14 DAY TRIAL // The space probe Cassini is currently starting to show its age, NASA officials have announced, saying that the machine is beginning to exhibit signs of weakness when it comes to its thrusters, which are the very thing that keeps it afloat over its targets. Since October 2008, one of the eight thrusters that currently power the aircraft has been acting up, causing concerns amidst members of the control team. Only recently did a second one begin to show decreased levels of performance as well, so, after consulting with the engine's manufacturers, NASA has decided to swap thrust set A with thrust set B, which is a block made up of another 8 thrusters, completely identical to the failing set. Hopefully, this will allow the 11 year-old space craft to continue its mission for years to come.
According to the team that has analyzed all aspects of the swap, the earliest time for this procedure will be in mid-March, when a 7-day window will become available. This means that, during that time, no additional maneuvers will solicit the thrusters, in order to keep the probe on its course. Also, the science team behind the project will have enough time to write the code lines needed for a smooth transition, and send them to Cassini's onboard computer, by March.
Moreover, the experts have to ensure that the swap is done at a time when no critically-important scientific data are stored on the space craft. This will avoid losing vital images and having to wait another long stretch of time before those pictures can be taken again. On the bright side of things, there are no pyrotechnic effects involved with the process. The only thing computer programmers need to do is to create a routine that will command a latch valve to open a hydrazine flow to the B side. Once this happens, the second set of thrusters should come online without a hitch.
The best part about the swap is that it's completely reversible, meaning that, if something is to go wrong with the auxiliary set of engines, the first can be switched back on, although there is the risk that the craft's orbit will deteriorate in the meantime. The Cassini mission engineers say that most systems on the craft have back-ups and that, in its 11 years of operation, the space probe has only had to undergo one such swap, when a reaction wheel failed, and its replacement was brought online. It's currently functioning within the correct parameters.