Form 9.B Project Summary



Proposal Number:


Project Title:

Autonomous Unified Orbit and Attitude

Control for Formation Flying using GPS

and LQG/LTR Controller

Technical Abstract (Limit 200 words)

This proposal provides an approach to the problem

of autonomous orbit and attitude control of

satellites flying in formation. In this approach, the

GPS data will be used for autonomous real-time

estimation and closed-loop on-board feedback

control of both the satellite orbit and attitude. While

existing literature show some progress on modeling

of formation flying dynamics with control law based

on nearest neighbor-tracking, the implementation

details of such control, including the method of

obtaining necessary observational information for

implementation have not been solved. Additionally,

the control system proposed here not only

maintains the formation pattern using GPS code

pseudorange data, but also provides the attitude

determination and control using GPS differential

phase pseudorange. Because attitude dynamics and

kinematics equations are nonlinear, one of the

innovations being proposed is application of

nonlinear control technique to solve the nonlinear

feedback problem. The additional innovation is the

unified architecture for orbti and attitude control

system. This topic is in direct response to NASA

GSFC's specific interest in advanced formation

flying for its 'Mission to Planet Earth' Guidance,

Navigation and Control need of the future.

Potential Commercial Applications (Limit 200 words)

With commercial communication satellite operators

shifting their attention to low-earth orbit satellites,

opportunities are opening up for commercial

application of designs involving autonomous

on-board orbit and attitude control systems. While

initial efforts are on constellation operations,

formation flying is of potential interest to these

operators because of their inherent advantages in

providing precise patterns and advantages such as

in providing 'virtual aperture' and similar advanced

techniques. There is also potential application of

formation flying to geostationary communication

satellite operations. With increasing number of

satellites vying for shrinking number of available

geostationary slots, multiple satellites are being

station-kept within the same stationkeeping box

using the techniques of co-location. These

collocation methods involve phasing the eccentricity

and inclination vectors of the satellite orbits to

provide sufficient spatial separation between

satellites. However, there is enough uncertainty

and inaccuracy in the current methods to warrant

implementation of formation flying for co-location.

Formation flying will also enable co-location of a

much larger number of satellites than is currently


Name and Address of Principal Investigator (Name,

Organization Name, Mail Address, City/State/Zip)

Shabbir A. Parvez

Space Products and Applications

2702 Copper Creek Road

Herndon , VA 20171-3520

Name and Address of Offeror (Firm Name, Mail Address,


Shabbir A. Parvez

Space Products and Applications

2702 Copper Creek Road

Herndon , VA 20171-3520