16:08:20 60 51 60 51 300 519 304 UNK 16:09:00 554 626 559 630 16:13 219 496 213 495 16:17 60 36 60 36 1039 968 1073 928 16:32:45 1122 994 1123 958 16:44 60 51 60 51 540 685 560 688 16:47:36 60 51 60 51 209 493 218 493 16:52:26 719 719 698 725 (amb load) Ts = 20.1 Tx = 21.4 16:54:11 215 493 221 494 (sky) ================================================================== Fourth Orbit (Magellan Orbit #13034) X-band: Between orbits we concluded that the adjustments to the tuning file had been applied with the wrong sign. That is, if the direct signal had been 5 kHz below the expected echo frequency, we had subtracted 5 kHz from the direct signal tuning predicts rather than adding. By adding TWICE the difference plus the -1500 Hz empirical correction (see note at 14:29) we expected to obtain the correct frequency. The POCA rates would always work against us, and these ad hoc corrections would never be truly good at X-band, but this was the best we could do under the circumstances. We also agreed to switch the XRO-1 maser to X-LCP, where we would see the stronger direct signal and (hopefully) the majority of the quasi-specular reflection from Maxwell. Execution was nominal, but no echo was seen in real time. The occultation was captured. ------------------------------------------------------------------ 17:02:00 BEGIN CONFIGURATION FOR X-BAND ONLY 17:23:09 AOS (FROM EARTH OCCULTATION) 17:31 BEGIN DSP RECORDING 17:32 Direct signal SNR approximately 50 dB in SSI with peak at 9450 Hz (SSI = ODAN B, X-LCP). Despite the very strong X-LCP signal (nearly 2 V RMS), there was no clipping in the ADC. 17:34:30 Direct signal moved to 11250 Hz in SSI with FRO change. 17:41:44 ENGINEERING DATA OFF 17:43:44 LOS (SPACECRAFT BEGINS TURN TO SURFACE TARGET) 17:45:51 DSP TUNES TO ECHO FREQUENCY (NO ACTION REQUIRED) 17:47:00 REMOVE 25 DB ATTENUATION FROM CHANNELS 1,3 (XR,XL) 17:51:44 SPACECRAFT BEGINS TRACKING SURFACE TARGET 18:14:32 SPACECRAFT ENDS TRACKING SURFACE TARGET 18:14:33 Direct signal (?) at approximately 16 kHz in SSI moving to lower frequencies and about 4 dB above noise. 18:16:00 Direct signal (?) at 13 kHz 18:16:00 ADD 25 DB ATTENUATION TO CHANNELS 1,3 (XR,XL) 18:17:32 AOS 18:17:49 ENTER OCCULTATION 18:18:50 Signal fading (occultation ingress) 18:19:04 Signal gone 18:19:32 ENGINEERING DATA ON 18:25:00 FOR BOTH CHANNELS (XR,XL) SWITCH MASER TO AMBIENT LOAD FOR TWO MINUTES. REPORT TIME AND PHYSICAL TEMPERATURE OF AMBIENT LOAD TO JPL. AFTER 2 MINUTES, SWITCH MASERS BACK TO COLD SKY AND END DSP RECORDING (NO LATER THAN 18:35). 18:27:45 DSP end recording Table of Frequency Offsets Time FRO (Hz) -------- -------- 17:31:00 -1000. 17:34:30 -1500. 17:53:49 +4000. 17:58 +7000. 18:02:39 +10000. 18:10:09 +5000. 18:13:19 0. 18:18:34 -1500. POCA Equivalent S-Band Sky Frequencies Time Frequency (Hz) -------- -------------- 18:06:34 2298000136. Attenuator Settings and RMS Levels Time Attenuators (dB) RMS Levels (mV) J1 J2 J3 J4 AD1 AD2 AD3 AD4 -------- -- -- -- -- ---- ---- ---- ---- 17:32 60 51 60 51 137 1987 139 1986 18:16:30 65 51 65 51 137 220 140 220 18:17:24 137 1107 139 1101 18:19:39 65 51 65 51 138 64 140 64 18:21:42 60 51 60 51 138 101 139 98 18:26:34 138 271 139 275 (amb load) Tx = 27.6 18:27:30 138 101 139 101 (sky) ================================================================== Fifth Orbit (Magellan Orbit #13035) DSS 63 S-band, DSS 14 X-band: This orbit was less carefully monitored because there were two stations involved. We calculated a set of offset frequencies (FRO values) in advance and had them sent to the stations; both stations used the same