Flight Dynamics Michael Mesarch Frank Vaughn Marco Concha 08/19/99 MAXIM Flight Dynamics Michael Mesarch Frank Vaughn Marco Concha 08/19/99

Mission Assumptions Orbit Assumptions Maneuver Requirements Two spacecraft (optics and detector) in near-circular Heliocentric orbit at 1 AU ( Drift-away orbit) Launch in 2007-2010 Mission Lifetime: 3 years required Maneuver Requirements Desire to point to 150 inertial targets over 3 year mission lifetime Separation along optical axis to be maintained at 450 km  10’s of meters Misalignment perpendicular to optical axis  5 mm

MAXIM Range from Earth

MAXIM Trajectory in Solar Rotating Coordinates

Formation Flying Challenge The MAXIM formation flying concept is new - combination of previous implementations with a wrinkle Landsat-7 and EO-1 maintain a constant distance between each other in the same orbit while imaging the earth - image comparison is achieved because of close distance between s/c Constellation-X utilizes multiple s/c to observe the same target without any restriction on relative position MAXIM combines both constant separation and constant attitude/pointing. The detector s/c must ‘fly’ around the optics s/c continuously during an observation - its orbit will continually change. L7 EO1 d L2 Constellation-X d Maxim

Stationkeeping and Pointing Control Only simple cases have been considered : Continuous viewing of Ecliptic Pole Optics and detector S/C are in circular orbits which differ by a small inclination angle to achieve initial 450 km separation Continuous acceleration of detector S/C away from optics S/C at  1.7x10-8 (m/s2) will cancel relative out-of-plane motion for short periods Rotation to view opposite pole requires acceleration on the order of 4 degrees of magnitude higher Long-term effects require additional analysis Targets in Ecliptic plane Optics and detector S/C are in circular co-planar orbits which differ in semi-major axis to achieve initial 450 km separation Preliminary analysis indicates that maintaining 450 km separation is feasible in the short-term by canceling the initial velocity difference between the S/C, but this results in a larger separation in the long-term,( i.e, half an orbit later). How to maintain pointing in this case is not clear - requires management of multiple orbital variables Design of a pointing control strategy will not be a trivial undertaking

Ecliptic Pole Pointing - Uncontrolled Optics Detector

Ecliptic Pole Pointing - Controlled Detector Optics

Further Work Perform more detailed analysis on the simple cases considered to be certain the dynamics is fully understood Formulate a pointing control strategy Determine control authority (acceleration,thrust) required to transition from one target to another in a ‘reasonable’ amount of time (days?)