Large Aperture Telescope Technology


Funded by: European Space Agency  
Calls: ITT 5768
Start date: 2011-07-01  End date: 2015-06-30
Total Budget: EUR 800.000,00  INO share of the total budget: EUR 108.827,00
Scientific manager: Duò Fabrizio   and for INO is: D’Amato Francesco

Organization/Institution/Company main assignee: Compagnia Generale Spazio

other Organization/Institution/Company involved:
ADS International
Istituto Nazionale di Astrofisica

other INO’s people involved:

Abstract: The LATT (Large Aperture Telescope Technology) activities, developed in Phase 1 of ESTEC/Contract No. 22321/09/NL/RA, are focused to the advancement of the technology needed to increase the aperture of the space telescope for LIDAR application to increase in this way the Signal to Noise ratio that cannot be improved by increasing the transmitted laser power because of the limits put by eye-safety regulations.
The Active Deployable Primary Mirror is the solution identified to increase the aperture of the space telescope. The primary mirror shall be deployable on orbit because of the limitation of the launcher fairing diameter. Tanks to the active mirror the accuracy of deployment is not anymore a problem because thermo elastic distortions, deployment and manufacturing error can be corrected on orbit.
The primary mirror identified in this study is composed by a central part where are constrained six deployable petals (deployment obtained by means of a passive actuator); both the central and deployable parts of the primary mirror are active and composed by a backplane made of CFRP and a thin shell made of Zerodur (~1mm thick) joined together by the actuators. The fragility is the drawback of the thin Zerodur mirror that shall be launched in a heavy vibration environment.
The mirror during the launch is electrostatically glued to the backplane, to do this the facing skin of the backplane and the backing surface of the mirror are coated by a conductive layer protected by a dielectric material; once a voltage is applied to the conductive layers the two part are attracted one against the other guaranteeing the survivability of the mirror during launch.
The design of the Voice coil actuators for space application started from that used successfully for the adaptive optic in ground application. The advantage of this kind of actuator is to be fail safe in the sense that it doesn’t lock the mirror if damaged or not powered.
The aim is to obtain with this technology a mass areal density of the primary mirror, including the deployment mechanism, lower than 16Kg/m^2 and a power for the control of the primary mirror lower than 40W.

INO’s Experiments/Theoretical Study correlated:
Large Aperture Telescope Technology (LATT)

The Scientific Results:
1) Last results of technological developments for ultralightweight, large aperture, deployable mirror for space telescopes
2) Development of large aperture telescope technology (LATT): Test results on a demonstrator bread-board