offsets. They appeared to work for DSS 63 at S-band. DSS 14 had problems from the beginning. Sal Abbate was at the station; operationally the station came up well. It appeared that the pre-cal tests were being executed. But the signal levels once we began tracking were never good. On this orbit, the X-band direct signal was weak compared with the noise. ------------------------------------------------------------------ 18:35:00 BEGIN CONFIGURATION FOR S-BAND ONLY AT DSS 63 18:56:06 AOS (FROM EARTH OCCULTATION) 19:04 BEGIN DSP RECORDING AT DSS 63 19:04:02 DSP idle at DSS 63 19:07 DSS 63 unable to clear "tape drive mode change" error; reloading Radio Science software. 19:10:22 DSP recording again at DSS 63, but with no FRO. 19:14:44 ENGINEERING DATA OFF Big jump in DSS 63 SSI SNR as engineering data went off. SNR approximately 32 dB, with peak at 12100 Hz. 19:16:44 LOS (SPACECRAFT BEGINS TURN TO SURFACE TARGET) 19:17:34 DSS 63 Signal fading (SNR 5 dB) as spacecraft begins turn. 19:20:51 DSP TUNES TO ECHO FREQUENCY (NO ACTION REQUIRED) 19:21:00 REMOVE 15 DB ATTENUATION FROM CHANNELS 2,4 (SR,SL) 19:21:50 15 dB removed from DSS 63 attenuation on S-band 19:24:41 SPACECRAFT BEGINS TRACKING SURFACE TARGET 19:26:49 Possible echo seen in DSS 63 SSI 19:27:15 Big echo at 12 kHz in DSS 63 SSI 19:30:00 Broad echo at 13 kHz in DSS 63 SSI 19:35:00 BEGIN DSP RECORDING AT DSS 14 19:40:00 Big echo in DSS 63 SSI; but overall the echoes have been intermittent. 19:47:29 SPACECRAFT ENDS TRACKING SURFACE TARGET 19:49 Direct signal beginning to build on DSS 63 SSI 19:49:00 ADD 15 DB ATTENUATION TO CHANNELS 2,4 (SR,SL) AT DSS 63 ADD 25 DB ATTENUATION TO CHANNELS 1,3 (XR,XL) AT DSS 14 19:50:29 AOS 19:50:46 ENTER OCCULTATION 19:52 S-LCP attenuation at DSS 63 has not updated to 51 dB as it should have. 19:52:29 ENGINEERING DATA ON 19:54 Occultation appeared to be OK at DSS 63, but signal was at a lower frequency than expected. 19:54 Tony says the X-band signal disappeared from the DSS 14 SSI when the FRO changed from +4000 to -1500. 19:58:00 FOR BOTH DSS 14 CHANNELS (XR,XL) SWITCH MASER TO AMBIENT LOAD FOR TWO MINUTES. FOR BOTH DSS 63 CHANNELS (SR,SL) SWITCH MASER TO AMBIENT LOAD FOR TWO MINUTES. REPORT TIMES AND PHYSICAL TEMPERATURES OF AMBIENT LOADS TO JPL. AFTER 2 MINUTES, SWITCH MASERS BACK TO COLD SKY AND END DSP RECORDING (NO LATER THAN 20:08). 19:59 Ambient load measurement at DSS 14 was done after 25 dB had been added to S-RCP and S-LCP (instead of the X- band channels). Expect all samples to be badly clipped. The Track Controller apparently misunderstood my timeline and confused S and X band settings. 20:00 Sal Abbate reports the following from the DSS 14 pre-cal Cold Sky Attenuators Ambient Load Ambient Load for 1 V RMS Attenuator Settings Temperatures for 1 V rms -------------------- ------------------- ------------ X-RCP 31 42 17.16 S-RCP 31 42 UNK X-LCP 27 38 19.11 S-LCP 32 43 20.88 Table of Frequency Offsets Time FRO (Hz) -------- -------- 19:04:00 -1500. 19:10:22 0. (63 only) 19:11:44 -1500. 19:25:00 0. 19:27:00 +2000. 19:29:00 +4000. 19:31:00 +6000. 19:34:00 +8000. 19:39:00 +9000. 19:44:00 +8000. 19:46:00 +6000. 19:48:00 +4000. 19:50:00 -1500. Attenuator Settings and RMS Levels (63 only) Time Attenuators (dB) RMS Levels (mV) J1 J2 J3 J4 AD1 AD2 AD3 AD4 -------- -- -- -- -- ---- ---- ---- ---- 19:14:43 60 51 60 51 554 648 565 642 19:18:00 216 493 210 495 19:21:50 60 36 60 36 1098 947 1131 948 19:58:20 60 51 60 51 745 746 735 746 ================================================================== Sixth Orbit (Magellan Orbit #13036) DSS 63 X-band, DSS 14 S-band: The frequency offsets were becoming routine. The S-band signal at DSS 14 was not very good. No echoes were seen in the SSI displays from either station. ------------------------------------------------------------------ 20:08 BEGIN DSP CONFIGURATION FOR X-BAND ONLY AT DSS 63 BEGIN DSP CONFIGURATION FOR S-BAND ONLY AT DSS 14 20:29:04 AOS (FROM EARTH OCCULTATION) 20:37 BEGIN DSP RECORDING 20:37 DSS 14 recording with FRO = 0. 