I believe that you would need another microcontroller to do the memory
management, while the PIC would only do the data gattering and transfer
it to the second processor.  Power will be an issue, doesn't matter if
you use hard disk or pure silicon storage... memory chips *always*
consume great share of energy.

You are not opening much information, but +100G is only obtained in
certain environments and one of them is at pure bright sun, so if it is
the case why not use a nice plastic flexible solar cell to keep battery
size reduced?  Also, a secondary memory system, to store the valid data
on flash, while the full-time data collecting memory system, you can
call it "cache", would be a DRAM SIMM, smaller, less power.

Also, remember radio data link to download your data... GigaHertz is
here to flow wideband in highspeed, a transmitter and battery could be
smaller and light weight.

--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:  http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm