Inspired by the "Mars Webcam," the Cluster mission decided it was worth a try to turn on the VMCs, and has been posting frequent updates about the effort on its Twitter account, which I'll paraphrase here. Because of the spacecraft's depleted power condition, there is not ordinarily enough power to run these cameras -- all of the power is needed to continue science. But there are two periods each year when the spacecraft experience daily eclipses. Their batteries having long since died, the spacecraft have to shut down completely through every eclipse, and be reactivated after. Under these conditions, it's difficult to operate the science instruments, so most instruments are kept turned off through eclipse season. That leaves power available for VMC to be turned on during the part of the orbit when the spacecraft is not in eclipse. So far they have just attempted to turn one back on, Samba (because Samba has greater power margins than Rumba).

The Cluster spacecraft also have virtually no maneuvering fuel left, and what little they have won't be used for pointing photos. So the mission controllers have to make do with whatever happens to pass through the camera fields of view. What could the Cluster VMCs image? The bottom side of the spacecraft, and with it the VMC, perennially point north, perpendicular to the ecliptic. That means only one view of Earth can ever pass through the field of view -- a view of the southern hemisphere.

But don't get too excited about potential images of Antarctica like Mars Express VMC gets of Mars' south pole. The Cluster orbit is not a polar one; it's inclined 131 degrees. The camera field of view is 40 degrees wide. They'll image Earth from a distance of about 60000 kilometers. There's only a small part of the orbit in which they can hope to see Earth. So the best they can hope for is to catch part of Earth in one corner of the field of view.

At least that's what they thought. Yesterday, they got their first test images down, expecting them to be entirely black. Many were black, but a few were not quite entirely black; some bright pixels showed up in one corner of the images, changing position slightly from image to image. It turned out to be the spacecraft's low-gain antenna, poking up from the same deck on which the VMC is mounted. Seeing it gave the team confidence that the camera was working (beautifully, in fact), and incidentally helped them determine "exactly how the Field of View is oriented in the spacecraft and relative to the Sun."