Titan Fly-by - 21 December 2008
19 December 2008
Sixteen days after its previous fly-by, the Cassini spacecraft returns to Saturn's largest moon for the mission's fiftieth targeted encounter with Titan. The closest approach to Titan occurs on Sunday, 21 December, at 12:59:53 UT at an altitude of 970 kilometres above the surface and at a speed of 6.3 kilometres per second. The latitude at closest approach is 43.9°S and the encounter occurs on orbit number 97.This encounter is set up with two manoeuvres: an apoapsis manoeuvre on 13 December and a Titan approach manoeuvre, scheduled for 17 December. T49 is the thirteenth in a series of outbound encounters and the fifth Titan encounter in Cassini's Equinox mission. It occurs just under four days after Saturn closest approach.
Science Highlights
- Cassini Radar (RADAR)
RADAR: T49 features altimetry across Ontario Lacus, the first time in the mission RADAR has obtained altimetry across a known or suspected lake. The topography profile will help understand the slopes driving drainage into Ontario as well as providing evidence about whether it is presently liquid-filled. T49 also includes SAR of the almost completely unmapped southwestern quadrant of Titan, as well as of south polar terrain. - Ion and Neutral Mass Spectrometer (INMS)
INMS On T49, INMS will be riding with RADAR during a relatively rare wakeside pass. INMS will get good ride-along measurements of non-reactive neutrals, and limited coverage of the ionosphere near closest approach. - Visual and Infrared Mapping Spectrometer (VIMS)
VIMS will acquire mid-resolution and high resolution images south of Xanadu. We expect VIMS to point to the Hotei region and to acquire a 2×2 mosaic at 10 km/pixel of this 5 micron bright region. The instrument will then map a part of the southern hemisphere that has never been mapped at 5 km/pixel resolution. Observation of Titan's bright side will end with a glance at Ontario Lacus if pointing is possible. On the dark side, VIMS will observe Titan's limb looking for some more CO and CH4 emission features. - Imaging Science Subsystem (ISS)
ISS will acquire global- and regional-mapping mosaics of Titan's leading hemisphere at mid-southern latitudes and will ride along with VIMS to acquire high-resolution coverage at higher southern latitudes. - Composite Infrared Spectrometer (CIRS)
CIRS continues to extend spatial and temporal coverage of our Titan dataset, performing most major observational activity types. These include: global temperature mapping, vertical profiles of minor gas species in the mid-infrared, and global mapping of far-infrared trace species such as CO, H2O and HCN. - Magnetospheric Imaging Instrument (MIMI)
MIMI measures energetic ion and electron energy input to Titan's atmosphere. - Dual Technique Magnetometer (MAG)
MAG: T49 is an upstream flank-out fly-by with a minimum altitude of 970 km. The geometry of this fly-by is suitable to study the magnetic pileup region and the pressure balance between the magnetic pressure in the magnetic barrier and the thermal pressure in the ionosphere. T49 also takes place in Saturn's near-noon sector (10.5 hours SLT), where Titan could be found in the magnetosheath if the solar wind pressure is high. - Radio and Plasma Wave Science (RPWS)
RPWS will measure thermal plasmas in Titan's ionosphere and surrounding environment; search for lightning in Titan's atmosphere; and investigate the interaction of Titan with Saturn's magnetosphere.
Table of Events
26 November 2008
| Time UTC | Time wrt T-49 |
Activity |
| 17:55:00 | -24d 19h | Start of sequence S46 that contains Titan-49 |
17 December 2008
| Time UTC | Time wrt T-49 |
Activity |
| 13:58:00 | -03d 23h | OTM #178 prime, Titan-49 targeting manoeuvre |
| 17:25:26 | -03d 20h | Periapse |
18 December 2008
| Time UTC | Time wrt T-49 |
Activity |
| 23:58:00 | -02d 13h | OTM #178 backup |
20 December 2008
| Time UTC | Time wrt T-49 |
Activity |
| 16:29:00 | -20h 30m | Start of the TOST segment |
| 16:29:00 | -20h 30m | Turn cameras to Titan |
| 17:09:00 | -19h 50m | New waypoint |
| 17:09:00 | -19h 50m | Deadtime, 15 minutes and 32 seconds long. Used to accommodate changes in fly-by time |
| 17:24:32 | -19h 35m | Titan atmospheric observations - CIRS. Obtain information on the thermal structure of Titan's stratosphere. |
| 23:59:52 | -13h 00m | Titan atmospheric observations - CIRS. Obtain information on CO, HCN, CH4. Integrate on disk at airmass 1.5-2.0 |
21 December 2008
| Time UTC | Time wrt T-49 |
Activity |
| 03:59:52 | -09h 00m | Titan surface observations - ISS. NAC global map |
| 07:59:52 | -05h 00m | Titan surface observations - ISS. NAC regional map |
| 09:59:52 | -03h 00m | Titan atmospheric observations - CIRS. Vertical sounding of stratospheric compounds on Titan, including H2O. Integrations at two locations on the limb displaced vertically |
| 10:59:52 | -02h 00m | Titan surface observations - VIMS. Regional map |
| 12:13:52 | -00h 46m | Transition to thruster control |
| 12:14:52 | -00h 45m | Titan surface observations - VIMS. Regional map during transition to thruster control |
| 12:35:52 | -00h 24m | Titan RADAR observations. Inbound HiSAR |
| 12:50:52 | -00h 09m | Titan RADAR observations. Inbound altimetry over Ontario |
| 12:55:52 | -00h 04m | Titan RADAR observations. Outbound SAR |
| 12:59:53 | +00h 00m | Titan-49 Fly-by Closest Approach Time. Altitude = 970 km, speed = 6.3 kms-1, 83° phase at closest approach |
| 13:04:11 | +00h 05m | Apoapse |
| 13:17:52 | +00h 18m | Titan RADAR observations. Outbound altimetry |
| 13:29:52 | +00h 30m | Titan RADAR observations. Outbound HiSAR |
| 13:34:20 | +00h 35m | Ascending ring plane crossing |
| 13:49:52 | +00h 50m | Transition off of thruster control |
| 14:11:06 | +01h 12m | Titan RADAR observations. Outbound scatterometry |
| 14:59:52 | +02h 00m | Titan RADAR observations. Outbound radiometry |
| 18:29:52 | +05h 30m | Titan atmospheric observations - CIRS. Obtain vertical profiles of temperatures in Titan's stratosphere. The arrays are stepped along the limb at two altitudes at 5° latitude intervals |
| 21:59:52 | +09h 00m | Titan surface observations - VIMS. Cloud mapping |
22 December 2008
| Time UTC | Time wrt T-49 |
Activity |
| 01:59:52 | +13h 00m | Titan surface observations - ISS. Monitoring for surface/atmosphere changes; attempt to see surface colour variations; monitor limb hazes |
| 02:29:52 | +13h 30m | Titan atmospheric observations - CIRS. Obtain information on the thermal structure of Titan's stratosphere |
| 05:59:52 | +17h 00m | Titan surface observations - ISS. Long range monitoring |
| 06:29:52 | +17h 30m | Deadtime, 17 minutes and 30 seconds long. Used to accommodate changes in fly-by time |
| 06:34:00 | +17h 35m | Turn to Earth-line |
| 07:14:00 | +18h 15m | Playback of T49 data. Goldstone 70m groundstation |
| 14:29:00 | +01d 02h | Playback of T49 data. Canberra 70m groundstation |
Last Update: 1 September 2019