Monday 16 January 2012

More thoughts on the Phobos-Grunt reentry

It appears that the Russian news bulletins claiming that Phobos-Grunt reentered over the southern Pacific at 17:45 UT yesterday (see my previous post) rather were model predictions than reentry times based on actual final track detections. The Russians (nor the US, for that matter) actually do not have much in terms of tracking facilities in the indicated area (S-Pacific, S-America and S-Atlantic).

The southern Oceans: a blind spot

This highlights the problem, and the similarity between the UARS case last September and the current Phobos-Grunt case. In both cases, determining where it came down was likely hampered by the final revolution and final half hour or more of its trajectory being largely over remote and empty territory. Specifically, in both cases: the southern Oceans.

A lack of tracking facilities (and humans in general) in these areas, mean that they represent a large blind spot for those who's profession it is to track these objects. Once a satellite near decay starts to make its final passes and significant parts of that happen to be over these remote locations, it basically disappears into a black hole. That's what happened with UARS in September, and what now happened with Phobos-Grunt.

Not as in the movies

While some in the media and public have expressed frustration about the lack of published information (and the contradictory information) right after Phobos-Grunt presumably came down, I feel those people lack a realistic outlook on these matters. These people apparently expect that the military is able to determine a clearcut point of reentry within minutes after the satellite has reentered.

In reality, this is not how it works. The military has intermittent detections when the object moves over tracking facilities, spread wide and far over a number of places around the globe. They do not have continuous coverage. They cannot track where they have no tracking facilities. And the big and empty southern oceans represent a large swath of Earth where that is the case.

In Hollywood movies and TV-series, the military (or "NASA", even though in reality it is not NASA doing the tracking) are portrayed as having a second-to-second real-time tracking opportunity of objects, with a moving dot on the screen that disappears in real-time as soon as the satellite reenters. That however, as most things in movies, is a highly unrealistic view which has little resemblance to reality.

It will take the professional analysts at USSTRATCOM and elsewhere some time to ponder the last tracking data, detections and non-detections, and maybe even then there will remain uncertainty about where Phobos-Grunt came down. Such is life, and reality.

Space-Based detections?

In the case of UARS last September, some of us have had some suspicion that Space-Based observations (Infra-Red detections by the early warning satellites of Missile Defense) were perhaps involved in the final determination of the point of reentry. These resort under another part of the military, and comments by those "in the loop" have indicated that normally there is little data exchange between these guys and the groundbased tracking guys. There is also the open question whether reentry fireballs are bright enough for these space-based systems (the DSP and SBIRS satellites) to detect them. As the specifications of these systems are of course classified, little is known about this.

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