Blighty gets DARPA cash to put sat-phones in satellites

Pentagon crazytech chiefs have hit upon a new plan: they will equip future US military satellites with satellite phones. British firm Inmarsat has got the job.

It's not as barmy a scheme as it sounds right off. The idea is to make it much easier to communicate with a satellite, even when it's on the wrong side of the world from its control centre. The idea would be to hook up a military satellite to Inmarsat's BGAN mobile broadband service, provided by the firm's I-4 commsat constellation.

This would mean that the military sat was always reachable, rather than only intermittently as it came into line-of-sight of suitable US space control stations. If there were a sudden need for the sat to do something fast - for instance shut down in advance of a solar radiation storm, or change orbit in a hurry to snap a pic of a given target on the surface - it could be quickly ordered to do so via the BGAN hookup rather than waiting for the next comms window.

According to the Pentagon contract announcement, the capability would also be useful for "defense manoeuvres". A satellite might be about to get taken out by an enemy antisatellite strike of some kind, and the Pentagon would know about this somehow - perhaps by the use of other specialised satellites - but there might ordinarily be no time to tell the threatened US spacecraft to adjust orbit away from danger.

Thus, then, the Persistent Broadband Ground Connectivity for Spacecraft in Low Earth Orbit plan, announced by our old friends at DARPA last year and now to be implemented by Inmarsat. According to DARPA, announcing the decision yesterday:

Of all the proposed solutions, and following an independent survey by Government experts, the Broadband Global Area Network (BGAN) service provided by the Inmarsat I-4 communications satellite constellation was deemed to be the sole viable end-to-end solution for providing the necessary robust communications capability within the specified timeframe.

A space-based BGAN terminal for LEO use appears to be a technically feasible solution with only modest adaptations to the airborne version of the terminal, specifically relating to Doppler compensation, radiation hardened components, and software changes for rapid beam-to-beam handover without loss of service.

DARPA intends to try out the new spaceborne BGAN terminal in its System F6* "fractionated spacecraft" cluster-sat prototype, now being designed. If things go well, there could be a lot of business down the road for Inmarsat. ®

Bootnote

*Future, Fast, Flexible, Fractionated, Free-Flying Spacecraft. The idea is to have the various components of a normal big satellite organised in a wirelessly-linked cluster of small orbiting machines, a so-called virtual satellite. The idea is that this would avoid the expense, limited launch opportunities, inability to upgrade and high risks of critical failure that come with big integrated sats.