MIDAS is able to add or delete deep space maneuvers and powered planetary swingby maneuvers as dictated by the optimization process. The program is able to optimize intermediate rendezvous and gravity assist or flyby trajectories of planets and small bodies. A gravity assist swingby or flyby of a body can be either free (unpowered) or powered. In the latter case, the location of the maneuver on the flyby hyperbola is optimized.
The program can manage a maximum of eight intermediate flyby or rendezvous events and a maximum of eight deep space maneuvers. Planetary gravity assists can include a pair of "resonant" flybys of the same body which occur an integral number of planet years apart. Resonant terminal phasing orbits between either launch or arrival small bodies and a deep space maneuver can also be handled.
Planetary state vectors in MIDAS are calculated from an analytic conic ephemeris containing secular terms. Asteroid and comet state vectors are retrieved from external ephemeris files containing data for both numbered and unnumbered asteroids and for over 600 comet apparitions. An ephemeris for a fictitious body may also be input to the program.
MIDAS is designed as a flexible general purpose ballistic trajectory optimization tool that can handle different types of trajectories. As a consequence, a certain amount of input is necessary to initialize and setup the trajectories properly. Instances of conflicting or missing input will generally result in an error message. Problems that are encountered in running the program should be directed to the author together with a listing of the input and any output for inspection.
The optimization code in MIDAS is defaulted to minimize total weighted mission DV. In addition, a capability exists to perform a fairly rudimentary mass optimization. This latter capability should not be used until a satisfactory minimization of total DV has been performed. In order to handle mass optimization, both launch vehicle and spacecraft propulsion parameters to allowance must be input to the program. Use of either launch vehicle or spacecraft parameters will have no effect on DV optimization but will give an indication of spacecraft capability for a given mission.
Adapted from: User's Guide To MIDAS, Draft, JPL, 1991.