Calibration is crucial for space instruments: it enables the correct interpretation of the raw data that is returned to earth. TNO has a leading position in providing calibration technologies for earth observation instruments, involving onboard calibration hardware for space instruments as well as on-ground calibration of components or even complete instruments.
ACS is supplying them with a Thermal Vacuum Chamber for the calibration of space or pseudo-space instruments at flight representative environmental conditions.
As TNO says, “as space instrument designs can be different so is their calibration”: for this purpose, we designed a special TVC for their specific needs.
TVC main features
• Size: vertical cylinder of 2.7 m diameter and 3.1 m height
o volume: 7300 l
o temperature range: -80 °C to + 80 °C
o temperature rate of change: up to 3 °C/min
• Two independent cold plate systems:
o temperature range: -173 °C to + 80 °C
• Ultimate pressure chamber: < 1x10-7 mbar
The chamber is equipped with a 6-DOF instrument manipulation system and a set of standard optical stimuli designed to serve a wide range of earth observation instruments that measure in the wavelength range of 270 up to 2500 nm.
The TVC is a vertical cylinder with an internal shroud diameter of approximately 2.4 m; large enough for mid-sized instruments. The chamber and thermal shrouds are cut diagonally, resulting in a wedge shaped bottom half and top half. The top half can be removed, thus reducing the total height required for opening the chamber and allowing easy and safe access for instruments and installation personnel.
The bottom and top thermal shroud halves have independent temperature control. In addition, there are two independent cold plates available for space environment simulation and/or cooling specific parts of the instrument.
Inside the chamber, there is a mechanical manipulation system that allows precise movement of the instrument with 6 degrees of freedom. The manipulation system consists of a hexapod on top of a rotation stage and is designed for a total (instrument + GSE) mass of up to 300 kg. The manipulation system is designed and manufactured by the France company Symetrie.
A set of generic optical stimuli is developed and will be available for future calibration actions of space instruments. This will consist of standard equipment such as integrating spheres and a target diffuser but also a generic optical collimator that can be used for many purposes. The optical stimuli will be positioned outside the chamber, which has multiple large flanges enabling flexible positioning of one or more windows.
The thermal vacuum chamber, the manipulation system and the optical stimuli are controlled by a single CSI Control System which ensures easy remote operation and a single interface with the instrument under test and its GSE.
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Thanks to TNO staff for their precious info:
Tim Luijkx, Freek Molkenboer, Rik Jansen, Willem van Werkhoven, Wouter Mulckhuyse, Gerard Otter, Eleonie van Schreven, Brigitte de Roode, Hans Haasnoot, Alfred Abutan, Nick van der Valk.