Small scale version of a hypertelescope experiement

The Collège de France and Observatoire de la Cote d’Azur have started a long term project to build a Hypertelescope in Southern Alps.  

https://lise.oca.eu/spip.php?rubrique41

This first prototype involves placing very precisely (precision of a micron) a series of mirrors along a virtual sphere of 202m of radius, and collecting the image 101m above the ground using a gongola suspended to main cables (blue in this picture). The gondola position and orientation is controlled using 6 auxiliary cables (represented in red).

The rays coming from the star (yellow) are reflected by the mirrors and form the image in the gondola. When the star moves in the sky due to the earth rotation, the image travels along the black and white dotted line, which the gondola needs to follow thanks to the red cables.

For education and training purpose, we are building a small scale version of the valley using a 3D printer. The area of interest is about 1km square, which will print at a size of 12.5 cm if using a 1/8000 scale.

A 3D model of the valley has been constructed using course data for the outside part (rectangular mesh in the picture below), and accurate points for the mirror areas and characteristic points using equipment provided by IGN. Three series of points were captured in 2010, 2012 and 2013, with an accuracy of a few cm. The accurate tessellation and course rectangular mesh were merged together. Then further details added such as engraving the access trail, placing the two existing mirror locations and piercing holes for the 5 locations where cables reach the ground.

One of the challenges is to represent small details in such a large area. For example the 15cm mirrors would be less than .02mm if printed at 1/8000 scale and need to be enlarged. The constraint of printing only in one color also imposes to model geometrically the characteristic point locations.

Some experiment also needs to be done to find the best way to attach small threads to the printed model to simulate the gondola position and control.