Hi Gents,   I have been working on an excel spreadsheet regarding ARISSat-1, orbital decay and atmospheric density. Its a small workbook with some calculations and a  chart.   The idea is to work out the volume that ARISSat-1 sweeps through per orbit, then calculate the mass of atomic material it will colloid with. Math is NOT my best subject . Is there a math guru on the list willing to take a quick look and tell me if I am on the right lines.   Let me know and I will send it off list.   Thanks   John G7HIA