dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos DARA The new Three-Cavity Digitally- Controlled Radiometer for Space Application

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos Features 3 independently controllable cavities Offers several open/close measurement sequences Independent PID controllers for closed and open shutter state ~20 bit data acquisition for each I, U and PWM channel Measurement period down to a few seconds Uncorrelated sinus carrier for thermal error signal Convex cavities with minimal dynamic “Non-Equivalence” Very fast shutter speed (one step) Two data analysis methods were available –Tail Integration Method (TIM) –Phase Sensitive Analysis (PSA)

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos Overview

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos 3 Cavity Design

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos Thermal Simulation

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos Instrument Geometry A) Precision Aperture B) Cavity, Aeroglaze Z302 Coating C) Heat Sink D) Thermal Resistor E) Thermometer F) Electrical Heater G) Radiation Shield H) Shutter I) View Limiting Aperture

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos Design Goals Reduce dynamic & static „Non- Equivalence“ Reduce the number of Bonds New Aperture Geometry Reduce Stray Light Remove uncertainties due to “Aperture Warming”

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos Sinus Carrier for Thermal Balancing Decoupling from PWM by using an uncorrelated sine carrier Means f Sin is not an overtone of f PWM f PWM = 20 Hz, f Sin = 1010 Hz

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos PID Controller Switching How can the settling time be reduced when changing the shutter state? Two PID controllers per channel Significantly less settling time is needed Measurement period can be reduced

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos Power Measurement and Sampling PWM frequency: 20 Hz Duty cycle resolution 19.9 bit The heater current can be set by a DAC The effective heater current is measured by a 20 bit ADC Heater voltage is sampled when PWM is high and measured by a 20 bit ADC

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos TIM Measure Tail Integration Method or Traditional Irradiation Measure The tail data are integrated The sun power is calculated as the difference of 2 measurements made with closed shutter and 1 with open shutter One measure per open/close turn

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos PSA Measure Phase Sensitive Analysis Measure Heater PWM signal is weighted by a synchronous sine signal All data are taken into account for the analysis Two measures per open/close turn

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos Data Management RS422 communication Robust communication protocol EGSE software for data visualization and data storage

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos First Measurements Not characterized yet!

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos First Measurements Ratio Cavity A/Cavity C PWM Signal

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos IPC Results

dlab GmbH CH-8400 Winterthur Physikalisch-Meteorologisches Observatorium Davos Outlook Characterization (Ground & Space) Visit Calibration Facilities Verify WRR Scale SuMo Instrument on PROBA III (2015?)