Automatic Gain and Offset Control Algorithm for Millimeter-Wave Humidity Sounder Payload

This paper reports the Automatic Gain and Offset Control Algorithm (AGOC), and its lab and flight-testing results for Millimeter-wave Humidity Sounder (MHS) Payload. MHS payload, ISRO’s first high frequency (mm-wave) payload was successfully launched on 10th February 2023 on-board EOS-7 satellite. It is ISRO’s first step towards showcasing the in-house development and demonstration capability in mm-wave technology advancement from space-borne platform. It is a 6-channel cross-track scanning radiometer, operating over water vapor absorption band at $183.31 \pm 17.25 \mathrm{GHz}$. It is designed to generate 3D humidity profiles of Earth’s atmosphere from surface to 12 km altitude with vertical resolution ${\lt}2 \mathrm{~km}$ and spatial resolution of 10 km at nadir from 450 km altitude. AGOC algorithm was implemented onboard FPGA to compensate for gain and temperature drift in receiver, and to optimally map the receiver output to Analog to Digital Converter (ADC) dynamic range. Two types of AGOC algorithm, namely Baseband (BB)-AGOC and Intermediate Frequency (IF)AGOC were implemented and successfully demonstrated in lab and space.