PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 2007-07-27 NOTE = " E-mail and other messages concerning MGS Radio Science on or about 1998/037." END_OBJECT = TEXT END From trish@rodan.jpl.nasa.gov Fri Feb 6 11:18:36 1998 Received: from rodan.Jpl.Nasa.Gov (rodan.jpl.nasa.gov [128.149.43.24]) by magellan.Stanford.EDU (8.8.5/8.8.3) with ESMTP id LAA11970 for ; Fri, 6 Feb 1998 11:18:31 -0800 (PST) Received: from 128.149.43.27 (trish-mac.jpl.nasa.gov [128.149.43.27]) by rodan.Jpl.Nasa.Gov (8.8.5/8.6.6) with SMTP id LAA00419; Fri, 6 Feb 1998 11:18:30 -0800 (PST) Message-Id: <199802061918.LAA00419@rodan.Jpl.Nasa.Gov> Date: 06 Feb 98 11:25:25 -0800 From: Trish Priest Subject: Occultation #16 To: David Hinson , Richard Simpson , Joe Twicken , Len Tyler CC: Salvadore Abbate , Sami Asmar , Jennifer Caetta , Paula Eshe X-Mailer: QuickMail Pro 1.0.2d1 X-Priority: 3 Reply-To: Trish Priest Content-Type: text/plain; charset="iso-8859-1" Content-Length: 460 Status: RO Hello, Occultation #16 went smoothly at DSS 65. Paula queried for and obtained the ODS data just after 8:00 AM this morning. Record Times: 037-14:47:00 to 037-15:01:00 One-way Times: 037-14:57:07 to 037-15:00:19 Expected Surface Begin: 037-14:58:19 There was one attenuation change at 14:48:37. SPK: spk_i_980205_OD119_129_V1 SOE: p120a.01.soe Script: 98037.65.a119.scr Then next occultation occurs about 1:00 AM PST Saturday morning. -Trish ------------------------------------------------------------------ From trish@rodan.jpl.nasa.gov Fri Feb 6 14:43:23 1998 Received: from rodan.Jpl.Nasa.Gov (rodan.jpl.nasa.gov [128.149.43.24]) by magellan.Stanford.EDU (8.8.5/8.8.3) with ESMTP id OAA21991 for ; Fri, 6 Feb 1998 14:43:22 -0800 (PST) Received: from 128.149.43.27 (trish-mac.jpl.nasa.gov [128.149.43.27]) by rodan.Jpl.Nasa.Gov (8.8.5/8.6.6) with SMTP id OAA00852 for ; Fri, 6 Feb 1998 14:43:22 -0800 (PST) Message-Id: <199802062243.OAA00852@rodan.Jpl.Nasa.Gov> Date: 06 Feb 98 14:50:18 -0800 From: Trish Priest Subject: RE: Re: Occultation #16 To: "Dick Simpson 723-3525" X-Mailer: QuickMail Pro 1.0.2d1 X-Priority: 3 Reply-To: Trish Priest Content-Type: text/plain; charset="iso-8859-1" Content-Length: 435 Status: R According to the weather monitor data, there was no precipitation and only 5 km/h wind in Spain. Maybe there is a constant 6 dB or so missing. -Trish -------------------------------------------------------------------- From joe@neptune.Stanford.EDU Mon Feb 9 10:45:07 1998 Received: from nova.stanford.edu (nova.Stanford.EDU [36.10.0.123]) by magellan.Stanford.EDU (8.8.5/8.8.3) with ESMTP id KAA22343 for ; Mon, 9 Feb 1998 10:45:06 -0800 (PST) Received: from neptune.Stanford.EDU (neptune.Stanford.EDU [36.10.0.149]) by nova.stanford.edu (8.8.8/8.8.4) with ESMTP id KAA08052; Mon, 9 Feb 1998 10:45:05 -0800 (PST) Received: (from joe@localhost) by neptune.Stanford.EDU (8.8.5/8.8.3) id KAA11483; Mon, 9 Feb 1998 10:41:30 -0800 (PST) Date: Mon, 9 Feb 1998 10:41:30 -0800 (PST) From: Joe Twicken Message-Id: <199802091841.KAA11483@neptune.Stanford.EDU> To: trish@zygra.jpl.nasa.gov Cc: hinson@nova.Stanford.EDU, len@nova.Stanford.EDU, rsimpson@nova.Stanford.EDU Subject: Problems with Occultation #16 Content-Length: 1013 Status: RO Hello, Trish- I just processed the ODR from occultation #16. Dave and I have just looked at the carrier power and frequency estimates from the steered data. There appears to be a problem similar to the one which occurred in occultation #1 when the buffer had overflowed due to very high speed sampling for Lunar Prospector. Is there any chance that something like that occurred during this occultation? The samples do not seem to be synchronized with the POCA data and that produces a sawtooth in the steered frequency residuals. There are also a few dropouts in the carrier frequency estimates just before 14:54 when there appears to be some "slips" in the (already bad) synchronization... Joe ----------------------------------------------------------------------- From hinson@nimbus.Stanford.EDU Wed Feb 11 10:09:30 1998 Received: from nimbus.Stanford.EDU (nimbus.Stanford.EDU [36.10.0.96]) by magellan.Stanford.EDU (8.8.5/8.8.3) with ESMTP id KAA16317 for ; Wed, 11 Feb 1998 10:09:30 -0800 (PST) Received: (from hinson@localhost) by nimbus.Stanford.EDU (8.8.4/8.8.3) id KAA26977; Wed, 11 Feb 1998 10:09:29 -0800 (PST) Date: Wed, 11 Feb 1998 10:09:29 -0800 (PST) From: Dave Hinson Message-Id: <199802111809.KAA26977@nimbus.Stanford.EDU> To: joe@neptune.Stanford.EDU, rsimpson@magellan.Stanford.EDU, len@nova.Stanford.EDU, trish@rodan.jpl.nasa.gov Subject: poca problem X-Sun-Charset: US-ASCII Content-Length: 406 Status: RO Trish sent me the predict file that was used for occultation #16. Based on a quick comparison, it matches the poca information that Joe extracted from the ODR. (If they had been different, I was hoping we could use the predict file to steer and salvage the data, but that won't work.) It's clear from the ODR data that the poca did something different than what was in the