 0, 0000) https://www.ngdc.noaa.gov/stp/space...ha/tables/0000/solar-flares-halpha_000000.pdf https://www.ngdc.noaa.gov/stp/space...ha/tables/0000/solar-flares-halpha_000000.pdf https://www.ngdc.noaa.gov/stp/space...lar-flares/x-rays/solrad/0000/solard_0000.txt​ Apollo 00 