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Archive for October, 2007

Jupiter From New Horizons

October 14th, 2007 2 comments

Jupiter seen from the New Horizons space probe in Google Earth SkyLast week NASA released a stunning bird’s-eye montage of Jupiter and its closest moon Io taken by the New Horizons robotic spacecraft. 

Since the pictures weren’t taken from Earth there seems little point placing them in Google Sky as if they were being viewed from Earth – in fact, because we’re much closer to the sun we never see a crescent Jupiter from Earth. So instead , I’ve removed Io and used the imaging date given in the NASA press release (February 28 2007, 01:40) to locate and scale it as seen from the point of view of the spacecraft, which at the time was 2.3 million km from Jupiter and 800 million km from Earth.

Here’s the file for viewing in GoogleSky:

Jupiter from New Horizons (2.7MB)

The file also includes overlays of Earth, the Sun and Pluto (New Horizons’ primary target) for size and distance comparison.  Again these are positioned from the point of view of the space probe.

For the astro-referencing I used the online JPL Horizons interface (no relation to New Horizons) which very cleverly allows you to generate an ephemeris for one Solar System object observed from any other major body, including spacecraft!  

More details about the original montage on the NASA news website here.  

Image Credits – Jupiter: NASA/JHU/APL – Earth: Screenshot from Celestia – Pluto: Eliot Young (SwRI) et al., NASA

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Hurricane Followspot Animations

October 2nd, 2007 No comments

From top to bottom: hurricanes Florence, Gordon and Helene, 14th September 2006, in Google EarthGoogle Earth time animations of Atlantic hurricanes from 2006 – Ernesto, Florence, Gordon, Helene and Isaac.

One drawback of using animated sequences of picture overlays in Google Earth is that they tend to result in large, often memory hungry files.  With that in mind, I’ve been experimenting with some Python scripts that dynamically crop small regions out of large map images, then wrap them in KML.

This one is a quick mashup of hurricane tracking data from the National Oceanic & Atmospheric Administration (NOAA), and satellite imagery from the global cloud archive.  Rather than using a sequence of large rectangular(ish) overlays stuck over one area, every hurricane has its own set of circular image overlays, each centred on the eye of the storm.  When played back as a time animation in Google Earth  the satellite images move along with the weather feature.  The video shows it in action:

It comes in two versions:  opaque (GIF images) and one with transparency (PNG).  The GIF version contains higher detail imagery. Download either file here:

2006 Hurricanes (GIF) 7MB

2006 Hurricanes (PNG) 7MB

Note, you can change the transparency of either file using the slider in the Layers panel. It can take a while for everything to load into memory first time the file is opened.

A coupe of  noteworthy things about this:

  • For an animation using the full-sized global cloud PNG maps over the same time period,  the filesize would be 320MB! – that’s 40 day, 8 maps per day, 1MB each. 
  • Although not apparent in GE,  each image overlay is a slightly different shape to take into account spherical projection. 
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