SPECS 2004 Dynamics and Control Control modes: (1) Orbit insertion (2) Acquisition (3) On-station Determined by: mission requirements, mission geometry, insertion type Design Issues: - How are control modes related to spacecraft configuration, deployment, etc. - Must quantify control needed in each option to compare with others.

SPECS 2004 Dynamics and Control 2 Main spacecraft configurations: Side Top Mirror Spacecraft (MSC) Central Spacecraft (CSC)

SPECS 2004 Dynamics and Control 2 Main spacecraft configurations: “Stack”

SPECS 2004 Dynamics and Control 2 Main spacecraft configurations: “Hinge”

SPECS 2004 Dynamics and Control Control modes: (1) Orbit insertion Upper stage does transfer burn Upper stage despins (yo-yos) and separates SPECS now 3-axis controlled If 3-axis control: If Spin stabilized: Can further reduce spin by deploying solar panels, etc. Upper stage separates Can control spin by deploying solar panels, etc. SPECS now spin stabilized

SPECS 2004 Dynamics and Control Advantages of spinning: - formation must spin for most of life. - almost constant mission geometry from Earth region to L2. - potential control savings? Disadvantages of spinning: - Earth/Sun pointing during early mission phase more difficult (Acquisition). - deployment while spinning more difficult (“Stack”)

SPECS 2004 Dynamics and Control Spinning? Minor axis? Major or Minor axis? Probably Major axis

SPECS 2004 Dynamics and Control Spinning? Most of life at L2 Sun and Comm directions Possible situation during transfer Sun vector Comm. vector

SPECS 2004 Dynamics and Control Design combinations? 1) Direct transfer, spin stabilized, early deployment or augmented control, likely “Hinge” type. 2) Phasing loops, 3-axis control, late deployment, “Hinge” or “Stack” type, spin-up at L2. 3) Same as (2) but direct transfer