Troubled Galaxy
On 07-07-2010, in Satellite Navigation, by steve
That space around planet Earth is teeming with man-mad objects is common knowledge and not so long ago we got a good demonstration of what happens when stray metal hits another satellite. For a time it was unclear where a sizeable piece of junk would fall on the surface of the Earth.
The satellites serve a variety of purposes from serving up television to providing internet access and guiding aircraft. It is no exaggeration to say that our modern world would be paralyzed should there be a mass extinction of orbiting satellites. But how robust or fragile is this system in reality?
Galaxy 15 is an Intelsat bird which went out of control in April and has been drifting from its assigned orbital slot ever since. It has threatened to interfere with the functioning of nearby satellites and efforts by ground engineers to disable its payload have initially been unsuccessful.
Does this have an impact on aviation? You bet!
One of the transponders on Galaxy 15 was leased by the FAA to provide Wide Area Augmentation System (WAAS) signals for GPS based approach procedures. With the satellite now useless, 16 airports (mainly in Northwestern Alaska) will see service interruptions in the availability of their LPV (Localizer Performance with Vertical Guidance) approaches as these fall back on a GPS-only operating mode.
The reasons for Galaxy 15’s misbehavior are apparently unclear although an unexpected nudge from unusual solar winds is seen as a real possibility.
We worry a lot about the sensitivity of GPS to malicious jamming and there are lots of cautionary voices about predicating our air transport system on fickle satellites. But as the case of Galaxy 15 shows, there are other dangers out there that can cause havoc with wide ranging consequences once satellite based procedures become truly widespread.
Apparently, the Sun is one of the bad guys when it comes to listing the potential trouble makers.
