1 Nanometric positioning with IASI -NG ‘s Beam Splitter Mechanism Actuator  

Francois Barillot *, Jocelyn Rebufa* , Gladys Jaussaud*  and Adrien Guignabert * 

Abstract  

This paper presents a piezoelectric motor  which provides linear motion and very high resolution (40 nm  steps). First, the space application ( IASI-NG instrument  onboard METOP -SG satellite) and associated  performance requirements are presented. The internal architecture of the motor and its main components   are then explained. A first focus is done on the experimental verification of the threaded interface lifetime  which is a key element of the mechanism. A second focus is on the nanometric position test bench.  Achieved results are provided for resolu tion, motion quality and position stability. Finally, results from the  vibration test campaign are presented.  

Introduction  

Many space projects have shown need for stable sub -micrometer  positioning linear actuators. They are  typically needed to adjust the mirror position of sensitive optical instruments after launch during initialization   or throughout flight life to accommodate aging and other long- term variations. In addition, as long periods  can be expected between position changes, it is mandatory that the actuator remains passive (i.e. , not  powered) once the adequate position is achieved.  This need is met in the IASI -NG space instrument , where  a linear actuator offering a 30- nm step resolution and an unpowered position stability of 0.30 µm over  6 months  was requested. Combined with the requirement of surviving launch, t hese specifications are  beyond the capacity  of existing linear piezo motors. For example,  in [1] the piezomotor survival against  vibration loads  was not proven. Such external forces will apply directly on both the motor friction surface  and the piezo ceramic and may damage the motor. This can be circumvented using a launch lock  mechanism at a price of added mass and complexity .   

In order to meet such a need, Cedrat Technologies (CTE C) has built a hybrid actuator, starting from its  patented Fine Stepping Piezoelectric Actuator (FSPA)  [2], but using a combination of its magnetic and  piezoelectric technologies to reduce electrical requirements. This new linear stepping actuator first  generates a rotating movement and then turns it into a translation movement. It offers nanometric  positioning resolution combined with the ability to hold its position without power and during launch without  the need for any launch lock mechanism.  

IASI-NG & Beam Splitter  Mechanism  

The Infrared Atmospheric Sounding Interferometer New Generation (IASI -NG) is a key payload element of  the second generation of European meteorological polar -orbit satellites (METOP -SG) dedicated to  operational meteorology, oceanography, atmospheric chemistry, and climate monitoring. It will provide  operational meteorology data such as temperature and humidity atmospheric profiles and also monitor  other gases like ozone, methane or carbon monoxide on a global scale.  

The instrument is developed under the lead of CNES, who is responsible for the development and  procurement of the IASI -NG System (Instrument, Ground Processing software, Technical Expertise  Center). Airbus Defence and Space was selected for development of the “Space Segment” mainly  consisting of the Instrument itself.  

* CEDRAT Technologies, Meylan, France ;  francois.barillot@cedrat -tec.com  

Proceedings of the 45th Aerospace Mechanisms Symposium, NASA Johnson Space Center, 20 20