Perijove-specific color correction multipliers

By Bjorn_Jonsson on 2023-05-26 UT

This is a plot of the values I use for correcting the color in the JunoCam images. I keep red constant and mulitply the green and blue values. Here the correction is in percent. If the correction for blue is e.g. 250% I am multiplying blue by 2.5.

Until recently the images were getting redder and that trend was if anything accelerating. Interestingly, this trend appears to have reversed following the anomaly at PJ48.

The reddening probably didn't start until sometime after PJ20 (possibly at PJ22 or PJ23).

The values were determined by measuring the color of regions on Jupiter that should be roughly white, e.g. STrZ. I occasionally checked calibrated HST images for possible color changes on Jupiter and also as a 'sanity check'.

I used decompanded images after applying (rudimentary) flat fielding and dark current correction. Omitting flat fielding and dark current correction resulted in only negligible changes to the color correction values. The accuracy varies a bit as a function of perijove. In particular it is probably lower for the first ~5 perijoves, mainly because the most useful whitish areas (e.g. STrZ) were near the terminator and therefore dimly lit.



  1. comment by Bjorn_Jonsson AUTHOR on 2024-02-08 01:17 UT

    This is an updated plot of the values I use for correcting the color in the JunoCam images. It covers perijoves 1 to 58 (the earlier plot included perijoves 1 to 51). Interestingly, the trend became more irregular once the JunoCam anomalies started at PJ48. In particular, the images temporarily became less red after PJ48 but are now again getting redder - there was a *very* large change (reddening) from PJ57 to PJ58.

  2. comment by Philosophia-47 on 2023-07-13 19:56 UT

    Bjorn, this is really interesting.  Your values agree very well with Gerald's, showing progressive reddening only from approx. PJ23 to PJ48.  I wonder why that is?