News | September 10, 2008
Simulated Snafus -- Operational Readiness Test
Todd J. Barber, Cassini lead propulsion engineer
Hello from the other side of solar conjunction and a tricky Operational Readiness Test (ORT)! I'm happy to say the spacecraft breezed through our annual cosmic alignment with the sun, eager to continue its campaign to unlock the mysteries of the ringed planet.
During this otherwise somewhat quiet time, Cassini management again took the opportunity to challenge the flight team with a simulated anomaly. Almost exactly one year ago, I was writing this column within a particularly unpleasant spacecraft safing event, one that we simulated exactly one year earlier still, in the 2006 ORT! Let's hope this year's simulated irregularity, admittedly less heinous than last year's safing, will never come to pass. However, if it does, the flight team will be ready, thanks to the twists and turns encountered this week during the ORT. Incidentally, last year's anomaly and 2006's ORT was a a solid-state power switch trip that rendered Cassini temporarily unable to send telemetry. The real incident occurred painfully close to our unique Iapetus flyby, but the team responded quickly and recovered nearly all the science from this key encounter with Saturn's perplexing moon. The 2006 ORT certainly helped us pull off the impossible in 2007!
Our spacecraft team manager diabolically simulated a spacecraft safing event just before a critical maneuver, OTM-168, a key propulsive burn to set up next month's Titan-46 and Enceladus-6 flybys. This maneuver also will occur near a dust-hazard crossing, so even mere hours before the virtual maneuver, the main-engine cover was still closed, precluding main-engine operation. Within a few hours, the flight team managed to confirm the replicated spacecraft was in safing, diagnose the problem and spacecraft response, and begin recovery, including opening the main-engine cover and designing a maneuver. This was truly a team effort, cutting across engineering and science teams, navigation, uplink operations -- you name it!
ORTs are not always easy, but they never fail to enlighten and improve the way we do business. I'm especially pleased by how wonderfully these simulated snafus help train new team flight members quickly and painlessly. We often forget how smoothly Cassini is sailing on her mission of continual discovery. These exercises help make sure the flow of science data will continue even in the face of interplanetary adversity. Sail on, Cassini, and may you never be tested in space as we virtually challenge you (and your flight team) on planet Earth.