Tuesday May 19th 2009. Day 5.


Today has been a good day for Herschel. As announced yesterday, our first instrument was switched-on. A successful SPIRE switch-on happened at 11:39UT. Data was received all afternoon as SPIRE scientists gave the instrument a careful check-out. Our first instrument is on and functioning. Tomorrow the SPIRE team will continue running through their tests, in preparation for the first trial observations on Friday. The SPIRE team is rightly jubilant and say that everything is worked just as it did in ground testing. To operate SPIRE the team went to Mission Control in Darmstadt and controlled the instrument directly through the link to the tracking station.


Meanwhile, preparations continue for the first science observations with Herschel in the autumn. Hundreds of observations need to be updated now that changes have been made in the configuration of the instruments as a result of the tests made through the autumn and winter. Many parameters have been measured and checked and all kinds of fine-tuning made to get the best out of the three instruments. This operation will continue in space as, when we start to look at stars, it is inevitable that new information will come to light that makes us change further the way that observations are made: it is all part and parcel of operating in space.


Today we have had a silly season story. Apart from the four main pieces flying together in space (Herschel, Planck, the Sylda and the Ariane upper stage), the Minor Planet Center is tracking two other, unexplained objects near to the Ariane. However, deep images have revealed a series of other, faint unconfirmed objects. These have been widely discussed on the Internet with comments ranging from them being evidence that alien spacecraft were pursuing Herschel, to hysterical suggestions that something had broken off Herschel (this last suggestion totally ignoring the fact that all the telemetry from Herschel shows that it is in excellent shape). By one count there are as many as 14 additional objects tracking Herschel and Planck. What could they be?


We have discussed this widely over the last couple of days. As far as we can work out, there are two probable explanations. It is quite likely that some of the faint blobs are due to the covers of the thrusters on the Ariane upper stage. However, the most likely explanation for most of them is that they are pieces of ice that shook off the upper stage around separation. Some of the ice would have stayed in shadow for much of the ascent, finally breaking off as it warmed. Fresh ice has an albedo of up to 90%, meaning that even rather small pieces could be quite bright. Explaining all this has kept us entertained for a couple of days and led to a lot of brainstorming. Maybe though we are wrong and need to add Mr. Spock to the picture below!






Frequent updates are provided during the day on the Herschel Twitter (ESAHerschel) here: