Voyager and Galileo Ganymede Images – Ganymede Osiris mosaic (Voyager 2)

A color mosaic showing a large area around Ganymede's Osiris crater. North is up and the color should be fairly accurate - possibly a bit too reddish and saturated but Ganymede's color from Voyager images is a complicated subject. This mosaic is composed of 21 clear filter images obtained by Voyager 2 on July 9, 1979 at a range of 91,000 to 118,000 km (resolution 0.9 to 1.2 km/pixel). Its northern half has been colorized using a three frame color mosaic obtained at a range of a little over 300,000 km (resolution 3 km/pixel). The southern half (starting from just south of Osiris) has been colorized using a single wide angle color composite obtained when Voyager 2 was ~75,000 km from Ganymede (resolution ~5.6 km/pixel). Some of the lower resolution color coverage is included in the mosaic outside of the area covered by the higher-res clear filter images. I mosaicked everything in simple cylindrical projection and also did all of the color processing there and then rendered the resulting map using the viewing geometry Voyager 2 had when it obtained its best image of Osiris (image C2063759).

Ganymede exhibits big albedo differences and this can complicate the image processing. I took great care not to overexpose/saturate any parts of the brightest terrain (Osiris in particular). This preserves every detail but makes the terminator area a bit dark.

A huge variety of interesting terrain can be seen in the mosaic. With the benefit of hindsight there are clear hints of the extreme roughness of some terrain types covered by some of the higher resolution Galileo images but there is also terrain that looks smooth in the Voyager mosaic. I look forward to seeing Osiris in hi-res JUICE images and also the bright smooth-looking terrain around the bright crater SSW of Osiris.