| Table of Contents | Introduction | Matrix of Transformation | Attitude Data Files | Software | Data Availibility | Additional Information |

1. Introduction

Tail Probe is a spin-stabilized spacecraft spinning around the main axis of the maximum moment of inertia. The angle between the spin axis and direction towards the Sun should not exceed a certain value.

As this angle increases with the rate of about 1^o/day (because of the Earth orbital motion) the attitude control system periodically (once per ~7 days) restores the direction of the spin axis to the Sun.

To know the spacecraft attitude for a given time we use a matrix N to transform any vector V from the Geocentric Solar-Ecliptic (GSE) coordinate system to the Spacecraft Construction (S/C) coordinate system

V_S/C = N * V_GSE

or a matrix M for the inverse transformation

V_GSE = M * V_S/C

The both systems S/C and GSE are spacecraft-centered ones.

The GSE coordinate system:

• X_G axis is directed to the Sun,
  
• Z_G axis is directed to the North Pole of Ecliptic,
  
• Y_G axis supplements the right three.
  

The S/C coordinate system:

• X_S axis is the spacecraft struclural axis which is close to the spin axis and to the main axis of the maximum moment of inertia X_m,
  
• Y_S axis is the structural axis close to the axis of the intermediate moment of inertia Y_m,
  
• Z_S axis is the structural axis close to the axis of the minimum moment of inertia Z_m.
  

By attitude sensors data processing the attitude coefficients arrays have been obtained. It gives the possibility to calculate matrixes N,M for a given time.

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