The End of Hitomi..
First here’s a new plot of the debris (via Jonathan McDowell):
This shows more pieces of debris than the one I showed previously, and also demonstrates that some of the pieces are in rapidly-decaying orbits. A rough estimate suggests that some of these – those in the lower right of the diagram- will burn up in the atmosphere within a week or so. This behaviour is consistent with them being rather light fragments, on which the effect of drag is greater, and consequently possibly rather small. Their behaviour does not therefore necessarily imply anything too catastrophic about the main spacecraft.
However, there is now strong evidence that the main spacecraft actually did break up fairly completely rather than shedding a few pieces of casing or whatever. Two of the brightest pieces are of roughly equal size and, ominously, the original identification of one of them with the main part of the spacecraft has been shown to be wrong. Furthermore, no signals have been received from the onboard beacon for six days now. It all sounds very terminal to me.
So what happened? Of course I don’t know for sure, but the above picture suggests the possibility of an explosion (possibly violent outgassing of cryogens needed for the instruments near the rear of the main body of the vehicle). The structure to the rear of the vehicle is a deployable optical bench used to increase the focal length of the telescope for hard X-ray work. This could well have broken off during such an explosion, as could all or part of the solar panels used to supply power to the satellite.
The Japanese Space Agency JAXA has not officially given up on Hitomi (formerly known as ASTRO-H) but I think the hopes of most commenters I’m aware of have now faded away.
It’s all very sad.Follow @telescoper