predicts. Strange. ---------------------------------------------------------------------- From joe@neptune.Stanford.EDU Wed Feb 11 10:12:07 1998 Received: from neptune.Stanford.EDU (neptune.Stanford.EDU [36.10.0.149]) by magellan.Stanford.EDU (8.8.5/8.8.3) with ESMTP id KAA16336 for ; Wed, 11 Feb 1998 10:12:06 -0800 (PST) Received: (from joe@localhost) by neptune.Stanford.EDU (8.8.5/8.8.3) id KAA15603; Wed, 11 Feb 1998 10:08:29 -0800 (PST) Date: Wed, 11 Feb 1998 10:08:29 -0800 (PST) From: Joe Twicken Message-Id: <199802111808.KAA15603@neptune.Stanford.EDU> To: hinson@nimbus.Stanford.EDU Cc: hinson@nova.Stanford.EDU, len@nova.Stanford.EDU, rsimpson@magellan.Stanford.EDU, trish@rodan Subject: Re: poca problem Content-Length: 578 Status: RO Dave- I am more inclined to believe that the POCA information is probably correct and that the samples themselves are out of sync (perhaps very much so). Joe ------------------------------------------------------------------- From joe@neptune.Stanford.EDU Thu Feb 12 11:42:41 1998 Received: from nova.stanford.edu (nova.Stanford.EDU [36.10.0.123]) by magellan.Stanford.EDU (8.8.5/8.8.3) with ESMTP id LAA03936 for ; Thu, 12 Feb 1998 11:42:40 -0800 (PST) Received: from neptune.Stanford.EDU (neptune.Stanford.EDU [36.10.0.149]) by nova.stanford.edu (8.8.8/8.8.4) with ESMTP id LAA02277; Thu, 12 Feb 1998 11:42:39 -0800 (PST) Received: (from joe@localhost) by neptune.Stanford.EDU (8.8.5/8.8.3) id LAA16726; Thu, 12 Feb 1998 11:39:00 -0800 (PST) Date: Thu, 12 Feb 1998 11:39:00 -0800 (PST) From: Joe Twicken Message-Id: <199802121939.LAA16726@neptune.Stanford.EDU> To: hinson@nova.Stanford.EDU, len@nova.Stanford.EDU, rsimpson@nova.Stanford.EDU, trish@rodan.jpl.nasa.gov Subject: Occultations and Synchronization Problem Content-Length: 3334 Status: RO Hello all- As you know, we have seen three open-loop recordings recently where the synchronization appears to have been lost between the raw data samples and the POCA. This loss of sync produces a sawtooth pattern in the carrier frequency estimates from the steered data. The problem has occurred as follows: Occ #01 1998/024 DSS15 Occ #13 1998/035 DSS45 Occ #16 1998/037 DSS65 I have spent quite a bit of time looking at the occultation #16 data. I first modified our steering coefficient maker (SCM) to account for all deterministic frequency drifts *except* for that due to the changing POCA; the program simply assumed a single POCA ramp for the entire data set. After steering the data with the new coefficients, all of the POCA ramp rate changes were obvious in the carrier frequency estimates (the frequency estimates were piecewise continuous with changing slope). Sad to say, there was (approximately) a 5-second discrepancy between the time that the POCA changes were actually observed in the data and the time that the POCA ramp rate changes were reported in the ODR headers. The observations were as follows: Change POCA Time Observed Time of Change of Change 1 53350 ~53355 2 53500 ~53505 3 53640 ~53645 4 53770 ~53775 The five second-discrepancy coincides with the duration of the leading edge of the sawtooth which we saw following our normal processing. Dave Hinson observed this and mentioned it yesterday at our weekly meeting. So, it is possible that the POCA times are being reported five seconds early. It is also possible (and my contention) that the data time tags are approximately 5 seconds too late. I ran my experiment geometry (EXPGEOM) program with a reconstructed SP-kernel for the given orbit to estimate the time of the occultation. The estimated occultation time was 53896.2 sec past midnight. According to our original data processing, the occultation appears to have occurred at 53905.6 sec (some 9.4 seconds after the predict). Dave Hinson also observed this problem which led his software to conclude that the planetary radius was a few km smaller than expected (thereby causing the late occultation). After discussing this situation with Dave, I modified our PREPMO program to subtract 5 seconds from all of the *data* time tags, leaving the POCA alone. I then reprocessed the occultation #16 ODR from start to finish. Because the actual time discrepancy is not exactly 5 seconds, there is still a bit of a sawtooth in the steered frequency residuals, However, the magnitude of the sawtooth is one order of magnitude smaller (~0.3 Hz versus the original ~3.2 Hz). The occultation now occurs 5 seconds closer to the predicted time (which is actually somewhat early itself for ingress occultations because I do not account for bending of the ray in the martian atmosphere). The signal is also properly steered to the center of the band using our usual USO frequency model. I think it is pretty clear that the data time tags are on the order of 5 seconds too late. I do not know how the data acquisition system works at the DSN or how this might occur. We can go back and look at the other two problematic occultations to see what the time discrepancy is in those cases. I will keep you all posted on my findings. Joe