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 1998/192." END_OBJECT = TEXT END From flemoine@ares.gsfc.nasa.gov Mon Jan 25 16:19:11 1999 Received: from ares.gsfc.nasa.gov (ares.gsfc.nasa.gov [128.183.201.183]) by magellan.Stanford.EDU (8.8.5/8.8.3) with ESMTP id QAA18707 for ; Mon, 25 Jan 1999 16:19:10 -0800 (PST) Message-Id: <199901260019.QAA18707@magellan.Stanford.EDU> Received: by ares.gsfc.nasa.gov; Tue, 26 Jan 1999 00:19:21 GMT From: Frank Lemoine Subject: Re: Doy 194 solar array orientation To: flemoine@ares.gsfc.nasa.gov Date: Tue, 26 Jan 1999 0:19:20 UTC Cc: rsimpson@magellan.Stanford.EDU, drowland@olympus.gsfc.nasa.GOV, balmino@pontos.cnes.fr In-Reply-To: from "Frank Lemoine" at Jan 26, 99 12:05 (midnight) X-Mailer: Elm [revision: 212.2] Content-Length: 328 Status: RO -- There is another reason why the 980710-980714 arc is anomalous. It looks like for about 1.5 hours on 980713, starting around 22:00 they decided to change the solar array orientation from +32 deg in +X to 0 deg ... not sure why... Looks like I will have to dump the solar array quaternions now for ALL of the SPO arcs. FGL ------------------------------------------------------------------------------------------- From flemoine@ares.gsfc.nasa.gov Mon Jan 25 18:06:29 1999 Received: from ares.gsfc.nasa.gov (ares.gsfc.nasa.gov [128.183.201.183]) by magellan.Stanford.EDU (8.8.5/8.8.3) with ESMTP id SAA19296 for ; Mon, 25 Jan 1999 18:06:29 -0800 (PST) Message-Id: <199901260206.SAA19296@magellan.Stanford.EDU> Received: by ares.gsfc.nasa.gov; Tue, 26 Jan 1999 02:06:35 GMT From: Frank Lemoine Subject: Re: Doy 194 solar array orientation To: rsimpson@magellan.Stanford.EDU, flemoine@ares.gsfc.nasa.gov Date: Tue, 26 Jan 1999 2:06:35 UTC Cc: drowland@olympus.gsfc.nasa.GOV In-Reply-To: <199901260022.QAA18740@magellan.Stanford.EDU>; from "Dick Simpson 723-3525" at Jan 25, 99 4:22 pm X-Mailer: Elm [revision: 212.2] Content-Length: 546 Status: RO Dick, Thanks for converting the quaternion solar array file for day 192. >From the SA quaternions for day 192, it is apparent that the funkiness lasts until about 00:49 or so then they return to normal orientation (about +32.9 deg canted toward +X, for that part of SPO-2) So the total off-nominal solar array orientation lasts about ~1.75 hrs in the first case and (980710 23:06 to 980711 00:49) and (980713 22:03 - 980713 23:48) in the second case - also about 1.75 hrs. No wonder this data arc is not behaving properly. Frank L. ----------------------------------------------------------------------------------------- From flemoine@ares.gsfc.nasa.gov Tue Jan 26 12:05:28 1999 Received: from ares.gsfc.nasa.gov (ares.gsfc.nasa.gov [128.183.201.183]) by magellan.Stanford.EDU (8.8.5/8.8.3) with ESMTP id MAA23119 for ; Tue, 26 Jan 1999 12:05:28 -0800 (PST) Message-Id: <199901262005.MAA23119@magellan.Stanford.EDU> Received: by ares.gsfc.nasa.gov; Tue, 26 Jan 1999 20:05:40 GMT From: Frank Lemoine Subject: Re: MGS Solar array question To: charles.w.whetsel@jpl.nasa.gov Date: Tue, 26 Jan 1999 20:05:39 UTC Cc: flemoine@ares.gsfc.nasa.gov, rsimpson@magellan.stanford.edu, drowland@olympus.gsfc.nasa.GOV, dsmith@tharsis.gsfc.nasa.gov, trish@rodan.jpl.nasa.gov In-Reply-To: ; from "Charles W. Whetsel" at Nov 5, 98 11:07 am X-Mailer: Elm [revision: 212.2] Content-Length: 2224 Status: RO Charles: I have some questions regarding the orientation of the MGS solar array during SPO. We have been looking at the MGS solar array quaternions, and I'm puzzled by the "blips" occur periodically, which seem to be periodic changes in the solar array orientation. I'd like to ask some questions to be sure that we are interpreting the output correctly. 1. From a dump of the SA quaternion files, it appears in general the solar arrays were canted approx. 30deg toward +X during SPO (ie sunward). Is this correct? Ie as per the mission documentation which states when the s/c is in ANS the solar arrays are canted +30 deg in +X? 2. This "cant" angle appears to change slightly every few weeks: ie, this angle was 27.98 deg in SPO-1; 32.96 deg mid June through July, 23.95 deg. after Aug. 27, etc. Why were these angle changes in the SA orientation implemented? (Assuming I'm reading the output correctly)? 3. There appear on some days to be step changes in the solar array orientation that last maybe an hour to an 1 1/2 hrs. Did such changes really occur, and what was the rationale? For instance on our anon. ftp site, I've placed three postscript files: quats.94001.doy98175.ps; quats.94001.doy98214.ps; quats.94001.doy98213.ps. (geodesy.gsfc.nasa.gov anon ftp; cd to dist/quats/) (June 24, July 13, and Aug. 1) It looks like in SPO-1 and the first two weeks of SPO-2, there were no periodic changes in the SA quaternions. For portions of latter June and July, they happend about once a day. In August, they seem to occur once per rev. 4. Was there supposed to be any change in solar array orientation during the MOLA ISH's? The reason for my concern is that our force modelling requires us to model the orientation of the spacecraft - including the solar array - as a function of time in order to compute the best possible orbits. I want to confirm my impression of the general orientation of the arrays during SPO and that these periodic changes are real phenomena. I hope you can direct me to the proper source or person to get answers to these questions, or clear up any misconceptions I might have. Best regards, Frank G. Lemoine MOLA/POD