ROUND-OFF ERROR IN LONG-TERM ORBITAL INTEGRATIONS USING MULTISTEP METHODS

Techniques for reducing roundoff error are compared by testing them on high-order Stormer and summetric multistep methods. The best techniqu e for most applications is to write the equation in summed, function-e valuation form and to store the coefficients as rational numbers. A la rger error reduction can be achieved by writing the equation in backwa rd-difference form and performing some of the additions in extended pr ecision, but this entails a larger cpu cost.