044 - Hollow Corner Cube Retro-Reflectors In-Orbit PNT
Optical solid Corner Cube Retro-reflector (CCR) arrays are often implemented to allow laser tracking of satellites from ground. In order to achieve a measurable return signal, such arrays are typically rather large, and as conventional corner cubes are made of glass, the arrays are typically high in mass. However, in recent years, interest has grown in using hollow corner cubes for space applications, partly due to the possible mass reduction they enable.
A hollow CCR, made of three orthogonal flat mirror surfaces, offers theoretically superior performance in comparison with arrays of small solid reflectors, which are currently in common use. The main advantage of hollow CCRs is their capability to tune the far field characteristics, i.e. the maximized energy distribution, to the specific needs of tracking.
However, technologically there are still too many disadvantages and uncertainties for hollow cubes to be considered a viable option. Currently the mass advantage that hollow cubes could potentially allow is lost by the need for a stable opto-mechanical support structure, and the tolerance accuracy achievable does not match that of solid cubes.
Despite this, there is still a clear interest in qualifying hollow cube technology for satellite PNT. It will possibly provide added value in the form of mass reduction, and improved ranging precision (which enables better independent precision orbit determination, as well as geodesy applications). Additionally, it could be deployed on the Moon for Earth-Moon distance measurements, which is strongly desired by the scientific community.
Hollow CCRs have the potential to deliver the same functionality as solid CCRs, and with improved performance and lower mass. However, an advance in technology is required to achieve long-term mechanical stability and accurate control of the corner cube angles.
The main objective of the proposed activity is to develop a lightweight and space- qualifiable hollow corner cube with high thermo-mechanical stability for improved inorbit ranging.
The task to be performed is the development of a hollow Corner Cube Retro-reflector for space PNT applications. A potential starting point for that could be the existing hollow corner cubes built for other applications (e.g. Fourier Transform Spectrometers). This activity will require innovation within mirror design for highthermo-mechanical stability, precision alignment, assembly, mounting and coating techniques.
The main results of the activity will provide:
- feasibility assessment;
- a Proof-of-concept of an opto-mechanical design for a hollow Corner Cube Retro-reflector for space PNT, which in comparison to solid cubes should have reduced mass and improved ranging performance.
The relevant development does not intend to prepare for next generation Galileo Laser Retro-reflectors for ODTS purposes