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« Blast From The Past | Main | How Howard Dean Got His Start? »

A Head Scratcher

Here's a piece by a Greg Autrey in the Baltimore Sun on space policy. It's kind of a mess:

Why should we care about missiles threatening low Earth orbit? When the Chinese get on with reabsorbing Taiwan - the most likely trigger for a U.S.-China confrontation - U.S. drivers may find that the navigation systems in their SUVs (not to mention their ambulances) aren't working. Low-flying U.S. military spy satellites are the first target of the new weapon, but the slightly higher GPS (global positioning system) satellites that guide our weapons systems are also attractive to Chinese war planners.

Or, what about when the censorship-savvy Chinese government decides it has had enough of Howard Stern corrupting the youth and takes out Sirius satellite radio?

GPS isn't "slightly higher." It's thousands of miles higher. GEO, where satellite radio satellites reside is thousand of miles higher than that.

But the real problem is that the whole thing is incoherent. What does the "sands of the moon" have to do with ASATs? Just what is it that he's recommending, policy-wise? More money for NASA? More encouragement of private enterprise? How?

You'd think that with all the knowledge out here on the web, newspapers could find better commentators on space than "a lecturer on business strategy and entrepreneurship."

Posted by Rand Simberg at January 24, 2007 09:06 AM
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How about handling the issue in a dissimilar manner? For the two scenarios he provides (GPS and radio broadcast), I have alternative solutions than space.

GPS type navigation is already being performed by large network arrays. Cellphones don't actually pick up GPS signals, but rather triangulate their location with signal strengths from fixed based cell towers. Mobile Ad-Hoc networks have been able to perform similar capability. Over the battlefield, the military could launch long loiter drones to provide GPS functionality in a small space.

In addition to providing GPS capability, long loiter drones can take the place of communication satellites. When the US military wants to provide Voice of America broadcasts, they use C-130s. This could be done elsewhere. In addition, civilian long loiter drones could be constantly upgraded to provide improved bandwidths (Moore's law taken to the sky).

Space satellites still provide better capabilities than these other solutions, but they are not the only way to solve the problem. I think in certain scenarios, they may not even be the most cost efficient over time.

Now as far as the "sands of the moon" comment, I agree with you, Rand, that it seems really a dumb thing to say. The moon can be a difficult satellite for China to destroy, but its utility to the US is otherwise limited in terms of Navigation and Communication.

Posted by Leland at January 24, 2007 01:37 PM

Aw, Rand, lighten up. It's just a quotidian vague manifest-destiny call to space arms, mixed in with a little old-fashioned fear of the Yellow Peril. It's a newspaper column, not a policy white paper. An effort to stir up the plebs enough to care two cents, not any kind of serious discussion. Sixth-grade reading (and thinking) level assumed.

I mean, about all he's saying is:

(1) Space is important to national security!

(2) The Chinese know that, and are moving to exploit space as best they can. Ignore this at your peril, America.

(3) And since everyone's all het up about the Iraq war, let me just grab your attention by saying that I think being on top of things in space is ultimately more important than being on top of things in Iraq.

None of this is directed at people like you. Furthermore, if the Sun asked an expert to do a similar piece satisfying to you, that might well result in something so turgid with debate and detail about technical how-to issues fascinating only to insiders that Joe Sixpack would tune out about two polysyllabic sentences in. Not good.

Posted by Carl Pham at January 24, 2007 06:28 PM

Carl, all that's true, but people like Our Host can and should reserve the right to protest when that sort of things start happening. Once in a very great while they might succeed in derailing the latest and greatest oversimplification.

A proper engineer's motto is "As simple as possible, but no simpler." In the last analysis the thing's gotta work, and simplisme is not a useful approach to accomplishing that.


Posted by Ric Locke at January 24, 2007 07:24 PM

I thought GPS sattelites were in a medium earth orbit in a 24 sat constellation?

Posted by Aaron at January 25, 2007 05:29 AM

"What does the "sands of the moon" have to do with ASATs? "

I don't know if he was making this specific connection or not, but a fundamental part of the Vision is the creation of an infrastructure for routine access to cislunar space. This has both commercial and national strategic implications. The "sands of the Moon" are the feedstock from which we'll ultimately make propellant to fuel the cislunar transport system.

Posted by Paul Spudis at January 25, 2007 06:15 AM

I agree with that, Paul, but there's no way to tell that from his piece. It's a confused/confusing mess.

Posted by Rand Simberg at January 25, 2007 06:27 AM

Does anyone else think it's a bit ridiculous that anyone could look at a confrontation between nations with arsenals of thermonuclear warheads on ICBMs and somehow pick out the loss of GPS navigation on the highway or Sirius satellite radio as the most distressing element?

If the US and China were to go to war with one another, the destruction of satellites on either side would be the least of our worries.

Posted by Robin Goodfellow at January 25, 2007 08:30 AM

Robin, he's trying to get through to a nation of Marie Antoinettes. He has to suggest we might get our cake taken away.

Posted by Carl Pham at January 25, 2007 06:31 PM

Howard Stern being blasted out of orbit would be a national crisis of the deepest proportions.

Posted by X at January 26, 2007 12:15 AM

"Cellphones don't actually pick up GPS signals, but rather triangulate their location with signal strengths from fixed based cell towers."

This may not be quite applicable. The majority of cell-phones world-wide run on GSM and in the US most GSM location does use triangulation. However, the accuracy of such location is nowhere near that of GPS. Typically the mean error is of the order of 50-75 meters. The obvious problem is multipath. If the cell tower infrastructure is very dense, one could possibly achieve much higher accuracy with triangulation. But this would require enabling the phones to return netwrok measurements that are optional in the specification. Also the current effort by GSM carriers is to move towards AGPS where part of the computational effort is performed at the base stations. This penetration is low and initial reports are that the yield is quite low as well (only about 35% of the phones really seem to be able to self-locate). Of course AGPS requires GPS to work. In any case, in the longer term, the plan for most cellular networks is NOT to use triangulation due to the cost of installing extra equipment at the cell towers. There are other techniques viable in a GSM network such as computing the base station time offsets using pair-wise TDOA on the (unsynchronized) base station signals, which can be solved by the network to result in a location; accuracy is again not too high, and this is in essence still a form of triangulation, albeit with more unknowns. This applies to UMTS though not GSM.

In principle, if you want to achieve high accuracy with triangulation you have to have a very high density of cell towers or have very very tall cell towers. If you go with increasing the density, this number would be much higher than the number required for the primary communication function, so that it's not economically pratical. Alternately you would have to bump up the power on the cell-phones which would mess up your network. The best way to avoid multipath and still cross-correlate your signals so you can achieve good resolution is to move your transmitters (or receivers) out of the multipath scenario. And there's only one way to do that: move them high up in the sky, aka satellites!

Posted by Toast_n_Tea at January 26, 2007 05:38 AM

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