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DARPA Funds Development on Modular Satellite Network
coondoggie points out a Networkworld story about plans for modular satellite technology which is intended to replace modern, "monolithic" devices. The project hopes to solve issues of scalability and reliability by separating the typical satellite systems and allowing the different modules to change function when necessary. Quoting:
"According to DARPA such a virtual satellite effectively constitutes a "bus in the sky" - wherein customers need only provide and deploy a payload module suited to their immediate mission need, with the supporting features supplied by a global network of infrastructure modules already resident on-orbit and at critical ground locations. In addition, there can be sharing of resources between various "spacecraft" that are within sufficient range for communication. DARPA said ... within the F6 network all subsystems and payloads can be treated like a uniquely addressable computing peripheral or network device. Such an approach can provide a long sought after "plug-n-play" capability, according to the agency."
there is no good reason for this to be a huge research priority (although arguably, it isn't huge). When I first read the summary, I thought that DARPA was funding a next generation version of Hughes Aerospace's 'modular' satellites system, where Hughes builds 1 bus and offer 1 of three payload configurations to customers.
But I'm more confused as to the goals of this project. I read a few of the linked pdf's and true to form, the government request for grant applications were not enlightening. The best I can hash of it seems like this:
DARPA wants to build and test satellites that are placed into orbit in a micro-constellation of sorts, communicating between various parts via wireless signals. Let's leave aside security and interference concerns, because they are--frankly--minor. My primary concerns would be duplication of elements. Assuming that they still have traditional roles for satellites, such as remote imaging and relay, payloads still need to be handled nicely. The camera for the remote sensing system needs to:
1. Know where it is.
2. Know where it is pointing.
3. Point there without too much wobble.
The first 2 can still be done with a distributed satellite--you just put the start tracker and the computational hardware on another cluster. The second requires that you keep the stabilizing hardware on the same bus as the payload. Beyond that, how will they manage stationkeeping? Each microsat would have to be fitted with jets or be replaced in a few years time.
Can anyone fill me in on what I am missing here?
Link to the original 7.2007 funding announcement WORD doc directly from DARPA...
Gotta' get going on that marine turtle study grant before they give that one away to someone looking to make soup...darn!
As someone who worked on several satellites I can attest you are dead on in your analysis. Fuel, Solar Panels and Payload (Transmitters, CPUS, etc) are going to be important. The more capability the satellites need the more power they need and the bigger the panels and fuel tanks and thus the overall size and weight go up and with that the costs.
The orbit is also key, you want them in a low orbit with the right inclination but not so low that atmospheric drag is significant. They also have to be line of sight to their n neighbors to communicate. So until the full netwotk is up you are going to have gaps. Also, when new technologies emerge how to you upgrade? Do you cripple the new birds to have a compatiability mode with the old ones in terms of data rate and communication bands?
The bus concept has been around 10-12 yrs from Hughes, the "network of satellites" has been around longer, think GPS and Iridium. Also the NASA TDRS system falls into this concept too.
All and ASAT has to do is take out two satellites such that there is a gap in the network that can't be bridged and the concept degrades to darn near useless. You also have to build Ground Stations to communicate and to manage the network. Take out the satellite that a critical ground station uses as an uplink and you've forced then to ship the data to another uplink point via terristrial means which negates the whole reason for the satellite network.
All things considered, this is a stupid R&D project. Seems somoene at DARPA read a re-hased proposal from the 1980's and decided it was something cool to throw money at.