GIOVE-B
Center of Mass Information:
The ESA publication "Specification of Galileo and GIOVE Space Segment Properties Relevant for Satellite Laser Ranging" provides retroreflector and spacecraft information (view request cover letter). According to this document, the LRR is located on the +Z facet (see figure 1 below). The coordinates of the CoP of the LRR array with respect to the satellite reference frame (see figure 2 below for the position of the reflective surface; cube height is 19.1 mm, refractive index is 1.46)
X = -807.5 mm
Y = 297.5 mm
Z = 2267.6 mm
Coordinate of the S/C CoM (beginning of life, deployed solar array configuration) with respect to the satellite reference frame:
X = -3.2 mm
Y = 3.4 mm
Z = 937.5 mm
Fig 1. Position of LRR in GIOVE-B. Spacecraft is shown with solar array in stowed configuration.
Fig 2. LRR schematic in GIOVE-B.
Attitude Law:
GIOVE-B follows a yaw steering law such that the body +Z axis points continuously to Nadir, together with a rotation performed around the Z axis that maintains the S/C Y axis perpendicular to the Sun. The +X spacecraft panel is maintained away from the sun. (RD-10).
As with GIOVE-A, it is foreseen that the theoretical attitude will not be achieved at times where the beta angle (angle between the sun and the orbital plane) is small, due to limitations in the reactions wheels and to poor yaw measurement (sun co-linearity). In addition, during eclipse, it is expected that the yaw error can reach values of the same order as GIOVE-A.
Other Navigation Data:
L-band phase centres (RD-13 and RD-14):
| E5a + E5b | E6 | E2/L1/E2 |
|---|---|---|
| X = 0.0 mm | X = 0.0 mm | X = 0.0 mm |
| Y = 0.0 mm | Y = 0.0 mm | Y = 0.0 mm |
| Z = 2288.7 mm | Z = 2287.6 mm | Z = 2289.15 mm |
The s/c mass is 497.6 Kg (BOL). The approximate cross-section Area is 12 squared metres, with a CBSRPB (Solar Pressure Radiation factor) equals 1.37 (assuming cannonball model, according to equation 1).
