From: Jet Propulsion Laboratory
Posted: Saturday, November 21, 2009
The most recent spacecraft telemetry was acquired on Nov. 10 from the Deep Space Network tracking complex at Canberra, Australia. The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at: http://saturn.jpl.nasa.gov/operations/present-position.cfm .
Wednesday, Nov. 4 (DOY 308)
Today a meeting was held to present and discuss the results of the Enceladus 7 flyby. The Spacecraft Team used AACS telemetry data gathered from the 100 km E7 flyby to derive an estimate of the Enceladus plume density and of the torque experienced by the spacecraft due to the plume. After reviewing results from AACS and the Ion and Neutral Mass Spectrometer (INMS), the Project gave the go ahead to do the E9 flyby on reaction wheels. INMS data was in good agreement with the AACS analysis. The E9 flyby is nearly identical to the E7 flyby, but with different instruments having pointing priority.
For the E9 flyby, Science Planning had asked all teams to deliver two sets of input files, one for reaction wheels, and one for thrusters. The version on thrusters will be archived and the reaction wheel version will continue on in the sequence development process.
Thursday, Nov. 5 (DOY 309)
Orbit Trim Maneuver (OTM) #221 was performed today. This was the cleanup maneuver from the Enceladus 7 encounter on Nov. 2. The main engine burn began at 2:44 AM PST. Telemetry immediately after the maneuver showed a burn duration of 1.73 seconds, giving a delta-V of 0.298 m/s. All subsystems reported nominal performance after the maneuver.
After the S55 final sequence approval meeting was held today, eight Instrument Expanded Block files were uplinked for five instruments and Optical Navigation. The background sequence will go up to the spacecraft on Monday.
A scientist on the Visual and Infrared Mapping Spectrometer team wrote an update on the JPL Blog about the "First Morsels of Science" coming back from the Enceladus flyby on Nov. 2. It is available at http://blogs.jpl.nasa.gov/?p=58. The blog entry notes that mission managers have cleared the spacecraft to do an April 28, 2010, Enceladus flyby on reaction wheels, enabling scientists to do very sensitive radio science measurements.
Friday, Nov. 6 (DOY 310)
At the S59 Science Forum on Nov. 2, it was pointed out that the Dione 2 flyby is only 1.5 days after the Titan 67 flyby, which brought up an unlikely but not impossible scenario: If something were to happen during or shortly after the T67 flyby such that the Project needed to weigh the return of D2 science versus T67 science, which should be considered of higher science importance?
To start the evaluation it is important to know that in this case the Project regards the science on both flybys as important. Both Imaging Science (ISS) and Composite Infrared Spectrometer (CIRS) observations are tagged as being high priority science for both flybys. Science Planning pinged members of the instrument teams to get their feedback on, if they had to choose, which would it be? After reviewing the responses, the answer was both flybys contain observations that are at the highest priority. It would appear to be a draw. So now the flight team would have to factor in what is happening operationally at the time. There is no way in this still hypothetical case to determine what the exact results would be, but factors in making a decision include 1) what caused the incident, 2) is the DSN involved, 3) when is the next pass for downlink, 4) what is being kept on the SSR, what is being overwritten, and when, 5) how much time does the team have to decide, 6) is there time to command changes to what is programmed in the background sequence, and, 7) are there other scheduled onboard events that occur in the near term - such as a maneuver or engineering activity - that might have an affect on the plans that are made? It never is a simple decision, but at least the flight team has given the matter some thought and will be prepared to respond should it become necessary.
Monday, Nov. 9 (DOY 313)
The Target Working Team (TWT)/ Orbiter Science Team (OST) integrated products for S60, covering orbits 131 through 133 in May and June, 2010, were delivered today. The integrated products are in their final form and no re-integration is planned. The next step in sequence development, Science Operations Plan (SOP) implementation, will kick off on Nov. 23. The handoff package template from integration to the SOP process has been updated to better track more involved prime-rider pointing designs, and two new milestones have been added to the S60 schedule for prime-rider coordination. Between now and the kickoff, the instrument teams will be working on pointing designs for the sequence.
Participating teams delivered Port 1 SASFs today as part of the SOP process for S59. As was mentioned earlier in this report, the files include the Enceladus 9 flyby as designed for reaction wheels.
Tuesday, Nov. 10 (DOY 314)
An image of the recently illuminated north side of Saturn's rings was Astronomy Picture of the Day today. Check it out at: http://antwrp.gsfc.nasa.gov/apod/ap091110.html.
Science in a nutshell: This week ISS obtained wide angle camera data for Saturn photopolarimetry 1x2 mosaics, collected images for satellite orbit determination, searched for lightning on Saturn, took a look at the outer moon Bestla, observed the E-ring at low resolution, low elevation, and high-phase, and obtained narrow angle camera images of Titan's shadow on Saturn. Looking at the shadow of Titan on Saturn is useful for Titan aerosol science. This is a unique geometry that only occurs a few times during the Extended Mission and not at all in the prime tour or proposed Extended Extended Mission.
CIRS wrapped up the far-IR hemisphere mapping activity, with scans of the northern hemisphere and pole of Saturn, and measured oxygen compounds - H2O, CO2 - in the stratosphere as a function of latitude.
Magnetospheric and Plasma Science (MAPS) instruments continued the southwest auroral campaign, began a magnetospheric boundaries campaign, and began a southwest auroral campaign to observe the auroral magnetosphere and Saturn Kilometric Radiation source regions. The Cosmic Dust Analyzer conducted an observation that is part of the ISD survey campaign.
UVIS performed several apoapse system scans of the Saturn magnetosphere and mapped volatiles in the immediate neighborhood of Enceladus. These icy atmosphere observations test the connection of volatile changes to plume eruptions.
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