Towards a fast background radiation subtraction technique for the Juno mission

The Juno spacecraft will go into polar orbit after it arrives at Jupiter in 2016. Scientific instruments on Juno will make in situ charged particles and magnetic fields measurements. Remote sensing instruments will measure thermal and non-thermal emissions from the atmosphere and magnetosphere. Gravitational field measurements will be derived using radio tracking signals. The Microwave Radiometer (MWR) Instrument, one of the nine instruments on Juno, has been designed to measure the brightness temperatures of Jupiter at six microwave frequencies, sounding the atmosphere from 0.5 atm to over 100 atm pressure. Synchrotron emission generated by ultra-relativistic electrons trapped in Jupiter's magnetosphere will be detected and measured by the MWR Radiometer over a range of wavelengths from 2 cm to 50 cm. Synchrotron data collected with the MWR Radiometer will be used for two purposes: a) to improve the atmospheric measurements, and b) to provide new constraints on the synchrotron emission itself. The ancillary MWR data analysis requires a fast synchrotron radiation model that can be used in conjunction with the atmospheric retrieval algorithm. This paper describes an extension of the Levin at al. (2001) multi-zonal, multi-parameter model to a spacecraft point of view, along with a few testing and validation cases.