Cassini Significant Events 01/25/07 - 01/30/07

February 2, 2007

(Source: Cassini Project)


Cassini Significant Events 01/25/07 - 01/30/07

The most recent spacecraft telemetry was acquired on Tuesday, January 30, from the Goldstone tracking complex. 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" web page at http://saturn.jpl.nasa.gov/operations/present-position.cfm .


The schedule for Significant Events production has been adjusted by one day due to the implementation of the 9/80 Work Week at JPL. This week the report covers a 6-day period from Thursday to Tuesday. Beginning next week the new reporting period will cover a 7-day period from Wednesday to Tuesday. This will then be the standard reporting period. Variations will occasionally occur.


Thursday, January 25 (DOY 025):


Both the S28 and S29 final sequence development processes continued this week. For S28, a Sequence Change Request (SCR) approval meeting was held with all five submitted changes approved. S29 also held an SCR approval meeting where 11 requests were approved and two placed on hold pending further analysis. During this process, there are three opportunities for SCRs to be approved. As the process continues and the time for uplink approaches, SCRs will not be accepted for "make better" changes, but will only be considered if they deal with health and safety issues for either the spacecraft or instruments. As a result, the number of SCRs submitted towards the end of the process tends to drop.


Friday, January 26 (DOY 026):


Orbit Trim Maneuver (OTM) #91 was performed today. This is the approach maneuver setting up for the Titan 24 encounter on January 29. The reaction control subsystem (RCS) burn began at 2:30 AM PST. Telemetry immediately after the maneuver showed a burn duration of 7.9 seconds, giving a delta-V of 0.015 m/s. The 7.9 second burn makes this the smallest RCS burn to date. The previous record holder was OTM-09 in December of 2004 with a duration of 18.75 seconds and a delta-V of 0.016 m/sec. All subsystems reported nominal performance after the maneuver.


As Cassini began to close in on Titan for the T24 flyby, the Composite Infrared Spectrometer (CIRS) devoted nine hours to a composition map of the satellite studying its rich atmosphere of organics and other molecules.


On Saturday, the Ultraviolet Imaging Spectrograph (UVIS) will observe an occultation of the star Eps PsA by Saturn's rings to provide detailed information on ring structure, dynamics, ring-moon interactions, and ring particle sizes, and RADAR will seek to determine global ring properties with low spatial resolution images from medium inclination.


Just prior to closest approach, the Visible and Infrared Mapping Spectrometer (VIMS) and Imaging Science Subsystem (ISS) will observe the stellar occultation of Gamma Cru to help understand the structure of Titan's atmosphere.


Monday, January 29 (DOY 029):


Closest approach for Titan 24 occurred today at 2007-029T07:15:55 GMT. Cassini, inbound toward Saturn, reached an altitude of 2631 km above Titan's surface. For this flyby, the Magnetosphere And Plasma Science (MAPS) instruments observed the interaction of Titan with Saturn's magnetosphere in the upstream, inner flank, and wing regions.


Inbound to Titan, ISS searched for lightning and aurorae using night side imaging with the wide-angle camera, and UVIS made several slow scans across Titan's visible hemisphere to form spectral images in the ultraviolet.


During closest approach, the Visible and Infrared Mapping Spectrometer (VIMS) took high spatial resolution images of the development and decay of mid-latitude clouds. In the north polar region, VIMS mapped volatiles and other materials.


Today began a weeklong series of meetings and presentations that comprise the 41st Cassini Project Science Group (PSG) meeting. One item on the agenda for this week is for the science teams and working groups to come to a consensus on a tour extension trajectory to be used in a proposal to NASA for a continuation of the Cassini mission beyond its current nominal plan of four years. Ten tours and a number variations to those tours have been offered up for consideration by the scientists.


The Spacecraft Operations Office (SCO) hosted a meeting today to discuss with project management a new flight software build for the Command Data System (CDS). Version 10 of the software is desired in order to add the capability to remove a "bad" SSR memory submodule from use. This capability has been on the implementation list for several years but has not been included due to workforce and time limitations. CDS proposed that implementation of Version 10 would be a good opportunity to add this and other capabilities. The project has concurred, and SCO will now begin addressing the issues related to this development effort.


Because the best things deserve to be repeated, Cassini's image of Hyperion -- originally Astronomy Picture of the Day in October 2005 -- was Astronomy Picture of the Day again yesterday.


The preliminary product input port for the S30 Science Operations Plan Update process occurred today. The official port is scheduled next week on Feb. 6.


The Aftermarket Process for the S32 sequence began today. This 5-week process will address proposed changes that require re-integration of the segments contained in the S32 sequence.


Tuesday, January 30 (DOY 030):


The spacecraft team began the procedure to uplink AACS flight software version A8.7.5 to the spacecraft today. Uplinks will continue through Feb. 5 with normalization scheduled for March 4. This software update changes parameters and vectors only. There are no logic changes.


The Navigation team has reported that since the Titan 24 encounter was a high altitude flyby on reaction wheel control, the orbit determination solution is already well converged. The current estimate for Orbit Trim Maneuver (OTM) #92 is only 9 mm/s, and there is a slight delta V saving for canceling and accomplishing all of the correction at OTM-093. Based on these factors, there is no driving reason to execute OTM-092, so it has been cancelled.


The Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference for January was held today. The topic, Basics of Interplanetary Flight, was presented by the Cassini Real Time Mission Control lead from the Mission Support and Services Office. The presentation offered an introduction to the online tutorial http://www.jpl.nasa.gov/basics.
A PDF copy of the presentation can be found here: http://saturn.jpl.nasa.gov/multimedia/products/pdfs/20070130_CHARM_Doody.pdf (1.1 MB).


Cassini Outreach has released an interactive flash - Saturn Moons Explorer: Titan. To view this feature link to: http://saturn.jpl.nasa.gov/news/features/feature20070129.cfm
and click on the link provided.


Today CIRS made a temperature map in the infrared to obtain information of the thermal structure of Titan's stratosphere from roughly 70 to 400 km in altitude. Variations in longitude, latitude, and altitude are all of interest in understanding the dynamics of the stratosphere.


Upcoming:


Saturn will be at its closest point to Earth this year during the beginning of February. As a result, it looks bigger and brighter both visually and with the aid of a telescope than it will for all the rest of 2007. Because Saturn is slowly moving away from the Sun, it will not be this close to Earth again until 2029. Saturn Opposition is coming up Feb. 10. This means that Saturn will be 180 degrees opposite the Sun as seen from Earth. Saturn Observation Campaign members around the globe are organizing observing events for viewing at opposition. An event local to JPL is scheduled for Monrovia Library Park from 6-10 p.m. Viewing may run later if there are still interested viewers and decent weather conditions. Saturn viewing in 2007 details here: http://soc.jpl.nasa.gov/viewing.cfm