20:37 DSS 63 recording with correct FRO 20:41:25 DSS 63 SSI shows signal with 45 dB SNR, peak at 10550 Hz. 20:43 DSS 14 signals are weak in both OLR and CLR 20:47:38 ENGINEERING TELEMETRY OFF 20:48 DSS 63 SSI shows 44 dB SNR 20:49 DSS 14 SSI shows 10 dB SNR 20:49:38 LOS (BEGIN SPACECRAFT TURN TO SURFACE TARGET) 20:50:24 DSS 63 SNR down to 15 dB (signal fading as spacecraft turns to surface target) 20:53:50 DSP TUNES TO ECHO FREQUENCY (NO ACTION REQUIRED) 20:54:00 DSS 63 REMOVE 25 DB ATTENUATION FROM CHANNELS 1,3 (XR,XL) DSS 14 REMOVE 15 DB ATTENUATION FROM CHANNELS 2,4 (SR,SL) 20:57:38 SPACECRAFT BEGINS TRACKING SURFACE TARGET 21:12 Nothing has been visible in SSI from either station 21:20:00 SPACECRAFT ENDS TRACKING SURFACE TARGET 21:20:00 END OF TRACK AT DSS 63 21:22:00 ADD 15 DB ATTENUATION ON CHANNELS 2,4 (SR,SL) 21:23 DSS 14 SSI shows direct signal, but only 4 dB above noise. 21:23:26 AOS 21:24:52 ENTER OCCULTATION 21:25:11 ENGINEERING DATA ON 21:31:00 FOR BOTH CHANNELS 2,4 (SR,SL) SWITCH MASER TO AMBIENT LOAD FOR TWO MINUTES. REPORT TIME AND PHYSICAL TEMPERATURE OF AMBIENT LOAD TO JPL. AFTER 2 MINUTES SWITCH MASERS BACK TO COLD SKY AND END DSP RECORDING (NO LATER THAN 21:41) 21:36:12 DSS 14 DSP to idle Table of Frequency Offsets Time FRO (Hz) -------- -------- 20:37:00 -1500. (63) 20:37:00 0. (14) 20:43:00 -1500. (14) 20:58:00 0. 21:00:00 +2000. 21:02:00 +4000. 21:04:00 +6000. 21:07:00 +8000. 21:12:00 +9000. 21:17:00 +7000. 21:19:00 +5000. 21:21:00 +3000. (14 only) 21:23:00 -1500. (14 only) POCA Equivalent S-Band Sky Frequencies (DSS 63) Time Frequency (Hz) -------- -------------- 20:58:54 2298035932. 21:03:54 2298017848. 21:08:54 2298011164. Attenuator Settings and RMS Levels (63 only) Time Attenuators (dB) RMS Levels (mV) J1 J2 J3 J4 AD1 AD2 AD3 AD4 -------- -- -- -- -- ---- ---- ---- ---- 20:40:00 60 51 60 51 138 1323 140 1310 20:48 60 51 60 51 138 1188 138 1222 20:57 40 51 40 51 182 1105 186 1089 Attenuator Settings and RMS Levels (14 only) Time Attenuators (dB) RMS Levels (mV) J1 J2 J3 J4 AD1 AD2 AD3 AD4 -------- -- -- -- -- ---- ---- ---- ---- 20:49 42 48 38 49 143 327 134 328 21:32 42 42 38 43 1068 1079 1108 1012 (amb load) 21:35:37 42 42 38 43 276 388 276 400 (sky) Tsr=21.71 Tsl=24.29 ================================================================== Seventh Orbit (Magellan Orbit #13037) X-band: This was a very strange orbit. We could see only a very weak direct signal in the X-RCP SSI before the maneuver and almost no signal in X-LCP (where DSS 63 had given us 50 dB SNR). We, in the NOPE area, spent most of the time talking to Sal Abbate and trying to figure out what had happened to the signals at DSS14. DSS 15 had been brought up in the meantime to get engineering data; it was reporting normal signals with no problems. ------------------------------------------------------------------ 21:41:00 BEGIN DSP CONFIGURATION FOR X-BAND ONLY 22:02:02 AOS (FROM EARTH OCCULTATION) 22:10:00 BEGIN DSP RECORDING SSI shows very weak signal on ODAN A (X-RCP) and almost no signal on ODAN B (X-LCP) 22:20:36 ENGINEERING DATA OFF 22:22:36 LOS (SPACECRAFT BEGINS TURN TO SURFACE TARGET) 22:24:50 DSP TUNES TO ECHO FREQUENCY (NO ACTION REQUIRED) 22:25:00 REMOVE 25 DB ATTENUATION FROM CHANNELS 1,3 (XR,XL) 22:30:36 SPACECRAFT BEGINS TRACKING SURFACE TARGET 22:45 Percy will FAX copies of some representative DSS 14 and 63 SSI plots to Sal to show how badly the 14 signals compare with 63. 