Cassini Mission status report - T4 flyby
Thu Apr 7, 2005 at 19:51 UTC
NASA's Cassini spacecraft successfully flew by Saturn's moon Titan at a distance of 2,402 kilometers (1,493 miles) on Thursday, March 31. Cassini's multiple instruments are providing new views of the haze-enshrouded world.
On this recent flyby, Titan's haze was the focus of ultraviolet observations. By mapping the haze, scientists hope to learn about particle size and properties. Titan's transient clouds were also studied during the flyby.
Titan's northern hemisphere was previously imaged with Cassini's radar instrument in October 2004 and February 2005. This time, Cassini's optical cameras got their best view of the same area, as did the visual and infrared mapping spectrometer.
Titan is a prime target of the Cassini-Huygens mission because it is the only moon in our solar system with a thick, smoggy atmosphere. Cassini was launched over seven years ago and has traveled 3.55 billion kilometers (2.2 billion miles).
Image Credit: NASA/JPL/Space Science Institute
This view of Titan uncovers new territory not previously seen at this resolution by Cassini's cameras. The view is a composite of four nearly identical wide-angle camera images, all taken using a filter sensitive to wavelengths of infrared light centered at 939 nanometers. The individual images have been combined and contrast-enhanced in such a way as to sharpen surface features and enhance overall brightness variations.
The images for this composite view were taken with the Cassini spacecraft on March 31, 2005, at distances ranging from approximately 146,000 to 130,000 kilometers (91,000 to 81,000 miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of about 57 degrees. The image scale is 8 kilometers (5 miles) per pixel. Previous observations indicate that, due to Titan's thick, hazy atmosphere, the sizes of surface features that can be resolved are a few times larger than the actual pixel scale.
All 12 of Cassini's instruments have been returning data, including tantalizing images. Recently, scientists noticed episodic interferences on the composite infrared spectrometer that were traced back to the time of orbit insertion. A mirror on the spectrometer is showing some signs of jitter. The movement may be associated with the use of the spacecraft reaction wheels, used for spacecraft pointing control. A motor on one of three sensors on the magnetospheric imaging instrument and another motor on the plasma spectrometer are also not working properly. However, a workaround has been identified for the latter. All three instruments continue to function, although with some reduced level of science data collection.
"We are working to understand why the instruments are not performing properly but it is likely to be a few weeks before we have definitive answers," said Robert T. Mitchell, Cassini program manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "When running a mission for this long, you expect to have a few glitches. Cassini has been working remarkably well considering the duration and complexity of the mission."
Cassini's next encounter is with Titan on April 16 at an altitude of 1,025 kilometers (637 miles). This will be Cassini's closest flyby of Titan yet.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Science Mission Directorate, Washington, D.C.
