| Paper: | FR-A1.1 |
| Session: | Instruments and Calibration (Posters) |
| Time: | Friday, March 30, 09:00 - 10:20 |
| Presentation: |
Poster
|
| Topic: |
Advanced radiometer techniques: |
| Title: |
Calibration of RapidScat Brightness Temperature |
| Authors: |
Ali Al-Sabbagh; Florida Institute of Technology | | |
| | Ruaa Alsabah; Florida Institute of Technology | | |
| | Josko Zec; Florida Institute of Technology | | |
| Abstract: |
NASA RapidScat is the first satellite scatterometer that flew in non-Sun-synchronous orbit. It’s unique orbit enabled co-located measurements with multiple satellite remote-sensing instruments that mostly fly in Sun-synchronous orbits. RapidScat primary mission was retrieval of global ocean wind vectors from normalized radar backscatter measurements. Instrument operated onboard the International Space Station between September 2014 and November 2016 covering latitude range between ±51.6o. To serve as a cross-calibration reference with other instruments, RapidScat must be internally calibrated. This paper describes process that combines RapidScat’s active/passive mode, simultaneously measuring both the radar surface backscatter (active mode) and microwave emission from the system noise temperature (passive mode). The radiometric calibration of RapidScat that enables the surface brightness temperature measurement is presented. Seasonal measurement biases have been evaluated using the Radiative Transfer Model (RTM). Systematic brightness temperature biases for both polarizations have been calculated as a function of atmospheric model (water vapor and cloud liquid water) and ocean brightness temperature models (wind speed, sea surface temperature, and wind direction). These deviations were averaged over 1084 RapidScat revolutions. Trends from observations during a 20-month period between January 2015 and August 2016 have been described. Results obtained indicate that most of the measured data in 2015 show good overall average agreement. Following the further analysis of the RapidScat measurement set may help estimate relative validity and stability of other scatterometers/radiometers. This research was performed under the grant from the NASA Headquarters. And both L2A and L2B Rapidscat data sets were provided by the NASA Physical Oceanography Distributed Active Archive Center (PODAAC) at the Jet Propulsion Laboratory. |
