Call me a conspiracy nut, but here's what I believe may have happened:
It's almost a certainty that the US government has spy satellites video recording the entire planet at all times, at a level good enough to distinguish individual aircraft. The US spy agencies probably knew where the plane was right away, but they can't just tell everybody or the jig is up.
So they may have just contacted this satellite company, told them where the plane is, and came up with a technical explanation of how it was located.
The US certainly has a bloated defense budget, but I strongly doubt that we have satellites constantly trained on the typically empty oceans that cover 70% of the Earth.
While I don't subscribe to GP's view that satellites have bandwidth for "video recording the entire planet at all times", it seems plausible that SIGINT satellites would have a relatively constant bandwidth available for observation. As a (non-geostationary) satellite passes over relatively unpopulated areas (e.g., the southern Indian Ocean), it will be "bored" and thus far more likely to notice a single low-power transmission.
On the other hand, if it is storage and downlink bandwidth that is limited, sats would probably be programmed to ignore or discard uninteresting signals. This seems likely to me.
So the question may be whether commercial airliner pings from the southern Indian Ocean area were considered 'interesting' at the time and, if not, did anyone realize there was a rogue 777 in time to re-task the satellites?
Regardless, I'd bet those signals are considered interesting going forward.
The other complication is that Inmarsat up-link is a steered spot-beam ( the antenna on the aircraft is stabilsed and driven, or phased-array in recent implemenations ). So the SIGINT sat would have to be passing through the up-link 'beam' precisely as it was transmitting.
Down-links are ( depending on generation and usage ) either from one of an array of narrow-beam antennae on the Inmarsat or from the wide-area general broadast antenna; much easier to intercept, you and I can do it with a sat-TV dish and an RTL dongle.
Brochures I saw years ago indicated that least some portable Inmarsat terminals are also directed beams. Taliban/AQ was known to use directional antennas for communications security, at least later in the war. So possibly we could say the same thing about Bin Laden's satphone, and we know how that turned out.
Call me a conspiracy nut, but here's what I believe may have happened:
It's almost a certainty that the US government has spy satellites video recording the entire planet at all times, at a level good enough to distinguish individual aircraft. ...
You are a conspiracy nut. :-)
Spy satellite time is expensive. And they typically have a narrow field of view (the better to read the license plate number off of your car). Basically they are orbiting telescopes like the Hubble, except they are pointed down instead of up.
It is inconceivable to me that they'd waste time having a spy sat looking at empty stretches of the Indian Ocean for no good reason. Especially when there are more interesting things to look at (Afghanistan, Ukraine, North Korea, etc.).
While I don't think this particular suggestion is likely given the shear amount of data that would need transmitted, it might be possible that there is more data being transmitted by these planes than has been admitted.
based on the region where this occurred, you can rest assured that one, if not several, state intelligence services knows exactly what happened to the plane and has near continuous knowledge of its position. the area of asia where this occurred would likely be of interest to US, CN and RU.
the fact that none of these countries gave information about the whereabouts of the plane in a timely fashion suggests to me that they have a vested interest in not sharing what they know.
It's almost a certainty that the US government has spy satellites video recording the entire planet at all times, at a level good enough to distinguish individual aircraft. The US spy agencies probably knew where the plane was right away, but they can't just tell everybody or the jig is up.
So they may have just contacted this satellite company, told them where the plane is, and came up with a technical explanation of how it was located.