Calibration
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Calibration

CPR has a function designed for performance verification of both the transmitter and receiver, as well as for improving accuracy of Doppler velocity. This function includes five modes: the Nominal Observation mode, Internal Calibration-1 mode, Internal Calibration-2 mode, External Calibration mode, and Sea Surface Calibration mode. These modes provide useful data for calibrating the CPR.

During the Commissioning and calibration/validation phase (COM), calibration of the CPR will be performed using calibration data obtained through the observation mode and various calibration modes (Internal Calibration, External Calibration, and Sea Surface Calibration). The types of calibration, their content, and the measurement items are described below.

Purpose Measurement Item
Nominal
Observation		 The calibration is aimed to calibrate the received power of the receiver and the transmitted power of the transmitter.
① and ② are used to calibrate the received power, while ③ is used to calibrate the transmitted power.		 ①Hot Load noise power
②Nominal Load noise power
③Tx power
④The power at the Log input termination.
Internal
Calibration-1		 The purpose is to correct the aging changes in the log detection and IQ detection characteristics of the signal processing unit. Data are collected for 120 seconds. ①Log detector linearity
②IQ detection system orthogonality
③Linearity of IQ detection system AD converter
④IQ detection offset voltage
Internal
Calibration-2		 The purpose is to calibrate the temperature dependency of the IQ detection in the Signal Processing Unit.
Internal Calibration data are collected over one orbit (approximately 92.5 minutes).
External
Calibration		 The purpose is to calibrate the received sensitivity and Doppler measurement performance in radar performance calibration, using an external calibration device installed on the ground. This calibration is carried out by NICT. ①CPR transmit power
②Transmission antenna pattern, transmission antenna beam direction
③Receiver gain
④Delay time of internal equipment
⑤Overall performance
Sea Surface Calibration The purpose is to perform calibration using sea surface scattering data observed when the satellite tilts its attitude during operations.
The duration of the operation is approximately 420 seconds.		 ①Intensity signal
②Doppler velocity signal

The maximum number of data acquisitions for each calibration mode during the COM and the Measurement/Operation phase (MOP) is determined according to an agreement with ESA, as outlined in the table below. Note that Internal Calibration-1 and Internal Calibration-2 refer to the same internal calibration mode, but they differ in operational settings and duration.

Operation frequency of calibration mode
Calibration Maximum number of
observations during COM		 Maximum number of
observations during MOP
1 Internal Calibration-1 2/cycle 1/cycle
2 Internal Calibration-2 1/3 months 1/3 months
3 External Calibration up to 4/cycle 1 or 2/cycle
4 Sea Surface Calibration 2/cycle 1/cycle

Operation Record

CPR calibration operations

After completing the initial performance verification of CPR, data will be publicly available. However, due to calibration operations (refer to the frequency in the table above), there may be missing data. Please check the CPR operation status below to confirm if there are any missing CPR data.

< Now preparing the link to the CPR operation status >

Silent state operation over Radio Astronomy Sites (RAS)

During orbital operations, the CPR will enter a "Silent state" when passing over Radio Astronomy Sites (RAS). The radio wave transmission will be paused, and the pause is controlled via a command. The transmission will resume after the specified time has elapsed.

The CPR's silent state operation, designed to avoid interference with radio telescopes, is incorporated into the satellite operational plan based on the RAS location information, coordinated by ESA. Past RAS operations and upcoming plans for the next week are summarized at the following link:

https://ec-pdgs-monitor.eo.esa.int/flyover/