Cynthia Vaskis

SLM521 Spring 2004

Dropin #3 Assignment

4/6/04

File: dp3steci.htm

The Space Object’s State Vector’s definition in ECI coordinates can be calculated from the Euler orbital parameters. The State Vector STATE(x,y,z) which points to the Space Object’s coordinate system origin can be added to the Star Tracker’s Translation Vector to get a new Earth to Tracker E2T vector from the ECI origin of the Earth directly to the Star Tracker’s origin. The STFOVC gets moved back (by subtracting the E2T vector) to the Earth’s ECI coordinate system origin as the STFOVECI vector and is then unitized to be the STFOVECIU vector used in step 7 on dropin 3’s top page Topic 3.

Star Tracker’s Translation Vector from Space Object’s origin to Star Tracker’s origin (defined by placement of tracker onto space object during construction)

The Star Tracker’s pointing vector STFOVECI in Earth’s ECI coordinate system

A new Earth to Tracker vector E2T(x,y,z) in ECI coordinates

STATE Vector from center of Earth to Space Object’s origin of its Cartesian coordinate system

Space Object (blown up to show its Cartesian coordinate system origin)

Earth with ECI Cartesian coordinate system

Star 2