1 / 16

Diarad_SovaP instrument performance ( IRMB C. Conscience for S. Dewitte )

Radiometric equations Ground characterizations Flight calibrations Tasks to finalize. Diarad_SovaP instrument performance ( IRMB C. Conscience for S. Dewitte ). A02, A03 Radiometric equations. Ideal radiometer : Real radiometer :.

venus
Download Presentation

Diarad_SovaP instrument performance ( IRMB C. Conscience for S. Dewitte )

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Radiometric equations Ground characterizations Flight calibrations Tasks to finalize Diarad_SovaP instrument performance( IRMB C. Conscience for S. Dewitte )

  2. A02, A03 Radiometric equations Ideal radiometer : Real radiometer : “It becomes absolute when all corrections are characterized and the measurements are traceable to international standards.”

  3. Radiometric equation • Precision aperture : A • Power measurements : P • Cavity efficiency : αeff • Corrections • C1 : wires heating effect • C2 : precision of the servo-system • C3 : shutter emission • C4 : mirror emission • C5 : optical effects (diffraction, scattering, backscattering ) • C6 : sensors thermal equilibrium • Δ : mirror free thermal dilatation • Δ'  : mirror thermo-mechanical effects • Δ'' : mirror initial deformation due to the fixture torque • cos θ : depointing

  4. Ground characterizations • Electrical characterisations : • Current measurement Resistor, R100 , in the lab. • Reference voltages, V1-->V6, V'1-->V'6 during Th.Vac. • Heating Resistor, R120 , during Th.Vac. • the sensitivity is measured in air & vacuum • Determination of parasitic Resistors, rc & rd , based on sensor sensitivity. • Adjusting power equilibrium of the cavities • Adjusting sensors equilibrium • Calibration of thermometer sensor • Optical characterisations : • Quasi cylindrical tube profile • Cavity bottom uniformity • Cavity reflectance • Mechanical characterisations : • Precision aperture, A, measured by NIST & NPL

  5. Electrical characterization : Calibration voltages

  6. Electrical characterization : Heater resistor - A third order model of the heater resistor was established during the Th.Vac, and is valid for [-30°C  45 °C], with a traceable AGSE. This model serves also for quality control of the acquisition chains.

  7. Electrical characterization : Heater parasitic resistor Current flowing through the wires and the soldered joints produce a small power that is detected by the sensor and thus must be taken into account in the radiometric equation. Charaterization done with traceable DVM, and based on the sensivity of the detector

  8. Optical characterization : C5: Correction factor for optical effects Diffraction on precision aperture (δ’) Scattering around the intrance aperture (Σ) Backscattered radiation from volume between shutter and precision area (Σ')

  9. Mechanical characterization : Precision Apertures • Area measured by NIST at 20°C • based on optical method • NPL has measured 4 diameters at 20°C • based on a mechanical method • with a measure of the departure from roundness Aperture Sun side Aperture Sensor side

  10. Mechanical Correction : free dilatation Δ negligible • Δ = 0,00021 @ T = 32 °C

  11. Flight calibration : corrections C3&C4 This correction has been calculated from the first stellar pointing. • ~ - 1,15 W/m² ( loss of energy when the shutter is opened & T mirror decreases ) Tright shutter (closed) Solar pointing Stellar pointing Tleft shutter (opened/closed) ΔP =L_(shutter + mirror)

  12. Flight calibration : corrections C3&C4 ΔTog = -13 °C ΔTmg = -1.5 °C

  13. Flight calibration : acquisition system During the 3’ that lasts a radiometric cycle, 6 calibration voltages are fed into the acquisition system to calibrate it. A linear equation is established between each counter and the 6 voltages.

  14. Flight calibration : acquisition system V_channel = A . counts + B switch off/on First switch on Coefficients A, and B since the beginning of the mission : they track variations in the acquisition system. The effect of the decreasing of the Temperature of the V/F, due to “eclipses”, is visible in the green circles.

  15. Uncertainty of the SI measurements in A02, A03

  16. Tasks to be finalized WP1 : Optical corrections (Σ, Σ’, σ) need to be updated for SovaP WP2 : Depointing correction Analyse CNES report for depointing between SovaP and reference surface. WP3 : shutter & mirror corrections Analyse in details stellar pointings to improve the correction. WP4 : efficiency of the cavity Extra calibration of tiles has been asked WP5 : corrections Δ’ , Δ’’ need to be characterized Description of new setup and test is requested WP6 : estimate the global Uncertainty of the SI measurement Case of A08 ( other radiometric equation for this mode ).

More Related