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 Side

Top 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 stagedoes 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 directionsPossible 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