Slit Change Mechanism

Almatech Contribution

Almatech was responsible for the complete design, development and delivery of the 3 models of the SPICE Slit-Change Mechanism.

In order to guaranty optical cleanliness level (PAC<30ppm) while fulfilling stringent positioning accuracies (±10 μm / 200 arcsec) and repeatability (±3 μm) requirements for slit positioning in the optical path of the instrument, a linear guiding system based on a double flexible blade arrangement has been selected. The concept of the mechanism is compliant (wear-free), compatible with cryogenic conditions with an integrated calibration system and does not require a launch-lock system. All requirements including cyclability (over 54’000 cycles) have been fulfilled.

“The Slit-Change Mechanism is a perfect example of all the benefits compliant mechanisms can bring in terms of reliability and absence of contamination. I am convinced that this type of design is the future!”

Gabriel Paciotti

Principal Engineer

About the mission

Solar Orbiter is a Science mission of jointly developed between ESA and NASA, that was selected as the first medium (M)-class mission of ESA’s Cosmic Vision  programme for launch in 2019. Solar Orbiter’s goal is to address the central question of Heliophysics: how does the Sun create and control the heliosphere? Solar Orbiter is designed to identify the origins and causes of the solar wind, the heliospheric magnetic field, the solar energetic particles, the transient interplanetary disturbances, and the Sun’s magnetic field.

About the payload

SPICE is one of 10 instruments on board Solar Orbiter. It is a high resolution imaging spectrometer operating at extreme ultraviolet wavelengths. SPICE will address the key science goals of the Solar Orbiter mission, by providing the quantitative knowledge of the physical state and composition of the plasmas in the solar atmosphere, in particular investigating the source regions of outflows and ejection processes which link the solar surface and corona to the heliosphere. SPICE is designed to study the structure, dynamics and composition of the transition region and corona by observing key emission lines on the solar disk on timescales from seconds to tens of minutes.

The Solar Orbiter mission (Credit ESA)

slit carrier positionning accuracy


slit carrier position repeatability


Paciotti G., Humphries M., Rottmeier F., Blecha L., Development and preliminary testing of a high precision long stroke Slit Change Mechanism for the SPICE instrument
presented at the 42nd Aerospace Mechanisms Symposium, NASA Goddard Space Flight Center, May 2014

Khanenya N., Paciotti G., Forzani E., Blecha L., Development and Testing of a High-Precision Position and Attitude Measuring System for a Space Mechanism
presented at the 43rd Aerospace Mechanisms Symposium, NASA Ames Research Center, May 4-6, 2016