Titan Flyby - 31 July 2008
30 Jul 2008
Just over two months after its last visit, Cassini once again approaches Titan for the mission's forty-sixth targeted encounter with the large moon: T45. This is the first Titan encounter in Cassini's Equinox Mission.
The closest approach to Titan occurs on Thursday, 31 July, at 02:13:11 UT at an altitude of 1613 kilometres above the surface and at a speed of 6.3 kilometres per second. The latitude at closest approach is 43.3° S and the encounter occurs on orbit number 78.
This encounter is set up with two manoeuvres: an apoapsis manoeuvre on 22 June, and a Titan approach manoeuvre, scheduled for 27 July. T45 is the tenth in a series of outbound encounters and occurs roughly two and a half days after Saturn closest approach.
Science Highlights
- Radio Science Subsystem (RSS)
This flyby was designed to be an optimized gravity field determination flyby for the RSS, the prime instrument at closest approach. An instrument might be given a couple of hours near closest approach for a typical Titan flyby, but in this special case, RSS was given over 16 hours around closest approach. RSS observations of Titan's gravity field should allow for determining the internal structure of Titan. There is the possibility that Titan may have an interior ocean below its frozen surface. Complicating matters is Titan's shifting shape: the moon deforms as it rotates and as it orbits around Saturn. That means that Titan's gravity field changes, as well. If Titan has a subsurface interior ocean, gravity field measurements from this flyby, as well as from the flybys T11, T22 and T33, may be able to confirm its presence.
- Imaging Science Subsystem (ISS)
ISS will be acquiring a full-disk mosaic of Titan's leading hemisphere, including coverage of Hotei Arcus. The instrument will also continue to monitor clouds.
- Composite Infrared Spectrometer (CIRS)
The instrument will continue to search for trace atmospheric molecular species in Titan's winter polar (currently northern) hemisphere by limb sounding of the stratosphere. CIRS also continues a mapping campaign in the mid- and far-infrared to obtain the spatial and temporal variations of temperature and hydrocarbon and nitrile molecules. This provides information on seasonal changes in weather, climate and chemistry that may be occurring.
Table of Events
1 July 2008
| Time UTC |
Time wrt
T-45 |
Activity |
| 19:08:00 |
-29d 07h |
Start of sequence S42 that contains Titan-45 |
27 July 2008
| Time UTC |
Time wrt
T-45 |
Activity |
| 08:36:00 |
-03d 18h |
OTM #160 Prime |
28 July 2008
| Time UTC |
Time wrt
T-45 |
Activity |
| 11:25:30 |
-02d 15h |
Pan non-targeted flyby.
Altitude = 97 453 km |
| 12:14:41 |
-02d 14h |
Descending ring plane crossing |
| 12:18:39 |
-02d 14h |
Prometheus non-targeted flyby.
Altitude = 24 652 km |
| 12:37:41 |
-02d 14h |
Saturn periapse.
R = 2.693 RS, lat = -10°, phase = 158° |
| 13:01:44 |
-02d 13h |
Epimetheus non-targeted flyby.
Altitude = 106 964 km |
| 17:00:00 |
-02d 09h |
OTM #160 Backup |
30 July 2008
| Time UTC |
Time wrt
T-45 |
Activity |
| 07:20:00 |
-18h 53m |
Start of the TOST segment |
| 07:20:00 |
-18h 53m |
Turn cameras to Titan |
| 07:50:00 |
-18h 23m |
New waypoint |
| 07:50:21 |
-18h 23m |
Deadtime, 15 minutes long.
Used to accommodate changes in flyby time |
| 08:05:21 |
-18h 08m |
Titan atmospheric observations - CIRS. Obtain information on the thermal structure of Titan's stratosphere |
| 12:13:11 |
-14h 00m |
Titan surface observations - ISS. Global map |
| 14:13:11 |
-12h 00m |
Turn cameras to new waypoint |
| 14:43:11 |
-11h 30m |
New waypoint |
| 14:43:11 |
-11h 30m |
Titan gravity measurements - RSS. Experiment to determine Titan's gravity field, including its Love number, and infer constraints on its internal structure |
31 July 2008
| Time UTC |
Time wrt
T-45 |
Activity |
| 02:13:11 |
+00h 00m |
Titan-45 Flyby Closest Approach Time.
Altitude = 1613 km, speed = 6.3 kms-1, 49° phase at closest approach |
| 06:58:11 |
+04h 45m |
Titan atmospheric observations - CIRS. Obtain vertical profiles of temperatures in Titan's stratosphere. |
| 03:01:23 |
+00h 48m |
Ascending ring plane crossing |
| 10:29:00 |
+08h 16m |
Titan gravity measurements - RSS. Experiment to determine Titan's gravity field, including its Love number, and infer constraints on its internal structure. |
| 15:06:11 |
+12h 53m |
Deadtime, 13 minutes 49 seconds long.
Used to accommodate changes in flyby time |
| 15:20:00 |
+13h 07m |
Turn to Earth-line |
| 15:50:00 |
+13h 37m |
Playback of T45 data. Goldstone 34m array |
| 19:51:47 |
+17h 38m |
Cassini at apoapse, farthest distance from Saturn in this orbit (1.2 million km) |
Titan Ground Trace
 |
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Image courtesy NASA/JPL/Space Science Institute |
The above image shows the ground trace of the Titan-45 flyby on a mosaic of Titan's surface, for a period of 32 hours around closest approach (going from ~55° to ~270° longitude). The colour of the trace indicates Cassini's altitude above the surface. Blue: > 100 000 km, green: < 100 000 km, light blue: < 50 000, yellow: < 10 000 km, orange: < 5000 km, red: < 2000 km. The point of closest approach is marked T45 (Cassini at 1613 km altitude).
Last Update: 13 Aug 2008
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