Perijove 1 Context Map (Preliminary)

2016-10-19 12:23 UT
Credit : NASA / JPL / SwRI / MSSS / Gerald Eichstädt
Submitted By : Maquet-80
Mission Phase : PERIJOVE 1

This image demonstrates, that it's possible to create a context map of Jupiter from JunoCam Marble Movie images. The map covers almost the full surface of Jupiter.

The map consists of 4272x1800 pixels. Each pixel corresponds to a planetocentric square of 0.1 degrees longitude times 0.1 degrees latitude.

The latitude range is from -90 degrees (south pole) at the bottom to +90 degrees (north pole) at the top. The longitude ranges over 427.2 degrees, resulting in an overlap (doubling) at the left and right end.

The map is derived from 40 Marble Movie images, the 20 color images #6121 to #6159 immediately before the perijove 1 (PJ1) images, and the 20 color images #6189 to #6227 immediately after the PJ1 images.

The 20 images before PJ1 cover Jupiter's northern hemisphere, the other 20 images cover the southern hemisphere. The two sequences overlap in the equator region.

Each of the comprised Marble Movie images has been transformed geometrically to a partial map without brightness adjustment, using a rotating rigid Jupiter (MacLaurin) spheroid model. The partial maps have then been composed by selecting the brightest pixel of all maps for each given pixel position.

The resulting map underwent several post-processing steps: multiplying with the negative of the mean grey value over all pixels of the same latitude as a crude de-lamberting avoiding the brightess singularity near the poles, hipass-filtering (radius 100) to prepare for small-scale enhancement, then enhancing brightness and saturation by respective linear stretches.

The map is preliminary in several ways:

Alignment of the partial maps mostly along longitude can be improved considerably. This should be followed by a longitude crop to 360 degrees of one of the standard Jupiter models. Accurate de-lamberting before merging the partial maps should reduce most of the horizontal brightness oscillations induced by the 40 partial maps. This requires a refined merging method, since brightness then can't be used as a criterion for which partial map(s) to use for a final pixel. The maps should be cleaned from noise by energetic particles, hot pixels and small dark spots on JunoCam's camera filters.