OMI Level 0 Telemetry Plots

The plots below show instrument telemetry data for the complete duration of the mission. This telemetry is derived from the Level 0 engineering data of the OMI instrument. Apart from the individual data points, the telemetry plots contain daily averages, plotted in black.
Violations of red or yellow limits, as defined by the instrument operations team, are plotted in red or yellow respectively. Also, in the plots the actual limits are provided as well as the number of limit violations.

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CCD Temperatures

The CCD temperatures are actively stabilised. For this reason the variation in temperature is only about 10 mK.





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Optical Bench Temperatures

There are four temperature sensors on the Optical Bench of the instrument. The optical bench contains a heater that keeps the optical bench around the desired temperature. This heater is not actively controlled, hence temperature variations - in the order of several tenths of a Kelvin - are visible over the orbit.
A small increase of the optical bench temperature is visible over the duration of the mission. This is attributed to dirt that accumulates on the instrument's radiator, thus decreasing the efficiency of this radiator.









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ELU Circuit Board Temperatures







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Calibration Source Status

The instrument contains two sets of LEDs and a White Light Source (WLS) that are used for calibration of the instrument. The LED is typically used on a daily basis; the WLS on a weekly basis.
In the plots below, a value of 0 indicates that the calibration source is switched off; a value 1 indicates that the calibration source is switched on.







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Mechanism Status

The instrument contains three mechanisms that are controlled by a stepper motor. The Solar Aperture Mechanism (SAM) is used to open and close the solar observation port. The diffuser mechanism (DM) is used to select one of the diffusors for solar irradiance measurements. The Folding Mirror Mechanism (FMM) controls the folding mirror that switches the instrument from earth radiance mode to calibration mode. The FMM, being a critical component in the instrument, is equipped with a redundant set of coils.
The plots below show the status for the stepper motors for the mechanisms. A value of 0 indicates that the motor is switched off; a value of 1 indicates that the motor is in 'hold' mode; a value of 2 indiciates that the motor is in 'drive' mode; a value of 3 indicates a failure of the motor.









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CCD Heater Control Status

The heaters on the CCD detectors are controlled by means of an active P-controller. This controller has a Pulse Width Modulation (PWM) output signal. The PWM varies between 0% and 50% duty cycle.





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Heater Currents







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Digital Co-adder Status

The instrument contains a digital co-adder that co-adds individual measurements in order to increase signal-to-noise and decrease the data rate of the instrument. The co-adder provides information on the status of the ADC for individual pixels, specifically when underflow or overflow occurs. The underflows typically occur when one of the amplifiers in the signal chain is saturated. Overflows can occur for scenarios with high signal levels, for example cloudy scenes.
For the underflows, a value of 0 indicates that no underflows have occurred; a value of 1 indicates that one or more underflows have been detected. For overflows, the total number of pixels for which overflow was detected is provided, but when this exceeds 255 pixels per measurement, this value is clipped at 255.









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Calibration Source Voltages







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CCD Driver Voltages







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ELU Power Supply Voltages















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