22:53:24 SPACECRAFT ENDS TRACKING SURFACE TARGET 22:55:00 ADD 25 DB ATTENUATION TO CHANNELS 1,3 (XR,XL) 22:56:24 AOS 22:56:41 ENTER OCCULTATION 23:01 DSS 14 has been faithfully reporting FRO changes throughout; I haven't had time to note them. Everything seems to have gone according to my schedule, however. 23:04:00 FOR BOTH CHANNELS 1,3 (XR,XL) SWITCH MASER TO AMBIENT LOAD FOR TWO MINUTES. REPORT TIME AND PHYSICAL TEMPERATURE OF AMBIENT LOAD TO JPL. AFTER 2 MINUTES SWITCH MASERS BACK TO COLD SKY AND END DSP RECORDING (NO LATER THAN 23:14) 23:05:38 DSS 14 reports that they have had masers into ambient load and "have attenuator settings." This suggests they have adjusted the attenuators to 1 V rms (contrary to our intentions); the readings are consistent with this interpretation. 23:06:53 DSP to idle Table of Frequency Offsets Time FRO (Hz) -------- -------- 22:10:00 -1500. 22:31:00 0. 22:33:00 +2000. 22:35:00 +4000. 22:37:00 +6000. 22:40:00 +8000. 22:45:00 +9000. 22:50:00 +7000. 22:52:00 +5000. 22:54:00 +3000. 22:56:00 -1500. POCA Equivalent S-Band Sky Frequencies (DSS 63) Time Frequency (Hz) -------- -------------- 23:05:38 2298004549. Attenuator Settings and RMS Levels Time Attenuators (dB) RMS Levels (mV) J1 J2 J3 J4 AD1 AD2 AD3 AD4 -------- -- -- -- -- ---- ---- ---- ---- 22:10 59 42 55 43 42 328 42 327 22:23:13 42 327 44 327 22:25 34 42 30 43 717 716 712 739 23:02:25 59 42 55 43 43 327 40 327 23:05:38 42 42 38 43 1147 947 1110 965 (amb load) Tx=21.67 23:06:43 42 42 38 43 282 404 284 403 (sky) ================================================================== Eighth Orbit (Magellan Orbit #13038) S-band: We hoped to see some kind of echo on this pass, but the direct signals were weak and we found nothing that looked like a reflection from Venus. I wouldn't be surprised if we detect an echo in the data on tape, but it won't compare well in terms of strength with the DSS 63 data. The pass ended before we saw the spacecraft return to Earth point and go into occultation. ------------------------------------------------------------------ 23:14:00 BEGIN DSP CONFIGURATION FOR S-BAND ONLY 23:34:59 AOS (FROM EARTH OCCULTATION) 23:39 Requested that DSS 14 start DSP recording early. 23:41 SSI shows signal with approximately 10 dB SNR at 11800 Hz (S-RCP) 23:53:33 ENGINEERING DATA OFF 23:53:44 SSI peak about 17 dB SNR at 11800 Hz. 23:55:33 LOS (SPACECRAFT BEGINS TURN TO SURFACE TARGET) 00:00:50 DSP TUNES TO ECHO FREQUENCY (NO ACTION REQUIRED) 00:01:00 REMOVE 15 DB FROM CHANNELS 2,4 (SR,SL) 00:03 Clipping on S-LCP; the attenuator setting of 27 dB is too low. 00:03:33 SPACECRAFT BEGINS TRACKING SURFACE TARGET 00:26:00 SPACECRAFT ENDS TRACKING SURFACE TARGET 00:28 DSP to idle 00:28:00 END OF TRACK Table of Frequency Offsets Time FRO (Hz) -------- -------- 23:39:00 -1500. 00:03:00 0. 00:05:00 +2000. 00:07:00 +4000. 00:09:00 +6000. 00:12:00 +8000. 00:17:00 +9000. 00:22:00 +7000. 00:24:00 +5000. Attenuator Settings and RMS Levels Time Attenuators (dB) RMS Levels (mV) J1 J2 J3 J4 AD1 AD2 AD3 AD4 -------- -- -- -- -- ---- ---- ---- ---- 23:41 42 48 38 49 121 331 122 333 23:44 42 44 38 44 195 391 189 387 23:53:44 42 44 38 44 208 410 214 406 00:00:30 42 44 38 44 190 388 190 397 00:01:30 42 33 38 34 669 833 686 868 00:03 42 31 38 27 828 1832 825 1780 00:04:15 42 31 38 32 811 1038 848 1019 Compiled by Dick Simpson