Emily LakdawallaNov 01, 2008

On its way to the Moon, Chandrayaan-1 photographs Earth, but flips the photo

The Indian lunar orbiter Chandrayaan-1 is still on the long loop of its latest orbit, but scientists on the mission aren't wasting any time; they've turned one of its cameras toward its erstwhile home, Earth. I love it when planetary spacecraft take images of Earth -- there's just something about using the eyes meant to study strange worlds to study our own that produces a fresh perspective on our home planet. Here's the image:

Earth from Chandrayaan-1

ISRO

Earth from Chandrayaan-1
Chandrayaan-1 took this photo of Earth from Earth orbit on October 29, 2008 at 07:00 UTC. Near the center of the disk is the northwestern coast of Australia; the Sun glints off the Indian Ocean adjacent to that coast. This image has been flipped horizontally from its originally published version to match the proper orientation.

I figured it out because I could not for the life of me make the visible coastline of Australia match up with a map of Australia. I thought we might be seeing Earth from an unusual perspective -- maybe from a high latitude or something -- and that's why I couldn't figure it out. So I decided to go check out what one of our geostationary weather satellites saw at the same time, because those satellites are parked over the equator, and thus have a perspective that's easy to recognize; I figured I could match the cloud patterns in the weather satellite photo with the ones in the Chandrayaan-1 photo to help me orient myself. Here's the image I found, taken by the Japanese satellite Himawari-6 (also known as MTSAT-1R), about an hour before the Chandrayaan-1 photo:

Image of Earth taken near the same time as the Chandrayaan-1 photo by Himawari-6

Japan Meteorological Agency / courtesy EUMETSAT / NERC Satellite Receiving Station, University of Dundee

Image of Earth taken near the same time as the Chandrayaan-1 photo by Himawari-6
Himawari-6, also known as MTSAT-1R, is a geostationary weather satellite parked in an orbit over Australasia. This photo was taken at 06:00 UTC on October 29, about an hour before a Chandrayaan-1 photo of Earth.
Earth from Chandrayaan-1 as originally published

ISRO

Earth from Chandrayaan-1 as originally published
When the Chandrayaan-1 image of Earth was released to the public, it was erroneously flipped (mirrored) horizontally.

If you're in a hurry, and you don't yet have a lot of experience working with your spacecraft's data -- as is certainly the case for a newly launched spacecraft that you're trying to ballyhoo to your taxpayers with quick press releases and status reports -- it'd be easy to make that mistake. It's actually much more understandable for ISRO to have made this mistake with a spacecraft launched only a week before, and whose camera was being tested for the first time, than it was for ESA to make the mistake with Rosetta, a spacecraft that had been launched more than three years prior, whose camera had been used during two previous flybys.

The error is not really important. Kudos to the Chandrayaan-1 team; the image is absolutely gorgeous in its detail, and bodes well for the spacecraft's images of the Moon, which will be taken from a much closer distance.

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