Attitude control methods and systems for multiple-payload spacecraft

A method of determining the attitude of a master payload and at least one slave payload of a spacecraft, the method comprising the steps of:

• successively differencing master attitude measurements Ym and a master predicted measurement Ym* to form a master residual Rm;
• successively differencing slave attitude measurements Ys and said master predicted measurement Ym* to form a slave residual Rs;
• successively differencing said master residual Rm and said slave residual Rs to form slave relative attitude measurements Rsrel;
• in response to said slave relative attitude measurements Ysrel, estimating a slave relative attitude estimate Xsrel;
• successively differencing said slave residual Rs and said slave relative attitude estimate Xsrel to form a corrected slave residual Rscrctd;
• and
• filtering said master residual Rm and said corrected slave residual Rscrctd to estimate said master predicted measurement Ym* and a master attitude estimate Xm*;
• attitudes of said master payload and said slave payload thereby determined by said master attitude estimate Xm* and said slave relative attitude estimate Xsrel*.

A spacecraft, comprising:

• a satellite body;
• a master payload carried by said body;
• at least one slave payload carried by said body;
• an attitude control system that includes:
• a) at least one master attitude sensor proximate to said master payload;
• and
• b) at least one slave attitude sensor proximate to said slave payload;
• at least one solar panel carried by said body to provide power to said attitude control system;
• and
• at least one data processor in said attitude control system that is programmed to perform the steps of:
• a) successively differencing a master predicted measurement Ym* and master attitude measurements Ym from said master attitude sensor to form a master residual Rm;
• b) successively differencing said master predicted measurement Ym* and slave attitude measurements Ys from said slave attitude sensor to form a slave residual Rs;
• c) processing said slave residual Rs to derive a slave relative attitude estimate Xsrel* and a corrected slave residual Rscrctd;
• d) filtering said master residual Rm and said corrected slave residual Rscrctd to realize said master predicted measurement Ym* and a master attitude estimate Xm*;
• and
• e) in response to said master attitude estimate Xm* and said slave relative attitude estimate Xsrel*, controlling the attitude of said master and slave payloads with said attitude control system.