are you sure the satellites from that time had *radar* at 6 meters resolution? Weren't they just optical?
Jim's wikipedia ref and links above cover that. Here's another SAR dataset... https://en.wikipedia.org/wiki/Shuttle_Radar_Topography_Mission Paid for with money stolen from US "taxpayers" and the best 30m data witheld as CLASSIFIED as further insult upon the payers as the true owners for 14 years. The US Govt (NGIA) doesn't release stuff like that unless it's: beyond lifetime dead, or under heavy political / humanitarian pressure, or long surpassed by public tech... the likely case here. Quasi commercial radar imaging seems now at or better than 1m. Optical is said to be better. TOP SECRET of either... you're beyond fucked. Here's a few more... https://en.wikipedia.org/wiki/Seasat https://en.wikipedia.org/wiki/Spaceborne_Imaging_Radar https://en.wikipedia.org/wiki/Advanced_Spaceborne_Thermal_Emission_and_Refle... https://en.wikipedia.org/wiki/TopSat https://en.wikipedia.org/wiki/TerraSAR-X https://en.wikipedia.org/wiki/TanDEM-X "Seasat was able to detect the wakes of submerged submarines, a discovery not anticipated before launch.[8] The conspiracy theory holds that once this was discovered, the military shut SEASAT down, with a cover story of a power supply short."