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Friday, March 21, 2008

GOES Direct Readout Ground Station

The GOES "Direct Readout Ground Station", or DGRS, is essentially a multi-channel radio receiver for environmental data being relayed from DCP's (Data Collection Platforms) by GOES weather satellites. GOES central is located just North of NASA's Wallops Station (formerly known as Chincoteague Naval Air Station). They have about ten really big (50 feet in diameter, more or less) satellite dish antennaes. Inside the main building they have two banks of these receivers: one bank for the 100 odd channels on GOES West, and another for the channels coming from GOES East.

Vitel got the contract for development of the new HDR (High Data Rate) receiver, but when they attempted to integrate the new receivers into the existing system, it soon became apparent that there was a problem. All the receivers were connected to an old Data General mini-computer that must have been twenty years old. After much tail chasing and finger pointing, it devolved on me to find a solution. Everyone was convinced that the problem lay in the internal communications of the DGRS. It incorporated several single channel receivers and a single multiplexer. All the data from the receivers was passed to the multiplexer, which transmitted the combined data stream to the host computer. After an exhaustive analysis, a trip to the East coast for some testing, and finally a simulation run, it became apparent that the problem lay with the Data General computer and not with the receiver. Once we informed Wallops of our findings, we did not hear any more about it. Presumably they reanimated their long past DG expert and turned him loose on the problem.

I also made an attempt to modify the firmware for the DSP used in the individual receiver boards. After a couple of months of study of DSP programming techinques, the actual DSP chip in question, and the algorithms that had been programmed into it, it became apparent that any further effort would be a waste of time, as it was unlikely we would be able to build, much less sell enough receivers to recoup our investment, much less the cost of developing a new set of firmware.

Of course we could have figured out the business angle before starting on this project, but that would have made sense, and we can't have any of that.

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