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JMR Noise Diode Stability and Recalibration Methodology after Three Years On-OrbitThe Jason Microwave Radiometer (JMR) is included on the Jason-1 ocean altimeter satellite to measure the wet tropospheric path delay (PD) experienced by the radar altimeter signal. JMR is nadir pointing and measures the radiometric brightness temperature (T(sub B)) at 18.7, 23.8 and 34.0 GHz. JMR is a Dicke radiometer and it is the first radiometer to be flown in space that uses noise diodes for calibration. Therefore, monitoring the long term stability of the noise diodes is essential. Each channel has three redundant noise diodes which are individually coupled into the antenna signal to provide an estimate of the gain. Two significant jumps in the JMR path delays, relative to ground truth, were observed around 300 and 700 days into the mission. Slow drifts in the retrieved products were also evident over the entire mission. During a recalibration effort, it was determined that a single set of calibration coefficients was not able to remove the calibration jumps and drifts, suggesting that there was a change in the hardware and time dependent coefficients would be required. To facilitate the derivation of time dependent coefficients, an optimal estimation based calibration system was developed which iteratively determines that set of calibration coefficients which minimize the RMS difference between the JMR TBs and on-Earth hot and cold absolute references. This optimal calibration algorithm was used to fine tune the front end path loss coefficients and derive a time series of the JMR noise diode brightness temperatures for each of the nine diodes. Jumps and drifts, on the order of 1% to 2%, are observed among the noise diodes in the first three years on-orbit.
Document ID
20070023652
Acquisition Source
Jet Propulsion Laboratory
Document Type
Preprint (Draft being sent to journal)
External Source(s)
Authors
Brown, Shannon
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Desai, Shailen
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Keihm, Stephen
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Ruf, Christopher
(Michigan Univ. MI, United States)
Date Acquired
August 23, 2013
Publication Date
February 28, 2006
Subject Category
Acoustics
Meeting Information
Meeting: IEEE Microrad 2006
Location: San Juan
Country: Puerto Rico
Start Date: February 28, 2006
End Date: March 3, 2006
Sponsors: Institute of Electrical and Electronics Engineers
Distribution Limits
Public
Copyright
Other
Keywords
Jason 1
Jason Microwave Radiometer (JMR)
alimeter signal

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