Probing Titan’s Atmosphere


NASA / JPL / Val Klavans


Q U I C K   F A C T S

  • Date : July 19, 2014 (12:40 PM UTC) – July 21, 2014 (10:40 AM UTC)
  • Time of Closest Approach : July 19, 2014 @ 10:40 PM UTC
    (What time Cassini is closest to Titan)
  • Altitude at Closest Approach : 3,171 miles (5,103 kilometers)
  • Speed : 13,000 mph (5.8 km/sec)
  • Goal : To learn more about Titan’s atmosphere

* * *


F l y b y   b e g i n s
(Inbound part of the flyby)

  • Date : July 19, 2014
  • Time : 12:40 PM UTC

On Cassini’s way to Titan, its camera system, also known as the Imaging Science Subsystem (ISS) instrument, will observe Titan’s southern hemisphere. ISS will also acquire a global mapping mosaic of Titan. It will cover much of the visible face of Titan and will be centered just south of eastern Aztlan.

Below is a simulated view from Celestia of ISS’ global mapping mosaic of Titan.

Celestia / CICLOPS

Cassini’s Composite Infrared Spectrometer (CIRS) instrument will measure Titan’s atmospheric and surface temperatures. CIRS’ observations will be used to study Titan as its seasons change from spring to summer (in the northern hemisphere).

In addition, Cassini’s Visible and Infrared Mapping Spectrometer (VIMS) instrument will carry out  cloud monitoring and surface mapping observations of Titan.

C l o s e s t   a p p r o a c h
After closest approach, Cassini begins to travel away from Titan (outbound part of the flyby).

  • Date : July 20, 2014
  • Time : 10:40 AM UTC

The overall goal of this flyby is to learn more about Titan’s atmosphere. In order to accomplish this, Cassini’s  Ultraviolet Imaging Spectrometer (UVIS) instrument will gather data as Titan passes in front of two stars. First, UVIS will observe Titan as it passes in front of the star Alpha Eridani. (This type of astronomical event is called a stellar occultation.) This stellar occultation will provide information on the hydrocarbons, haze, temperature and pressure in Titan’s atmosphere. UVIS can probe deep into Titan atmosphere — down to an altitude of 200 kilometers (124 miles) — well below the minimum altitude Cassini can safely approach Titan.

Alpha Eridani (also known as Achernar) is the brightest star in the constellation Eridanus and the tenth-brightest star in the night sky. This is a view of the star as seen from Earth.

© Rolf Wahl Olsen
© Rolf Wahl Olsen

At closest approach, when Cassini is closest to Titan during the flyby, UVIS will observe as Titan’s atmosphere blocks the Sun (also known as a solar occultation). Like the stellar occultation, this will be used to probe the temperature and pressure of Titan’s atmosphere even deeper into its atmosphere.

Below is a simulated view from Celestia of the solar occultation.

Celestia / CICLOPS
Celestia / CICLOPS

O u t b o u n d

As Cassini leaves Titan, ISS will observe a crescent Titan over its northern hemisphere, covering its north pole.

CIRS will acquire more data about the structure, temperature, and composition of Titan’s upper haze layers. ISS will be riding along again, snapping more photos along the way.

Below is an ultraviolet image of Titan focusing on its upper haze layers, snapped by the ISS. Click on the image to learn more.


E n d   o f   f l y b y

  • Date : July 21, 2014
  • Time : 10:40 AM UTC

Be sure to check here for the latest news from the flyby!

* * *


Want to know even more about this flyby? Check out Cassini Imaging Central Laboratory for Operations’ (CICLOPS) website with information on Cassini’s activities every day: Rev206: Jul 2 – Aug 3 ’14. (All of my information from this post, unless otherwise specified, comes from this source.)


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