News | May 29, 2013
Cassini Significant Events 05/22/2013 - 05/28/2013
Cassini is orbiting Saturn with a 12-day period in a plane inclined 59.4 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on May 29 using one of the 34-meter diameter Deep Space Network stations at Canberra, Australia. Except for some science instrument issues described in previous reports (for more information search the Cassini website for CAPS and USO), the spacecraft continues to be in an excellent state of health with all of its subsystems operating normally. Information on the present position of the Cassini spacecraft may be found on the "Present Position" page at: http://saturn.jpl.nasa.gov/mission/presentposition/.
The T-91 Titan targeted encounter was this week's highlight. Targeted encounters are those for which the flight team invests spacecraft propellant as well as effort; encounters of the non-targeted kind happen along the way, providing specific opportunities for additional science observations. When Cassini played back its telemetry after T-91, the Deep Space Network (DSN) captured virtually every bit. This included synthetic-aperture radar imaging, which provides the mission's highest-resolution glimpses of Titan's surface features. Based on the DSN's radiometric tracking data following the encounter, the Navigation Team's orbit-determination solutions converged neatly, and the spacecraft executed a small post-flyby orbit cleanup maneuver using the small rocket thrusters. As a result of T-91's gravity assist, Cassini's orbital inclination decreased by 2.3 degrees, precisely as planned. Further details on the encounter are posted here: http://saturn.jpl.nasa.gov/mission/flybys/titan20130523/
Wednesday, May 22 (DOY 142)
The Ultraviolet Imaging Spectrograph (UVIS) wrapped up a 23-hour observation of Saturn's northern auroral region today. Next, the Magnetospheric Imaging Instrument, Radio and Plasma Wave Science Subsystem, Magnetometer, Cosmic Dust Analyzer, and Ion and Neutral Mass Spectrometer collected data while Cassini's high-gain antenna was trained on Earth for nine hours. During this period the DSN conducted one of this week's seven flawless interplanetary communications sessions before Cassini turned away for its close encounter with Titan.
Thursday, May 23 (DOY 143)
Cassini spent the day rotating about all three axes, pointing its telescopes and in-situ instruments as needed to scrutinize Titan, Saturn's largest, atmosphere-enshrouded satellite. In particular, RADAR pointed the spacecraft's high-gain antenna dish to Titan and operated in all of its modes, one at a time: Synthetic Aperture (imaging), Altimetry, Radiometry, and Scatterometry. A "Quick-look" PDF page illustrates the "ground track" of this passage, and gives a brief description of all the observations: http://saturn.jpl.nasa.gov/files/20130523_Titan91_flyby_quicklook.pdf (PDF, 307 KB)
Friday, May 24 (DOY 144)
The Imaging Science Subsystem (ISS) acquired global-scale mosaics of Titan's mid-southern latitudes on the trailing hemisphere, which have only been imaged at lower resolution. The Composite Infrared Spectrometer (CIRS) then continued temporal coverage of gas species and temperature distributions in the stratosphere. ISS rode along with CIRS's observations to image Titan's surface and atmosphere. Last, the Visible and Infrared Mapping Spectrometer (VIMS) monitored Titan's cloud activity, riding along with ISS and CIRS.
Saturday, May 25 (DOY 145)
ISS monitored Titan to track clouds and their evolution for an extra day after the encounter.
Sunday, May 26 (DOY 146)
Cassini passed apoapsis, having coasted 1.4 million kilometers from the planet, slowing to 14,671 kilometers per hour relative to Saturn. This marked the beginning of Cassini's orbit #191.
ISS and UVIS spent nearly fifteen hours observing Saturn's irregular moon Siarnaq, named after a giant in Inuit mythology. This very dark object has a diameter of about 32 kilometers and orbits Saturn once every 896 days at a distance of 17.5 million kilometers.
Monday, May 27 (DOY 147)
ISS created a fifteen-hour low resolution F-ring movie; this amount of time covered one complete revolution of the ring's particles around Saturn. A still image featured today illustrates this ever-changing ring: /resources/15819
Orbit Trim Maneuver 350, the post-T-91 trajectory cleanup maneuver, executed today using the small thrusters. The 45-second burn provided Cassini a change in velocity of 51 millimeters per second.
Tuesday, May 28 (DOY 148)
ISS carried out an observation in the satellite orbit campaign, looking at small satellites near Saturn. Next, VIMS observed the garnet-red star Mu Cephi as it was being occulted by Saturn's rings.