The Radio and Microwave Sky from Juno

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I found out about an interesting paper by Anderson et al. at a discussion group this morning. The abstract reads:

We present six nearly full-sky maps made from data taken by radiometers on the Juno satellite during its 5-year flight to Jupiter. The maps represent integrated emission over ∼4% passbands spaced approximately in octaves between 600 MHz and 21.9 GHz. Long time-scale offset drifts are removed in all bands, and, for the two lowest frequency bands, gain drifts are also removed from the maps via a self-calibration algorithm similar to the NPIPE pipeline used by the Planck collaboration. We show that, after this solution is applied, residual noise in the maps is consistent with thermal radiometer noise. We verify our map solutions with several consistency tests and end-to-end simulations. We also estimate the level of pixelization noise and polarization leakage via simulations.

arXiv:2405.08388

For those of you unaware about Juno, it is a NASA space mission (launched in 2011) intended to study the planet Jupiter (which it is still doing). On the way there, however, this spacecraft made continuous measurements of the radiation field around it, at radio and microwave frequencies. The work described by Anderson et al. involved turning these observations into maps at a range of frequency; they also studied the polarization properties of the radiation.

The full maps and other relevant data can be downloaded here. Here are some pretty pictures (the grey bits represent the parts of the sky that were not covered; radio emission from our own Galaxy is the most obvious component at low frequencies, but it looks more complicated at higher frequencies).

It’s always fun when data sets are used for something so different from the purpose originally intended, and what has come out of this analysis are rather nice maps of the emission from the Milky Way. These might turn out to be useful for many things, such as foreground removal for extragalactic surveys or studies of our own Galaxy.

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