Calibration
CSL has the ability to carry out end2end space instrument calibration with the generic goal: "Calibrate as you flight"
This means:
- The understanding of instrument scientific goals
- The comprehension of the instrument behavior to review the instrument model and calibration model
- The definition of Key Data Parameters needed in the models
- The method to measure each Key Data Parameter (with associated preliminary Ground System Equipment principle)
- The computation of full error budget (to reach requirements at L1b1 level i.e. on top of atmosphere), including preliminary Ground System Equipment design properties
- The definition of Ground System Equipment requirements and calibration plan to fulfill the error budget
- The definition and implementation of all algorithms in Matlab:
- Instrument model and calibration model,
- Key Data Parameter algorithms.
- The Ground System Equipment final design, manufacturing, assembly, integration and acceptance. These systems are almost always vacuum compatible to minimise the contribution of the caliration system on the instrument error budget
- The use of these Ground System Equipments for instrument charaterisation and calibration
- Consideration of cryogenic environment and thermo mechanical constraints are also part of Ground System Equipments and the calibration approach
CSL has been involved in the calibration of VGT, MERIS, PROBAV, TROPOMI, MTG…, and many many scienctific instruments.
Geometrical calibration Optical Ground Sytem Equipment
Several collimators are available at CSL to perform geometrical calibrations from the EUV to SWIR.
Focal length between 0.1 to 8 m have been developed.
Most of time focal planes are adapted to fufill the payload geometrical performances.
Full end2end Opical Ground System Equipment collimator are also developed for dedicated customers
Radiometric calibration Optical Ground System Equipment
Radiometric calibration are generaly achieved by Integrating Sphere. CSL has the capabilities to design integrating spheres to achieve good isotropies (better than 99%), high radiance levels (equivalent to maximum earth radiance), vacuum compatible system and radiometrically calibrated by international standard.
Sun Simulator for in flight calibration Unit calibration
Sun Simulator Optical Ground System Equipment are generaly used to illumintate the on board diffuser use for in orbit radiometric calibration. CSL developed and used Sun simulator to validate solar panel efficiencies, to simulate 25 Solar Constant on payload going close to the sun and to simulate a standard optical sun for Calibration Unit charaterization.
Spectral Calibration Optical Ground System Equipment
With the development of new spectrometer concepts, it is required to adapt the calibration facilities to characterize correctly their performances. These spectro-imaging performances are mainly Modulation Transfer Function, spectral response, resolution, and registration; polarization, straylight and radiometric calibration.
CSL developped a telecentric achromatic design to fulfill such measurements from 400nm to 2300 nm using an Offner design, a monochromator and a QTH lamp.
An upgrade of the facility allows covering the range from 330 nm to 2600 nm using an accordable laser.
Other Key parameters need to be calibrated prior to launch. For each of these parameters CSL has the capabilities to develop adequate Optical Ground System Equipment for in-home use as well as for a delivery to external custumers.
Optical Ground System Equipment from the X-rays till submillimeter wavelengths has been realized.
Typical Optical Ground System Equipment to measure Effective area, Polarisation, wavefront errors, ... and straylight (see Straylight expertise) are created.
Challenging thermo-mechanical constraints are also managed.
Capabilities to consider a full opto cryogenic calibration set up are availlable.
