DEVELOPMENT OF A V-BAND 2-PATH (2SQCC) CONTINUOUS CALIBRATING SPECTROMETER BASED ON THE MULTI PATH CROSS CORRELATION RADIOMETRY (MXCR) TECHNIQUE

A. Venkitasubramony^1,2, A. Gasiewski^2,1, M. Marques¹, S. Mckee¹, D. Lee¹, R. Belter¹, M. Hurowitz¹

¹Weather Stream Inc., ²University of Colorado at Boulder

Long term direct thermal measurement of the earth’s middle and lower tropospheric temperature on a global basis along with the determination of a diurnal temperature climatology is needed to 1) correct historic satellite mid-tropospheric temperature data, 2) estimate the impact of atmospheric greenhouse warming in response to anthropogenic CO2 emissions, 3) inter-calibrate the international fleet of weather satellites, and 4) monitor naturally occurring atmospheric temperature trends. Quantifying anticipated temperature trends on a timely basis requires the globally averaged mid-tropospheric temperature to be observed with a satellite temperature sounding instrument of very high stability and traceability. Stable on-orbit reference instruments are needed to also prevent instrumental drift or deterioration from obscuring trends occurring over several decades. With increased anticipated anthropogenic emission resulting from the imminent deployment of 5G communications electronics and related consumer and defense applications at V-band, radio frequency interference (RFI) detection and mitigation also becomes indispensable for accurate temperature retrievals. Given the historical trend of spectral occupancy doubling every ~6 years, RFI detection and mitigation is an indispensable feature for all future passive remote sensing instruments.

This talk summarizes the work done towards the development of a prototype instrument based on the novel (patent pending) Multipath Cross Correlation Radiometry (MXCR) technique that attempts to satisfy the above discussed capabilities desired in future radiometers. The MXCR implementation enables 1) stable spectral detection to precisely characterize satellite instrument sub-channel spectral variation, 2) kurtosis computation capability to perform real-time RFI detection and mitigation, 3) rejection of errors in antenna temperature estimate due to receiver path gain fluctuations and gain compression caused by RFI, and 4) a continuous calibrating scheme thereby eliminating the need for external calibration views. The first ever 2-path (2SQCC) digital correlating V-band spectrometer based on the MXCR technique was developed at the University of Colorado at Boulder (CU) Center for Environmental Technology (CET). The theoretical background, laboratory prototype development, and preliminary test results of this 2SQCC MXCR spectrometer is discussed. The sensitivity and long-term stability of the instrument is studied using the real-time multi-channel data processing solution at Weather Stream Inc. and the results are presented.