News | May 8, 2013
Cassini Significant Events 05/01/2013 - 05/07/2013
Cassini is orbiting Saturn with a 9.6-day period in a plane inclined 61.7 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on May 7 by the 34-meter diameter Deep Space Network station at Canberra, Australia. Except for some science instrument issues described in previous reports, 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/.
Cassini operated under control of the ten-week command sequence S78 while teams continued working on S79, S80, and S81, which will go active in June, August, and October respectively. Planning also continued for the 2016 start of Cassini's F-ring and Proximal Orbits phase.
During observations when one instrument is primarily responsible for pointing the spacecraft, other instruments often carry out "ride-along" observations when room is planned to be available for their data on Cassini's solid-state recorder.
Wednesday, May 1 (DOY 121)
The Visible and Infrared Mapping Spectrometer (VIMS) made regional mapping mosaics of Saturn's southern hemisphere, focusing on "Storm Alley" around 40 degrees latitude. The Ultraviolet Imaging Spectrometer (UVIS) then observed an ingress solar occultation as Saturn slid in front of the Sun due to Cassini's motion in orbit. While the Sun was behind the night-side limb, the Imaging Science Subsystem (ISS) conducted a limb scan. UVIS and the Composite Infrared Spectrometer (CIRS) then watched an occultation of the star Lambda Tauri as it passed behind the rings.
CIRS conducted regional mapping of Saturn at latitudes of 75 to 80 degrees south while ISS searched for lightning, then ISS led observations of plumes coming out of the small crescent moon Enceladus from half a million kilometers away. CIRS then turned back to Saturn to observe a "beacon" of warmer-than-normal air shining brightly in the infrared at 37 degrees north latitude to derive information on composition.
The Magnetospheric and Plasma Science (MAPS) instruments sampled the inner magnetosphere as the spacecraft crossed through the ring plane. Cassini then passed through periapsis going 45,219 kilometers per hour relative to Saturn, at about 316,000 kilometers above the cloud tops. The Radio and Plasma Wave Science subsystem (RPWS) continued observing in a campaign to obtain high-resolution data with its wide-band receiver.
Thursday, May 2 (DOY 122)
VIMS led an observation of cloud motion and atmospheric dynamics at Saturn's north pole, while MAPS teams continued to observe the inner magnetosphere and auroral regions.
It came as little surprise that Cassini's widely publicized view of Saturn's north-pole hurricane, with its infrared "colors" translated into visible colors which indicated cloud height, was featured as Astronomy Picture of the Day: http://apod.nasa.gov/apod/ap130502.html
Seasonal changes in Saturn's magnetosphere are described in a paper that is the subject of today's news feature:
Friday, May 3 (DOY 123)
VIMS made regional mapping mosaics of Saturn's northern hemisphere, then ISS imaged selected Saturn latitudes at a range of emission angles as the planet rotated. MAPS instruments continued their survey of the magnetosphere.
Saturday, May 4 (DOY 124)
With UVIS riding along, CIRS “sat and stared” at a single location on the surface of Saturn in order to derive chemical composition.
The Deep Space Network carried out tracking and communications sessions with Cassini only four times this week, employing its large parabolic antenna facilities in Spain, Australia, and California. The round-trip communications delay due to the speed of light was two hours twenty-seven minutes today; it is decreasing now, after opposition, by a couple seconds per day as Earth moves in its solar orbit.
During today's tracking activity, the Radio Science team conducted an Operations Readiness Test to prepare to for the Saturn ring and atmospheric occultation coming up next Friday. Also during this activity, the realtime operations team saw that RPWS had unexpectedly undergone an instrument reset and recovered to normal operation by itself. The RPWS team subsequently confirmed this was the case; it seems to happen once every year or two.
Sunday, May 5 (DOY 125)
ISS made an observation in the satellite orbit campaign looking at small objects near the planet. It then watched the G ring's likely source object Aegaeon for sixteen hours at low phase-angle lighting. This moonlet's orbital period about Saturn is twenty hours. Previous views of the object may be seen here: /resources/14947
Monday, May 6 (DOY 126)
CIRS observed the albedo of ring particles in the thermal infrared part of the spectrum. Later, ISS began a low-resolution F-ring movie lasting 14 hours.
Cassini passed through apoapsis, having coasted "up" 1.36 million kilometers from the planet since Wednesday's periapsis, and slowing to 12,507 kilometers per hour relative to Saturn. This marked the beginning of Cassini's orbit #189.
The myriad particles that make up Saturn's complex rings are captured in this image as they plunge into Saturn's shadow and disappear: /resources/15809
Tuesday, May 7 (DOY 127)
UVIS and VIMS observed Saturn's small icy moon Mimas. ISS then performed another observation in the Satellite Orbit Campaign.