Sunday May 17th 2009. Day 3.


Things continue to be quiet. Check-out is still going on. Mission Control has now got a really accurate orbit determination for Herschel and has decided to make one more, tiny correction to the trajectory of 0.9m/s (compare this with the approximately 11km/s that Herschel had initially). Last night Herschel passed the Moon just before 00UT. At 00UT tonight Herschel will be well beyond the Moon, now 484 000km from Earth and receding at 0.99km/s. Signals will take 1.6s to reach Herschel from Earth. Herschel right now is in the constellation of Serpens.


There is great confusion as to the identification the different objects in telescopic images. The Minor Planet Center (MPC) has identified the brightest object in the field as definitely Planck. This however disagrees with the fact that Herschel is much bigger and thus presumably brighter than Planck and that the object that they identify as Planck has lower radial velocity, despite the fact that Planck has a higher energy orbit. Mission Control now has a high-quality orbit determination for both Herschel and Planck that apparently confirms that the brightest object in the field is, as we thought, Herschel and that the MPC identification seems to be wrong. It is still difficult to work out of the pair of fainter objects, close together, is Planck and which is the Sylda. I am also getting reports that three other objects, two of them much fainter, are being seen, further away from Herschel, Planck and the Sylda.


With the new orbit of Herschel and Planck that should be available tomorrow I hope that the definitive identifications can be confirmed.


Amateur astronomers continue to get amazing sequences of images. You can check out some of the best ones in the unofficial Herschel Image of the Day archive, here:


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