From: Jet Propulsion Laboratory
Posted: Wednesday, May 14, 2008
The most recent spacecraft telemetry was acquired on Tuesday, May 6, from the Goldstone, California tracking complex. The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at: http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, April 30 (DOY 121)
Non-targeted flybys of Telesto and Pallene occurred today.
Thursday, May 1 (DOY 122):
An encounter strategy meeting was held today to cover the period between May 12 and May 28, Titan flybys T43 and T44, and maneuvers 155 - 157.
Friday, May 2 (DOY 123):
Getting ready for open house this weekend.
Saturday & Sunday May 3 & 4:
JPL Open House this weekend was another smash success! Over 15,500 people walked through the Cassini exhibit. Amazingly, the longest wait in line was only six minutes. This year the Cassini exhibit was moved from the mall area to the first floor of Bldg 303. The fact that this is a cafeteria went completely unnoticed by attendees. All windows had been draped with blue fabric to cut out the excessive light and glare. The space looked just like a museum. Along with a quarter scale model, a full-scale mural of the Cassini spacecraft was available as a backdrop for a photo opportunity. And yes, it IS as big as a school bus. Bigger, in fact. The new inflatable Saturn globe was a big hit. Parents would lift their children to be able to touch it, and instead "bump" the child on the underside of Saturn. Many laughs ensued, and the kids loved it!
Monday, May 5 (DOY 126):
Today was the second DSS-47 proficiency test with Cassini since a Radio Science Receiver (RSR) was sent to Narrabri, Australia. The ~2.5 hour track overlapped supports with Goldstone's DSS-14 and DSS-26. The entire DSS-47 support was in 3-way mode with DSS-14 providing the uplink. The spacecraft was Earth pointed throughout the test with no rolling, providing a stable Ka-band signal. The DSS-47 support started with the full array of six antennas, then at the request of Radio Science (RSS), the station removed one antenna from the array at a time until only a single 22-m antenna was in use. As expected, the signal power decreased as the number of antennas in the array was reduced, and based on real-time monitoring, the difference in Ka-band power between the full array and single antenna support was about 8 dB. The data acquired is hoped to provide information on the impact of arraying on the frequency stability. The next planned proficiency test with Cassini is on June 5.
The first delivery port occurred today as part of the Science Operations Plan process for S44. The files were merged and reports were sent out to the teams for review and resolution. In addition, a kick off meeting was held today for S45.
A beautiful enhanced color image of Saturn's long-lasting electrical storm is Astronomy Picture of the Day today. Check it out at: http://antwrp.gsfc.nasa.gov/apod/ap080505.html
Tuesday, May 6 (DOY 127):
On May 6, the on-board Command Loss Timer (CLT) duration was reset in the background sequence from the nominal 90 hours to five days in order to accommodate potential unplanned pass losses due to Phoenix activities. It will be set back to 90 hours in the background sequence on June 6. A CLT command is sent to the spacecraft every pass to "touch base" so that Cassini knows the flight team is awake and listening. Should the CLT expire, the nominal response is for the spacecraft to assume there is a problem and execute system fault protection.
The sequence leads uplinked part two of the S40 background sequence to the spacecraft today. Part 2 will begin execution on May 13 and will continue to the end of May. Two additional commands sent were a telemetry mode change for DOY 131 and the RSS Live Moveable Block to execute on DOY 130.
Due to the accurate execution of Orbit Trim Maneuver (OTM)-153 and
accurate predictions of the effects of various biases, OTM-154 has a magnitude of about 5 mm/s. As a result, OTM-154 has been cancelled.
An issue under consideration was what impact the cancellation of OTM-154 would have on the probability of cancellation on OTM-157. OTM-157 is the Titan 44 approach maneuver. The maneuver was moved one day earlier to avoid overlap with the Phoenix Entry/Descent/Landing activities. The earlier execution reduces available tracking, and the backup maneuver would occur on the Memorial Day holiday. For these reasons it is desirable to cancel OTM-157 if at all possible. The cancellation of OTM-154 had no significant effect on the likelihood of cancellation of OTM-157. Now the flight team waits for normal events and processes to run their course.
Check out the Cassini web site at http://saturn.jpl.nasa.gov for the latest press releases and images.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.
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