Friday May 15th 2009. Day 1.


After the strong emotions of yesterday this was a much quieter day. Various people commented that they felt physically and emotionally exhausted after launch day. Today has basically been a quiet day, but with a difference: this is no longer a test, a simulation, or an exercise.


So far it seems to be a sequence of unbroken good news. The launch was well nigh perfect and the trajectory extremely accurate. A small trajectory correction manoeuvre was carried out successfully around 12UT today. We are now well on our way to L2. Tonight Herschel passes from the constellation of Libra into Serpens. At 00UT it will be at 280 000km (0.93 light seconds) from Earth. I have just had confirmation that Peter Birtwhistle has observed Herschel, Planck and the Scylda through a gap in the clouds from Great Shefford (MPC J95) in Southern England. Peter’s photometry says that Herschel is varying from 15.16-15.84, Planck from 15.46-15.72 and the Sylda from 16.43-17.47 against a CMC-14 reference star.


Various pieces of telemetry have been arriving giving basic information of spacecraft health. The radiation detectors on Planck and Herschel both detected a big peak in radiation as they passed through the Van Allen Radiation Belts. Among the first telemetry to come through has been spectacular images of the separation of Herschel from the Ariane upper stage ( and information on the temperature of various parts of the spacecraft. The temperature of the parts of the spacecraft that are not actively cooled by helium were expected to drop rapidly in the shadow of the sunshield. By this afternoon the temperature of the outer shield of the PACS camera-spectrograph had already dropped by 120º from the temperature that it had inside the fairing of the Ariane. The rate of drop was slowing progressively; we expect it to drop to around 70-80K over the next few weeks.


The amount of telemetry is limited everyone is throwing themselves at it with gusto. The difference between months of simulations and tests and having real data to study is tremendous and everyone has worked on the data, such as it is, with real gusto.


Mission Control reports that the mission has been a textbook exercise so far. They are tracking a couple of minor issues, neither of which are particularly worrying. Things are going astonishingly well.


As we are now in operations and preparing for people to update their observations. This means continuing acceptance testing of the new software upgrade, writing documentation and preparing to contact astronomers with the required updates.