The 0.5x1.0 m mosaic has been assembled at the Toulouse facility of Gaia prime contractor Astrium France. Technicians spent much of May carefully fitting together each CCD package on the support structure, leaving only a 1 mm gap between them. Each e2v-made CCD measures 4.7x6 cm. Working in double shifts in strict cleanroom conditions, technicians added an average four CCDs per day, finally completing their task on June 1st:
The completed mosaic is arranged in seven rows of CCDs. The main array comprises 102 detectors dedicated to star detection. Four others check the image quality of each telescope and the stability between the two telescopes that Gaia uses to obtain stereo views of stars. In order to increase the sensitivity of its detectors, the spacecraft will maintain their temperature of –110ºC.
Fanastic!!!
ReplyDeleteAs impressive I'm sure the sensor performance is, I think real credit has to be given to the people who designed and actually assembled such a large array. The accuracy tolerances, demands of space flight, and cleanliness requirements make this an exceptional piece of work, even among space instruments.
ReplyDeleteIf the sensors are super-accurately positioned, shouldn't their front glass faces be coplanar, or at least parallel? In the picture above, you can see the reflected light from the white wall panel in the right third of the array. There is an edge between black and white that crosses 7 CCDs, and that reflection is quite clearly not straight. There is another reflected line to the left which is harder to make out, but also may not be straight.
ReplyDeleteHopefully the individual CCDs can each be separately moved, to optimize focus, after the sensor has been mated to the lens. Otherwise this assembly looks suspicious to me.